This sub survey contains data from 8 mid-lake gill net sets that were first set in 1997. These nets were initially set to determine if catch rate and growth statistics for various fish species were similar to those of the 24 near-shore gill net sets.
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\nData from this survey should not be used to independently evaluate Lake Winnibigoshish fish populations, or to compare between years within lake or between different lakes as the data are from a subset of nets contributing to a larger study.
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Assessment of Lake Winnibigoshish is completed annually to track changes in abundance and growth of fish species, and physical and chemical characteristics of the lake. The assessment season typically starts with seining and gill netting in late June to early July. The goal of seining is to sample young game and non-game species (including minnows) and to track growth of age-0 walleye and yellow perch (perch). Gill netting is conducted from late June through July to sample game and non-game species age 1 and older. Abundance, growth rates, maturity, presence of parasites etc. is determined from these data. Trawling is conducted in August to continue tracking growth rates of age-0 walleye and perch. Trawling gives us the first clue to abundance of age-0 walleye and perch for that year. Temperature and dissolved oxygen profiles are taken from June through August and water chemistry analysis is done in August to track changes in the system that may affect the ability of some species to prosper or exist in the lake. Plankton sampling was included in standard sampling for 2012. Five samples were taken on eight dates for a total of 40 samples. These samples were taken to determine baseline planktonic species composition.
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\nWalleye; Walleye were sampled at a historic high rate of 9.6 per net. Walleye sampled varied from 8.3 to 26.7 inches with a mean length of 16.3 inches and mean weight of 1.4 pounds. The walleye population appeared to be healthy with most age classes sampled between age 1 and 16. Year-class strength was computed for walleye between age 2 and 7. Two average year classes (2005, and 2007), three strong year classes (2006 and 2009, and 2010), and one weak year class (2008) were sampled. Mean back calculated growth was similar to the Lake Winnibigoshish and statewide average for all ages, attaining 16.7 inches after five growing seasons.
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\nThe mean trawl catch rate of 35.6 walleye per hour was lower than average, however, low catch rates may not result in low abundance of that year class. For example, the trawl catch rate of 20.5 young of the year walleye per hour in 2005 resulted in an above average year class. An important factor in year-class strength is growth of those fish during their first year. Young of the year walleye growth was above average in 2012, reaching a mean length of 5.0 inches by mid-August. Fast growth of age 0 walleye often results in a strong year class.
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\nYellow perch; Perch are an important species both for anglers and as a prey item for predators. The catch of perch in assessment nets reached a historic low catch rate (at the time) in 2005 largely due to poor year classes in 2000 and 2002. A strong 2003 year class moved through the system resulting in higher assessment catch rates through 2007. Gill net catch rates then declined through 2011 to a new historic low of 43.6 per net that year.
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\nPerch were captured at a rate of 57.5 per net in 2012. Perch sampled varied from 5.0 to 11.5 inches with a mean length of 7.1 inches and mean weight of 0.2 pounds. Age classes 2 through 8 and were sampled by the gill nets. An index of year class strength was computed for ages 3 through 7. The 2005, 2008 and 2009 year classes were average, and the 2006 and 2007 year classes were weak. The previously strong 2003 and average 2004 year classes were not well represented in the catch. Natural mortality of perch increases at age 9 and few individuals live past age 10. The catch of perch in 2012 was primarily represented by younger individuals with 87% of the catch made up of age 3 through age 5 fish. Growth was relatively slow through age 2, then increased to average from age 3 to age 8. Perch grew to an average length of 9 inches at age 6.
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\nRelative health of the perch population can be described by the percent of perch longer than nine inches in the gill net catch. The catch of large perch declined to 6% in the early 1990's driven by high angler harvest. Changes in the perch population of Lake Winnibigoshish and other lakes prompted a statewide change in the perch bag limit to 20 daily and 40 in possession in 2001. Several strong year classes were produced during the same time period and the assessment catch of perch longer than nine inches increased to 30% in 2004. In 2005, the proportion of large perch sampled in near-shore gill nets declined for the first time since 1998. The proportion of perch longer than nine inches was about 17% in 2005 and 2006, then declined to 9.8% in 2007 as young perch were recruited to the fishery. Many small fish remain in the population and 10% of the perch sampled in 2012 were longer than nine inches.
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\nThe microsporidian parasite heterosporis has been documented in Lake Winnibigoshish yellow perch. No evidence of heterosporis was observed in perch during the 2012 population assessment, however, anglers report the presence of heterosporis in a few perch each year.
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\nThe catch rate for age-0 perch of 10,720 per hour of trawling was average. Growth of age-0 perch was slower than average with a mean length of 1.7 inches in mid August. No correlation is evident between trawl catch rates or growth of age-0 perch and year-class strength.
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\nNorthern pike; Catch rates of northern pike (pike) showed an increasing trend from 1999 through 2005 and exceeded the third quartile (9.6 per net) in five years between 2002 and 2009. The pike catch rate decreased to 7.3 per gill net in 2010 from 10.0 in 2009 then rose to 8.5 in 2011 and was the third highest observed in 2012 at 10.3 per net. Pike sampled in 2012 varied from 13.9 to 34.1 inches with a mean length of 21.6 inches. All age classes from 1 to 8 were sampled by gill net. The 2009 and 2010 year classes were most abundant and contributed 64% of the catch. Growth rates were similar to the statewide mean through all ages.
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\nSize structure of the pike population has been improving for the last three years. That trend continued in 2012 and extended to the largest fish in the system. Mean length and the number of pike longer than 30 inches was similar to those from 2011 and higher than in any assessments since 2000. Increased size structure can be attributed to several causes. Cisco abundance has increased (cisco are preferred prey that provides more energy than other similar size prey), which may lead to faster growth rates. Reduced abundance of pike may also be beneficial to the pike population since increased pike density can cause more competition for food and space which may lead to decrease growth. The recent increase in catch rate may resut in slower pike growth in the future. Anglers can help maintain the pike size structure by releasing most pike longer than 25 inches.
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\nCisco; Cisco are a primary prey for muskellunge, pike and walleye. Growth rates of these species can be reduced if cisco are not present in the system. The gill net catch of 16.0 cisco per net in 2012 was nearly identical to the catch of 16.4 per net in 2011. Cisco sampled varied from 6.9 to 16.4 inches with a mean length of 11.3 inches. Cisco catch rates were lower than average for 5 of the last 10 years. This is likely due to warmer than average summer and fall water temperatures that may affect reproduction and cause occasional summer kills. Summer water temperatures were warm during the summer of 2012. This resulted in a moderate summer kill of cisco. Any effect on the cisco population should be short term if average temperatures are experienced in the near future.
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\nWater Quality; Seven temperature and dissolved oxygen profiles were taken between June 25 and August 20, 2012. Dissolved oxygen stratification was evident between July 2 and July 27. No evidence of thermal stratification was found in 2012. Thermal and dissolved oxygen stratification may result during periods of high air temperatures and low wind. When wind speeds increase to moderate levels (15 mph) the entire water column appears to mix.
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\nInvasive Aquatic Species; Species that have been introduced through human activities to a location where they don't naturally occur are termed \"invasive\". Some invasive species are not necessarily harmful, but others cause ecological or economic problems. Several invasive species have been introduced to Lake Winnibigoshish. Three species of snail: banded mystery, Chinese mystery, and faucet have become established since 2000. Both species of mystery snail appear to have no negative effect at this time. The faucet snail carries a trematode parasite that can kill several species of ducks if ingested. Thousands of ducks were killed by these parasites during the falls of 2007 and 2008. Emerald shiners (often used as bait) are not native and were first sampled in 2005. Juvenile zebra mussel (veliger), were discovered while sampling for plankton in 2012. No adults were found during the summer of 2012. Each of these invasive species were likely introduced through human activities.
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This special assessment contains data from 8 mid-lake gill net sets that were established in 1997. Mid-lake gill nets were set to augment summer near-shore sampling. These nets were initially set to determine if catch rate and growth statistics for various fish species were similar to those of the 24 near-shore gill net sets, and were set in conjunction with the 24 near-shore sets.
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\nThe summer gill netting portion of this survey will be discontinued in 2018 and replaced with fall (September) gill netting. Summer netting was developed prior to availability of GPS. Due to this, most nets were set in near shore shallow water. Much of the Winnie fish populations utilize off shore habitat. Fall gill netting has been completed annually since 2007. Fall sampling locations were developed to sample shallow, mid-depth, and deep habitat in proportion to its availability. This should result in catch rates that are relatively unbiased. As zebra mussel have become established, and water clarity has improved, fall gill net catch rates of walleye have increased in deep water habitat.
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\nWalleye; Walleye catch rates typically vary similarly to near-shore, however, some years see gill net catch rates moving in opposite directions. That was the case in 2017 as near-shore catch for Walleye declined while mid-lake gill net catch increased from 4.0 per net to 4.4 per net. Mid-lake sampled Walleye varied from 12.8 to 23.3 inches with a mean length of 18.9 inches. The 2013 year class was dominant, making up 37 percent of the gill net catch. Catch rates for the 2012, 2014, and 2016 year classes were low.
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\nThe catch per gill net of Walleye longer than 19 inches has been used as an indicator of quality for the Walleye population. As with gill net catch rates, the catch of Walleye longer than 19 inches was lower in near-shore nets than mid-lake nets. The mean catch of Walleye longer than 19 inches sampled per mid-lake net since 1997 was 1.27 per net. This catch rate was similar to the mean catch of 1.19 Walleye longer than 19 inches per near-shore gill net set since 1997. The catch rate of Walleye longer than 19 inches of 1.9 per mid-lake net in 2017 far exceeded the catch of 1.1 per near-shore net.
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\nNorthern Pike; Mid-lake gill net catches of Northern Pike (pike) are typically less than near-shore nets, and that was the case in 2017. Reduced catch rates in mid-lake gill nets is likely due to sampling locations associated with open water vs vegetation. Gill net catch rates of pike in mid-lake nets decreased from 2013 through 2016. That trend reversed in 2017 with a new historic high catch of 9.5 pike per net. Pike sampled in 2017 varied from 16.9 to 34.1 inches with a mean length of 22.5 inches.
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\nYellow Perch; Yellow Perch (perch) have typically been sampled at a higher rate in mid-lake nets than from near shore nets. Results of the 2017 assessment followed that trend, with a catch rate of 63.3 per net in mid-lake net compared to 49.7 per near-shore net. The mean catch per gill net since 1997 has been higher in mid-lake gill nets (80.8) than near-shore gill nets (69.9). Although catch rates have been higher in mid-lake nets, unlike Walleye, the catch per gill net lift has varied similarly between near-shore and mid-lake gill nets. Perch sampled in mid-lake nets varied from 5.6 to 11.3 inches with a mean length of 7.1 inches.
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\nRelative health of the perch population has been described by the percent of perch longer than nine inches in the gill net catch. The catch of perch longer than 9 inches (large perch) in near-shore gill nets declined to 6% in the early 1990's driven by high angler harvest. Declining catch rates of large perch in Lake Winnibigoshish and other lakes prompted a statewide change in the perch bag limit to 20 daily and 40 in possession in 2001. Strong year classes, and reduced harvest resulted in high catch rates of large perch in the early 2000's. The catch of large perch started to decline in 2004 and has declined from 45.9% in 2004 to 11.5% in 2015. The catch rate of 7.2% longer than 9 inches in 2016 was the lowest observed for mid-lake gill netting. Decreased percent of large perch is likely due to high recruitment that resulted in a high overall catch rate. As these young perch mature, the percent of large perch should increase. Perch longer than 9 inches were somewhat more abundant in 2017 with 7.5% of the gill net catch longer than 9 inches.
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Lake Winnibigoshish, otherwise known as Winnie or Big Winnie, is a large reservoir located immediately north of the community of Bena, Minnesota. Winnie was a natural lake that was impounded in the 1880's with a dam controlled by the U.S. Army Corps of Engineers (USACE). Today the USACE maintains water levels within a narrow band of elevation that gives the lake its current surface area of approximately 56,472 acres and a maximum depth of 69 feet. The surrounding geology contains a high proportion of sandy soils, providing an abundance of sandy shoreline with very gradual slopes. With approximately 11 miles of open water between the north and south shores, the lake is prone to high wave action and frequent mixing of the water column when exposed to high winds. During the open water season, this keeps temperatures and oxygen levels much more uniform from the surface to the bottom of the lake, in comparison to smaller, more protected lakes with similar water depth. Sugar Lake, Cut Foot Sioux Lake, and Little Cut Foot Sioux Lake are all directly connected to Winnie. Some of the major tributaries include the First River flowage through Cut Foot Sioux Lake, the Third River, and the Mississippi River.
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\nWinnibigoshish is often thought of as a premier Walleye and Yellow Perch destination, but this lake offers angling opportunities for multiple species. Acknowledging the importance of this fishery, Winnibigoshish was included as one of ten lakes in the Large Lake Monitoring Program, which was developed by the Minnesota Department of Natural Resources (MN DNR) in 1983. Surveys are conducted on these lakes annually and typically include a suite of sampling methods that track trends in water quality, zooplankton, juvenile fish, periodic creel (angler) surveys, and the status of game fish targeted by anglers.
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\nMajor changes have been occurring within the system over the past 15 years. These changes began around the time of the discovery of invasive Faucet Snails in 2007, followed by the detection of larval Zebra Mussels in 2012, and adult Zebra Mussels in 2016. These invasives are filter feeders that can dramatically increase water clarity and reduce the abundance of plankton available to fish. Prior to the introduction of these invasives, water clarity (measured with a Secchi disc) averaged 6 to 7 feet and the highest ever recorded was 10 feet. There has been a post-invasion trend of increasing water clarity in Winnibigoshish, which continued during the 2024 field season when Secchi disc readings ranged from 9 to 27 feet. Increasing water clarity tends to improve habitat for Bass, Sunfish, and Northern Pike while decreasing habitat suitability for Walleye.
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\nWalleye is the primary management species in Winnie, and a large proportion of the field work completed is dedicated toward tracking the status of this species. The most important tool to assess the Walleye population is a gill net survey that is completed annually in September. The Walleye catch rate in the gill net survey was down from the previous year, and lower than the historic average. Walleye recruitment (survivability to the fishery) is naturally variable in any lake, and Winnie is no exception. The strongest year classes in recent history that are still present in the lake include the 2013, 2018, and 2019 year-classes. The very prolific 2019 year-class makes up much of the Walleye currently available to anglers. Males from this year class averaged 17 inches while females averaged 19 inches. The previously strong 2018 year-class now makes up a small percentage of the Walleye population and is likely due to a combination of high angler harvest and natural mortality. The 2013 year-class was 11 years old at the time of the fall survey, but there are still some that persist in Winnie.
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\nWinnibigoshish and its connected lakes currently have a protected slot of 18 to 23 inches for Walleye. The slot protects some spawning stock and promotes recycling of a portion of the population that is typically subjected to a high rate of harvest. As the 2019 year-class grows into the protected slot anglers will be looking ahead to the next year class that will provide \"eater sized\" Walleye to harvest. The 2020, 2021, and 2022 year classes were below average, but the 2023 year class is projected to be above average. The 2023 Walleyes averaged 10 inches during the fall gill net survey, and by the end of the 2025 growing season these should be approaching the size range of interest to anglers seeking harvestable sized fish.
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\nThere is a history of high angling pressure on Yellow Perch in Winnibigoshish. Perch are also a valuable prey item for predators such as Walleye and Northern Pike. Perch catch rates in gill net surveys have been declining for about two decades. In more recent history, there were several years of poor Perch recruitment leading up to a record low gill net catch rate in 2022. However, in the past two years there has been a record high number of age-2 Perch captured by gill nets which has brought the catch rate back within the expected range for Winnie. Perch growth has also been increasing in recent years. Some year classes sampled in the fall gill nets were nearly two years ahead of average growth rates.
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\nNorthern Pike is another popular species amongst Winnibigoshish anglers and spearers. Tributary inlet areas and connected waters provide a great deal of spawning habitat, which results in consistent recruitment of Northern Pike to the fishery. The population is generally characterized as having high abundance and relatively poor to moderate size structure when compared to other large lakes. In 2024 the fall gill net catch rates were low compared to historical catches for Winnibigoshish, but still within the expected range for similar lakes. The population peaked in abundance in 2017 and has stabilized at a lower level the past few years. Winnibigoshish is part of the north-central zone for Northern Pike regulations that includes a protected slot of 22 to 26 inches. Release of Northern Pike over 26 inches is encouraged to help improve the overall size structure of the population. About one-third of the gill net sampled Pike were within the protected slot limit, and lengths ranged from 15 to 35 inches.
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\nTullibee, otherwise known as Cisco, are an important prey fish in lakes where they occur, and at times can be a popular species for anglers to target. The population in Winnibigoshish has fluctuated over time, but over the past 15 years there has been a sharp decline in abundance. The gill net catch rate in 2024 was the second lowest ever recorded for Winnie surveys. The decline in the population is attributed to several factors. Tullibee feed primarily on zooplankton, which has decreased due to the presence of Zebra Mussels. Tullibee also require cold water and in some years the water temperatures in Winnibigoshish can surpass stressful or even lethal thresholds.
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\nOther species that may be of interest to anglers include Bluegill, Black Crappie, Burbot, Largemouth Bass, Rock Bass, and Muskellunge. Panfish and Bass in Winnie are typically low in abundance, with most of the population concentrated in certain areas of the lake where vegetation is abundant. Sunfish species are more commonly targeted in the Cut Foot Sioux chain. The popularity of that fishery and the high-quality size structure of the population led to the addition of a 5 fish bag limit for Sunfish throughout the entire Winnie reservoir. Muskellunge are difficult to sample in Winnie with traditional survey gear, making relatively accurate population estimates nearly impossible. It is generally accepted that this is a low-density population, and it is completely sustained by natural reproduction. Burbot are also difficult to assess with traditional open-water survey nets but appear to be popular with some anglers during the ice fishing season.
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\nInvasive species cause economic or environmental harm, or harm to human health. They are illegal to introduce into or move between state waters and can impact energy flow, food chains, and fish species assemblages. Current known invasive species in Winnibigoshish include Zebra Mussels, Faucet and Mystery Snails, and Starry Stonewort. Changes in environmental conditions affect fish habitat and behavior, which likely affect fish sampling and angling success. Gill net catches have likely been influenced by these changes, especially since water clarity began to increase. Movement of any type of equipment that can trap or hold contaminated water, plant fragments or aquatic organisms can be a potential vector of spread if precautions are not taken. To avoid the spread of these unwanted species, ensure that all equipment is thoroughly cleaned and dried before moving to a new body of water. More information is available at https://www.dnr.state.mn.us/invasives/ais/index.html
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The walleye population appeared to be healthy with ten age classes sampled between age 1 and age 12. Year class strength was computed for walleye between age 2 and age 7. Two weak year classes, three average year classes, and the strong 2001 year class were present. The 1994 and 1995 year classes exceeded age seven, were relatively abundant, and contributed to the above average catch of 18 to 23 inch walleye. Mean back-calculated growth was fast for most age classes, attaining 16.5 inches after four growing seasons.
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\nYellow perch were sampled at a rate of 54.7 per near-shore gill net. This was the lowest catch rate observed since 1983, and was lower than typical for Lake Winnibigoshish. Perch sampled in near-shore gill nets varied from 4.9 to 11.8 inches with a mean length of 7.9 inches.
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\nYellow perch growth was slow for age 1 and age 2, and average from age 3 through age 10. Near shore and mid-lake gill net catch rates were similar between 1997 and 2002. However, the mid-lake gill net catch rate was nearly double the near-shore gill net catch rate in 2003. From 1997 to 2000 the percent of perch larger than 9 inches was similar between near-shore and mid-lake gill nets. Since 2000 the percent of perch larger than 9 inches has been divergent, with a higher percentage larger than 9 inches sampled in mid-lake sets.
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\nAll age classes between age-2 and age-10 were sampled by gill net. Year class strength was computed for yellow perch between age 3 and age 7. Of these, the 1996 (age 4) through 1999 (age 7) year classes were average and the 2000 year class was considered weak. The catch of age-8, 9, and 10 perch was much lower than that of ages 3 through 7, and was a relatively small component of the total catch. Relative health of the yellow perch population has been described by the percent of perch larger than 9 inches in the gill net catch. Twenty six percent of the near-shore gill net sampled perch were larger than 9 inches. Yellow perch growth was relatively slow through age 2, and increased to near average from age 3 to age 10, attaining a mean length of 9.4 inches at age 6.
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\nNorthern pike were sampled at a rate of 8.3 per near-shore gill net which was typical compared to similiar lakes and for Lake Winnibigoshish. Pike sampled in near-shore gill nets varied from 6.7 to 34.3 inches with a mean length of 22.0 inches.
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\nAll age classes between age-1 and age-7 were sampled by gill net. Age 2, 3, 4,and 5 pike were similarly represented in the gill net catch. Northern pike sampled in near shore-gill nets reached a mean length of 24.7 inches at age 5. Stomach contents were evaluated for all pike sampled in 2003. Of 189 pike sampled, 32 had recognizable prey in their stomachs. The most frequent prey item observed was yellow perch, however, most perch were consumed by pike less than 22 inches in length. Cisco were the most frequent prey item of pike 22 inches and longer.
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\nThe gill net catch rates of cisco remained low in 2003. The catch rate of 18.0 per near-shore net followed the trend of reduced catch rates since 1997. Bony structures were not collected from cisco in 2003 and ages were not determined. Examination of the cisco length frequency indicates that recruitment was sporadic and year classes may be absent.
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The Lake Winnibigoshish assessment is completed annually to track changes in abundance and growth of fish species, and physical and chemical characteristics of the lake. The assessment season starts with seining and gill netting in late June to early July. The goal of seining is to sample young game and non-game species (including minnows) and to track growth of age 0 walleye and perch. Gill netting is conducted from late June through July to sample game and non-game species age 1 and older. Abundance, growth rates, maturity, presence of parasites etc. is determined from this data. Trawling is conducted in August to continue tracking growth rates of age-0 walleye and perch. Trawling gives us the first clue to abundance of age-0 walleye and perch for that year. Temperature and dissolved oxygen profiles are taken from June through August and water chemistry analysis is done in August to track changes in the system that may affect the ability of some species to prosper or exist in the lake.
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\n Walleye
\nGill nets
\nWalleye were sampled at a rate of 5.9 per net, which was above average for Lake Winnibigoshish. Walleye sampled varied from 7.3 to 26.2 inches with a mean length of 15.1 inches and mean weight of 1.3 pounds. The walleye population appeared to be healthy with most age classes sampled between age 1 and 13. Year-class strength was computed for walleye between age 2 and 7. Three average year classes (2003, 2004, and 2007), and two strong year classes (2005 and 2006) were sampled. Preliminary data suggests the 2008 year class may be weak. The last weak walleye year class for Lake Winnibigoshish was in 2000. Mean back-calculated growth was similar to the Lake Winnibigoshish and statewide average for all ages, attaining 17.8 inches after five growing seasons.
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\nSeine and trawl
\nRelatively few age-0 walleye were sampled by seine in 2010. Seine catch rates have not correlated to ultimate year-class strength for walleye in Lake Winnibigoshish. Growth of age-0 walleye has been a better predictor of year-class strength. Early spring warming and normal summer temperatures appear to have resulted in some of the fastest growth observed since 1983. Weekly average lengths of age-0 walleye sampled by seining varied from 3.0 inches to 4.7 inches from July 3 to July 31.
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\nMean trawl catch rates for age-0 walleye were average when compared to catch rates observed since 1972. However, many of the age-0 walleye were sampled from one location. Age-0 walleye growth recorded through the first week of August was the second fastest observed since 1983, reaching a mean length of 5.0 inches on August 8. Fast growth of age 0 walleye usually results in a strong year class.
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\n Walleye Experimental Regulation
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\nThe 17 to 26 inch protected slot limit for walleye was evaluated during the summer of 2010. Evaluation of the regulation showed that the fishery responded well to the regulation and that either the current 17 to 26 inch regulation, or a 18 to 26 inch protected slot with a bag limit of six fish would likely maintain the fishery at a healthy level. Results of the evaluation were open to public review in the fall of 2010 and public meetings were held at three locations in October. Two hundred forty seven comments were received through the public review period and meetings. Comments came from anglers varying from Baudette to Winona in Minnesota and eight other states from Wisconsin to Texas and Arizona. More than 85% of the comments favored either the 17 to 26 inch or 18 to 26 inch protected slots with a small advantage to the 17 to 26 inch slot. Of those favoring these two options, more than 1/3 agreed with either regulation. The final decision was to keep the 17 to 26 inch protected slot limit with a bag limit of six fish. This regulation was biologically suited to Lake Winnibigoshish and was viewed favorably by the majority of anglers.
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\n Yellow perch
\nGill nets
\n Yellow perch (perch) are an important species for anglers and as a prey item for walleye and northern pike. The catch of perch in assessment nets reached an historic low in 2005, largely due to poor year classes in 2000 and 2002. A strong year class was produced in 2003. Assessment catch rates have slowly increased as the strong 2003 year class has matured. As this year class continues to mature, abundance and size structure should continue to improve. The 2006 year class also appears to be weak which may reduce the rate of recovery.
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\nPerch were captured at a rate of 54.9 per net in 2010, which was lower than average for Lake Winnibigoshish. Perch sampled varied from 5.0 to 11.2 inches with a mean length of 7.4 inches and mean weight of 0.21 pounds. Age classes 2 through 8 were sampled by gill net. An index of year-class strength was computed for ages 3 through 7. The 2005 and 2007 year classes were average, the 2004 and 2006 year classes were weak, and the 2003 year class was strong. As the 2003 year class has matured, size structure has slowly improved. The catch of perch in 2010 was biased towards younger individuals with 86% of the catch made up of age-3 through age-5 fish. Growth was relatively slow through age 2, then increased to average from age 3 to age 9. Perch grew to an average length of 9.1 inches at age 6.
