The present fish population of Lake Minnetonka was found to be in good shape. Bluegill are still the most abundant species sampled and size structure of the population is above average for the Metro region. Northern Pike were sampled at record numbers as a result of high recruitment of year classes from 1992-1995. Average size of northern pike is approximately 2.2 pounds, but 6 percent of the individuals sampled were 5 pounds or over. The walleye population appears to be stable when compared the the 1992 population assessment. The largemouth bass population also appears to be in good shape with individuals of all sizes from young-of-year to 20-plus inch fish sampled. A continued shift of bullhead abundance continues with yellow bullhead outnumbering black bullheads in the sample in excess of 3 to 1. Crappie numbers reflect a decline in sample abundance from recent years, while yellow perch numbers are up slightly. Other species sampled reflect relatively stable populations.
"},{"surveySubType":"Special Assessment","headerInfo":{"survey_id":"5171113141057000","wb_alt_name":"","survey_type":"Special Assessment","wb_type":"Lake","id_date":"2011-05-24","wb_id":"27013300","county":"Hennepin","wb_name":"Minnetonka"},"surveyID":"5171113141057000","surveyType":"Targeted Survey","fishCatchSummaries":[{"CPUE":"75.71","totalCatch":385,"gearCount":5.08527777777778,"quartileCount":"N/A","quartileWeight":"N/A","species":"LMB","gear":"Standard electrofishing","averageWeight":"1.04","totalWeight":181838}],"surveyDate":"2011-05-24","lengths":{"LMB":{"minimum_length":5,"fishCount":[[10,41],[11,20],[12,45],[13,30],[14,50],[15,30],[16,17],[17,14],[18,5],[19,1],[20,1],[5,5],[6,21],[7,33],[8,41],[9,31]],"maximum_length":20}},"narrative":"The largemouth bass population in Lake Minnetonka has a reputation for quality fishing. A nighttime boat electrofishing assessment was performed during May