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\nRelative health of the yellow perch population can be described by the percent of perch longer than 9 inches in the gill net catch. The catch of large perch declined to 6% in the early 1990's driven by high harvest rates. Changes in Lake Winnibigoshish and other lakes prompted a statewide change in the perch bag limit to 20 daily and 40 in possession in 2001. Several strong year classes were produced during the same time period and the assessment catch of perch longer than 9 inches increased to 30% in 2004. In 2005, the proportion of large perch sampled declined for the first time since 1998. The proportion of perch longer than nine inches was 17% in 2005 and 2006, then declined to 9.8% in 2007 as young perch were recruited to the fishery. Although many small fish remain in the population, the strong 2003 year class has grown large enough to affect the proportion of perch longer than 9 inches. Twelve percent of the perch sampled were longer than 9 inches in 2010.
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\nThe microsporidian parasite heterosporis has been documented in Lake Winnibigoshish yellow perch. No evidence of heterosporis was observed in 2010.
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\nSeine and trawl
\n Catch rates for age-0 perch of 226 per seine haul and 6,928 per hour of trawling were average for both seine and trawl. Growth of age 0 perch was faster than average with a mean length of 2.2 inches in mid August. No correlation is evident between trawl catch rates or growth of age-0 perch and year-class strength.
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\n Northern pike
\nCatch rates of northern pike increased from 1999 through 2005 and exceeded the third quartile in five of the last eight years. The northern pike catch rate decreased to 7.3 per gill net in 2010 from 10.0 in 2009. Pike sampled varied from 14.9 to 35.0 inches with a mean length of 21.6 inches. All age classes from 1 to 7 and 9 were sampled by gill net. The 2007 and 2008 year classes were most abundant and contributed over 60% of the catch. Growth rates were similar to the statewide mean through all ages.
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\nAlthough the size structure for pike increased in 2010 only five pike longer than 30 inches were sampled. The increase in size structure can be attributed to several causes. Cisco abundance has increased (cisco are preferred prey that provides more energy than other similar size prey), which may lead to faster growth rates. Reduced abundance is also beneficial to the pike population since increased pike density can cause more competition for food and space which may lead to decrease growth.
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\nAlthough pike size structure has improved, further improvement is achievable. Angler harvest can have a large impact on the size structure of a pike population. This is also one of few factors people have any control over. When anglers harvest the largest fish they catch, they can cause a decrease in the size structure of the fish they are harvesting. This occurs because fish are removed faster than other fish can grow to replace them. Anglers can help increase the number of quality size pike in the population by releasing fish between 24 and 32 inches. This will allow pike the time to grow closer to their potential, and increase the chance of catching 8 to 10 pound fish.
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\n Cisco
\nCisco are a primary prey for muskellunge, pike and walleye. Growth rates of these species can be reduced if cisco are not present in the system. The gill net catch of 21.7 cisco per net in 2010 was nearly double the catch of 11.4 per net in 2009 and was near the historic average. The cisco population was lower than average for 8 of the last 10 years. This is likely due to warmer than average fall water temperatures that may affect reproduction combined with occasional summer kills. Cisco sampled in 2010 varied from 7.6 to 16.9 inches with a mean length of 11.0 inches.
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\n Water Quality
\nWater samples were taken on August 2, 2010. Physical and chemical parameters measured were within the range observed since 1983. Six temperature and dissolved oxygen profiles were taken between June 28 and August 11, 2010. Minor dissolved oxygen stratification was evident only on July 12. No evidence of thermal stratification was found in 2010. Thermal and dissolved oxygen stratification may result during periods of high air temperatures and low wind. When wind speeds increase to moderate levels (15 mph) the entire water column appears to mix. High wind speeds were common during the summer of 2010 which resulted in minimal oxygen stratification during the summer.
\n
\n
\n Invasive Aquatic Species
\nSpecies that have been introduced through human activities to a location where they don't naturally occur are termed \"invasive\". Some invasive species are not necessarily harmful, but others cause ecological or economic problems.
\n
\nSeveral invasive species have been introduced into Winnie. Three species of snail: banded mystery, Chinese mystery, and faucet have become established since 2000. Both species of mystery snail appear to have no negative effect at this time. The faucet snail carries a trematode parasite that can kill several species of duck if ingested. Thousands of ducks were killed by these parasites during the falls of 2007 and 2008. Emerald shiners (often used as bait) are not native to Winnie, and were first sampled in 2005. Each of these invasive species were likely introduced through human activities.
\n
\nThe movement of any type of equipment (boats, boat trailers, boat lifts, docks, personal watercraft, bait containers, etc.) between lakes may transfer invasive species if precautions are not taken. To avoid being an accomplice to the spread of these unwanted species, people should make sure all equipment is thoroughly cleaned before moving it to a new body of water. More information about invasive species is available from the Minnesota DNR website.
\n
This special assessment contains data from 8 mid-lake gill net sets that were first set in 1997. These nets were initially set to determine if catch rate and growth statistics for various fish species were similar to those of the 24 near-shore gill net sets and were set in conjunction with the 24 near-shore sets. After many years of sampling it appears that catch rate and size distribution can vary between the two net groups for Walleye, Northern Pike, and Yellow Perch while growth of fish appears to be similar.
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nets"},{"gearCount":12,"averageWeight":"0.00","species":"SPO","quartileWeight":"N/A","totalCatch":410,"totalWeight":0,"gear":"Standard trawling","CPUE":"34.17","quartileCount":"N/A"},{"species":"NRD","averageWeight":"0.00","gearCount":24,"CPUE":"0.08","quartileCount":"N/A","totalWeight":0,"gear":"Survey seining","totalCatch":2,"quartileWeight":"N/A"},{"quartileWeight":"N/A","CPUE":"0.33","quartileCount":"N/A","gear":"Survey seining","totalWeight":0,"totalCatch":8,"gearCount":24,"averageWeight":"0.00","species":"FHM"},{"averageWeight":"0.58","gearCount":24,"species":"TLC","quartileWeight":"0.4-0.5","CPUE":"2.58","quartileCount":"4.9-17.6","totalCatch":62,"totalWeight":16353,"gear":"Standard gill nets"}],"narrative":"Walleye; Walleye were sampled at a rate of 6.0 per net and varied from 8.0 to 24.2 inches with a mean length of 17.7 inches and mean weight of 2.0 pounds. The Walleye population appeared to be healthy with all age-classes sampled between age 1 and 11. Walleye year-class strength was computed for fish from age 1 to 7. One average year class (2011), three strong year classes (2009, 2010, and 2013), and two weak year classes (2012, and 2014) were sampled. The 2012 year class of Walleye continues to be as weak as any year class observed since the start of the large lake program. The 2014 year class has not fully recruited to the gill net, however, all indications are that it will be weak.
\n
\nAverage growth of Walleye was similar to the Lake Winnibigoshish and statewide average for all ages, attaining 17.7 inches after five growing seasons. However, growth of the 2012, 2013, and 2014 year classes was well above average for Lake Winnibigoshish. A 17 to 26 inch protected slot limit was in place between 2000 and 2014. During this time, age and length at maturity increased, spawning stock biomass increased, and overall abundance increased. This indicated that the Walleye population was likely fully recovered. Due to this, the protected slot limit was changed to 18 to 23 inches in 2015 so that anglers could utilize the harvestable surplus.
\n
\nThe average trawl catch rate of 1.9 age 0 Walleye per hour in 2016 was less than 3% of the long term average catch rate. Catch rates from 2013 through 2016 were the lowest seen since 1983. Increased water clarity was observed during this time period, which appears to affect trawl catch rates. Fish of many species were observed avoiding the boat during trawling. Due to this night electrofishing was conducted from late-August to late-September. Electrofishing catch rates for 2013 through 2015 indicated higher abundance than trawl catch rates would indicate. Electrofishing catch rates of age-0 Walleye were very low for trawling and electrofishing in 2016.
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\nElectrofishing catch rates in 2016 were similar to those of trawling. Young of the year Walleye were sampled at a rate of 0 to 4 per hour (data available in the Grand Rapids Area Fisheries Office), and growth was good, reaching 7.2 inches in mid-September. Due to adverse weather conditions during September of 2016, electrofishing was conducted during less than ideal conditions that may have affected catch rates.
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\nYellow Perch; Perch are an important species to anglers and as a prey item for predators. Gill net catch rates were average or better in all assessments prior to 2003. However, gill net catch rates have only been average or better four times since 2003. The 2003-2016 average gill net catch of 58.6 has declined by 40% from the 1983 to 2003 average catch. Gill net catch rates of Walleye and Northern Pike (pike) have increased since 2000. Decreased gill net catch of perch may be a response to increased predation associated with increasing Walleye and pike density. If predator abundance remains high, perch abundance may find a new norm with a average catch near 60 per net.
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\nPerch sampled in 2016 varied from 4.4 to 12.5 inches with a average length of 6.8 inches and weight of 0.16 pounds. Age-classes 2 through 10 were sampled by gill nets. An index of year-class strength was computed for year-classes sampled from 2009 through 2013. The 2011 and 2013 year-classes were weak while the 2009 and 2010 year-classes were average. The 2012 year class was strong. Natural mortality of perch increases at age 8 and few individuals live past age 10. The catch of perch in 2016 was primarily represented by younger individuals with nearly 85% of the catch made up of age 2 through age 4 fish. Although the perch population was composed primarily of small individuals, growth has not changed. Growth was relatively slow through age 2, then increased to average from age 3 to age 8. Perch grew to an average length of 8.9 inches at age 6.
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\nRelative health of the perch population has been described by the percent of perch longer than 9 inches (large perch) in the gill net catch. The gill net catch of large perch declined to 5.5% in the early 1990's driven by high angler harvest. Changes in Lake Winnibigoshish and other lakes prompted a statewide change in the perch bag limit to 20 daily and 40 in possession in 2001. Several strong year classes were produced during the late 1980's and the gill net catch of large perch increased to 30% in 2004. Since that time there has been a gradual decline in the percent of large perch. The perch catch of 7.5% longer than 9 inches in 2016 was similar to 2015. Part of the decline in large perch may be due to increased predator numbers. Both Northern Pike and Walleye catch rates have increased as the catch of large perch has declined.
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\nThe trawl catch rate for age 0 perch of 11,940 per hour was similar to the long term average. Growth of age 0 perch was average with a mean length of 1.9 inches in mid-August. Clear water conditions that appear to have affected trawl catch rates of young of the year Walleye may also affected catch rates of young of the year perch. Few age 0 perch were sampled in trawl hauls less than 10 feet of water. Catch rates of age 0 perch were typically highest in less than 8 feet of water prior to clearing water. No correlation is evident between trawl catch rates or growth of age 0 perch and year-class strength.
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\nThe heterosporis parasite has been documented in Lake Winnibigoshish perch. No evidence of heterosporis was observed in perch during the 2016 population assessment, although anglers report the presence of heterosporis in a few perch each year.
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\nNorthern Pike; Catch rates of Northern Pike (pike) showed an increasing trend from 1994 through 2005, and were higher than average (between 7.5 and 9.6 per net) in four years between 2002 and 2009. The pike catch rate was relatively stable and similar to average between 2006 and 2011. Gill net catch rates increased dramatically between 2011 and 2014, reaching a new historic high of 14.1 per net in 2013. Pike catch rate in 2016 was average for the first time since 2011 at 9.0 pike per gill net.
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\nPike sampled in 2016 varied from 12.5 to 33.9 inches with a mean length of 21.7 inches. Mean length of pike typically declines as catch rates increase. As catch rates have decreased since 2013, average length has increased. Mean pike length of 21.7 inches in 2016 increased from 2015 and 2014, but was below the average of 21.9 inches. Age-classes from 1 through 7 were sampled by gill net. Growth rates were similar to the statewide average through all ages.
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\nThe number of pike longer than 30 inches has been used as an indication of quality in the pike population. More than 10 pike longer than 30 inches were sampled in all assessments between 1994 and 2000. This was an indication of a high quality pike population. Since that time there has been a decrease in quality pike to 2 or 3 pike longer than 30 inches in all assessments since 2013.
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\nDecreased size structure may be attributed to several causes. Reproduction and recruitment were strong for the 2012, 2013, and 2014 year classes which made up 84% of the catch, and Cisco abundance decreased due to summer kill in 2012 (Cisco are preferred prey that provides more energy than other similar size prey). A strong prey base of Cisco may lead to faster pike growth rates. High angler harvest of pike may result in a recruitment response (increased reproduction to replace individuals removed from the system). Larger numbers of small pike vs smaller numbers of medium to large pike may cause reduced growth rates due to increased competition for food and space. The recent increase in catch rate may result in slower pike growth in the future. Fishers can help maintain the pike size structure by releasing, or not harvesting most pike longer than 22 inches.
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\nCisco; Cisco are a primary prey species for Muskellunge, pike, and Walleye. Growth rates of these species may be reduced if Cisco are not present in the system. The gill net catch of 4.1 per net in 2015 was the lowest since 1983. The historic low catch rate seen in 2015 was eclipsed in 2016 with a new historic low of catch rate of 2.6 Cisco per gill net. Cisco varied from 7.6 to 15.9 inches with a mean length of 10.6 inches. Cisco catch rates have been lower than average for 7 of the last 11 years. This is likely due to warmer than average summer and fall water temperatures that may affect reproduction and cause occasional summer kills. Water temperatures were warm during the summer of 2012 and caused a summer kill of Cisco. Summer kill of Cisco has been an irregular occurrence at Lake Winnibigoshish. It is normal for the population to decline following a summer kill, however, the population typically recovers several years following the summer kill. The Cisco population currently shows no signs of recovery.
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\nWater Quality; Five temperature and dissolved oxygen profiles were taken between June 22 and August 12, 2016. Dissolved oxygen stratification was evident on July 25 and August 23. No evidence of thermal stratification was found in 2016. Thermal and dissolved oxygen stratification may result during periods of high air temperatures and low wind. When wind speeds increase to moderate levels (15 mph) the entire water column appears to mix.
\n
\nWater chemistry measurements have been recorded for most years since 1983. Water clarity as measured by Secchi disc in 2016 of 8.0 feet was lower than the past several years. Recent increases in water clarity may be related to the introduction of filter feeding faucet snails around 2000. Faucet snails were dispersed throughout the system by 2008. Zebra Mussel are now established and likely will contribute to clear water.
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\nInvasive Aquatic Species; Invasive species are species that are not native to Minnesota and cause economic or environmental harm or harm to human health. Non-native species are not native to Minnesota but don't cause economic or environmental harm or harm to human health. All are illegal to introduce into or move between state waters. Several species have been introduced into Lake Winnibigoshish. Three species of snail: Banded Mystery, Chinese Mystery, and Faucet have become established since 2000. Both species of mystery snail appear to have no negative effect at this time. The Faucet Snail carries a trematode parasite that can kill several species of ducks if ingested. Thousands of ducks were killed by these parasites during the falls of 2007 and 2008. The Faucet Snail is a filter feeder and may be responsible for clearing water prior to the introduction of Zebra Mussel.
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\nJuvenile Zebra Mussels (veliger) were discovered while sampling zooplankton during the summer of 2012. No zebra mussel veliger were found while sampling for zooplankton in 2013. Zebra Mussel veliger have been sampled each year since 2013. Near-shore areas of hard substrate were inspected for adult Zebra Mussel each year since 2012, and divers have inspected likely offshore areas since 2014. No adults were discovered until 2016. Adults were found on near-shore driftwood in the early summer, then found by divers on mid-lake rock structure during August. Sampling for Zebra Mussels veliger will continue and the spread of adults will continue to be documented.
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\nStarry Stonewort (an algae) was discovered in Cass Lake during the summer of 2016. This discovery upstream of Lake Winnibigoshish prompted an investigation on Lake Winnibigoshish. Starry Stonewort was discovered along the south and west shores of the lake and appears to have been established for several years.
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\nEmerald Shiners (often used as bait) are not native to Winnie, were first sampled in 2005, and have been sampled each year since. Each of these invasive species were likely introduced through human activities. Rusty Crayfish are present in Cass Lake, and curly leaf pondweed is present in Dixon Lake. Both of these lakes are upstream of Lake Winnibigoshish. Introduction to Lake Winnibigoshish in the near future is likely.
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\nMovement of any type of equipment (boats, boat trailers, boat lifts, docks, personal watercraft, bait containers, etc.) between lakes may transfer invasive species if precautions are not taken. To avoid being an accomplice to the spread of these unwanted species, people should ensure that all equipment is thoroughly cleaned and dried before moving it to a new body of water. More information regarding invasive species is available at www.dnr.state.mn.us/invasives/index.html
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Lake Winnibigoshish is part of the Mississippi River headwaters reservoir system, and is located 15 miles northwest of Deer River, Minnesota. The lake is a large, shallow, wind-swept reservoir with a sandy shoreline and gently sloping shoal areas. Winnibigoshish has a surface area of 58,544 acres, mean depth of 15.1 feet, littoral area of 20,490 acres (35%), and a maximum depth of 66 feet. Water clarity has dramatically increased following the introduction of Zebra Mussels in 2012, yet clarity continues to vary seasonally.
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\nLake Winnibigoshish has been managed as part of the Minnesota Department of Natural Resources (DNR) large lake program since 1983. Management activities include special fishing regulations, fish stocking, occasional creel surveys, and annual fish surveys. Annual fall gill netting has been conducted since 2007 using 32 nets. Fall electrofishing has also been conducted since 2018 to evaluate Walleye production.
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\nA large annual Walleye spawning operation is conducted at Little Cut Foot Sioux Lake, which is a large connected flowage. The operational plan includes 10% of the egg take put back as fry. The relative contribution from these stockings is difficult to interpret due to the lack of non-stocked years. Walleye harvest has been regulated with a special regulation since 2000. The regulation was modified in 2015 to an 18 to 23 inch protected slot length (PSL) with one over in possession to allow some additional harvest of larger fish.
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\nWinnibigoshish is considered a high profile Walleye lake with a lot of effort directed towards the management of the species. Gill net catches have been variable with a decreasing trend. However, a recent uptick has been observed. Variability in Walleye catches are often associated with cycles in recruitment, described as year class strength. This trait is common on natural Walleye lakes and has been observed on Winnibigoshish. Recent surveys show a period of low recruitment from 2014 to 2017, while 2018 and 2019 appear to be stronger. The 2020 Walleye catch was the third highest observed in fall netting. However, the catch was largely driven by a high proportion of age-1 and -2 fish. Age-2 fish had an average length of 12.5 inches in the fall of 2020. This suggests favorable angling opportunities for the next few years as these fish continue to grow.
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\nWinnibigoshish is known to maintain a quality size distribution of Walleye, but the protected slot has limited harvest at times. Limited harvest was a product of reduced recruitment in recent years due to longer gaps between stronger year classes. The last strong year class was 2013 which was a large contributor to angler success. These fish were age-7 in 2020, with an average length of 22 inches and comprised 5% of the overall catch. Protected slot length fish comprised 17% of the sample in 2020. About one third of the slot length fish were from the 2013 year class. Walleye had an average length of 13 inches in 2020 with fish up to 26 inches. The low average length is a function of the disproportionately high catches of ages-1 and -2.
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\nWalleye age analysis identified ages 0 to 15 in the sample, and sex and maturity determination indicated a relatively even distribution between males and females. Both were similar to past surveys and suggests a balanced population. Other population exploitation indicators like female spawning stock biomass (SSB), female length at 50% maturity and female age at 50% maturity were within the expected range, similar to past surveys and indicative of a balanced population. The female fall SSB estimate was 1.7 lbs./acre and half the females were mature at 17.7 inches and 3.1 years in 2020. Walleye growth rates have been favorable on Winnibigoshish, typically exceeding statewide averages. Male and female growth rates diverge between ages-3 and -4. By age-4, male Walleye averaged 16 inches while females averaged 17.2 inches in 2020.
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\nWinnibigoshish is a destination Yellow Perch fishery with a history of producing large fish. Perch over 11 inches are regularly sampled. Perch greater than eight inches are considered quality size and greater than 50% of this size perch are harvested by both summer and winter anglers. The catch for eight inch and greater perch has averaged 8.4/net and the proportion has averaged 34% since 2007. Yellow Perch exceeding eight inches were sampled at a rate of 5.7/net and comprised 35% of the sample in 2020. This suggests roughly one third of perch caught while angling will be of a size anglers elect to harvest.
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\nYellow Perch are an important prey species besides being popular with anglers. The 2020 catch was typical for lakes with similar habitats, but below average for Winnie. The fall catches have been variable. Unevenness in fall catches is likely attributed to variability in recruitment, angling pressure and sampling conditions. Age analysis identified ages 1 to 9 present. Growth was similar to statewide averages and past surveys. Perch growth rates begin to diverge between age-2 and -3. Length at capture suggest perch begin to reach a harvestable size by age 5. By age-5, male perch averaged 7.7 inches while females averaged 8.3 inches in 2020.
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\nNorthern Pike are another popular species with anglers and are well suited for Winnibigoshish and connected waters. Winnibigoshish tends to have higher pike abundance than comparable lakes, and catches have been relatively stable in fall surveys. Lengths ranged from 15.1 to 28.8 inches with an average of 22.8 inches in 2020. The length frequency was similar to previous fall surveys. However, fish over 30 inches have been observed in every survey except 2020. It is believed harvest has likely influenced size quality. Winnibigoshish lies within the North-central Zone. Since 2018, lakes within this zone have had a Northern Pike protected slot length regulation from 22 to 26 inches, a bag limit of 10 fish but only two can be greater then 26 inches. Spearing has an exception of one fish in the PSL. In 2020, 43% of the catch was within the pike PSL, compared to 41% and 35% observed in 2019 and 2018.
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\nSex and maturity determinations for Northern Pike show a little over half were female and very few were immature. Age analysis indicated ages 1 to 6 present, with relatively consistent recruitment. Age, sex and maturity determinations were similar to past surveys. The proportion of pike older than age 4 was low, comprising only 10%. Age-4 pike averaged over 25 inches at the time of capture. Anglers and spear fishers are encouraged to take advantage of the expanded harvest opportunities offered by the North-central Zone regulation, but limit their take of fish over 22 inches to help improve size structure. Pike growth was favorable, exceeding statewide averages and was similar to past surveys. Male and female growth rates diverge between ages 1 and 2. Age-2 males averaged 15.3 inches while females averaged 17.1 inches, in 2020.
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\nCisco are an important prey species and an indicator species due to their environmental sensitivity. Catches have been variable, which is often associated with pelagic species like Cisco, but have had a declining trend over the past decade. Warmer water temperatures and Zebra Mussel infestations are two factors that have likely influenced this trend. Cisco lengths ranged from 7.2 to 16.3 inches with an average of 11.5 inches. Length frequency had a multimodal distribution. Scale and otolith analysis identified ages 1,2, and 4 to 8 present. Half of the Cisco sampled were age 1 and averaged 7.9 inches at the time of capture. Ages 4 to 8 had lengths within a relatively narrow band from 13 to 16 inches.
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\nOther species sampled include Burbot, Largemouth Bass, Rock Bass, Shorthead Redhorse, Silver Redhorse, White Sucker and Yellow Bullhead.
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\nWinnibigoshish has had several exotic or non-native species introduced in the last 20 years. Banded Mystery and Chinese Mystery snails were first noted around 2000, followed by Faucet Snails. A trematode parasite associated with Faucet Snails was responsible for a large diver duck die-off in 2007 and 2008. Lesser die-offs have occurred almost annually since.
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\nJuvenile Zebra Mussels (veligers) were discovered while sampling zooplankton in 2012. Adults were found on driftwood in 2016 and subsequent investigations found adults were present on nearly all firm structure by 2017. Recent zooplankton sampling suggest veliger density has decreased slightly.
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\nZebra Mussels and Faucet Snails have contributed to ecosystem changes. Both are effective filter feeders and are responsible for a large increase in water clarity. These species shunt nutrients to the benthic portion of the lake resulting in large filamentous algae mats. Decreased nutrient availability within the water column has changed species compositions and densities of phytoplankton, zooplankton and aquatic invertebrates. The impact of Zebra Mussels on the fish community is less apparent and unclear at this time. However, Winnibigoshish has been fully infested for only four seasons to date. Zebra Mussels have influenced angler use. With the increased water clarity, the traditional mid-day Walleye bite has shifted to a more crepuscular event.
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\nStarry Stonewort was discovered upstream in Cass Lake in 2016. Subsequent sampling found it along the south and west shores of Winnibigoshish, and it appeared to have been established for several years. It has been reported along the east shore in 2017, near Birches public access.
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\nEmerald Shiners ae not native to Winnibigoshish and were first sampled in 2015. This species is often used as bait and has been sampled while seining since. Rusty Crayfish and curly leaf pondweed are found in upstream connected waters and it is assumed introduction is likely.
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\nEach of these introductions have occurred through human activities. Movement of any type of equipment that can trap or hold contaminated water, plant fragments or aquatic organisms can be a potential vector of spread if precautions are not taken. To avoid being an accomplice to the spread of these unwanted species, people should ensure that all equipment is thoroughly cleaned and dried before moving it to a new body of water. More information is available at https://www.dnr.state.mn.us/invasives/ais/index.html.
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\nThe Lake Winnibigoshish assessment is completed annually to track changes in abundance and growth of all game species. The assessment season begins with seining in July. The goal of seining is to sample young game and non-game species (including minnows) and to track growth of age 0 walleye and perch. Gill netting is conducted in July to sample game and non-game species age 1 and older. Abundance, growth rates, presence of parasites etc. is determined from this data. Trawling is conducted in August to continue tracking growth rates of age-0 walleye and perch. Trawling gives us the first clue to abundance of age-0 walleye and perch for that year. Temperature and dissolved oxygen profiles are taken from June through August and water chemistry analysis is done in August to track changes in the system that may affect the ability of some species to prosper or exist in the lake.
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\n Walleye
\nGill nets
\nWalleye were sampled at a rate of 4.9 per net, which was average for Lake Winnibigoshish. Walleye sampled varied from 6.7 to 26.3 inches with a mean length of 15.0 inches and mean weight of 1.3 pounds. The walleye population appeared to be healthy with most age classes sampled between age 1 and 12. Year-class strength was computed for walleye between age 2 and 7. Three average year classes (2003, 2004, and 2007), and three strong year classes ( 2002, 2005 and 2006) were sampled. However, none of the strong year classes were exceptionally strong. Mean back-calculated growth was similar to the Lake Winnibigoshish and statewide average for all ages, attaining 17.3 inches after five growing seasons.
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\nSeine and trawl
\nSlow spring warming and below average summer temperatures appear to have resulted in some of the slowest growth observed since 1983. The shortened growing season resulted in smaller than average age-0 walleye. Slow growth and small size of age-0 walleye usually results in a weak year class.
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\nRelatively few age-0 walleye were sampled by seine in 2009. Seine catch rates have not correlated to ultimate year-class strength for walleye in Lake Winnibigoshish. Growth rate of age-0 walleye has been a better predictor of year-class strength. Weekly mean lengths of age-0 walleye varied from 2.5 inches to 3.1 inches from July 1 to July 31.
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\nMean trawl catch rates for age-0 walleye were high when compared to catch rates observed since 1972. However, many of the age-0 walleye were sampled from one location. Age-0 walleye growth recorded through the first week of August was the slowest observed since 1983, reaching a mean length of 3.8 inches on August 8. Slow growth of age 0 walleye nearly always results in a weak year class of walleye.
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\n Yellow perch
\nGill nets
\n Yellow perch (perch) are an important species for anglers and as a prey item for walleye and northern pike. The catch of perch in assessment nets reached an historic low in 2005, largely due to poor year classes in 2000 and 2002. Strong year classes were produced in 2003 and 2005. Catch rates of perch have slowly increased as the strong 2003 and 2005 year classes have matured. As these year classes continue to mature, abundance and size structure should continue to improve. However, the 2006 year class also appears to be weak which may reduce the rate of recovery.
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\nPerch were captured at a rate of 52.8 per net in 2009. This catch rate was lower than average for lake Winnibigoshish. Perch sampled varied from 4.1 to 11.6 inches with a mean length of 7.3 inches and mean weight of 0.20 pounds. Age classes 2 through 8 were sampled by gill net. An index of year-class strength was computed for ages 3 through 7. The 2004 year class was average, the 2002 and 2006 year classes were weak, and the 2003 and 2005 year classes were strong. As the 2003 and 2005 year classes continue to mature, abundance and size structure should improve. The catch was biased towards younger perch with 73% of the catch made up of age 2 through age 4 fish. Growth was relatively slow through age 2, then increased to average from age 3 to age 10. Perch grew to a mean length of 9.4 inches at age 6.
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\nRelative health of the perch population has been described by the percent longer than 9 inches in the gill net catch. As perch catch rates decreased during the mid 1990's, the proportion of large perch (longer than 9 inches) increased. The proportion of large perch peaked as gill net catch rates fell below the first quartile. In 2005, the proportion of large perch sampled in near-shore gill nets declined for the first time since 1998. The proportion of perch longer than nine inches was stable in 2005 and 2006 at 16.9 percent, then declined to 9.8% as young perch were recruited to the fishery in 2007. Many small fish remain in the population, and the proportion of perch longer than 9 inches continues to be low at 10.4%.
\nThe microsporidian parasite heterosporis has been documented in Lake Winnibigoshish yellow perch. No evidence of heterosporis was observed in 2009.
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\nSeine and trawl
\n Catch rates of age-0 perch were near average for both seine and trawl. No correlation is evident between catch rates of age-0 yellow perch and ultimate year-class strength.
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\n Northern pike
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\nCatch rates of northern pike increased from 1999 through 2005 and exceeded the third quartile in five of the last eight years. The northern pike catch rates increased to 10.0 per gill net in 2009. Pike sampled varied from 9.3 to 30.6 inches with a mean length of 20.5 inches. All age classes from 1 to 7 were sampled by gill net. Age two, three, and four pike were most abundant, and contributed 92% of the catch. Growth rates were similar to the statewide mean through all ages achieving an avearge length of 24 inches at age 5.
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\nOnly two pike longer than 30 inches were sampled in this assessment. This does not mean that they are not present in the system, but it is an indication that their abundance has decreased. The decrease in size structure can be attributed to several causes. Cisco abundance has declined (cisco are preferred prey that provides more energy than other similar size prey), this may lead to slower growth rates. Conditions for reproduction and survival have been good, this may lead to increased density and more competition for food, which can also cause decreased growth. Angler harvest can have a large impact on the size structure of a pike population. This is also one of few factors that people have any control over. When anglers harvest the largest fish they catch, they can cause a slow decrease in the size structure of the fish they are harvesting. This occurs because fish are removed faster than other fish can grow to replace them. Considering the current size structure, anglers should release all pike longer than 25 inches, which should result in those fish growing closer to their potential and increase the chance to catch large pike.
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\n Cisco
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\nThe gill net catch rate of 11.4 cisco per net in 2009 was similar to the catch rate in 2008. Catch rates for both years were below the 1st quartile and close to the historic minimum. The cisco population has been lower than average in 8 of the last 10 years. This is likely due to warmer than average fall water temperatures that may affect reproduction combined with occasional summer kills. Cisco sampled in 2008 varied from 6.4 to 17.1 inches with a mean length of 9.4 inches.
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\n Water Quality
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\nWater samples were taken on August 3, 2009. Physical and chemical parameters measured were within the range observed since 1983. Seven temperature and dissolved oxygen profiles were taken between June 24 and August 3, 2009. Dissolved oxygen stratification was evident from July 6, through July 13. No evidence of thermal stratification was found in 2009. Thermal and dissolved oxygen stratification may result during periods of high air temperatures and low wind. When wind speeds increase to moderate levels (15 mph) the entire water column appears to mix.
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\n Invasive Aquatic Species
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\nSpecies that have been introduced through human activities to a location where they don't naturally occur are termed \"invasive\". Some invasive species are not necessarily harmful, but others cause ecological or economic problems.
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\nSeveral invasive species have been introduced into Winnie. Three species of snail: banded mystery, Chinese mystery, and faucet have become established since 2000. Both species of mystery snail appear to be benign at this time. The faucet snail carries a trematode parasite that can kill several species of duck if ingested. Thousands of ducks were killed by these parasites during the falls of 2007 and 2008. Emerald shiners (often used as bait) are not native to Winnie, and were first sampled in 2005. Each of these invasive species were likely introduced through human activities.
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\nThe movement of any type of equipment (boats, boat trailers, boat lifts, docks, personal watercraft, bait containers, etc.) between lakes may transfer invasive species if precautions are not taken. To avoid being an accomplice to the spread of these unwanted species, people should make sure all equipment is thoroughly cleaned before moving it to a new body of water. More information about invasive species is available from the Minnesota DNR website.
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Thirty one gillnets were set during the last two weeks of September, 2010. This was the fourth consecutive year of fall sampling. The goals of this netting were: 1 - develop a population estimate of adult walleye using available walleye population models, and 2 - build on the long term data set of fall netting so that fall netting can eventually replace summer netting as the annual index of abundance for primary fish species in Lake Winnibigoshish. Fall gillnet catch rates for walleye followed the trend of higher catch rates (2 to 3X) than the summer gillnet catch. While perch and northern pike catch rates were consistently lower than the summer nets. Cisco catch rates have varied, some years having higher catch rates in the summer, while fall catch rates were higher on other years. \n\nData from this survey should not be used to evaluate Lake Winnibigoshish fish populations, or to compare between years within lake or between different lakes.
"},{"narrative":"Lake Winnibigoshish is sampled annually to track changes in abundance and growth of fish species, and physical and chemical characteristics of the lake. The assessment season typically starts with seining and gill netting in late June to early July. The goal of seining is to sample young game and non-game species (including minnows) and to track growth of age 0 Walleye and Yellow Perch (perch). Gill netting is conducted from late June through July to sample game and non-game species age 1 and older. Abundance, growth rates, maturity, presence of parasites etc. is determined from these data. Trawling is conducted in August to continue tracking growth rates of age 0 Walleye and perch. Trawling gives us the first clue to abundance of age 0 Walleye and perch for that year. Temperature and dissolved oxygen profiles are taken from June through August and water chemistry analysis is completed in August to track changes in the system that may affect the ability of some species to prosper or exist in the lake. Plankton sampling was included in standard sampling beginning in 2012 and were continued in 2013. Five samples were taken on seven dates for a total of 35 samples in 2013. These samples were collected to determine baseline planktonic species composition.
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\nWalleye; Walleye were sampled at a rate of 6.6 per net (Figure 1). Walleye sampled varied from 11.2 to 28.8 inches with a mean length of 17.1 inches and mean weight of 1.8 pounds. The Walleye population generally appeared to be healthy with most age-classes sampled between age 2 and 13. Year-class strength was computed for Walleye between age 2 and 7. Two average year-classes (2007, and 2011), three strong year-classes (2006, 2009, and 2010), and one weak year-class (2008) were sampled (Figure 2). Mean back-calculated growth was similar to the Lake Winnibigoshish and statewide average for all ages, attaining 17.4 inches after five growing seasons. The 17 to 26 inch protected slot limit has been in place since 2000. During this time, age and length at maturity has increased from a low of 14.6 inches and 3.2 years to 17.2 inches and 4.2 years (Figures 3 and 4). Spawning stock biomass has increased from 0.5 to 2.7 pounds per acre (Figure 5). This may indicate that the Walleye population has fully recovered from a period of high harvest and reduced recruitment between the mid 1980's and mid 1990's.
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\nThe mean trawl catch rate of 5.5 Walleye per hour was the lowest observed since 1983, however, low catch rates may not result in low abundance of that year-class. For example, the trawl catch rate of 20.5 young of the year Walleye per hour in 2005 resulted in an above average year-class. An important factor in year-class strength is growth of those fish during their first year. Young of the year Walleye growth for trawl sampled fish was far below average in 2013. Low catch rates can be explained by extremely clear water during the summer of 2013. Fish of many species were observed avoiding the boat during trawling. Due to this (and to collect samples for the \"Walleye Fry Stocking in Egg-Take Lakes\" project) night electrofishing was conducted during August. Results of electrofishing were counter to those of trawling. Walleye were sampled at a rate of 88 per hour (data available in the Grand Rapids Area Fisheries Office) and growth was faster than average when compared to historic trawl growth rates. Fast growth of age 0 Walleye often results in a strong year class.
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\nYellow Perch; Perch are an important species to anglers and as a prey item for predators. The catch of perch in assessment nets reached a historic low (at the time) in 2005, largely due to poor year-classes in 2000 and 2002. A strong 2003 year-class moved through the system resulting in higher catch rates through 2007. Catch rates declined from 2007 through 2011 to a new historic low catch of 43.6 per net. The catch rate for perch increased to 57.5 per net in 2012 and increased again to 74.4 in 2013 (Figure 6). Sampled Perch varied from 5.0 to 11.0 inches with a mean length of 7.0 inches and mean weight of 0.2 pounds. Age-classes 3 through 7 were sampled by gill nets. An index of year-class strength was computed for all year-classes sampled from 2006 through 2010. The 2006 and 2007 year-classes were weak while the 2009 and 2010 year-classes were strong and the 2008 year-class was average (Figure 7). The 2010 year-class appeared to be the strongest since 2003. Natural mortality of perch increases at age 8 and few individuals live past age 10. The catch of perch in 2013 was primarily represented by younger individuals with 95% of the catch made up of age 3 through age 5 fish. Growth was relatively slow through age 2, then increased to average from age 3 to age 8. Perch grew to an average length of 9 inches at age 6.
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\nRelative health of the perch population can be described by the percent of perch longer than nine inches in the gill net catch. The catch of large perch (longer than 9 inches) declined to 6% in the early 1990's driven by high angler harvest. Changes in Lake Winnibigoshish and other lakes prompted a statewide change in the perch bag limit to 20 daily and 40 in possession in 2001. Several strong year classes were produced during the same time period and the assessment catch of perch longer than nine inches increased to 30% in 2004. In 2005, the proportion of large perch sampled in near-shore gill nets declined for the first time since 1998. The proportion of perch longer than nine inches was about 17% in 2005 and 2006, then declined to 9.8% in 2007 as young perch were recruited to the fishery. No strong year classes were produced between 2003 and 2009. As a result the percent of perch longer than 9 inches fluctuated between 10% and 13% between 2007 and 2012. Strong year classes of perch were produced in 2009 and 2010. This resulted in increased catch rates (mostly young fish) and a reduced catch of perch longer than 9 inches (7.7%) in 2013 (Figure 8).
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\nThe catch rate for age 0 perch of 6,952 per hour of trawling was below average. Growth of age 0 perch was slower than average with a mean length of 1.8 inches in mid-August. The clear water conditions that appear to have affected trawl catch rates of young of the year Walleye likely affected catch rates of young of the year Yellow Perch also. No correlation is evident between trawl catch rates or growth of age 0 perch and year-class strength.
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\nThe microsporidian parasite heterosporis has been documented in Lake Winnibigoshish Yellow Perch. No evidence of heterosporis was observed in perch during the 2013 population assessment, although anglers report the presence of heterosporis in a few perch each year.
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\nNorthern Pike; Catch rates of Northern Pike (pike) showed an increasing trend from 1999 through 2005 and exceeded the third quartile (9.6 per net) in five years between 2002 and 2009. The pike catch rate decreased to 7.3 per gill net in 2010 from 10.0 in 2009 then rose to 8.5 in 2011 and was the third highest observed in 2012 at 10.3 per net. The gill net catch of 14.1 per net in 2013 was the highest observed (Figure 9). Pike sampled in 2013 varied from 13.0 to 32.6 inches with a mean length of 20.6 inches. Mean length of pike has been declining as catch rates have increased. Average pike length of 20.6 inches in 2013 was the lowest observed since 1983 (Figure 10). Age-classes from 1 to 5 were sampled by gill net. Growth rates were similar to the statewide mean through all ages.
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\nSize structure of the pike population improved between 2010 and 2012. That trend was reversed in 2013 as a strong component of small young pike were recruited to the gill net catch. Only two pike longer than 30 inches were sampled in the 2013 assessment vs 10 in the 2011 and 9 in the 2012 assessments (Figure 11). Decreased size structure may be attributed to several causes. Reproduction and recruitment was strong for the 2010 and 2011 year classes which made up 74% of the catch, and Cisco abundance decreased due to summer kill in 2012 (Cisco are preferred prey that provides more energy than other similar size prey). A strong prey base of Cisco may lead to faster pike growth rates. High angler harvest of pike may result in a recruitment response (increased reproduction to replace individuals removed from the system). Larger numbers of small pike vs smaller numbers of medium to large pike may cause reduced growth rates due to increased competition for food and space. The recent increase in catch rate may result in slower pike growth in the future. Anglers can help maintain the pike size structure by releasing most pike longer than 25 inches and harvesting pike smaller than 24 inches.
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\nCisco; Cisco are a primary prey for Muskellunge, pike and Walleye. Growth rates of these species may be less if Cisco are not present in the system. The gill net catch of 8.6 per net in 2013 was the second lowest since 1983 and decreased by nearly 50 percent from the catch of 16.0 per net in 2012 (Figure 12). Cisco sampled varied from 6.0 to 15.5 inches with a mean length of 11.2 inches. Cisco catch rates were lower than average for 6 of the last 10 years. This is likely due to warmer than average summer and fall water temperatures that may affect reproduction and cause occasional summer kills. Summer water temperatures were warm during the summer of 2012 and caused a summer kill of Cisco. Effects of that summer kill were a likely cause of decreased catch rate in 2013.
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\nWater Quality; Seven temperature and dissolved oxygen profiles were taken between June 24 and August 13, 2013. Dissolved oxygen stratification was evident between June 24 and July 24. No evidence of thermal stratification was found in 2013. Thermal and dissolved oxygen stratification may result during periods of high air temperatures and low wind. When wind speeds increase to moderate levels (15 mph) the entire water column appears to mix.
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\nWater chemistry measurements have been recorded for most years since 1983. Water clarity as measured by Secchi disc in 2013 was higher than in most years. Secchi disc measurement varies between 10.0 and 18.0 feet. The measurement on August 13 was 11.0 feet compared to the long term average of 7.0 feet. The Total Phosphorous concentration of 0.023 parts per million (ppm) in 2013 was within the recorded range of 0.015 to 0.051ppm, but was 30 percent lower than the long term mean of 0.030ppm.
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\nInvasive Aquatic Species; Species that have been introduced through human activities to a location where they don't naturally occur are termed \"invasive\". Some invasive species are not necessarily harmful, but others cause ecological or economic problems. Several invasive species have been introduced to Lake Winnibigoshish. Three species of snail: banded mystery, Chinese mystery, and faucet have become established since 2000. Both species of mystery snail appear to have no negative effect at this time. The faucet snail carries a trematode parasite that can kill several species of ducks if ingested. Thousands of ducks were killed by these parasites during the falls of 2007 and 2008. Emerald shiners (often used as bait) are not native and were first sampled in 2005. Juvenile zebra mussel (veliger), were discovered while sampling for plankton in 2012. No zebra mussel veliger were found while sampling for zooplankton in 2013 No adults were found during 2012 or 2013 assessments. Each of these invasive species were likely introduced through human activities.
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Thirty two gill nets were set during the last two weeks of September, 2014. This was the eighth consecutive year of fall sampling. The goals of this netting are: 1) develop a population estimate of adult walleye using available walleye population models, 2) determine accurate sex ratios and spawning stock biomass for the lake Winnibigoshish Walleye population, and 3) build on the long term data set of fall netting so that fall netting may eventually replace summer netting as the annual index of abundance for primary fish species in Lake Winnibigoshish.
"},{"surveyID":"4231309939763002","headerInfo":{"wb_id":"11014700","wb_name":"Winnibigoshish","county":"Cass","id_date":"2013-09-16","survey_id":"4231309939763002","survey_type":"Special Assessment","wb_alt_name":"","wb_type":"Lake"},"surveySubType":"Special Assessment","fishCatchSummaries":[{"species":"TLC","gearCount":32,"averageWeight":"0.68","CPUE":"8.16","quartileCount":"4.9-17.6","totalCatch":261,"totalWeight":80901,"gear":"Standard gill nets","quartileWeight":"0.4-0.5"},{"species":"BRB","averageWeight":"1.24","gearCount":32,"gear":"Standard gill nets","totalWeight":2808,"totalCatch":5,"quartileCount":"0.1-0.6","CPUE":"0.16","quartileWeight":"0.6-1.2"},{"species":"NOP","averageWeight":"2.39","gearCount":32,"quartileCount":"0.9-4.3","CPUE":"4.75","totalCatch":152,"totalWeight":164713,"gear":"Standard gill nets","quartileWeight":"2.4-4.3"},{"quartileWeight":"0.2-0.5","quartileCount":"0.1-0.7","CPUE":"0.09","totalWeight":123,"totalCatch":3,"gear":"Standard gill nets","averageWeight":"0.09","gearCount":32,"species":"BLC"},{"species":"WTS","averageWeight":"1.71","gearCount":32,"totalWeight":91429,"totalCatch":118,"gear":"Standard gill nets","quartileCount":"0.8-2.4","CPUE":"3.69","quartileWeight":"1.6-2.1"},{"species":"WAE","averageWeight":"1.65","gearCount":32,"totalWeight":155323,"gear":"Standard gill nets","totalCatch":208,"quartileCount":"3.3-14.8","CPUE":"6.50","quartileWeight":"0.9-1.5"},{"quartileWeight":"N/A","quartileCount":"N/A","CPUE":"0.06","totalCatch":2,"totalWeight":179,"gear":"Standard gill nets","averageWeight":"0.20","gearCount":32,"species":"PMK"},{"quartileWeight":"0.9-2.5","CPUE":"0.16","quartileCount":"0.1-0.9","gear":"Standard gill nets","totalWeight":2349,"totalCatch":5,"gearCount":32,"averageWeight":"1.04","species":"SHR"},{"species":"YEB","averageWeight":"1.14","gearCount":32,"CPUE":"0.06","quartileCount":"0.1-1.1","totalWeight":1034,"totalCatch":2,"gear":"Standard gill nets","quartileWeight":"0.6-1.1"},{"CPUE":"18.19","quartileCount":"9.9-57.1","totalCatch":582,"totalWeight":54013,"gear":"Standard gill nets","quartileWeight":"0.2-0.3","species":"YEP","averageWeight":"0.20","gearCount":32},{"species":"RKB","averageWeight":"0.08","gearCount":32,"gear":"Standard gill nets","totalWeight":76,"totalCatch":2,"quartileCount":"0.1-1.1","CPUE":"0.06","quartileWeight":"0.3-0.6"}],"surveyType":"Targeted Survey","lengths":{"YEB":{"fishCount":[[12,2]],"minimum_length":12,"maximum_length":12},"RKB":{"fishCount":[[5,2]],"minimum_length":5,"maximum_length":5},"BRB":{"fishCount":[[12,2],[13,3]],"minimum_length":12,"maximum_length":13},"NOP":{"maximum_length":30,"fishCount":[[10,1],[11,1],[14,1],[16,1],[17,7],[18,14],[19,14],[20,27],[21,24],[22,17],[23,11],[24,11],[25,6],[26,5],[27,2],[28,2],[29,4],[30,2],[9,2]],"minimum_length":9},"PMK":{"fishCount":[[5,1],[6,1]],"minimum_length":5,"maximum_length":6},"BLC":{"maximum_length":6,"fishCount":[[5,2],[6,1]],"minimum_length":5},"WAE":{"fishCount":[[10,1],[11,3],[12,5],[13,20],[14,31],[15,27],[16,29],[17,18],[18,13],[19,27],[20,19],[21,3],[22,1],[23,2],[25,2],[6,1],[7,6]],"minimum_length":6,"maximum_length":25},"TLC":{"maximum_length":16,"minimum_length":6,"fishCount":[[10,6],[11,11],[12,87],[13,103],[14,9],[15,1],[16,1],[6,1],[7,35],[8,6],[9,1]]},"SHR":{"maximum_length":17,"minimum_length":10,"fishCount":[[10,3],[14,1],[17,1]]},"WTS":{"minimum_length":7,"fishCount":[[10,8],[11,19],[12,3],[13,8],[14,4],[15,9],[16,18],[17,24],[18,13],[19,3],[20,5],[7,1],[9,3]],"maximum_length":20},"YEP":{"maximum_length":11,"minimum_length":3,"fishCount":[[10,30],[11,6],[3,3],[5,79],[6,191],[7,121],[8,81],[9,71]]}},"surveyDate":"2013-09-16","narrative":"Thirty two gill nets were set during the last two weeks of September, 2013. This was the seventh consecutive year of fall sampling. The goals of this netting are: 1 develop a population estimate of adult walleye using available walleye population models, and 2 build on the long term data set of fall netting so that fall netting may eventually replace summer netting as the annual index of abundance for primary fish species in Lake Winnibigoshish.
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\nThe gill net catch of 6.5 Walleye per net was the lowest observed since 2007. Summer catch rates have increased over time, while fall catch rates have been decreasing. Summer and fall catch rates were nearly identical in 2013. The trend of gill net catch rates moving in opposite directions makes comparison difficult. Size structure was good, with fish present from 6.8 to 25.1 inches. All ages of walleye between 0 and 15 were represented except 11, 13, and 14. An index of year class strength was computed for the 2006 through 2011 year classes. The 2009, 2010, and 2011 year classes were average, the 2006 and 2007 year classes were strong, and the 2008 year class was weak. No age one Walleye were sampled in summer near-shore or summer mid-lake nets. Five age one Walleye were sampled in fall gill nets.
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\nYellow Perch (perch) catch rates have varied from 17.5 to 38.5 since 2007. The catch rate of 18.2 per net in 2013 was similar to the 2012 catch rate of 19.9 per net. Perch varied from 3.3 to 11.6 inches with a mean length of 7.4 inches. Age classes 1 through 7 and 9 were sampled. Age two, three, and five were most frequently sampled. The proportion of perch longer than 9 inches has increased over the last two years. Sixteen percent of the 2012 fall captured perch and 18.4 percent of the 2013 sample were longer than 9 inches. Fall gill net catch rates continue to be lower than summer catch rates, and the percent of perch longer than 9 inches continues to be higher than summer near-shore netting. Neither of these appear to be explained by growth of perch between the two survey dates.
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\nNorthern pike (pike) were sampled at a rate of 4.8 per gill net. This catch rate is near the historic high since 2007 (range 3.0-4.9, mean 3.5). Pike length varied from 9.2 to 30.5 inches with a mean length of 21.6 inches. Pike age structure varied similarly to the summer assessment with ages one through seven represented. As with most Lake Winnibigoshish assessments, the majority of pike sampled were from the age two, three, and four cohorts.
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\nThe gill net catch of cisco decreased to a historic low of 8.2 per net in 2013 from the catch rate of 24.1 in 2011 and 13.9 in 2012. The decline in catch rate was expected due to continuing effects of a summer kill observed during the summer of 2012. Although the catch rate was low, cisco have shown the ability to recover from low catch rates in the past. Cisco length varied from 7.1 to 16.4 inches with a mean length of 12.1 inches.
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\nA preliminary comparison of summer and fall walleye gill net catch rates was completed using the Qabg model and direct comparison early in 2012. Results of that modeling indicated that more years of sampling are required before summer catch rates can be predicted from the fall gill net catch. Catch rates will be evaluated periodically until variance between predicted and actual catch rates is acceptable.
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Lake Winnibigoshish (Winnie) has a low-density native Muskie population but no attempt to sample the population has ever been made. Our goal in the spring of 2014 was to investigate likely Muskie spawning areas and determine the potential for setting nets in those areas in the future. An electrofishing boat was used to investigate the areas so that if any Muskies were encountered, we could attempt to capture them. The electrofishing boat provided addtitional information regarding the potential for by-catch (suckers, Yellow Perch, etc.) if we decide to attempt a netting assessment in the future. During the late spring of 2014, spring water temperatures were quite cold for the first 10 days after ice-out but than a stretch of uncommonly long and hot weather resulted in the water temperatures rising rapidly and remaining warm.
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\nAfter investigating four areas of Winnie and Cut Foot Sioux, we continue to suspect the Muskie population is low in Winnie and connected waters. In addition to us not having a great feeling for the available spring Muskie habitat, the spring conditions in 2014 likely hindered our ability to encounter more fish. Many challenges to sampling Muskies were identified during this initial investigation (e.g. large areas of wild rice). A total of four Muskies were encountered and this number likely does not reflect the population. However, it is probable that a future assessment with our improved knowledge of the habitat, an increase in effort, addition of some trap netting, and improved spring conditions would still result in a relatively low number Muskies being sampled. Although improved size structure and distribution would be described, and additional fish for genetic samples collected for ancestry, we would still conclude the population was generally low.
This special assessment contains data from 8 mid-lake gill net sets that were first set in 1997. These nets were initially set to determine if catch rate and growth statistics for various fish species were similar to those of the 24 near-shore gill net sets and were set in conjunction with the 24 near-shore sets. After many years of sampling it appears that catch rate and size distribution can vary between the two net groups for Walleye, Northern Pike, and Yellow Perch while growth of fish appears to be similar.
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\nWalleye; Walleye catch rates varied similarly to near-shore nets from 1997 to 2006, then appeared to move independently between 2006 and 2013. Gill net catch rates in near-shore and mid-lake gill nets were similar in 2014 and 2015. Walleye were sampled at a rate of 4.1 per net in 2015. Mid-lake sampled Walleye varied from 11.6 to 23.0 inches with a mean length of 18.6 inches. Gill net catch of the 2012 year class for near-shore gill nets was also low. The 2012 year class continues to be one of the weakest observed since the beginning of the Large Lake Program (1983).
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\nThe catch per gill net of Walleye longer than 19 inches has been used as an indicator of quality for the Walleye population. The mean catch of Walleye longer than 19 inches sampled per mid-lake net since 1999 was 1.19 per net. This catch rate was similar to the mean catch of 1.22 Walleye longer than 19 inches per near-shore gill net set since 2000. The catch rate of Walleye longer than 19 inches was 2.38 per mid-lake net in 2015.
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\nNorthern Pike; Mid-lake gill net catches of Northern Pike (pike) are typically less than near-shore nets and 2015 was no different. The mid-lake catch of pike per net decreased from 6.0 per net in 2014 to 4.3 per net in 2015. Pike sampled in 2015 varied from 17.1 to 25.8 inches with a mean length of 20.9 inches.
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\nYellow Perch; Yellow Perch (perch) sampled in mid-lake nets have typically been sampled at a higher rate than from near shore nets. Results of the 2015 assessment followed that trend, with a catch rate of 55.3 per mid-lake net compared to 43.1 per near-shore net. The mean catch per gill net since 1997 has been higher in mid-lake gill nets (81.6) than near-shore gill nets (72.2). Although catch rates have been higher in mid-lake nets, the catch per gill net lift has varied similarly between near-shore and mid-lake gill nets. Perch sampled in mid-lake nets varied from 4.5 to 11.9 inches with a mean length of 6.9 inches.
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\nRelative health of the perch population has been described by the percent of perch longer than nine inches in the gill net catch. The catch of perch longer than 9 inches (large perch) in near-shore gill nets declined to 6% in the early 1990's driven by high angler harvest. Changes in Lake Winnibigoshish and other lakes prompted a statewide change in the Yellow Perch bag limit to 20 daily and 40 in possession in 2001. Strong year classes were produced in 1994 and 1997 which resulted in high catch rates of large perch in the early 2000's. The catch of large perch started to decline in 2004 and has declined from 45.9% in 2004 to near 16% in 2010 and 2011. The percent of perch longer than 9 inches increased to 11.5% in 2015 from 10.5% in 2014.
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Thirty two gill nets were set during the last two weeks of September, 2015. This was the ninth consecutive year of fall sampling. The goals of this netting are: 1) develop a population estimate of adult Walleye using available population models, 2) determine accurate sex ratios and spawning stock biomass for the Lake Winnibigoshish Walleye population, and 3) build on the long term data set of fall netting so that fall netting may eventually replace summer netting as the annual index of abundance for primary fish species in Lake Winnibigoshish.
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\nThe gill net catch of 7.7 Walleye per net in 2015 increased by 20% from the catch of 6.4 per net in 2014. Developing a similar annual index of abundance has been difficult. Summer and fall mean gill net catch rates resulted in opposite trends between 2007 and 2011, making comparisons between the two challenging. Since that time, summer and fall gill net catch rates have resulted in similar trends, although much variability was still evident. It is likely that more time will be required to develop an comparable annual index. Size structure was good, with fish present from 7.5 to 25.3 inches. With the exception of age 11, all ages of Walleye between 0 and 15 were represented. An index of year class strength was computed for the 2008 through 2013 year classes. The 2009, 2010, 2011 and 2013 year classes were average, and the 2008 and 2012 year classes were weak.
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\nYellow Perch (perch) catch rates varied from 17.5 to 38.5 between 2007 and 2013. The catch rate of 17.3 per net in 2014 was a new low, and was followed by a historic high catch rate of 43.1 per net in 2015. The difference in catch rates was primarily due to high catch rates of the 2012 year class. Perch varied from 4.5 to 12.2 inches with a mean length of 7.1 inches. Age classes 2 through 10 perch were sampled, however, the 2012 year class made up 59% of the catch. The proportion of perch longer than 9 inches has varied between 16 and 18 percent between 2011 and 2014. The percent of perch longer than 9 inches decreased to 12.4 percent in 2015, primarily due to the abundant 2012 year class that were less than 7 inches in length. Fall gill net catch rates continue to be lower than summer catch rates, and the percent of perch longer than 9 inches continues to be higher than summer near shore netting. Neither of these appeared to be explained by growth of perch between summer and fall survey dates.
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\nNorthern Pike (pike) were sampled at a rate of 5.8 per gill net in 2015. This catch rate was the second consecutive historic high (range 3.0-5.8, mean 4.1). Pike length varied from 10.6 to 37.3 inches with a mean length of 22.8 inches. Pike age structure varied similarly to the summer assessment with ages one through seven represented. As with most Lake Winnibigoshish assessments, the majority of pike sampled were from the age two, three, and four cohorts.
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\nThe gill net catch of Cisco increased to 8.8 in 2015 from the historic low of 2.8 in 2014. Although the catch rate increased, the catch of 8.8 per net remains below the third quartile. Low catch rates of Cisco were expected in 2013 due to a summer kill during the summer of 2012. The continued low catch in 2015 was not expected, however, the increased catch may indicate that Cisco are recovering. Cisco length varied from 5.0 to 15.7 inches with a mean length of 12.0 inches.
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The Walleye population on Lake Winnibigoshish (Winnie) has seen its ups and downs over time. Presently, we are in a down period. Walleye reproduction and recruitment to the fishery was generally good between 2001 and 2011, with numerous strong year classes and increasing catch rates in DNR assessment nets. Since 2012 Winnie Walleye have seen below average recruitment, with only one strong year class produced (2013) and likely four weak year classes. Full evaluation of the 2016 and 2017 year classes is not complete, so evaluation of those year classes may change. Below average recruitment since 2012 has resulted in less small Walleye present in the system, which may result in anglers catching fewer keeper size fish.
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\nAlthough less small Walleye are currently in the lake, the 2015 year class appears to be average, and those fish should be 14 to 16 inches in length during the summer of 2018. Walleye from the strong 2013 and earlier year classes are still abundant in the lake which should result in good catches of fish longer than 18 inches. The larger Walleye are mostly mature fish that have the potential to produce a strong year class when conditions are right.
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\nClear water continues to drive Walleye fishing success. Walleye have large, light sensitive eyes and prefer to feed in low visibility conditions. Due to this, fishing in the early morning, evening, or on windy days should result in better success.
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\nNorthern Pike continue to be abundant in Winnie, and they are easily caught during mid-day! The population of pike has been increasing since the mid 1990's. As the pike population expanded, the average size and number of pike longer than 30 inches decreased. Although the pike population remains near the historic high, the average size has been increasing over the past several years and is now the largest since 2001. The number of pike longer than 30 inches sampled is still relatively low. However, with the 22 to 26 inch protected slot limit that will be in effect for north central MN lakes starting in 2018, the number of quality sized pike should increase. Pike prey heavily on Yellow Perch and Cisco. High numbers of pike can have a negative effect on those populations. The new pike regulation should help reduce the overly abundant pike population, reduce pressure on the perch population, and result in larger average size for pike.
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\nYellow Perch are an important species for anglers and as a prey item for pike, Walleye, and perch. Perch abundance and the percent of quality perch has varied over time. Perch were extremely abundant with many quality perch in the 1980's. As perch became more popular as a game fish, a booming perch fishery was created on Winnie. The increased harvest of perch caused a decline in average size and the number of quality size perch in the lake. The current limit of 20 daily and 40 in possession was implemented in 2001. Over time the perch population stabilized at a level that is less than the 1980's, but much higher than most lakes. Although anglers remove many large perch from Winnie each year, the increase in predators (both pike and Walleye) likely play a large role in observed changes to the perch population.
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\nThe 2017 assessment saw average catch rates of perch, an increasing number of perch longer than 9 inches, and good size structure. Gill net catch rates were similar between 2016 and 2017. Relative quality of the perch population is described by the percent of perch longer than 9 inches. The percent of perch longer than 9 inches increased to 15.6% in 2017 from 8.3% in 2016. Gill net sampled perch length varied from 4.6 to 12.1 inches and age 3 to 9.
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\nCisco (also known as tullibee or herring) are an important prey item for large Walleye and Northern Pike, and were caught in low numbers in 2017. There was a substantial summer kill observed during the summer of 2012. Catch rates typically recover two to three years following a summer kill as the remaining adults have better success spawning, and their off-spring have less competition from older fish and tend to do well. The Cisco population has not recovered as of the summer of 2017.
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\nLake Winnibigoshish and the Cut Foot Sioux Lakes also provide opportunities to fish for other species. Black Crappie, sunfish and bass are found in the big lake, but more so in Cut Foot Sioux. The lakes also provide an opportunity to catch a muskie. Few anglers actually target muskies but some are caught while fishing for other fish.
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\nWinnie and connected waters contain faucet snails, and zebra mussels have been sampled annually since 2012. Adult zebra mussel were found for the first time in 2016 and covered nearly all hard surfaces in 2017. With the discovery of zebra mussels it is important that all boaters do a thorough job draining and cleaning their equipment. If you are going to fish a couple of lakes in the same day, make Winnie the last stop so you don't inadvertently spread invasive species to other waters.
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\nStarry stonewort (a non-native algae that looks similar to chara) was discovered in 2016. By the fall of 2017 it had spread from the Third River in the northwest corner of the lake south and east to the Mississippi River outlet in the northeast corner of the lake. This plant spreads through fragmentation, so it is important to check equipment and remove all plant fragments.
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\nPlease feel free to contact the DNR Area Fisheries Office in Grand Rapids at (218) 328-8836 or by e-mail at grandrapids.fisheries@state.mn.us if you have any questions.
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Lake Winnibigoshish is part of the Mississippi River headwaters reservoir system and is located 15 miles northwest of Deer River. The lake is a large, shallow, wind-swept reservoir with a sandy shoreline and gently sloping shoal areas. Winnibigoshish has a surface area of 56,544 acres, mean depth of 15.1 feet, and a maximum depth of 70 feet. Water clarity was high in 2022 and Secchi depths ranged from 11 to 23 feet.
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\nLake Winnibigoshish has been managed as part of the Minnesota Department of Natural Resources large lake program since 1983. Management activities include special fishing regulations, Walleye fry stocking, occasional creel surveys, and annual fish surveys. Walleye harvest has been regulated with a special regulation since 2000. The regulation was relaxed to a 6 fish limit with a 18 to 23-inch protective slot limit in 2015 to allow some additional harvest of larger fish which were common at the time. Winnibigoshish lies within the North-central Pike Zone, which was established in 2018. Lakes within this zone are regulated with a 22 to 26-inch PSL with a bag limit of 10 fish but only two can be longer than 26 inches. Spearing has an exception of one fish in the PSL.
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\nWinnibigoshish is considered a premier Walleye destination and substantial effort is directed towards Walleye management. Fall gill net catches have varied due to fluctuations in year-class strength. The 2022 catch was below average for Winnibigoshish but within the typical range for lakes with similar habitats. The lower catch rate was largely driven by a decline in fish over 18 inches. The decreased number of larger individuals was not unexpected. Multiple below average year-classes were produced between 2014 and 2017 thus limiting the number of fish recruiting to larger sizes. Stronger year-classes were produced in 2018 and 2019 which contributed to a shift in size and age distributions favoring smaller individuals. Age distribution was heavily influenced by the strong 2019 year-class. The size distribution was favorable for anglers and featured good harvest opportunities. Walleye within the 18 to 23-inch protected slot comprised 7.4% of the sample. This compares to over 70% in 2017 and 2018 when the population was dominated by large individuals and few harvestable fish were available. Growth was typical for Minnesota lakes with Walleye averaging 14.8 inches by age-4. Walleye averaged almost 15 inches in 2022 and fish up to 25 inches were sampled. Thirty-two percent of the sampled Walleye exceeded 15 inches.
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\nWinnibigoshish provides a destination Yellow Perch fishery with a history of producing fish over ten inches. Yellow Perch is also an important prey species. Catch rates have varied but have declined following a 2016 peak and were lower than expected in the last four surveys. The 2022 catch rate was the lowest observed and low compared to similar lakes. Fisheries surveys have documented declines in perch catch rates across Minnesota since the 1970s but contributing factors are not well understood. Contributing elements on Winnibigoshish may include a combination of factors such as recent predation by strong Walleye year-classes, a prolonged decline in Cisco as an alternate prey item, ecosystem changes related to Zebra Mussel infestation and climate, and a prolonged period of reduced recruitment to larger sizes. All sizes of perch were sampled in relatively low numbers in 2022, but perch under 9 inches showed the greatest decline suggesting poor recruitment in the recent past. Growth resembled past surveys and was near the statewide average with fish typically reaching 8 inches by age-5. Despite low numbers, perch size distribution remained favorable for anglers and the presence of larger perch suggested modest angling opportunities. Perch averaged 8.2 inches and fish over 11 inches were sampled. Thirteen percent of the sampled perch exceeded 10 inches.
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\nNorthern Pike is another popular species and well suited for Winnibigoshish and connected waters. Winnibigoshish often had higher pike catch rates than comparable lakes, largely due to an abundance of preferred spawning habitats. The 2022 catch was low compared to previous surveys, but resembled pike catches on other large lakes. Lower pike numbers are often desirable because they are associated with faster growth and better size quality. The 2022 length distribution was modest and resembled previous fall surveys. Pike averaged 21.8 inches and fish over 32 inches were sampled. Only 5% of the pike exceeded 28 inches. The Winnibigoshish population has been dominated by 2- to 5-year-old pike and older fish have been rare. The 2022 age distribution resembled past surveys as ages ranged from one to six. Growth was similar to past surveys and relatively fast with pike averaging 24.8 inches by age-4. Protected slot sized fish comprised around 40% of the sample since 2018. In 2022, 38% of the catch was within the PSL. Anglers and spearers are encouraged to focus harvest on fish under 22 inches while releasing or passing on larger fish to help improve size quality.
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\nCisco are an important prey species and an indicator species due to their environmental sensitivity. Catches have declined over the past decade following a 2012 summer kill event. The 2022 catch was the lowest observed. Warmer water temperatures and Zebra Mussel infestations are two factors that have likely influenced poor Cisco numbers.
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\nInvasive exotic species are not native to Minnesota and cause economic or environmental harm or harm to human health. They are illegal to introduce into or move between state waters and can impact energy flow, food chains, and fish species assemblages. Several species have been introduced into Lake Winnibigoshish including Zebra Mussels, Faucet and Mystery Snails, and Starry Stonewort. Changing environmental conditions resulting from these introductions caused changes in gamefish habitat and habits, which likely impact fish sampling and anglers. Gill net catches have likely been influenced by these changes, especially since the establishment of Zebra Mussels in 2012. Zebra Mussels are an efficient filter feeder that have been shown to impact energy transfer and aquatic food webs. The median biomass of fish sampled in gill nets declined since 2016 suggesting a decrease in overall carrying capacity for fish following Zebra Mussel establishment. Each of these introductions have occurred through human activities. Movement of any type of equipment that can trap or hold contaminated water, plant fragments or aquatic organisms can be a potential vector of spread if precautions are not taken. To avoid being an accomplice to the spread of these unwanted species, people should ensure that all equipment is thoroughly cleaned and dried before moving it to a new body of water. More information is available at https://www.dnr.state.mn.us/invasives/ais/index.html.
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Walleye
\nNear-shore gill nets
\nWalleye were sampled at a rate of 4.6 per net, which was average for Lake Winnibigoshish. Walleye sampled varied from 6.5 to 26.3 inches with a mean length of 14.8 inches and mean weight of 1.4 pounds. The walleye population appeared to be healthy with most age classes sampled between age 1 and 12. Year class strength was computed for walleye from age 2 to age 7. One weak year class (2000), four average year classes (1999, 2002, 2003, and 2004), and two strong year classes (2001 and 2005) were sampled. Walleye catch rates were near average for most length groups in 2007. Mean back-calculated growth was similar to the Lake Winnibigoshish and statewide average for all ages, attaining 17.4 inches after five growing seasons.
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\nSeine and trawl
\nRelatively few age 0 walleye were sampled by seine in 2007. Seine catch rates have not correlated to ultimate year class strength for walleye in Lake Winnibigoshish. Growth rates of age 0 walleye has been a better predictor of year class strength. Rapid spring warming and above average summer temperatures appear to have resulted in faster than average growth and relatively large size of age-0 walleye. Fast growth and large size of fingerling walleye often correspond to strong year classes. Mean lengths of age 0 walleye varied from 3.3 to 4.4 inches from July 7 to July 30.
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\nThe mean trawl catch rate for age 0 walleye in 2007 was nearly double the highest catch rate observed since 1972. Age 0 walleye growth recorded through the first week of August was faster than mean growth since 1983, reaching a mean length of 4.7 inches on August 7. High trawl catch rates of age 0 walleye have not resulted in strong year classes, however, high catch rates combined with faster than average growth may result in above average abundance.
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\n Yellow perch
\nNear-shore gill nets
\nYellow perch were captured at a rate of 86.4 per net. This catch rate was considerably higher than the catch of 56.3 per net in 2006, and was near average for Lake Winnibigoshish. Perch sampled in 2007 varied from 2.3 to 11.7 inches with a mean length of 7.1 inches and mean weight of 0.18 pounds. Catch rates and size structure of sampled perch have changed recently. Catch rates started a slow decline in the late 1990s, but were within historic norms until 2003. Catch rates from 2003 through 2006 were below the first quartile for Lake Winnibigoshish due to weak 2000 and 2002 year classes. Catch rates recovered to average in 2007 due to increased abundance of small, young perch.
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\nAge classes 1 through 8 were sampled by gill net. An index of yearclass strength was computed for ages 3 through 7. The 2001 and 2004 year classes were average, the 2000 and 2002 year classes were weak, and the 2003 year class was strong. The catch was heavily biased towards younger perch with 88% of the catch made up of age 2 through age 4 fish. Yellow perch growth was relatively slow through age 2, increased to near average from age 3 to age 9, with perch attaining a mean length of 9.2 inches at age 6.
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\nRelative health of the yellow perch population has been described by the percent of perch longer than 9 inches in the gill net catch. As perch catch rates decreased the proportion of large perch (longer than 9 inches) increased. The proportion of large perch peaked as gill net catch rates fell below the first quartile. In 2005, the proportion of large perch sampled in near-shore gill nets declined for the first time since 1998. The proportion of perch longer than nine inches was stable in 2005 and 2006 at 16.9 percent, then declined to 9.8% in 2007 as young perch were recruited to the fishery.
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\nThe microsporidian parasite heterosporis has been documented in Lake Winnibigoshish yellow perch. Of 180 perch examined in 2007 no evidence of heterosporis was observed.
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\nSeine and trawl
\n Catch rates of age-0 yellow perch were near average for both seine and trawl. No correlation is evident between catch rates of age-0 yellow perch and ultimate year-class strength.
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\n Northern pike
\nNear-shore gill nets
\nCatch rates of northern pike increased from 1999 through 2005 and exceeded the third quartile in four of six years since 2002. Northern pike catch rates increased to 9.7 per near-shore gill net in 2007. Pike sampled in near-shore gill nets varied from 12.0 to 31.1 inches with a mean length of 21.0 inches. All age classes between age 1 and 8 were sampled by gill net. Age two, three, and four pike were most abundant and pike exhibited growth rates that were similar to state wide averages through all ages.
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\n Cisco
\nNear-shore gill nets
\nGill net catch rates of cisco were within historic bounds for both near-shore and mid-lake nets in 2007. The catch rate of 21.2 per near-shore net was near the first quartile. Cisco were not aged in 2007, however, examination of the length frequency indicates that at least one year class was poorly represented in the catch. Cisco sampled in near-shore gill nets varied from 6.6 to 16.5 inches with a mean length of 8.0 inches.
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\nWater Quality
\nWater samples were taken on August 6, 2007. Physical and chemical parameters measured were within the range observed since 1983 . Five temperature and dissolved oxygen profiles were taken from June 25 to July 23, 2007. Dissolved oxygen stratification was evident on July 5, July 9, and July 23. No evidence of thermal stratification was found in 2007. Thermal and dissolved oxygen stratification may result during periods of high air temperatures and low wind. When wind speeds increase to moderate levels (15 mph) the entire water column appears to mix.
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Walleye abundance decreased from the second highest observed in 1997 to below average in 1999. Walleye abundance rebounded to above average in 2000 due to the resilience of the 1994 and 1995 year classes and a strong 1998 year class. The Lake Winnibigoshish walleye fishery appears to be more robust than it has been since the late 1980s. Two strong year classes (1998 and 1994) and two average year classes (1995 and 1996) dominated the walleye population. Preliminary gill net and trawl data indicate that the 1999 year class may also be of above average abundance.
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\nA 17 to 26 inch protected slot limit was enacted in 2000. This resulted in the release of most walleye older than the 1995 year class, and may also have contributed to higher abundance indices. The 1998 year class of walleye experienced fast growth in 1998 and 1999. As a result, the average 2+ year old (1998 year class) walleye was nearly two inches larger than expected. The additional growth may also have resulted in higher abundance indices. Young of the year walleye were captured by trawl at near all time low rates in 2000. These walleye also experienced slow growth during their first summer and may ultimately be a weak year class. The mean length and weight for gill net captured walleye at 15.3 inches and 1.4 pounds in 2000 was similar to the long term mean.
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\nThe gill net catch rate for yellow perch of 92.6 per assessment net was similar to both 1999 and historic mean catch rates. The proportion of perch greater than 9 inches at 20.0% was 50% higher than in 1999, and the number of perch > 9 inches per net increased from 11.9 per net in 1999 to 18.5 per net in 2000. The majority of this increase was due to the strong 1994 year class growing to sizes exceeding 9 inches. As with the 1998 year class of walleye, the 1994 year class of yellow perch has experienced fast growth. This fast growth resulted in perch recruiting to the 9+ inch size faster which may also have resulted in greater numbers of 9+ inch perch. The 1994 year class appears to be strong with an index of year-class strength of 192. The majority of the 1994 year class has reached angler preferred sizes and likely made a large contribution to angler harvest during the 2000-2001 winter angling harvest. The 1995 and 1997 year class were of average abundance. Most individuals from those two year classes have attained angler preferred sizes. All other year classes sampled had below average indices of year- class strength, however, none would be considered weak.
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\nNorthern pike relative abundance increased to 8.2 per net in 2000 from 7.1 per net in 1999. Size structures for the northern pike population remained similar to all years sampled since 1983. The mean length and weight for northern pike of 22.8 inches and 3.1 pounds in 2000 was nearly identical to long term averages.
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\nStomach contents were examined for all gill net captured northern pike for the seventh consecutive year. Over those seven years the population of prey species has varied by year. During this time frame cisco and yellow perch have been the most important components in the northern pike diet. However, cisco continue to be the most common species that northern pike consume. It appears that pike select cisco over other prey species during the warm water period, regardless of the availability of other prey species.
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The Walleye population on Lake Winnibigoshish (Winnie) has seen its ups and downs over time. Presently, we are in a down period. Walleye reproduction and recruitment to the fishery was generally good between 2001 and 2011, with numerous strong year classes and increasing catch rates in DNR assessment nets. Since 2012 Winnie Walleye have seen below average recruitment, with only one strong year class produced (2013) and likely four weak year classes. I say likely, since full evaluation of the 2016 and 2017 year classes is not complete. Below average recruitment since 2012 has resulted in less small Walleye present in the system, which may result in anglers catching fewer keeper size fish.
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\nAlthough less small Walleye are currently in the lake, the 2015 year class appears to be average, and those fish should be 14 to 16 inches in length during the summer of 2018. Walleye from the strong 2013 and earlier year classes are still abundant in the lake which should result in good catches of fish longer than 18 inches. The larger Walleye are mostly mature fish that have the potential to produce a strong year class when conditions are right.
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\nClear water continues to drive Walleye fishing success. Walleye have large, light sensitive eyes and prefer to feed in low visibility conditions. Due to this, fishing in the early morning, evening, or on windy days should result in better success.
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\nNorthern Pike continue to be abundant in Winnie, and they are easily caught during mid-day! The population of pike has been increasing since the mid 1990's. As the pike population expanded, the average size and number of pike longer than 30 inches decreased. Although the pike population remains near the historic high, the average size has been increasing over the past several years and is now the largest since 2001. The number of pike longer than 30 inches sampled is still relatively low. However, with the 22 to 26 inch protected slot limit that will be in effect for north central MN lakes starting in 2018, the number of quality sized pike should increase. Pike prey heavily on Yellow Perch and Cisco. High numbers of pike can have a negative effect on those populations. The new pike regulation should help reduce the overly abundant pike population, reduce pressure on the perch population, and result in larger average size for pike.
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\nYellow Perch are an important species for both anglers and as a prey item for pike, Walleye, and perch. Perch abundance and the percent of quality perch has varied over time. Perch were extremely abundant with many quality perch in the 1980's. As perch became more popular as a game fish, a booming perch fishery was created on Winnie. The increased harvest of perch caused a decline in average size and the number of quality size perch in the lake. The current limit of 20 daily and 40 in possession was implemented in 2001. Over time the perch population stabilized at a level that is less than the 1980's, but much higher than most lakes. Although anglers remove many large perch from Winnie each year, the increase in predators (both pike and Walleye) likely play a large role in observed changes to the perch population.
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\nThe 2017 assessment saw average catch rates of perch, an increasing number of perch longer than 9 inches, and good size structure. Gill net catch rates were similar between 2016 and 2017. Relative quality of the perch population is described by the percent of perch longer than 9 inches. The percent of perch longer than 9 inches increased to 15.6% in 2017 from 8.3% in 2016. Gill net sampled perch length varied from 4.6 to 12.1 inches and age 3 to 9.
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\nCisco: Cisco (also known as tullibee or herring) are an important prey item for large Walleye and Northern Pike, and were caught in low numbers in 2017. There was a substantial summer kill observed during the summer of 2012. Catch rates typically recover two to three years following a summer kill as the remaining adults have better success spawning, and their off-spring have less competition from older fish and tend to do well. The cisco population has not recovered as of the summer of 2017.
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\nLake Winnibigoshish and the Cut Foot Sioux Lakes also provide opportunities to fish for other species. Black Crappie, sunfish and bass are found in the big lake, but more so in Cut Foot Sioux. The lakes also provide an opportunity to catch a muskie. Few anglers actually target muskies but some are caught while fishing for other fish.
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\nWinnie and connected waters contain faucet snails, and zebra mussels have been sampled annually since 2012. Adult zebra mussel were found for the first time in 2016 and covered nearly all hard surfaces in 2017. With the discovery of zebra mussels it is important that all boaters do a thorough job draining and cleaning their equipment. If you are going to fish a couple of lakes in the same day, make Winnie the last stop so you don't inadvertently spread invasive species to other waters.
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\nStarry stonewort (a non-native algae that looks similar to chara) was discovered in 2016. By the fall of 2017 it had spread from the Third River in the northwest corner of the lake south and east to the Mississippi River outlet in the northeast corner of the lake. This plant spreads through fragmentation, so it is important to check equipment and remove all plant fragments.
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\nPlease feel free to contact the DNR Area Fisheries Office in Grand Rapids at (218) 328-8837 or by email at grandrapds.fisheries@state.mn.us if you have any questions.
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Lake Winnibigoshish, otherwise known as Winnie or Big Winnie, is a large reservoir located immediately north of the community of Bena, Minnesota. Winnie was a natural lake that was impounded in the 1880's with a dam controlled by the U.S. Army Corps of Engineers (USACE). Today the USACE maintains water levels within a narrow band of elevation that gives the lake its current surface area of approximately 56,472 acres and a maximum depth of 69 feet. The surrounding geology contains a high proportion of sandy soils, providing an abundance of sandy shoreline with gradual slopes. With approximately 11 miles of open water between the north and south shores, the lake is prone to high wave action and frequent mixing of the water column when exposed to high winds. During the open water season, this keeps temperatures and oxygen levels much more uniform from the surface to the bottom of the lake, in comparison to smaller, more protected lakes with similar water depth. Sugar Lake, Cut Foot Sioux Lake, and Little Cut Foot Sioux Lake are all directly connected to Winnie. Some of the major tributaries include the First River flowage through Cut Foot Sioux Lake, the Third River, and the Mississippi River.
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\nWinnibigoshish is often thought of as a premier Walleye and Yellow Perch destination, but this lake offers angling opportunities for multiple species. Acknowledging the importance of this fishery, Winnibigoshish was included as one of ten lakes in the Large Lake Monitoring Program, which was developed by the Minnesota Department of Natural Resources (MN DNR) in 1983. Surveys are conducted on these lakes annually and typically include a suite of sampling methods that track trends in water quality, zooplankton, juvenile fish, periodic creel (angler) surveys, and the status of game fish targeted by anglers.
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\nMajor changes have been occurring within the system over the past 15 years. These changes began around the time of the discovery of invasive Faucet Snails in 2007, followed by the detection of larval Zebra Mussels in 2012, and adult Zebra Mussels in 2016. These invasives are filter feeders that can dramatically increase water clarity and reduce the abundance of plankton available to fish. Prior to the introduction of these invasives, water clarity (measured with a Secchi disc) averaged 6 to 7 feet and the highest ever recorded was 10 feet. There has been a post-invasion trend of increasing water clarity in Winnibigoshish. Secchi disc readings in 2025 were not as high as the previous two years, but still well above average with a range of 7 to 22 feet. Increasing water clarity tends to improve habitat for Bass, Sunfish, and Northern Pike while decreasing habitat suitability for Walleye.
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\nWalleye is the primary management species in Winnie, and a large proportion of the field work completed is dedicated toward tracking the status of this species. The most important tool to assess the Walleye population is a gill net survey that is completed annually in September. The Walleye catch rate in the gill net survey was up from the 2024 survey year but still less than the historic average. Walleye recruitment (survival to the fishery) is naturally variable in any lake, and Winnie is no exception. Two year classes make up the majority of the Walleye in the lake. The 2023 year class averaged 14 inches in the fall of 2025 and are currently providing the majority of the harvest opportunities for anglers. The other most commonly caught age group is the 2019 year class. These have now mostly grown into the protected slot, with males averaging 18 inches and females averaging 20 inches. These two year classes are the most prolific in the lake currently but there were a total of 12 year classes sampled during the 2025 fall gill net survey, with the oldest being a 17 year old male.
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\nThere is a history of high angling pressure on Yellow Perch in Winnibigoshish. Perch are also a valuable prey item for predators such as Walleye and Northern Pike. Perch catch rates in gill net surveys have been declining for about two decades. It is thought that the decline in Perch abundance is closely related to the decline in Tullibee, which are an important prey fish for Walleye and Northern Pike in Winnie. In more recent history, there were several years of poor Perch recruitment leading up to a record low gill net catch rate in 2022. However, in the past three years there has been good recruitment of young fish and catches have increased since then. Growth has been increasing the past several years and has now reached the point where some are reaching harvestable size two years earlier than average.
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\nNorthern Pike is another popular species amongst Winnibigoshish anglers and spearers. Tributary inlet areas and connected waters provide a great deal of spawning habitat, which results in consistent recruitment of Northern Pike to the fishery. The population is generally characterized as having high abundance and relatively poor to moderate size structure when compared to other large lakes. In 2025 the fall gill net catch rate was low compared to historical catches for Winnibigoshish, but still within the expected range for similar lakes. The population peaked in abundance in 2017 and has stabilized at a lower level the past few years, which is likely one of the biggest factors in the recovery of the Perch population. Pike averaged 22 to 23 inches and ranged from about 16 to 33 inches during the fall gill net survey. An additional targeted survey was completed shortly after ice-out in 2025. Sizes caught during that survey ranged from 8 to 37 inches. Winnibigoshish is part of the north-central zone for Northern Pike regulations that includes a protected slot of 22 to 26 inches. Release of Northern Pike over 26 inches is encouraged to help improve the overall size structure of the population.
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\nTullibee, otherwise known as Cisco, are an important prey fish in lakes where they occur, and at times can be a popular species for anglers to target. The population in Winnibigoshish has fluctuated over time, but has generally been trending down since annual surveys began in 1983. Over the past 15 years there has been a sharp decline in abundance. The gill net catch rate in 2025 was well below average for Winnie. The decline in the population is attributed to several factors. Tullibee feed primarily on zooplankton, which has decreased due to the presence of Zebra Mussels. Tullibee also require cold water and in some years the water temperatures in Winnibigoshish can surpass stressful or even lethal thresholds. The decline in Tullibee has changed the diet of predators such as Walleye and Northern Pike, which now primarily feed on Yellow Perch instead of Tullibees.
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\nOther species that may be of interest to anglers include Bluegill, Black Crappie, Burbot, Largemouth Bass, Rock Bass, and Muskellunge. Panfish and Bass in Winnie are typically low in abundance, with most of the population concentrated in certain areas of the lake where vegetation is abundant. Sunfish species are more commonly targeted in the Cut Foot Sioux chain. The popularity of that fishery and the high-quality size structure of the population led to the addition of a 5 fish bag limit for Sunfish throughout the entire Winnie reservoir. Muskellunge are difficult to sample in Winnie with traditional survey gear, making relatively accurate population estimates nearly impossible. It is generally accepted that this is a low-density population, and it is completely sustained by natural reproduction. Burbot are also difficult to assess with traditional open-water survey nets but appear to be popular with some anglers during the ice fishing season.
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\nInvasive species cause economic or environmental harm, or harm to human health. They are illegal to introduce into or move between state waters and can impact energy flow, food chains, and fish species assemblages. Current known invasive species in Winnibigoshish include Zebra Mussels, Faucet and Mystery Snails, and Starry Stonewort. Rusty Crayfish are found in Cass Lake upstream of Winnie, and one was found in a net immediately upstream of the lake in the Mississippi River in 2025. Crayfish are incidentally caught in gill nets and over the past three years over 1400 have been inspected to search for evidence of the presence of Rusty Crayfish. No Rusty Crayfish have been found in the lake as of 2025, but it is likely that this invasive will be found in Winnie in the near future.
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\nChanges in environmental conditions affect fish habitat and behavior, which likely affect fish sampling and angling success. Movement of any type of equipment that can trap or hold contaminated water, plant fragments or aquatic organisms can be a potential vector of spread if precautions are not taken. To avoid the spread of these unwanted species, ensure that all equipment is thoroughly cleaned and dried before moving to a new body of water. More information is available at https://www.dnr.state.mn.us/invasives/ais/index.html
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Gillnet catch rates for walleye decreased from 7.3 per net in 1997 to 5.6 per net in 1998, and to 3.6 per net in 1999. The 1999 catch rate was less than the mean catch of 4.6 per net observed since 1983. The 1994 and 1995 year classes were considered strong in 1998, however, assessment data for 1999 indicates that the 1994 year class is still strong while the 1995 year class is now considered average. Anecdotal information suggests that high fishing pressure and a corresponding high harvest of the 1994 and 1995 year-classes of walleye was seen during the 1998 and 1999 summer angling seasons. The rapid decline in gill net catch rate with 2 strong year classes present may indicate that walleye were being harvested at a rate that is not sustainable.
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\nIrregular recruitment which occurred between 1985 and 1994 resulted in one average year class (1991) and all others below average or week. This most likely resulted in the majority of harvested walleye during the 1997, 1998, and 1999 fishing seasons being from the 1994 and 1995 year classes. As intense fishing pressure was exerted on the fishery, walleye abundance may have been reduced to a point that approaches levels observed prior to the 1994 and 1995 year classes recruitment to the fishery. Recruitment for the 1996 and 1998 year classes appears to be average while 1997 is poor. The mean length and weight for gill net captured walleye at 14.9 inches and 1.3 pounds in 1999 was similar to 1998 and the long term mean.
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\nThe gill net catch rate for yellow perch of 90.4 per assessment net in 1999 was similar to both 1998 and historic mean catch per net values. The proportion of perch greater than 9 inches at 13.2% in 1999 was identical to 1998, however the number of perch > 9 inches per net decreased from 14.3 per net in 1998 to 11.9 per net in 1999. The 1994 and 1997 year classes of perch appear to be strong with indices of year-class strength of 207 and 181 respectively. The majority of the 1994 year class have reached angler preferred sizes and likely made a large contribution to angler harvest during the 1999-2000 winter season. The 1993 year-class is of average abundance and has attained angler preferred sizes. All other year-classes sampled had below average indices of year-class-strength, however, none would be considered weak.
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\nNorthern pike mean catch per gill net decreased to 7.1 per net in 1999 from 9.1 per net in 1998. Size structures for the northern pike population remained similar to all years sampled since 1983. The mean length and weight for northern pike of 22.9 inches and 3.3 pounds, respectively in 1999 increased slightly from 1998 levels.
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\nStomach contents of northern pike were examined for the sixth consecutive year. Over those six years the population of prey species has varied by year. During this time frame cisco and yellow perch have been the most important components in the northern pike diet. However, cisco continue to be the most common species that northern pike consume. It appears that pike select cisco over other prey species during the warm water period, regardless of the availability of other prey species.
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Walleye were captured at a rate of 6.7 per net, which was higher than typical for Lake Winnibigoshish. Walleye sampled varied from 6.7 to 27.4 inches with a mean length of 15.9 inches and mean weight of 1.6 pounds. The walleye population appeared to be healthy with all age classes sampled between age 1 and 10. Year-class strength was computed for walleye between age 2 and 7. Two weak year classes, three average year classes, and the strong 2001year class were sampled. The 1994 and 1995 year classes were also well represented, and contributed to the above average catch of 19 to 25 inch walleye. Relatively few age-1 walleye were captured by gill net indicating that the 2004 year class will likely be weak. Mean back-calculated growth was similar to the Lake Winnibigoshish average for most ages, attaining 15.7 inches after four growing seasons. The mean total weight of walleye per gill net of 10.9 pounds exceeded the third quartile for Lake Winnibigoshish, and was similar to the Lake-class 26 median.
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\nCold spring and early summer conditions may have caused lower hatch rates of walleye eggs with slower initial growth and higher mortality of walleye fry and fingerlings. Rapid warming in mid June appears to have resulted in good growth for age-o walleye that survived the inhospitable spring conditions.
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\nYellow perch were sampled at a historic low rate of 47.6 per near-shore gill net. Perch sampled in 2005 varied from 4.6 to 12.2 inches with a mean length of 7.4 inches. Catch rates and size structure of sampled perch have changed recently. Catch rates started a slow decline in the late 1990s, but were within historic norms until 2003. Catch rates from 2003 through 2005 were below the first quartile for Lake Winnibigoshish. Although recent catch rates have been low for Lake Winnibigoshish they were well within norms for lakes of this type.
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\nAge classes 2 through 7, 9, and 10 were sampled by gill net. Year class strength was computed for ages 3 through 7. The 1998, 1999, and 2001 year classes were average, while the 2000 and 2002 year classes were considered weak. Catch rates of age-6 through age 10-perch were much lower than that of ages 3 through 5, and were a relatively small component of the total catch. Yellow perch growth was relatively slow through age 2, increased to near average from age 3 to age 10, with perch attaining a mean length of 9.2 inches at age 6.
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\nRelative health of the yellow perch population has been described by the percent of perch longer than 9 inches in the gill net catch. As perch catch rates decreased the proportion of large perch (longer than 9 inches) increased. The proportion of large perch peaked as gill net catch rates fell below the first quartile. In 2005, the proportion of large perch sampled in near-shore gill nets declined for the first time since 1998. Seventeen percent of near-shore gill net sampled perch exceeded 9 inches.
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\nThe microsporidian parasite heterosporis has been documented in Lake Winnibigoshish yellow perch. Of 1,143 perch sampled in 2005 no evidence of heterosporis was observed.
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\nNorthern pike were sampled at a historic high rate of 11.5 per near-shore gill net. Catch rates have increased since 1999 and have exceeded the third quartile in three of the last four years. Pike sampled in near-shore gill nets varied from 12.8 to 32.2 inches with a mean length of 20.9 inches. All age classes between age 1 and 7 were sampled by gill net. Age-2 and age-3 pike were the most abundant age classes sampled.
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\nGill net catch rates of cisco rebounded to average levels for both near-shore and mid-lake nets in 2005. The catch rate of 25.0 per near-shore net was similar to the long-term average. Bony structures were not collected from cisco in 2005 and ages were not determined. Examination of the cisco length frequency indicates that the population was dominated by two year-classes of young fish with few cisco exceeding 12 inches.
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The lake Winnibigoshish assessment is completed annually to track changes in abundance and growth of all game species. The assessment season starts with gill netting in late June. Gill netting is conducted through July to sample game and non-game species age 1 and older. Abundance, growth rates, presence of parasites etc. is determined from this data. Seining is conducted during the month of July. The goal of seining is to sample young game and non-game species (including minnows) and to track growth of age 0 walleye and perch. Trawling is conducted in August to continue tracking growth rates of age-0 walleye and perch. Trawling gives us the first clue to abundance of age-0 walleye and perch for that year. Temperature and dissolved oxygen profiles are taken from June through August and water chemistry analysis is done in August to track changes in the system that may affect the ability of some species to prosper or exist in the lake.
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\nWalleye
\n Gill nets
\nWalleye were sampled at a rate of 5.0 per net, which was average for Lake Winnibigoshish. Walleye sampled varied from 7.1 to 25.2 inches with a mean length of 15.2 inches and mean weight of 1.4 pounds. The walleye population appeared to be healthy with most age classes sampled between age 1 and 12. Year-class strength was computed for walleye between age 2 and 7. Three average year classes (2003, 2004 and 2005), and three strong year classes (2001, 2002, and 2006) were sampled. However, none of the strong year classes were exceptionally strong. Mean back-calculated growth was similar to the Lake Winnibigoshish and statewide average for all ages, attaining 17.9 inches after five growing seasons.
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\n Seine and trawl
\nSlow spring warming and below average summer temperatures appear to have resulted in some of the slowest growth observed since 1983. The shortened growing season resulted in smaller than average age-0 walleye. Slow growth and small size of fingerling walleye usually results in a weak year class.
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\nRelatively few age-0 walleye were sampled by seine in 2008. Seine catch rates have not correlated to ultimate year-class strength for walleye in Lake Winnibigoshish. Growth rate of age-0 walleye has been a better predictor of year-class strength. Mean lengths of age-0 walleye varied from 2.5 inches to 3.2 inches from July 18 to July 31.
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\nMean trawl catch rates for age-0 walleye were average when compared to catch rates observed since 1972. Age-0 walleye growth recorded through the first week of August was slower than mean growth in all but three years since 1983, reaching a mean length of 3.8 inches on August 8. Slow growth of age 0 walleye nearly always results in a weak year class.
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\nYellow perch
\n Gill nets
\n Yellow perch (perch) are an important species for anglers and as a prey item for walleye and northern pike. The catch of perch in assessment nets reached an all-time low in 2005 largely because of poor year classes in 2000 and 2002. A strong year class was produced in 2003. As this year class has matured, the catch of perch has increased.
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\nPerch were captured at a rate of 68.4 per net in 2008. This catch rate was slightly lower than average for lake Winnibigoshish. Perch sampled in 2008 varied from 4.8 to 11.2 inches with a mean length of 7.3 inches and mean weight of 0.19 pounds. Age classes 2 through 8 were sampled by gill net. An index of year-class strength was computed for ages 3 through 7. The 2001 and 2004 year classes were average, the 2002 year class was weak, and the 2003 and 2005 year classes were strong. As the 2003 and 2005 year classes continue to mature, abundance and size structure should continue to improve. The catch was biased towards younger perch with 69% of the catch made up of age 2 through age 4 fish. Yellow perch growth was relatively slow through age 2, then increased to average from age 3 to age 10. Perch grew to a mean length of 9.3 inches at age 6.
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\nRelative health of the yellow perch population has been described by the percent of perch longer than 9 inches in the gill net catch. As perch catch rates decreased during the mid 1990's, the proportion of large perch (longer than 9 inches) increased. The proportion of large perch peaked as gill net catch rates fell below the first quartile. In 2005, the proportion of large perch sampled in gill nets declined for the first time since 1998. The proportion of perch longer than nine inches was stable in 2005 and 2006 at 16.9 percent, then declined to 9.8% as young perch were recruited to the fishery in 2007. Although many small fish remain in the population, the strong 2003 year class has grown large enough to affect the proportion of perch longer than 9 inches. The proportion of perch longer than 9 inches increased to 12.7 percent in 2008.
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\nThe microsporidian parasite heterosporis has been documented in Lake Winnibigoshish yellow perch. No evidence of heterosporis was observed 2008.
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\n Seine and trawl
\n Catch rates of age-0 yellow perch were near average for both seine and trawl. No correlation is evident between catch rates of age-0 yellow perch and ultimate year-class strength.
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\nNorthern pike
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\nGill net catch rates of northern pike (pike) increased from 1999 through 2005 and exceeded the third quartile in four of six years from 2002 through 2007. Northern pike catch rates declined to 8.2 per gill net in 2008. Pike sampled varied from 14.8 to 29.7 inches with a mean length of 21.4 inches. All age classes between age 1 and 6, and age 8 were sampled by gill net. Age two, three, and four pike were most abundant, and pike exhibited growth rates that were similar to state wide averages through all ages.
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\nNo pike longer than 30 inches were sampled in this assessment. This does not mean that they are not present in the system, but it is an indication that their abundance has decreased. The decrease in size structure can be attributed to several causes. Cisco abundance has declined (cisco are preferred prey that provides more energy than other similar size prey), this may lead to slower growth rates. Conditions for reproduction and survival have been good. This may lead to increased density and more competition for food, which also causes decreased growth rates. Angler harvest can have a large impact on the size structure of a pike population. When anglers harvest the largest fish they catch, they can cause a slow decrease in the size structure of the fish they are harvesting. This occurs because fish are removed faster than they can be replaced. Considering the current size structure anglers should release all pike longer than 25 inches. This should result in pike growing closer to their potential and increase the chance to catch 8 to 10 pound fish.
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\nCisco
\nGill net catch rates decreased to the third lowest level observed since 1983. The catch rate of 10.5 per net was well below the first quartile. The cisco population has been lower than average for 8 of the last 10 years. This is likely due to increasing water temperatures affecting reproduction and survival. Cisco sampled in 2008 varied from 5.4 to 15.4 inches with a mean length of 8.2 inches.
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\nWater Quality
\nWater samples were taken on August 5, 2008. Physical and chemical parameters measured were within the range observed since 1983. Six temperature and dissolved oxygen profiles were taken between June 23 and August 8, 2008. Dissolved oxygen stratification was evident from July 21, through August 5. No evidence of thermal stratification was found in 2008. Thermal and dissolved oxygen stratification may result during periods of high air temperatures and low wind. When wind speeds increase to moderate levels (15 mph) the entire water column appears to mix.
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Walleye were sampled at a rate of 6.4 per net, which was higher than typical for Lake Winnibigoshish. Walleye sampled varied from 7.3 to 25.1 inches with a mean length of 14.3 inches and mean weight of 1.2 pounds. The walleye population appeared to be healthy with all age classes sampled between age 1 and 10. Year-class strength was computed for walleye between age 2 and 7. Two weak year classes (1999 and 2000), two average year classes (2003 and 2004), and two strong year class (2001 and 2002) were sampled. Walleye catch rates were higher than average for most length groups in 2006. The high catch of 7, 8, and 9 inch walleye (age-one) may indicate that the 2005 year class will be strong. Mean back-calculated growth was similar to the Lake Winnibigoshish average for most ages, attaining 17.9 inches after five growing seasons.
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\nRapid spring warming and above average summer temperatures appear to have resulted in fast growth and large size of age-0 walleye. Fast growth and large size of fingerling walleye typically results in a strong year class.
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\nRelatively few age-0 walleye were sampled by seine in 2006. Seine catch rates have not correlated to ultimate year-class strength for Lake Winnibigoshish. Growth rates of age-1 walleye have been a better predictor of year-class strength. Growth of seine captured age-1 walleye was fast compared to historic norms. Mean lengths of age-0 walleye varied from 3.2 inches to 4.6 inches from July 4 to July 25.
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\nTrawling was done during the first two weeks of August. Mean trawl catch rates for age-0, 1, and 2 walleye were similar to historic means. Age-0 walleye growth recorded through the first two weeks of August was fast when compared with annual assessments since 1983 with a mean length of 5.1 inches. Average catch rates combined with fast growth typically results in above average to strong year-class strength.
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\nYellow perch were captured at a rate of 56.6 per net, which was lower than typical for Lake Winnibigoshish. Perch sampled in 2006 varied from 5.0 to 11.8 inches with a mean length of 7.3 inches. Catch rates and size structure of sampled perch have changed recently. Catch rates started a slow decline in the late 1990s, but were within historic norms until 2003. Catch rates from 2003 through 2006 were below the first quartile for Lake Winnibigoshish. Although recent catch rates have been low, they were well within norms when compared to similar lakes.
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\nAge classes 2 through 9 were sampled by gill net. Year-class strength was computed for ages 3 through 8. The 1998, 1999, and 2001year classes were average, the 2000 and 2002 year classes were weak, and the 2003 year class was strong. Catch rates of age-6 through age-9 perch were much lower than that of ages 3 through 5, and were a relatively small component of the total catch. Yellow perch growth was relatively slow through age 2, increased to near average from age 3 to age 10, with perch attaining a mean length of 9.5 inches at age 6.
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\nRelative health of the yellow perch population has been described by the percent of perch longer than 9 inches in the gill net catch. As perch catch rates decreased the proportion of perch longer than 9 inches increased. The proportion of large perch peaked as gill net catch rates fell below the first quartile. In 2005, the proportion of large perch sampled in near-shore gill nets declined for the first time since 1998. The proportion of perch longer than nine inches was stable in 2005 and 2006 at 16.9 percent.
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\nThe microsporidian parasite heterosporis has been documented in Lake Winnibigoshish yellow perch. Of 140 of perch sampled in 2006 no evidence of heterosporis was observed.
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\nCatch rates of northern pike increased from 1999 through 2005 and exceeded the third quartile in three of five years since 2002. Northern pike catch rates decreased to a near average rate of 8.6 per near-shore gill net in 2006. Pike sampled in near-shore gill nets varied from 15.2 to 36.5 inches with a mean length of 21.7 inches. All age classes between age 1 and 7 were sampled by gill net. Age-2 and age-3 pike were the most abundant age classes sampled.
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\nThe catch rate of 19.3 cisco per near-shore net was near the first quartile. Cisco sampled in near-shore gill nets varied from 6.9 to 17.1 inches with a mean length of 9.5 inches. Bony structures were not collected from cisco in 2006 and ages were not determined. Examination of the length frequency indicates that three year classes may have been sampled by gill net.
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\nWater samples were taken on August 8, 2006. Physical and chemical parameters measured were within the range observed since 1983. Seven temperature and dissolved oxygen profiles were taken between June 28 and August 5, 2006. Dissolved oxygen stratification was evident at various depths on June 28, July 24, and July 27. No evidence of thermal stratification was found in 2006. Thermal and dissolved oxygen stratification may result during periods of high air temperatures and low wind. When wind speeds increase to moderate levels (15 mph) the entire water column appears to mix.
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This is the third consecutive year that a fall special assessment was conducted on Lake Winnibigoshish. These assessments were conducted with the ultimate goal of converting standard gill net assessments from the traditional summer period to a fall time frame. Fall assessments are conducted on all large lakes except Lake Winnibigoshish. Those fall assessments have proven more effective in the development of, and use of tools that evaluate fish populations in the large lakes. It is necessary to conduct paired assessments (summer and fall) for several years so that comparisons can be made between the two sampling periods. This will allow the ultimate conversion of summer assessments completed from 1983 to 2006 to their fall equivalent, and allow more sophisticated analysis of Lake Winnibigoshish fish populations.
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\nGill net catch rates varied between summer and fall assessments in 2009. Walleye catch rates were 4.9 per net during summer and 15.2 per net in the fall. Yellow perch catch rates were 52.9 per net during summer and 32.7 per net in the fall. Northern pike catch rates were 10.0 per net during summer and 3.3 per net in the fall. Cisco catch rates were 10.5 per net during summer and 33.0 per net in the fall.
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Abundance indices for the walleye, northern pike, yellow perch, and cisco were within the normal range observed since 1983. Walleye abundance as measured by gill net catch rates decreased in 2001. However, the Lake Winnibigoshish walleye population appears healthy with two strong (1994, 1995), three average (1996, 1998, 1999), and two weak (1997, 2000), year classes. One reason for the decline in gill net catch rate may be the low abundance of age one (2000 year class) walleye. Age one walleye are typically captured at a rate of 0.5 to 1.0 per gill net. Only two individuals of the 2000 year class were captured in 2001 which represents 0.08 per gill net. Also, the strong 1994 and 1995 year classes are of high abundance, however, they are reaching sizes that the experimental gill net is less effective at catching. This may result in lower gill net catch rates.
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\nThe 17 inch to 26 inch protected slot regulation implemented in 2000 may be contributing to increased abundance of larger walleye. The proportion of walleye longer than 17 inches sampled by gill net increased from 29% in 1999 to 45% in 2001. An estimated 24,000, and 49,000 walleye were released due to the regulation in 2000 and 2001, respectively. However, the strong 1994 and 1995 year classes would likely have caused increased abundance of large walleye without the regulation. Further data collection and analysis is required to determine any relationship between the regulation, year-class strength and changing abundance of large walleye in Lake Winnibigoshish. The mean length and weight of walleye sampled in 2001 increased to 16.6 inches and 1.7 pounds.
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\nYellow perch abundance was similar to the mean catch rate observed since 1983. Perch captured ranged from 4.8 to 11.7 inches with a mean length of 7.8 inches and mean weight of 0.25 pounds. The proportion of perch longer than 9 inches of 20.1% in 2001 was similar to 20.2% observed in 2000 (historic range = 5.5 to 52.4, Mean = 23.9). Yellow perch captured in mid-lake gill net sets had a mean length and weight of 8.1 inches and 0.29 pounds respectively. The proportion of perch longer than 9 inches of 27% for mid-lake sets was also higher than the 24 historic sets.
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\nNorthern pike abundance as measured by gill net catch of 8.0 per net in 2001 was similar to 8.2 per net observed in 2000. Mean length and weight values for northern pike decreased for the second consecutive year to 22.2 inches and 2.5 pounds, respectively in 2001. The observed decrease in mean length and weight was driven by increasing abundance of young individuals. Environmental conditions were ideal for northern pike reproduction and recruitment during the springs of 1998 and 1999, which resulted in increased abundance of small pike.
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\nStomach contents were examined for all gill net captured northern pike for the eighth consecutive year. Over those eight years the population of prey species has varied by year. During this time frame, cisco and yellow perch have been the most important components in the northern pike diet. Cisco have been the most common species northern pike consume. However, the contribution of cisco in northern pike stomachs was secondary to yellow perch in 2001. Reasons for this change are unknown.
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\nCatch rates for cisco increased to near average levels in 2001. However, the gill net catch of 27 per net remains somewhat less than the historic mean of 31.1 observed since 1983. Cisco abundance indices have varied from 13.2 to 71.1 per lift since 1983. The mean length and weight of gill net captured cisco was 9.1 inches and 0.3 pounds, in 2001.
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Assessment of Lake Winnibigoshish is completed annually to track changes in abundance and growth of fish species, and physical and chemical characteristics of the lake. The assessment season typically starts with seining and gill netting in late June to early July. The goal of seining is to sample young game and non game species (including minnows) and to track growth of age 0 walleye and yellow perch (perch). Gill netting is conducted from late June through July to sample game and non game species age 1 and older. Abundance, growth rates, maturity, presence of parasites etc. is determined from this data. Trawling is conducted in August to continue tracking growth rates of age 0 walleye and perch. Trawling gives us the first clue to abundance of age 0 walleye and perch for that year. Temperature and dissolved oxygen profiles are taken from June through August and water chemistry analysis is done in August to track changes in the system that may affect the ability of some species to prosper or exist in the lake. Gill net sampling was modified in 2011 due to a state government shutdown during the first three weeks of July. The shutdown also resulted in no seining, no water quality measurements, and reduced temperature and dissolved oxygen testing. The change in schedule may affect catch rates and may complicate comparison of 2011 data with other years.
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\n Walleye
\nGill nets
\nWalleye were sampled at a rate of 7 per net, which was the third highest for Lake Winnibigoshish. Walleye sampled varied from 8.0 to 26.0 inches with a mean length of 16.0 inches and mean weight of 1.5 pounds. The walleye population appeared to be healthy with all age classes sampled between age 1 and 14. Year class strength was computed for walleye between age 2 and 8. Three average year classes (2004, 2005, and 2009), two strong year classes (2006 and 2007), and one weak year class (2008) were sampled. The last weak year class for Lake Winnibigoshish was in 2000. Mean back calculated growth was similar to the Lake Winnibigoshish and statewide average for all ages, attaining 17.5 inches after five growing seasons.
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\nTrawl
\nThe mean trawl catch rate of 42.5 per hour was lower than average, however, low catch rates may not result in low abundance of that year class. The trawl catch rate of 20.5 young of the year walleye in 2005 resulted in an above average year class. An important factor in year-class strength is growth of those fish during their first year. Young of the year walleye growth was above average through the first week of August in 2011, reaching a mean length of 4.5 inches. Fast growth of age 0 walleye usually results in a strong year class.
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\n Yellow perch
\nGill nets
\nYellow perch (perch) are an important species for both anglers and as a prey item for predators. The catch of perch in assessment nets reached an all-time low in 2005 largely due to poor year classes in 2000 and 2002. A strong 2003 year class moved through the system resulting in higher assessment catch rates in 2007. Gill net catch rates have been declining since then.
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\nPerch were captured at a rate of 43.6 per net in 2011, which was a new historic low for Lake Winnibigoshish. Perch sampled varied from 5.1 to 11.7 inches with a mean length of 7.4 inches and mean weight of 0.2 pounds. Age classes 2 through 8 and 10 were sampled by gill net. An index of year class strength was computed for ages 3 through 7. The 2004, 2005 and 2007 year classes were average, and the 2006 and 2008 year classes were weak. The previously strong 2003 year class was not well represented in the catch. The catch of perch in 2011 was primarily represented by younger individuals with 95% of the catch made up of age 3 through age 5 fish. Growth was relatively slow through age 2, then increased to average from age 3 to age 9. Perch grew to an average length of 9 inches at age 6.
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\nRelative health of the perch population can be described by the percent of perch longer than nine inches in the gill net catch. The catch of large perch declined to 6% in the early 1990's driven by high angler harvest. Changes in lake Winnibigoshish and other lakes prompted a statewide change in the perch bag limit to 20 daily and 40 in possession in 2001. Several strong year classes were produced during the same time period and the assessment catch of perch longer than nine inches increased to 30% in 2004. In 2005, the proportion of large perch sampled in near-shore gill nets declined for the first time since 1998. The proportion of perch longer than nine inches was about 17% in 2005 and 2006, then declined to 9.8% in 2007 as young perch were recruited to the fishery. Although many small fish remain in the population, size structure has slowly improved. Nearly 14 % of the perch sampled in 2011 were longer than nine inches.
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\nThe microsporidian parasite heterosporis has been documented in Lake Winnibigoshish yellow perch. No evidence of heterosporis was observed in 2011.
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\nTrawl
\nThe catch rate for age 0 perch of 10,720 per hour of trawling was average. Growth of age 0 perch was slower than average with a mean length of 1.7 inches in mid August. No correlation is evident between trawl catch rates or growth of age 0 perch and year class strength.
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\n Northern pike
\nCatch rates of northern pike increased from 1999 through 2005 and exceeded the third quartile in five years between 2001 and 2009. The northern pike catch rate decreased to 7.3 per gill net in 2010 from 10.0 in 2009 then rose to 8.5 in 2011. Pike sampled in 2011 varied from 12.7 to 35.4 inches with a mean length of 21.7 inches. All age classes from 1 to 8 were sampled by gill net. The 2008 and 2009 year classes were most abundant and contributed 61% of the catch. Growth rates were similar to the statewide mean through all ages.
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\nSize structure of the pike population has improved for the last two years. That trend has now extended to the largest fish in the system. More pike longer that 30 inches were sampled than in any assessment since 2000. Increased size structure can be attributed to several causes. Cisco abundance has increased (cisco are preferred prey that provides more energy than other similar size prey), which may lead to faster growth rates. Reduced abundance is also beneficial to the pike population since increased pike density can cause more competition for food and space which may lead to decrease growth.
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\n Cisco
\nCisco are a primary prey for muskellunge, pike and walleye. Growth rates of these species can be reduced if cisco are not present in the system. The gill net catch of 16.4 cisco per net in 2011 decreased from the catch of 21.7 per net in 2010 but indicates a healthy population. Cisco catch rates were lower than average for 5 of the last 10 years. This is likely due to warmer than average summer and fall water temperatures that may affect reproduction and cause occasional summer kills. Cisco sampled in 2011 varied from 7.1 to 17.1 inches with a mean length of 10.5 inches.
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\n Water Quality
\nTwo temperature and dissolved oxygen profiles were taken on June 28 and July 21, 2011. Dissolved oxygen stratification was evident only on July 21. No evidence of thermal stratification was found in 2011. Thermal and dissolved oxygen stratification may result during periods of high air temperatures and low wind. When wind speeds increase to moderate levels (15 mph) the entire water column appears to mix.
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\n Invasive Aquatic Species
\nSpecies that have been introduced through human activities to a location where they don't naturally occur are termed \"invasive\". Some invasive species are not necessarily harmful, but others cause ecological or economic problems. Several invasive species have been introduced to Lake Winnibigoshish. Three species of snail: banded mystery, Chinese mystery, and faucet have become established since 2000. Both species of mystery snail appear to have no negative effect at this time. The faucet snail carries a trematode parasite that can kill several species of ducks if ingested. Thousands of ducks were killed by these parasites during the falls of 2007 and 2008. Emerald shiners (often used as bait) are not native and were first sampled in 2005. Each of these invasive species were likely introduced through human activities.
Lake Winnibigoshish (Winnie) has been sampled annually since 1983. Surveys have primarily included seining, summer gill netting, water quality indices, and trawling. Annual zooplankton sampling was included in standard sampling beginning in 2012, while night electrofishing for juvenile Walleye was started in 2018.
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\nChanging environmental conditions resulting from the introduction of invasive species have caused changes in gamefish habitat and habits. Walleye appear to be using deeper water habitat more frequently, which likely affects near-shore gill net catchability. Methods of data collection have been modified due to these changing conditions. The 2018 assessment year saw standard gill netting changed from summer sampling to fall, and the location and number of nets set was changed to better sample the entire basin. Thirty two gill nets were set in proportion to 3 broad habitat types, which included near-shore, mid-lake, and open-basin (more than 30 feet deep) during the last two weeks of September.
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\nFall gill nets have been set annually since 2007, along with summer nets. The fall data set is now long enough to be viewed independently, and is likely a better sampling plan than summer nets. Catch rates of fall nets should be less affected by changing fish movements since water depths were sampled in proportion to their availability. Fall netting is also more desirable due to the ability to better determine sexual maturity of fish. Other large lakes are sampled in the fall, and tools that have been developed to evaluate Walleye in those lakes can now be used more effectively on Winnie.
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\nZooplankton Sampling was initiated in 2012 and initially sampled 4 stations on Winnie. Station 6 was added in 2013 due to its proximity to 3 resorts and the amount of traffic in that area. Six samples were taken on seven dates for a total of 42 samples in 2018. These samples were collected to continue baseline planktonic species composition and biomass.
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\nTrawling had been a good method to track abundance and growth rates of age-0 Walleye. As water cleared due to the zebra mussel expansion, sampling fish in shallow water became more difficult. Clearing water also allowed filamentous algae to flourish. Abundant algae quickly clogged the trawl and was difficult to clean, potentially reducing the effectiveness of the trawl. Due to this, electrofishing was evaluated as an alternative sampling method for age-0 Walleye. Electrofishing proved successful in replacing trawling, and stations were set in 2018.
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\nFall assessment catch rates should not be used to compare with Winnie summer data, and be used cautiously when comparing Winnie with other lakes.
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\nWalleye:
\nThe gill net catch of 4.1 Walleye per net in 2018 declined from 5.8 per net in 2017. Gill net catch rates have shown a declining trend since fall netting began in 2007. The apparent trend is likely due to three consecutive strong year classes produced between 2005 and 2007 that affected gill net catch during the first years of fall sampling. Consecutive strong year classes are rarely seen. Average year classes were produced between 2008 and 2013. Reduced recruitment, and resulting low year class strength since 2013 has contributed to lower catch rates in recent years.
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\nReduced gill net catch in 2018 was also likely due to difficult environmental conditions during the fall assessment. High winds with frequent changes in direction thoroughly mixed the water column and distributed filamentous algae throughout the system. Filamentous Algae coated the nets and increased visibility of those nets to fish. Gill net catches of all species decreased in 2018 indicating that something systematic may have affected catch rates in the 2018 assessment.
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\nSampled Walleye length varied from 7.2 inches to 23.7 inches, although the majority of sampled fish were longer than 15 inches. All ages of Walleye between 0 and 13 were represented. An index of year class strength was computed for the 2011 through 2016 year classes. The 2010, 2011, and 2015 year classes were average, the 2012, 2014, and 2016 year classes were weak, and the 2013 year class was strong. Recent growth rates have exceeded the long-term lake and statewide averages, likely due to adequate prey densities and lower Walleye densities.
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\nAge and length at maturity are commonly used in Minnesota's large lake monitoring program as indicators regarding the health of Walleye populations. These biological performance indicators (BPI) are typically related to mortality rates of the Walleye population. The importance of BPI's increase when gill net catch rates are thought to be biased, as in the 2018 Winnie assessment. Age and length of maturity for Walleye have changed on Winnie as recruitment and growth rates changed. A 17 to 26 inch protected slot limit was in place between 2000 and 2014. During this time, age and length at maturity increased from a low of 14.6 inches and 3.2 years, to 18.0 inches and 4.7 years. This indicated that the Walleye population was recovering from a period of poor recruitment and relatively high angler induced mortality. By 2008, the Walleye population had fully recovered and began to exceed expectations, indicating that surplus spawning stock was available. Due to this, the slot limit was reduced to 18 to 23 inches in 2015. Age at maturity has remained near optimal, however, length at maturity has continued to increase since that time. Walleye sampled in 2018 matured at a longer length than expected for a balanced Walleye population. This may be due to high prey abundance and reduced competition resulting from reduced recruitment of Walleye.
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\nSpawning stock biomass is another useful indicator of a healthy Walleye population. Spawning stock biomass (pounds of mature females) increased from 0.5 pounds per acre in 2002 to 2.0 pounds per acre in 2008. This also indicated that the Walleye population had likely recovered fully from the period of high harvest and reduced recruitment between the mid-1980s and mid-1990s. Spawning stock biomass continued to increase through 2012, and has been fluctuating near the top of the preferred level of 2.0 pounds per acre since then. Computation of spawning stock is tied to gill net catch. The decrease in spawning stock observed in 2018 is likely due to decreased gill net catch rates influenced by nets fouled with filamentous algae.
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\nRecent low recruitment of Walleye led to an investigation of water level manipulation and its potential impact on Walleye year class strength during the winter of 2017 (Winnie is a reservoir with an outlet dam controlled by the Army Corps of Engineers). Comparison of these two factors revealed a potential limiting factor in recruitment. Investigation of available ice out date and water level data indicates that water levels higher than an elevation of 1,298 and rising at ice out typically resulted in stronger year classes. The DNR has worked with the US Army Corps of Engineers in an effort to create more favorable spawning conditions starting in the spring of 2018.
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\nReduced recruitment of Walleye has been typical in recent years, but 2018 was not a typical year. Early indicators of a good Walleye year class were observed in shoreline seining. Fall electrofishing was conducted in September, and validated seine sampling with high catch rates. Fall sampled age-0 Walleye varied from 4.8 to 7.3 inches long, with an average length of 6.2 inches during the first week of September. High catch rates may be in part due to water level manipulation and stocking, however, environmental conditions associated with a long winter and delayed ice out may have been the driving force.
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\nYellow Perch:
\nYellow Perch (perch) are an important species to anglers and as a prey item for predators. Perch catch rates have generally declined since 2001, but have remained at or above average when compared to lake class 26 lakes (the largest lakes in Minnesota). Summer gill net catch rates in all assessments prior to 2003 were high, while summer gill net catch rates were generally lower than average since 2003. The perch population will be discussed as it relates to the fall assessment.
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\nPerch catch rates varied from 17.3 to 46.9 per net between 2007 and 2017. The catch rate of 20.2 per net in 2018 was lower than the Winnie average, but above the average compared to similar lakes. Perch varied from 5.1 to 12.2 inches in 2018 with an average length of 7.4 inches and weight of 0.2 pounds. Age classes 2 through 8 were sampled by gill nets in 2018. The catch was primarily represented by younger individuals, with nearly 93% of the catch made up of age 2 through 5 fish. Mortality of perch increased at age 8 and few individuals live past age 10. As is typical for Lake Winnibigoshish perch, growth was relatively slow through age 2, then increased to average from age 3 to age 8. Perch grew to an average length of 9.4 inches at age 6.
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\nAn index of year class strength was computed for the 2008 through 2014 year classes. The 2012, and 2013 year classes were strong, the 2014 year class was average, and all other year classes were weak. The proportion of perch longer than 9 inches varied between 8 and 20 percent between 2007 and 2018, with an average of 16 percent. The proportion of perch longer than 9 inches was similar to the long term average of 16%.
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\nHeterosporis is a parasite that causes fish flesh to look cloudy, and has been documented in Winnie perch. No evidence of heterosporis was observed in perch during the 2018 population assessment, although anglers report the presence of heterosporis in a few perch each year.
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\nNorthern Pike:
\nNorthern Pike (pike) were sampled at a rate of 4.8 per gill net in 2018, which was a relatively large decline from 6.4 per net in 2017. The reduced catch rate followed an increasing trend since 2010. This decline, combined with reduced catch rates for other species, supports the possibility that gill net catch rates in 2018 don't accurately describe changes to fish populations. Fouling of the nets by filamentous algae may have affected catch rates of all species sampled in gill nets. The increasing trend of pike (as indicated by gill net catch rates up to 2017), coupled with decreasing catch rates of perch, may indicate that pike biomass is higher than optimal. This is further supported by decreases in average length of those pike. Smaller pike need to consume more prey per pound of weight than larger pike. Increased predation due to more small pike can cause reductions in prey species. Perch are a favored prey species of pike. Pike length varied from 15.4 to 33.9 inches with an average length of 22.0 inches. Pike age structure varied similarly to summer assessments with ages one through nine represented. As with most Lake Winnibigoshish assessments, the majority of pike sampled were from the age two, three, and four fish.
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\nNew pike regulations were established in 2018. Due to differences in pike biology, the state was divided into three zones, and three different regulations were implemented in those zones. Winnie lies within the North Central zone, where anglers have a 10 fish bag limit with no fish allowed between 22 and 26 inches and only two longer than 26 inches. Spearing regulations vary slightly from angling regulations, and one pike is allowed within the protected slot. This regulation should improve the average length, and number of medium sized pike in Winnie.
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\nCisco:
\nThe Cisco gill net catch rate remained near the historic low level at 2.1 per gill net. The gill net catch of Cisco has been at or below average since 2013. Low catch rates of Cisco were expected in 2013 due to a summer kill during the summer of 2012. Higher recruitment is typically seen after a summer kill, however, recruitment has not increased since the 2012 summer kill. Cisco length varied from 7.2 to 15.4 inches with an average length of 12.7 inches. The majority of Cisco were longer than 12 inches indicating that the population is mature, and recruitment is low. The continued low catches since 2013 and reduced catches of young small Cisco indicate a population that may be stressed.
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\nWater Quality:
\nThree temperature and dissolved oxygen profiles were taken between August 7 and September 10, 2018. No evidence of thermal stratification was found in 2018. Dissolved oxygen stratification was evident during August 7 and August 20 sampling. Dissolved oxygen stratification typically occurs during periods of high air temperatures and low wind. When wind speeds increase to moderate levels (15 mph), the entire water column appears to mix.
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\nWater chemistry measurements have been recorded for most years since 1983. Water clarity sampling (Secchi Disk) was accomplished on 10 dates between May 18 and September 10, 2018. Water clarity during May and Early June was lower than observed in recent years. Water clarity is usually high early in the open water period. Reasons for the change in water clarity are unknown, however, it would be logical to assume that the zebra mussel population was reduced which allowed higher density of phytoplankton. Water clarity increased from mid-June through most of July indicating that the zebra mussel population may have recovered.
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\nTotal phosphorous concentration can affect phytoplankton abundance, but recent increases in water clarity do not appear to be related to changes in total phosphorous concentration as phosphorous continues to remain within historic norms. Attaining and maintaining 70 degree or higher surface temperatures appears to allow large phytoplankton to attain populations sufficient to decrease water clarity.
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\nZooplankton:
\nZooplankton sampling has been accomplished since 2012 to determine a baseline of zooplankton density. Two zebra mussel veligers, as well as high density of zooplankters were captured during the initial year of sampling. As zebra mussel colonized the lake, zooplankton density decreased, but maintained a relatively high level. Zooplankton density in 2018 was similar to 2017, and density of small cladocerans more than doubled from density observed in 2017.
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\nInvasive Aquatic Species:
\nSeveral species have been introduced into Winnie. Three species of snail: Banded Mystery, Chinese Mystery, and Faucet have become established since 2000. Both species of mystery snail appear to have no negative effect at this time. The Faucet Snail carries a trematode parasite that can kill several species of ducks if ingested. Thousands of ducks were killed by these parasites during the falls of 2007 and 2008. The Faucet Snail is a filter feeder and may be responsible for clearing water prior to the introduction of Zebra Mussel.
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\nJuvenile Zebra Mussel (veliger) were discovered while sampling zooplankton during the summer of 2012. No zebra mussel veliger were found while sampling for zooplankton in 2013. Zebra Mussel veliger have been sampled each year since 2013. Near shore areas of hard substrate were inspected for adult Zebra Mussel each year since 2012, and divers inspected likely offshore areas from 2014 to 2016. No adults were discovered until 2016. Adults were found on near shore driftwood in the early summer, then found by divers on mid lake rock structure during August. Zebra mussel appear to have spread to nearly every hard or firm structure by the summer of 2017. Zebra Mussel veliger counts have been increasing, and were higher in 2017 than have been observed in any Minnesota samples to this point. Veliger density decreased in 2018 supporting the theory that the adult zebra mussel population had decreased. Sampling for veliger will continue and the spread of adults will continue to be documented.
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\nStarry Stonewort (an algae) was discovered in Cass Lake during the summer of 2016. This discovery upstream of Winnie prompted an investigation on Winnie. Starry Stonewort was discovered along the south and west shores of the lake in 2016, and appears to have been established for several years. Starry Stonewort continued to spread in 2017 and 2018, and was reported along the east shore of Winnie near Birches public access.
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\nEmerald Shiners (often used as bait) are not native to Winnie, were first sampled in 2005, and have been sampled each year since. Each of these invasive or non-native species were likely introduced through human activities.
\nRusty Crayfish are present in Cass Lake, and curly leaf pondweed is present in Dixon Lake. Both of these lakes are connected to and upstream of Winnie. Introduction to Winnie in the near future is likely.
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\nMovement of any type of equipment (boats, boat trailers, boat lifts, docks, personal watercraft, bait containers, etc.) between lakes may transfer invasive species if precautions are not taken. To avoid being an accomplice to the spread of these unwanted species, people should ensure that all equipment is thoroughly cleaned and dried before moving it to a new body of water. More information regarding invasive species is available at www.dnr.state.mn.us/invasives/index.html.
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Lake Winnibigoshish is part of the Mississippi River headwaters reservoir system, and is located 15 miles northwest of Deer River, Minnesota. The lake is a large, shallow, wind-swept reservoir with a sandy shoreline and gently sloping shoal areas. Winnibigoshish has a surface area of 58,544 acres, mean depth of 15.1 feet, littoral area of 20,490 acres (35%), and a maximum depth of 66 feet. Water clarity has dramatically increased following the introduction of Zebra Mussels in 2012, yet clarity continues to vary seasonally.
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\nLake Winnibigoshish has been managed as part of the Minnesota Department of Natural Resources (DNR) large lake program since 1983. Management activities include special fishing regulations, fish stocking, occasional creel surveys, and annual fish surveys. Annual, fall gill netting has been conducted since 2007 using 32 nets. Fall electrofishing has also been conducted annually, since 2018, to evaluate juvenile Walleye production.
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\nA large, annual Walleye spawning operation is conducted at Little Cut Foot Sioux Lake, which is a large connected flowage. The operational plan includes 10% of the egg take put back as fry. The relative contribution from these stockings is difficult to interpret due to the lack of non-stocked years. Walleye harvest has been regulated with a special regulation since 2000. The regulation was modified in 2015 to an 18 to 23 inch protected slot length (PSL) with one over in possession to allow some additional harvest of larger fish.
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\nWinnibigoshish is considered a premier Walleye lake with substantial effort directed towards the management of the species. Fall gill net catches have been variable. Variability in Walleye catches are often associated with fluctuations in recruitment, measured as year-class strength. Year-class strength is a product of natural reproduction and its variability is common on Walleye lakes. Strong recruitment in 2018, and most likely 2019, influenced recent fall catches. A high proportion of the 2021 Walleye catch was age 3 or younger. This suggests favorable angling opportunities for the next few years as these fish grow to a size anglers desire.
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\nWinnibigoshish is known to maintain a quality size distribution of Walleye. However, sporadic recruitment with longer gaps between strong year classes has limited harvest at times. Walleye averaged almost 14 inches in 2021 with fish up to 26 inches sampled, similar to 2020. Walleye within the 18-23 inch protected slot comprised 8% of the sample. The moderate average size observed in recent surveys is a product of above average recruitment combined with a lack of larger/older individuals. The decreased number of larger/older individuals was not unexpected. Multiple consecutive below average year classes limited the number of fish recruiting to larger sizes. Also, reducing the PSL from 17-26 to 18-23 inches in 2015 potentially (by design) allowed increased angler harvest of larger fish previously protected by the more conservative regulation. The proportion of slot length fish was over 70% in 2017 and 2018, indicating few harvestable size fish were available at that time. Conversely, the 2021 survey indicates favorable harvest opportunities now and for the future.
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\nWalleye age analysis identified fish from age 0 to 14 in the sample, and sex and maturity determination indicated a relatively even distribution between males and females, both similar to past surveys. Other population exploitation indicators like female length and age at 50% maturity were within the expected range, similar to past surveys. Half the females were mature at 17.5 inches and 3.1 years in 2021. The female fall spawning stock biomass (SSB) estimate was 0.6 lbs/acre, down from 1.7 lbs./acre in 2020. The decrease in SSB was not unexpected due to many factors. Additionally, it is unclear what the optimal SSB range is for Winnibigoshish due to the nature of estimating the contribution to recruitment and year class strength from the annual put-back fry stocking associated with the Cut Foot Sioux spawning operation. Walleye growth rates have been favorable on Winnibigoshish, typically exceeding statewide averages. Male and female growth rates diverge between ages 3 and 4. Male Walleye averaged 16.5 inches while females averaged 17.2 inches by age 4 in 2021.
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\nWinnibigoshish is a destination Yellow Perch fishery with a history of producing large fish. Perch over 11 inches are regularly sampled. Perch longer than 8.0 inches are considered quality and greater than 50% of this size perch are harvested by summer and winter anglers. The catch for 8.0 inch and longer perch has averaged 8.2/net and the proportion has averaged 34% since 2007. Yellow Perch exceeding 8.0 inches were sampled at a rate of 4.4/net and comprised 53% of the sample in 2021. This suggests that roughly half of perch caught while angling will be of a size anglers prefer to harvest.
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\nYellow Perch are an important prey species besides being popular with anglers. The 2021 catch was the lowest observed in fall surveys. The catch was near the typical range for lakes with similar habitats, but below average for Winnie. The fall catches have been variable. Inconsistency in fall catches can be attributed to variability in recruitment, angling pressure and sampling conditions. Age analysis identified ages 2 to 8 present. Growth has typically been slower than statewide averages but not slow enough to be concerning. Male and female perch growth rates begin to diverge between age 2 and 3. Length at capture suggest perch begin to reach a harvestable size by age 5. Male perch averaged 7.6 inches while females averaged 8.3 inches by age 5 in 2021.
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\nNorthern Pike are another popular species with anglers and are well suited for Winnibigoshish and connected waters. Winnibigoshish tends to have higher pike abundance than comparable lakes, and catches have been relatively stable in fall surveys. Lengths ranged from 14.8 to 30.5 inches with an average of 22.2 inches in 2021. The length distribution was similar to previous fall surveys. It is believed harvest has likely influenced size quality. Winnibigoshish lies within the North Central Pike Zone. Beginning in 2018, lakes within this zone have had a Northern Pike protected slot length regulation from 22 to 26 inches, a bag limit of 10 fish but only two can be longer than 26 inches. Spearing has an exception of one fish in the PSL. Slot sized fish comprised an average of 40% of the sample, since 2018. In 2021, 26% of the catch was within the pike PSL.
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\nNorthern Pike age analysis indicated ages 1 to 6 present with relatively consistent recruitment, similar to past surveys. Age, sex and maturity determinations were similar to past surveys, a little over half were female and very few were immature. The proportion of pike older than age 4 was low, comprising 7%. Age-4 pike averaged 25 inches at the time of capture. Anglers and spear fishers are encouraged to take advantage of the expanded harvest opportunities offered by the North Central Zone regulation, but limit their take of fish over 22 inches. Pike growth was favorable, exceeding statewide averages and was similar to past surveys. Male and female growth rates diverge between ages 1 and 2. Age-4 males averaged 22.8 inches while females averaged 25.7 inches, in 2021.
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\nCisco are an important prey species and an indicator species due to their environmental sensitivity. Catches have been variable, which is often associated with pelagic species like Cisco, but have had a declining trend over the past decade. Warmer water temperatures and Zebra Mussel infestations are two factors that have likely influenced this trend. Cisco lengths ranged from 10.5 to 16.6 inches with an average of 11.7 inches. Length frequency was not very diverse. Age analysis identified ages 2, 3 and 6 present. Age-2 fish comprised 92% of the sample with an average length of 11.2 inches. This year class, as age 1, comprised half the 2020 sample and had an average length of 7.9 inches.
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\nOther species sampled include Burbot, Largemouth Bass, Muskellunge, Rock Bass, Shorthead Redhorse, Silver Redhorse, White Sucker and Yellow Bullhead.
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\nWinnibigoshish has had several exotic or non-native species introduced in the last 20 years. Banded Mystery and Chinese Mystery snails were first noted around 2000, followed by Faucet Snail. A trematode parasite associated with Faucet Snails was responsible for a large diver duck die-off in 2007 and 2008. Lesser die-offs have occurred almost annually since.
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\nJuvenile Zebra Mussels (veligers) were discovered while sampling zooplankton in 2012. Adults were found on driftwood in 2016 and subsequent investigations found adults were present on nearly all firm structure by 2017. Recent zooplankton sampling suggest veliger density has decreased slightly.
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\nZebra Mussels and Faucet Snails have contributed to ecosystem changes. Both are effective filter feeders and are responsible for a large increase in water clarity. These species shunt nutrients to the benthic portion of the lake resulting in large filamentous algae mats. Decreased nutrient availability within the water column has changed species compositions and densities of phytoplankton, zooplankton and aquatic invertebrates. The impact of Zebra Mussels on the fish community is less apparent and unclear at this time because Winnibigoshish has been fully infested for only five seasons to date. Zebra Mussels have influenced angler use. With the increased water clarity, the traditional mid-day Walleye bite has shifted to more low light periods.
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\nStarry Stonewort was discovered upstream in Cass Lake in 2016. Subsequent sampling found it along the south and west shores of Winnibigoshish, and it appeared to have been established for several years. It was reported along the east shore in 2017, near Birches public access.
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\nEmerald Shiners are not native to Winnibigoshish and were first sampled in 2015. This species is often used as bait and has been sampled while seining since. Rusty Crayfish and curly leaf pondweed are found in upstream connected waters and it is assumed introduction is likely.
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\nEach of these introductions have occurred through human activities. Movement of any type of equipment that can trap or hold contaminated water, plant fragments or aquatic organisms can be a potential vector of spread if precautions are not taken. To avoid being an accomplice to the spread of these unwanted species, people should ensure that all equipment is thoroughly cleaned and dried before moving it to a new body of water. More information is available at https://www.dnr.state.mn.us/invasives/ais/index.html.
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Lake Winnibigoshish is sampled annually to track changes in abundance and growth of fish species, and physical and chemical characteristics of the lake. The assessment season typically starts with seining and gill netting in late June to early July. The goal of seining is to sample young game and non-game species (including minnows) and to track growth of age 0 Walleye and Yellow Perch (perch). Gill netting is conducted from late June through July to sample game and non-game species age 1 and older. Abundance, growth rates, maturity, presence of parasites etc. is determined from these data. Trawling is conducted in August to continue tracking growth rates of age 0 Walleye and perch. Trawling gives the first clue to abundance of age 0 Walleye and perch for that year. Temperature and dissolved oxygen profiles are typically taken from June through August, and water chemistry analysis is completed in August to track changes in the system that may affect the ability of some species to prosper or exist in the lake. Plankton sampling was included in standard sampling beginning in 2012, and was continued through 2015. Six samples were taken on seven dates for a total of 42 samples in 2015. These samples were collected to determine baseline planktonic species composition and biomass.
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\nWalleye; Walleye were sampled at a rate of 4.8 per net. Walleye sampled varied from 8.0 to 26.5 inches with a mean length of 17.0 inches and mean weight of 1.8 pounds. The Walleye population appeared to be healthy with most age-classes sampled between age 1 and 13. Walleye year-class strength was computed for fish from age 1 to 7. One average year class (2011), three strong year classes (2009, 2010, and 2013), and two weak year classes (2008, and 2012) were sampled. The 2012 year class of Walleye continues to be as weak as any year class observed since the start of the large lake program (1983). Poor Walleye year classes occur occasionally. Historic early ice out (March 30 - 2012) followed by a cold spring likely affected reproduction, and growth and survival of the 2012 year class.
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\nGrowth of Walleye was similar to the Lake Winnibigoshish and statewide average for all ages, attaining 17.7 inches after five growing seasons. The 17 to 26 inch protected slot limit was in place between 2000 and 2014. During this time, age and length at maturity increased from a low of 14.6 inches and 3.2 years, to 18.0 inches and 4.7 years. Spawning stock biomass increased from 0.5 lbs. per acre in 2002 to 2.7 lbs. per acre in 2013. This indicated that the Walleye population is likely fully recovered from a period of high harvest and reduced recruitment between the mid 1980's and mid 1990's. Due to this, the protected slot limit was changed to 18 to 23 inches in 2015 so that anglers could utilize the harvestable surplus.
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\nThe mean trawl catch rate of 2.5 Walleye per hour in 2015 declined by 45% from catch rates observed in 2013, and 2014. Catch rates from 2013 through 2015 were the lowest observed since 1983. Increased water clarity was observed during this time period, which appears to affect trawl catch rates. Fish of many species were observed avoiding the boat during trawling. Due to this (and to collect samples for the \"Walleye Fry Stocking in Egg-Take Lakes\" project) night electrofishing was conducted from late-August to mid- September. Electrofishing catch rates for 2013 through 2015 indicated higher abundance than trawl catch rates would indicate. Electrofishing catch rates in 2013 (88 per hour) were substantiated by higher than average catch of yearling Walleye in 2014 summer gill nets. Walleye may either avoid the trawl during years with high water clarity, or they utilize habitat that is not sampled by trawling.
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\nNight electrofishing has been conducted primarily to collect young-of-the-year Walleye to augment sample size requirements for the \"Walleye Fry Stocking in Egg-Take Lakes\" project. Due to changes in water clarity and corresponding decreased trawl catch rates, electrofishing is being considered as an alternative sampling method to collect young Walleye. Electrofishing results from 2014 and 2015 are being used to standardize sampling locations and timing. The following results are from non-standard sampling and may not be comparable with future sampling events.
\nResults of electrofishing in 2015 were counter to those of trawling. Young of the year Walleye were sampled at a rate of 33 to 201 per hour (data available in the Grand Rapids Area Fisheries Office), and growth was good, reaching 6.6 inches on September 24th. Fast growth of age 0 Walleye often results in a strong year class.
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\nPerch; Perch are an important species to anglers and as a prey item for predators. The catch of perch in assessment nets reached a historic low (at the time) in 2005, largely due to poor year-classes in 2000 and 2002. A strong 2003 year-class moved through the system resulting in higher catch rates through 2007. Catch rates declined from 2007 through 2011 to a new historic low catch of 43.6 per net. The catch rate for perch increased to 57.5 per net in 2012 and increased again to 74.4 in 2013. The gill net catch rate for perch declined to 53.9 per net in 2014. The gill net catch of perch declined to a new historic low of 43.1 fish per net in 2015.
\nPerch sampled in 2015 varied from 3.2 to 11.7 inches with a mean length of 6.9 inches and mean weight of 0.2 pounds. Age-classes 2 through 8 were sampled by gill nets. An index of year-class strength was computed for all year-classes sampled from 2008 through 2012. The 2011 year-class was weak while the 2008, 2009, 2010, and 2012 year-classes were average. Natural mortality of perch increases at age 8 and few individuals live past age 10. The catch of perch in 2015 was primarily represented by younger individuals with 85% of the catch made up of age 2 through age 4 fish. Although the perch population was composed primarily of small individuals, growth has not changed. Growth was relatively slow through age 2, then increased to average from age 3 to age 8. Perch grew to an average length of 9.3 inches at age 6.
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\nRelative health of the perch population can be described by the percent of perch longer than 9 inches in the gill net catch. The gill net catch of large perch (longer than 9 inches) declined to 5.5% in the early 1990's driven by high angler harvest. Changes in Lake Winnibigoshish and other lakes prompted a statewide change in the perch bag limit to 20 daily and 40 in possession in 2001. Several strong year classes were produced during the same time period and the gill net catch of large perch increased to 30% in 2004. In 2005, the proportion of large perch sampled in near-shore gill nets declined for the first time since 1998. The proportion of large perch was about 17% in 2005 and 2006, then declined to 9.8% in 2007 as young perch from the 2003 year class were recruited to the fishery. No strong year classes were produced between 2004 and 2009. As a result the percent of large perch fluctuated between 10% and 13% between 2007 and 2012. A strong year class of perch was produced in 2010 (reduced to average by 2015). This resulted in increased gill net catch rates (mostly young fish) and a reduced catch of large perch (7.7%) in 2013. The catch of perch continued to be dominated by small young fish in 2014 and 2015. The perch catch of 7.8% longer than 9 inches in 2015 increased slightly from 6.8% in 2014.
\nThe trawl catch rate for age 0 perch of 2,991 per hour was lower than any seen since 2005, and was the third lowest since 1987. Growth of age 0 perch was average with a mean length of 2.0 inches in mid-August. Clear water conditions that appear to have affected trawl catch rates of young of the year Walleye may have affected catch rates of young of the year perch also. Few age 0 perch were sampled in trawl hauls less than 10 feet of water. Catch rates of age 0 perch are typically highest in less than 8 feet. No correlation is evident between trawl catch rates or growth of age 0 perch and year-class strength.
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\nThe microsporidian parasite heterosporis has been documented in Lake Winnibigoshish perch. No evidence of heterosporis was observed in perch during the 2015 population assessment, although anglers report the presence of heterosporis in a few perch each year.
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\nNorthern Pike; Catch rates of Northern Pike (pike) showed an increasing trend from 1994 through 2005 and exceeded the third quartile (9.6 per net) in four years between 2002 and 2009. The pike catch rate was relatively stable and considered average between 2006 and 2011. Gill net catch rates increased dramatically between 2011 and 2014, reaching a new historic high of 14.1 per net in 2013. Catch rates continue to be above average in 2015 at 10.4 pike per gill net. Pike sampled in 2015 varied from 15.8 to 35.4 inches with a mean length of 21.3 inches. Mean length of pike has been declining as catch rates have increased. Mean pike length of 21.3 inches in 2015 increased from 2014 but was well below average. Age-classes from 1 through 5 and 7 were sampled by gill net. Growth rates were similar to the statewide mean through all ages.
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\nSize structure of the pike population improved between 2010 and 2012. That trend was reversed in 2013 as a strong component of small young pike were recruited to the gill net catch. Two pike longer than 30 inches were sampled in the 2013 and 2014 assessment vs 10 in the 2011 and 9 in the 2012 assessments. Three pike longer than 30 inches were sampled in the 2015 assessment. Decreased size structure may be attributed to several causes. Reproduction and recruitment was strong for the 2011, 2012, and 2013 year classes which made up 94% of the catch, and Cisco abundance decreased due to summer kill in 2012 (Cisco are preferred prey that provides more energy than other similar size prey). A strong prey base of Cisco may lead to faster pike growth rates. High angler harvest of pike may result in a recruitment response (increased reproduction to replace individuals removed from the system). Larger numbers of small pike vs smaller numbers of medium to large pike may cause reduced growth rates due to increased competition for food and space. The recent increase in catch rate may result in slower pike growth in the future. Anglers can help maintain the pike size structure by releasing most pike longer than 22 inches.
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\nCisco; Cisco are a primary prey species for Muskellunge, pike and Walleye. Growth rates of these species may be reduced if Cisco are not present in the system. The gill net catch of 4.1 per net in 2015 was the lowest since 1983. Cisco sampled varied from 7.8 to 15.1 inches with a mean length of 10.0 inches. Cisco catch rates were lower than average for 7 of the last 10 years. This is likely due to warmer than average summer and fall water temperatures that may affect reproduction and cause occasional summer kills. Water temperatures were warm during the summer of 2012 and caused a summer kill of Cisco. Due to the low and decreasing catch rates discontinuation of Whitefish and Cisco Sport Gill Netting should be considered.
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\nWater Quality; Five temperature and dissolved oxygen profiles were taken between June 22 and July 23, 2015. Dissolved oxygen stratification was evident on July 10th and July 17th. No evidence of thermal stratification was found in 2015. Thermal and dissolved oxygen stratification may result during periods of high air temperatures and low wind. When wind speeds increase to moderate levels (15 mph) the entire water column appears to mix. Water chemistry measurements have been recorded for most years since 1983. Water clarity as measured by Secchi disc in 2015 was the highest measured since 1983. Secchi disc measurements have varied between 12.5 and 19.0 feet. Total Phosphorous concentration can affect phytoplankton abundance which may affect water clarity. Total Phosphorous has remained within historic norms as water clarity increased over time. Recent increases in water clarity do not appear to be related to changes in Total Phosphorous concentration.
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\nInvasive Aquatic Species; Invasive species are species that are not native to Minnesota and cause economic or environmental harm or harm to human health. Several invasive species have been introduced to Lake Winnibigoshish. Three species of snail: banded mystery, Chinese mystery, and faucet have become established since 2000. Both species of mystery snail appear to have no negative effect at this time. The faucet snail carries a trematode parasite that can kill several species of ducks if ingested. Thousands of ducks were killed by these parasites during the falls of 2007 and 2008. Emerald shiners (often used as bait) are not native to Lake Winnibigoshish and were first sampled in 2005. Juvenile zebra mussel (veliger), have been discovered while sampling plankton since 2012. Shoreline and mid lake areas of rock were investigated for adult zebra mussel in August of 2014 and 2015. No adult Zebra Mussel have been discovered in any assessments. Each of these invasive species were likely introduced through human activities.
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Walleye were captured at a rate of 4.3 per near-shore gill net, which was similar to the long-term average for Lake Winnibigoshish. Near shore sampled walleye varied from 7.5 to 25.4 inches with a mean length of 15.6 inches.
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\nThe walleye population appeared to be healthy with all age classes sampled between age 1 and 10. Year class strength was computed for walleye between age 2 and 7. Two weak year classes, three average year classes, and the strong 2001year class were present . The 1994 and 1995 year classes exceeded age seven, were relatively abundant, and contributed to the above average catch of 19 to 25 inch walleye. Mean back-calculated growth of near-shore sampled walleye was faster than the Lake Winnibigoshish average for most ages, attaining 16.9 inches after four growing seasons. The mean total weight of walleye per near-shore gill net of 6.0 pounds was also similar to the long-term average.
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\nCold spring and early summer conditions may have caused lower hatch rates of walleye eggs with slower growth and higher mortality of walleye fry and fingerlings. Indicators of poor reproduction and slow growth were seen in seine and trawl catch rates, and growth of walleye and yellow perch fingerlings.
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\nYellow perch were sampled at a rate of 73.8 per near-shore gill net. This catch rate increased from the historic low of 56 per net in 2003, however, was still lower than typical for Lake Winnibigoshish. Length of perch sampled in near-shore gill nets varied from 4.9 to 13.1 inches with a mean length of 8.1 inches.
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\nAll age classes between age 2 and 9 were sampled by gill net. Year class strength was computed for yellow perch between age 3 and 7. Of these, the 1997 (age 7) through 1999 (age 5) year classes were average, while the 2000 year class was considered weak. The catch of age 8, and 9 perch was much lower than that of ages 3 through 7, and was a relatively small component of the total catch. Relative health of the yellow perch population has been described by the percent of perch larger than 9 inches in the gill net catch. Thirty percent of the near-shore gill net sampled perch were larger than 9 inches. Yellow perch growth was relatively slow through age 2, and increased to near average from age 3 to age 9, attaining a mean length of 9.6 inches at age 6.
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\nGrowth of yellow perch sampled in near-shore and mid-lake nets was compared and no significant difference was found, consequently samples were pooled in 2004. Growth was slow for age 1 and 2, and average from age 3 through 10.
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\nAge-0 yellow perch were sampled by seine, however, many perch escaped through the mesh due to their small size, consequently catch rates were low. Trawl catch rates were also low at 6,718 per hour of trawling time. Many young of the year yellow perch escaped through the � inch mesh of the trawl due to slow growth and resulting small size. Escapement biased catch rates to and unknown extent.
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\nNorthern pike were sampled at a rate of 9.6 per near-shore gill net, which was higher then typical when compared to similar lakes, but within the range of catch rates observed on Winnibigoshish since 1983. Pike sampled in near-shore gill nets varied from 8.5 to 35.6 inches with a mean length of 21.2 inches.
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\nAll age classes between age 1 and 8 were sampled by gill net. Age 2 and 3 pike were similarly represented in the gill net catch and were the most abundant age classes sampled. Growth of near-shore gill net sampled northern pike was similar to statewide averages, attaining a back calculated mean length of 24.7 inches at age 5.
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\nGill net catch rates of cisco remained low in 2004. The catch rate of 9.3 per near-shore net was the second lowest observed, and followed the trend of reduced catch rates since 1997. Bony structures were not collected from cisco in 2004 and ages were not determined. Examination of the cisco length frequency indicates that recruitment was sporadic and year classes may be absent.
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Lake Winnibigoshish is part of the Mississippi River headwaters reservoir system, and is located 15 miles northwest of Deer River, Minnesota. The lake is a large, shallow, wind-swept reservoir with a sandy shoreline and gently sloping shoal areas. Lake Winnibigoshish has a surface area of 58,544 acres, mean depth of 15.1 feet, littoral area of 20,490 acres (35%), and a maximum depth of 66 feet. Water clarity has generally increased since the 1980s. The increased clarity trend accelerated following Zebra Mussel establishment in 2012, although clarity has varied considerably in recent years. Water clarity sampling (Secchi disk) was accomplished on 7 dates between May 15 and September 23, 2019 and varied from 8.5 feet in late May to 16 feet in late July.
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\nLake Winnibigoshish has been managed as part of the Minnesota Department of Natural Resources (DNR) large lake program since 1983. Management activities include special fishing regulations, fish stocking, occasional creel surveys, and annual fish surveys to determine the status of the fishery and evaluate management actions. Data collection in 2019 included summer near shore seining, water quality monitoring, and zooplankton surveys during the open water season. A fall gill net survey is conducted annually on Winnibigoshish using 32 gill net sets, and this survey has been the primary assessment tool to determine the status of game fish populations since 2007. Fall electrofishing has also been conducted since 2018 to evaluate Walleye production.
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\nResults
\nThe 2019 fall gill net survey was conducted from September 15th through the 26th. Thirty two nets were set around the lake, sampling all habitat types. High winds and poor weather occurred during the sampling period, which likely influenced fish movement and gill net catchability.
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\nYellow Perch- Yellow Perch are important as a prey species and are also popular with anglers. The 2019 catch was typical for lakes with similar habitats, but below average for Winnibigoshish. Variations in perch catch rates are expected and may represent variations in year class strength, angling or predation pressure on adult fish, or simply natural variation in annual gill net catches. No clear population trends could be determined. Age analysis identified 8 year classes (ages 1-8). Age 2 and 3 fish were most abundant, making up 31% and 33% of the sample. Growth was similar to past surveys and near the statewide average. Perch averaged 8.3 inches at age 5.
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\nLake Winnibigoshish has a history of producing large perch, making it a perch angling destination. Perch length ranged from 5.4 to 11.7 inches and averaged 7.2 inches in 2019. The number of perch over 9 inches was below average for Winnibigoshish in 2019, but indicates that some opportunities for catching large perch continue to exist.
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\nWalleye- Walleye are a primary management species on Winnibigoshish, because they are well suited for the lake, are actively managed through stocking and special regulation, and are popular with anglers. The population is maintained by natural reproduction and fry stocking. Walleye eggs are taken each spring at the Cut Foot Sioux egg take site and ten percent of the egg take has been returned to the system as newly hatched fry. The relative contribution of stocked and natural fry is difficult to determine because there are no non-stocked year classes to evaluate. Harvest has been regulated with special regulations since 2000. The original 17-26 inch protected slot limit was modified to an 18-23 inch PSL in 2015 to allow additional harvest of adults.
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\nWalleye were the second most common fish captured in gill nets 2019. The catch was typical for lakes with similar habitats, but below average for Winnibigoshish. Walleye populations are typically maintained by sporadic recruitment (reproduction and survival of young) events that impact population cycles and angler success. Sporadic recruitment is a common trait for Walleye in stocked and natural fisheries, so variations in Winnibigoshish are expected. Recruitment patterns on Winnibigoshish strongly influence the gill net catch. Recruitment was poor between 2014 and 2017, resulting in below average gill net catches. The presence of fish from the 2018 and 2019 year classes was confirmed in the 2019 gill net survey and are expected to contribute to higher catch rates in the near future. Lake Winnibigoshish supports a quality size distribution for Walleye, but harvest regulations used to protect spawning stock can affect angler harvest during periods of reduced recruitment. Poor recruitment between 2014 and 2017 resulted in reduced availability of harvestable fish for anglers. Over 70% of the Walleye sampled in 2017 and 2018 surveys were within the 18-23 inch protected slot. Improved recruitment in 2018 and 2019 resulted in higher catches of fish under 18 inches in the 2019 gill net survey, as 62% of sampled fish were less than 18 inches. These fish were generally too small to interest anglers at the time of sampling, but are expected to grow to an acceptable size in 2020 and provide good harvest opportunities in the near future.
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\nBiological measurements continue to indicate a healthy Walleye population with appropriate harvest levels. In 2019, Walleye lengths ranged from 6.9 to 26.1 inches and averaged 14.5 inches indicating a diverse size structure. Age analysis indicated 15 year classes were present, ranging from age 0 to 14. The 2018 and 2019 year classes were well represented, comprising 14% and 43% of the sample, suggesting good initial survival from these years. The 2013 year class remains the strongest class of adult fish, and comprised 16% of the sample. Growth rates have been above the statewide average in the last three assessments. In 2019, Walleye averaged 14.5 inches by age 3. Evaluation of spawning stock biomass is useful to determine appropriate harvest levels and establish safeguards to maintain an adequate adult population for natural reproduction. A female spawning stock biomass (SSB) of one to two pounds per acre is considered optimal for natural reproduction on Winnibigoshish. Surveys in 2018 and 2019 resulted in estimates of 1.1 pounds per acre. Age and length at maturity are also useful indicators to determine appropriate harvest levels and relative population status. Since 2007, female Walleye on Winnibigoshish typically reached maturity in 3.5 years at 17.3 inches. Both values are near statewide standards and suggest appropriate harvest levels are occurring.
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\nNorthern Pike- Northern Pike are considered a primary management species because they are popular with anglers and well suited for the lake. The 2019 catch was typical for lakes with similar habitats and for Winnibigoshish. Pike size structure has typically been moderate, with around 5% of the sampled pike exceeding the angler preferred size of 28 inches. Fish over 30 inches have been present in all fall surveys, indicating that some opportunities to catch large pike exist. Lengths ranged from 10.4 to 32.7 inches in 2019, and averaged 22 inches. Only 3% of the sampled pike exceeded 28 inches. As in past surveys, recruitment was consistent, with ages 0-8 present. Growth was similar to past surveys and near the statewide average, as pike averaged 23.6 inches by age 4.
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\nNew pike regulations were established in 2018. Due to differences in pike biology, three different zone regulations were implemented. Winnibigoshish lies within the North Central zone, where anglers have a 10 fish bag limit with no fish allowed between 22 and 26 inches and only two longer than 26 inches. Spearing regulations vary slightly from angling regulations, and one pike is allowed within the protected zone. This regulation is expected to improve the average length and number of medium sized pike. Anglers and spear fishers can help to further improve size quality by only harvesting pike under 22 inches.
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\nCisco- Cisco are an important prey species and an indicator of environmental change. Cisco catches have declined dramatically on Winnibigoshish, following a trend observed across Minnesota. The cause of the decline is not clearly known, but population trends are likely influenced by sub-optimal climate conditions, interactions with invasive Zebra Mussels, and relatively high predator numbers. The 2019 catch was the lowest observed and is the seventh consecutive survey with a below average catch. The size structure favored large individuals, as length ranged from 11.3 to 17.5 inches. The lack of smaller cisco suggest poor recruitment in recent years. The impact of cisco declines are unknown, but could negatively impact growth rates of large predators such as Northern Pike, Muskellunge, and Walleye.
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\nExotic Aquatic Species- Several species have been introduced into Winnibigoshish. Three species of snail: Banded Mystery, Chinese Mystery, and Faucet have become established since 2000. Both species of mystery snail appear to have no negative effects at this time. The Faucet Snail carries a trematode parasite that can kill several species of ducks if ingested. Thousands of ducks were killed by these parasites during the falls of 2007 and 2008. The Faucet Snail is a filter feeder and may be responsible for clearing water prior to the introduction of Zebra Mussel.
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\nJuvenile Zebra Mussels (veligers) were discovered while sampling zooplankton during the summer of 2012. Adults were found on near shore driftwood in the early summer of 2016, then found by divers on mid lake rock structure during August. Zebra Mussel appear to have spread to nearly every hard or firm structure by the summer of 2017. Zebra Mussel veliger counts have been increasing, and were higher in 2017 than have been observed in any Minnesota samples to this point.
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\nStarry Stonewort (an algae) was discovered in Cass Lake during the summer of 2016. This discovery upstream of Winnibigoshish prompted an investigation on Winnibigoshish. Starry Stonewort was discovered along the south and west shores of the lake in 2016, and appears to have been established for several years. Starry Stonewort has continued to spread in 2017, and was reported along the east shore of Winnibigoshish near Birches public access.
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\nEmerald Shiners (often used as bait) are not native to Winnibigoshish, were first sampled in 2005, and have been sampled each year since. Each of these invasive or non-native species were likely introduced through human activities.
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\nRusty Crayfish are present in Cass Lake, and curly leaf pondweed is present in Dixon Lake. Both of these lakes are tributaries to and upstream of Winnibigoshish. Introduction to Winnibigoshish in the near future is likely.
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\nMovement of any type of equipment (boats, boat trailers, boat lifts, docks, personal watercraft, bait containers, etc.) between lakes may transfer invasive species if precautions are not taken. To avoid being an accomplice to the spread of these unwanted species, people should ensure that all equipment is thoroughly cleaned and dried before moving it to a new body of water. More information regarding invasive species is available at https://www.dnr.state.mn.us/invasives/ais/index.html.
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This is the second consecutive year that a fall special assessment was conducted on lake Winnibigoshish. These assessments were conducted with the ultimate goal of converting standard gill net assessments from the traditional summer period to a fall time frame. Fall assessments are conducted on all large lakes except Lake Winnibigoshish. Those fall assessments have proven more effective in the development of, and use of tools that evaluate fish populations in the large lakes. It is necessary to conduct paired assessments (summer and fall) for several years so that comparisons can be made between the two sampling periods. This will allow the ultimate conversion of summer assessments completed from 1983 to 2006 to their fall equivalent, and allow more sophisticated analysis of Lake Winnibigoshish fish populations.
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\nGill net catch rates varied between summer and fall assessments in 2008. Walleye catch rates were 5.0 per net during summer and 11.5 per net in the fall. Yellow perch catch rates were 68.4 per net during summer and 27.6 per net in the fall. Northern pike catch rates were 8.2 per net during summer and 3.1 per net in the fall. Cisco catch rates were 10.5 per net during summer and 11.8 per net in the fall.
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Lake Winnibigoshish, otherwise known as Winnie or Big Winnie, is a large reservoir located immediately north of the community of Bena, Minnesota. Winnie was a natural lake that was impounded in the 1880's with a dam controlled by the U.S. Army Corps of Engineers (USACE). Today the USACE maintains water levels within a narrow band of elevation that gives the lake its current surface area of approximately 56,472 acres and a maximum depth of 69 feet. The surrounding geology contains a high proportion of sandy soils, providing an abundance of sandy shoreline with very gradual slopes. With approximately 11 miles of open water between the north and south shores, the lake is prone to high wave action and frequent mixing of the water column when exposed to high winds. During the open water season, this keeps temperatures and oxygen levels much more uniform from the surface to the bottom of the lake, in comparison to smaller, more protected lakes with similar water depth. Some of the major tributaries to Winnibigoshish include the First River flowage through Cut Foot Sioux Lake, the Third River, and the Mississippi River.
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\nWinnibigoshish is often thought of as a premier Walleye and Yellow Perch destination but offers angling opportunities for multiple other species as well. Acknowledging the importance of this fishery, Winnibigoshish was included as one of ten lakes in the Large Lake Monitoring Program, which was developed by the Minnesota Department of Natural Resources in 1983. Surveys are conducted on these lakes annually and typically include a suite of sampling methods that track trends in water quality, zooplankton, juvenile fish, periodic creel surveys, and the current status of game fish targeted by anglers.
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\nMajor changes have been occurring within the system over the past 15 years. These changes began around the time of the discovery of invasive Faucet Snails in 2007, followed by the detection of larval Zebra Mussels in 2012, and adult Zebra Mussels in 2016. Filter feeding invasives can dramatically increase water clarity and reduce the abundance of plankton available to fish, including many species found in the lake during their juvenile life stage. Prior to the introduction of these invasives, water clarity (measured with a Secchi disc) averaged 6 to 7 feet and the highest ever recorded was 10 feet. There has been a post-invasion trend of increasing water clarity in Winnibigoshish, which continued during the 2023 field season when Secchi disc readings ranged from 10.5 to a record setting 27 feet.
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\nWalleye is the primary management species in Winnie, and a large proportion of the field work completed is dedicated toward tracking the current status of this species. Walleye catch rates in fall survey nets were up from the previous year, and within the expected range for the lake. The Winnibigoshish Walleye population is supported by both fry stocking and some natural reproduction. In years with the right conditions Walleye year classes tend to boom with one strong year class, which is often followed by multiple weak year classes. The 2019 year class is the most recent strong year class, making up about two-thirds of the total number of Walleye caught in the sample nets this year. These are averaging 16 inches and most reached maturity over the past year. The 2013 year class was also strong, and some of these older fish are still in the system. There is a protected slot of 18 to 23 inches for Walleye, with the intent to protect some of the spawning stock while still providing ample harvest opportunities for anglers. Ten percent of the Walleye caught in the fall survey nets in 2023 were within the protected slot of 18 to 23 inches.
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\nThere is a history of heavy angling pressure on Yellow Perch in Winnibigoshish. Perch are also a valuable prey item for predators such as Walleye and Northern Pike. Perch catch rates in fall gill nets have had a declining trend for several years, caused by a lack of recruitment of young fish. Perch reach sizes large enough to be effectively sampled in fall gill nets at a size of five to six inches, which is reached during their third growing season. By 2022 there had been several years in a row with very few Yellow Perch surviving to this age, leading to record low abundance and a population consisting of mostly older fish. Fortunately, in 2023 catch rates did increase due to an increase in young fish from the 2021 year class showing up in the catch. However, catch rates are still below the expected range for the lake. It is difficult to identify one sole cause for the declining trend in abundance with a lake that has undergone such dramatic physical change in recent years. Changes in the zooplankton community due to Zebra Mussels may be leading to lower survival through the first year. There has also been a sharp decline in Tullibee (Cisco) abundance, which would shift more predation pressure toward Yellow Perch. Northern Pike abundance peaked in 2017, followed by the strong 2019 year class of Walleye and both of these predators feed heavily on Yellow Perch. A combination of these and other factors all likely played a role in the decline of Yellow Perch abundance in recent years. While the population has declined in abundance, growth rates appear to be increasing.
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\nNorthern Pike is another popular species amongst Winnibigoshish anglers. Tributary inlet areas and connected waters provide a great deal of spawning habitat, which results in consistent recruitment of Northern Pike to the fishery. The population is generally characterized as having high abundance and relatively poor to moderate size structure when compared to other large lakes. Pike tend to have slower growth and poor condition (how heavy a fish is for its length) when population densities are high. In 2023 the fall gill net catch rates were low when compared to historical catches for Winnibigoshish, but still near the top of the expected range for similar lakes. The population peaked in abundance in 2017 and has stabilized at a lower level the past few years. There was a declining trend in condition over the past decade when Northern Pike abundance was high and prey abundance was declining. This trend turned around in 2023 when condition improved to a 10 year high. This is an indicator that prey was abundant in 2023, likely in the form of a good year class of Tullibee Cisco or Yellow Perch. Winnibigoshish is part of the north-central zone for Northern Pike regulations that includes a protected slot of 22 to 26 inches. Release of Northern Pike over 26 inches is encouraged to help improve the overall size structure of the population. About one-fourth of the Northern Pike sampled in 2023 were within the protected slot limit.
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\nTullibee (Cisco) are an important prey item in lakes where they occur, and at times can be a popular gamefish for anglers. The population in Winnibigoshish has fluctuated over time, but over the past 15 years there has been a steady decline in abundance. Similar to Yellow Perch, the Tullibee catch rates rebounded slightly in 2023 but remain below the expected range. The increase in catch was largely due to the recruitment of young fish that had been lacking in recent years. The 2021 year class made up about one-third of the sample and averaged 8 inches. The decline in the population is likely a combination of several factors. Tullibee feed primarily on zooplankton, which has decreased due to the presence of Zebra Mussels. Tullibee also require cold water and in some years the water temperatures in Winnibigoshish can surpass stressful or even lethal thresholds.
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\nMuskellunge are another gamefish in Winnibigoshish. Available sampling methods are not sufficiently effective to complete population estimates, but it is generally believed to be a low density population that is supported entirely by natural reproduction. Black Crappie, Bluegill, Largemouth Bass, and Burbot also exist in Winnibigoshish, but according to creel surveys the hours spent targeting these species is low in comparison to Walleye, Yellow Perch, and Northern Pike. A five fish bag limit for sunfish on Winnibigoshish will begin in 2024 to simplify enforcement, as this special regulation currently exists on the connected Cut Foot Sioux and Little Cut Foot Sioux lakes and anglers commonly travel between all three lakes.
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\nInvasive species are not native to Minnesota and cause economic or environmental harm, or harm to human health. They are illegal to introduce into or move between state waters and can impact energy flow, food chains, and fish species assemblages. Current known invasive species in Winnibigoshish include Zebra Mussels, Faucet and Mystery Snails, and Starry Stonewort. Changes in environmental conditions affect fish habitat and behavior, which likely affect fish sampling and angling success. Gill net catches have likely been influenced by these changes, especially since the establishment of Zebra Mussels. Zebra Mussels are an efficient filter feeder that have been shown to impact energy transfer and aquatic food webs. The overall decrease in pounds of fish sampled in gill nets since the establishment of Zebra Mussels suggests that there has been a decrease in overall carrying capacity for fish. Movement of any type of equipment that can trap or hold contaminated water, plant fragments or aquatic organisms can be a potential vector of spread if precautions are not taken. To avoid the spread of these unwanted species, ensure that all equipment is thoroughly cleaned and dried before moving to a new body of water. More information is available at https://www.dnr.state.mn.us/invasives/ais/index.html
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Lake Winnibigoshish is sampled annually to track changes in abundance and growth of fish species, and physical and chemical characteristics of the lake. The assessment season typically starts with seining and gill netting in late June to early July. The goal of seining is to sample young game and non-game species (including minnows) and to track growth of age 0 Walleye and Yellow Perch (perch). Gill netting is conducted from late June through July to sample game and non-game species age 1 and older. Abundance, growth rates, maturity, presence of parasites etc. is determined from these data. Trawling is conducted in August to continue tracking growth rates of age 0 Walleye and perch. Trawling gives us the first clue to abundance of age 0 Walleye and perch for that year. Temperature and dissolved oxygen profiles are taken from June through August and water chemistry analysis is completed in August to track changes in the system that may affect the ability of some species to prosper or exist in the lake. Plankton sampling was included in standard sampling beginning in 2012 and was continued through 2014. Six samples were taken on seven dates for a total of 42 samples in 2014. These samples were collected to determine baseline planktonic species composition.
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\nWalleye; Walleye were sampled at a rate of 4.6 per net. Walleye sampled varied from 7.6 to 26.6 inches with an average length of 17.3 inches and average weight of 1.9 pounds. The Walleye population generally appeared to be healthy with most age-classes sampled between age 2 and 13. Walleye year-class strength was computed for fish from age 2 to 7. Two average year-classes (2007, and 2011), two strong year-classes (2009, and 2010), and two weak year-classes (2008, and 2012) were sampled. The 2012 year class of Walleye was as weak as any year class observed since the start of the large lake program (1983). Poor Walleye year classes are expected occasionally. Historic early ice out (April 3 - 2012) with a cold spring following likely affected reproduction and growth of the 2012 year class.
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\nGrowth of Walleye was similar to the Lake Winnibigoshish and statewide average for all ages, attaining 17.4 inches after five growing seasons. The 17 to 26 inch protected slot limit has been in place since 2000. During this time, age and length at maturity has increased from a low of 14.6 inches and 3.2 years, to 17.3 inches and 4.2 years. Pounds of mature female Walleye increased from 0.5 lbs. per acre in 2002 to 2.7 lbs. per acre in 2013. This may indicate that the Walleye population fully recovered from a period of high harvest and reduced recruitment between the mid 1980's and mid 1990's.
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\nThe average trawl catch rate of 5.5 Walleye per hour in 2014 was the same as in 2013. These catch rates were the lowest observed since 1983. Both 2013 and 2014 saw increased water clarity which may have affected trawl catch rates. Electrofishing was accomplished between late August and mid-September in 2013 and 2014. Electrofishing catch rates for 2013 and 2014 indicated higher abundance than trawl catch rates would indicate. Electrofishing catch rates in 2013 (88 per hour) were substantiated by higher than average catch of yearling Walleye in 2014 summer gill nets. Walleye may either avoid the trawl during years with high water clarity, or they utilize habitat that is not sampled by trawling.
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\nLow catch rates can be explained by extremely clear water during the summer of 2014. Fish of many species were observed avoiding the boat during trawling. Due to this (and to collect samples for the \"Walleye Fry Stocking in Egg-Take Lakes\" project) night electrofishing was conducted during August. Results of electrofishing were counter to those of trawling. Walleye were sampled at a rate of 60 per hour (data available in the Grand Rapids Area Fisheries Office) and growth was faster than average when compared to historic trawl growth rates. Fast growth of age 0 Walleye often results in a strong year class.
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\nPerch; Perch are an important species to anglers and as a prey item for predators. The catch of perch in assessment nets reached a historic low (at the time) in 2005, largely due to poor year-classes in 2000 and 2002. A strong 2003 year-class moved through the system resulting in higher catch rates through 2007. Catch rates declined from 2007 through 2011 to a new historic low catch of 43.6 per net. The catch rate for perch increased to 57.5 per net in 2012 and increased again to 74.4 in 2013. The gill net catch rate for perch declined to 53.9 per net in 2014.
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\nSampled perch varied from 5.0 to 11.0 inches with an average length of 7.1 inches and average weight of 0.2 pounds in 2014. Age-classes 2 through 9 were sampled by gill nets. Natural mortality of perch increases at age 8 and few individuals live past age 10. An index of year-class strength was computed for all year-classes sampled from 2007 through 2011. The 2007 year-class was weak while the 2008 and 2009 year-classes were average and the 2010 year-class was strong. The 2011 year class appears weak, however, that year class has not been fully evaluated. The catch of perch in 2014 was primarily represented by younger individuals with 80% of the catch made up of age 2 through age 4 fish. Growth was relatively slow through age 2, then increased to average from age 3 to age 8. Perch grew to an average length of 8.9 inches at age 6.
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\nRelative health of the perch population can be described by the percent of perch longer than 9 inches in the gill net catch. The catch of perch longer than 9 inches (large perch) declined to 5.5% in the early 1990's driven by high angler harvest. Changes in Lake Winnibigoshish and other lakes prompted a statewide change in the perch bag limit to 20 daily and 40 in possession in 2001. Several strong year classes were produced during the same time period and the gill net catch of large perch increased to 30% in 2004. In 2005, the proportion of large perch sampled in near-shore gill nets declined for the first time since 1998. The proportion of large perch was about 17% in 2005 and 2006, then declined to 9.8% in 2007 as young perch were recruited to the fishery. No strong year classes were produced between 2003 and 2009. As a result the percent of large perch fluctuated between 10% and 13% between 2007 and 2012. A strong year class of perch was produced in 2010. This resulted in increased gill net catch rates (mostly young fish) and a reduced catch of large perch (7.7%) in 2013. The catch of perch continued to be dominated by small young fish in 2014. The perch catch of 6.8% longer than 9 inches in 2014 was the third lowest observed since 1983.
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\nThe trawl catch rate for age 0 perch of 10,351 per hour of trawling was similar to average catch rates since 1983. Growth of age 0 perch was average with a average length of 2.0 inches in mid-August. Clear water conditions that appear to have affected trawl catch rates of young of the year Walleye may have affected catch rates of young of the year perch also. Few age 0 perch were sampled in trawl hauls less than 10 feet of water during the first week of trawling. Catch rates of age 0 perch are typically highest in less than 8 feet. No correlation is evident between trawl catch rates or growth of age 0 perch and year-class strength.
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\nThe microsporidian parasite heterosporis has been documented in Lake Winnibigoshish perch. No evidence of heterosporis was observed in perch during the 2014 population assessment, although anglers report the presence of heterosporis in a few perch each year.
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\nNorthern Pike; Catch rates of Northern Pike (pike) showed an increasing trend from 1994 through 2005 and exceeded the third quartile (9.6 per net) in four years between 2002 and 2009. The pike catch rate was relatively stable and generally within the interquartile range between 2006 and 2011. Gill net catch rates increased dramatically between 2011 and 2014, reaching a new historic high of 14.1 per net in 2013. Catch rates decreased to 9.6 per net in 2014. Pike sampled in 2014 varied from 11.4 to 36.2 inches with a average length of 20.7 inches. Average length of pike has been declining as catch rates have increased. Average pike length of 20.7 inches in 2014 was the near the lowest observed since 1983. Age-classes from 1 to 6 were sampled by gill net. Growth rates were similar to the statewide average through all ages.
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\nSize structure of the pike population improved between 2010 and 2012. That trend was reversed in 2013 as a strong component of small young pike were recruited to the gill net catch. Only two pike longer than 30 inches were sampled in the 2013 and 2014 assessment vs 10 in the 2011 and 9 in the 2012 assessments. Decreased size structure may be attributed to several causes. Reproduction and recruitment was strong for the 2011 and 2012 year classes which made up 75% of the catch, and Cisco abundance decreased due to summer kill in 2012 (Cisco are preferred prey that provides more energy than other similar size prey). A strong prey base of Cisco may lead to faster pike growth rates. High angler harvest of pike may result in a recruitment response (increased reproduction to replace individuals removed from the system). Larger numbers of small pike vs smaller numbers of medium to large pike may cause reduced growth rates due to increased competition for food and space. The recent increase in catch rate may result in slower pike growth in the future. Anglers can help maintain the pike size structure by releasing most pike longer than 22 inches.
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\nCisco; Cisco are a primary prey for Muskellunge, pike and Walleye. Growth rates of these species may be less if Cisco are not present in the system. The gill net catch of 9.3 per net in 2014 was the third lowest since 1983, but increased somewhat from 2013. Cisco sampled varied from 6.5 to 16.3 inches with an average length of 10.8 inches. Cisco catch rates were lower than average for 6 of the last 10 years. This is likely due to warmer than average summer and fall water temperatures that may affect reproduction and cause occasional summer kills. Water temperatures were warm during the summer of 2012 and caused a summer kill of Cisco. Increased catch rate in 2014 may indicate that recovery from the 2012 summer kill has begun.
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\nWater Quality; Seven temperature and dissolved oxygen profiles were taken between June 24 and August 14, 2014. Dissolved oxygen stratification was evident on August 5th and August 14th. No evidence of thermal stratification was found in 2014. Thermal and dissolved oxygen stratification may result during periods of high air temperatures and low wind. When wind speeds increase to moderate levels (15 mph) the entire water column appears to mix. Water chemistry measurements have been recorded for most years since 1983. As in 2013, water clarity as measured by Secchi disc in 2014 was higher than in most years. Secchi disc measurement varied between 10.0 and 12.0 feet. The measurement on August 14 was 11.0 feet, compared to the long term average of 7.0 feet. The Total Phosphorous concentration of 0.022 parts per million (ppm) in 2013 was within the recorded range of 0.015 to 0.051ppm, but was nearly 30 percent lower than the long term average of 0.030ppm.
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\nInvasive Aquatic Species; Species that have been introduced through human activities to a location where they don't naturally occur are termed \"invasive\". Some invasive species are not necessarily harmful, but others cause ecological or economic problems. Several invasive species have been introduced to Lake Winnibigoshish. Three species of snail: banded mystery, Chinese mystery, and faucet have become established since 2000. Both species of mystery snail appear to have no negative effect at this time. The faucet snail carries a trematode parasite that can kill several species of ducks if ingested. Thousands of ducks were killed by these parasites during the falls of 2007 and 2008. Emerald shiners (often used as bait) are not native and were first sampled in 2005. Juvenile zebra mussel (veliger), were discovered while sampling for plankton in 2012 and 2014. Shoreline and mid lake areas of rock were investigated for adult zebra mussel in August of 2014. No adults have been discovered in any assessments. Each of these invasive species were likely introduced through human activities.
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This sub survey contains data from 8 mid lake gill net sets that were first set in 1997. These nets were initially set to determine if catch rate and growth statistics for various fish species were similar to those of the 24 near shore gill net sets. After 16 years of sampling it appears that catch rate and size for walleye, northern pike, and perch vary between the two net groups, while growth of fish appears to be similar.
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\nWalleye; Walleye catch rates varied similarly to near shore nets from 1997 to 2005, then appear to move independently from 2006 to 2012. Walleye were sampled at a rate of 5.9 per net in 2013. This catch rate was similar to the catch of 6.8 walleye per near shore gill net. Mid lake sampled walleye varied from 12.1 to 25.9 inches with a mean length of 18.1 inches. As with near-shore gill nets, no age 1 walleye were sampled.
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\nThe catch per gill net of Walleye longer than 19 inches has been used as an indicator of quality for the Walleye population. The mean catch of Walleye longer than 19 inches sampled per mid lake net since 1997 was 1.17 per net. This catch rate was similar to the mean catch of 1.18 Walleye longer than 19 inches per near shore gill net set since 1997. The catch rate of Walleye longer than 19 inches was 2.38 per mid lake net in 2013.
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\nNorthern pike; Mid lake gill net catches of Northern Pike (pike) are typically less than near shore nets and 2013 was no different. The mid lake catch of 9.3 pike per net was the highest since 1997 but was lower than the catch of 14.1 per near-shore gill net. Pike sampled in 2013 varied from 16.1 to 32.0 inches with a mean length of 21.8 inches.
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\nYellow perch; Yelow Perch (perch) were sampled at a rate of 72.9 per gill net. This was the highest catch since 2008 and was similar to the catch of 75.6 perch per near shore gill net lift. The mean catch per gill net since 1997 has been higher in mid lake gill nets (82.9) than traditional gill nets (73.3). Although catch rates have been higher in mid lake nets, the catch per gill net lift has varied similarly between near shore and mid lake gill nets. Perch sampled in mid lake nets varied from 4.3 to 11.7 inches with a mean length of 7.4 inches.
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\nRelative health of the perch population has been described by the percent of perch longer than nine inches in the gill net catch. The catch of large perch in near shore gill nets declined to 6% in the early 1990's driven by high angler harvest. Changes in Lake Winnibigoshish and other lakes prompted a statewide change in the perch bag limit to 20 daily and 40 in possession in 2001. Strong year classes were produced in 1994 and 1997 which resulted in high catch rates of large perch in the early 2000's. The mid lake catch of large perch started to decline in 2004 and has declined from 45.9% in 2004 to near 16% in 2010 and 2011, and 14.8 percent in 2012. The catch of perch longer than 9 inches increased to 20.9% in 2013.
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\nCisco; The Cisco population can vary significantly on an annual basis. Cisco gill net catch rates have varied between 11.3 and 49.3 per lift between 1997 and 2012. The variation appears to be linked to warm summers that cause summer kills and warm fall water temperatures that may cause reduced reproduction and recruitment. The gill net catch rate of 8.6 per net in 2013 was the lowest observed. Length frequency data indicates that young fish are present in the system but age 3 fish (9 to 11 inches) are of low abundance.
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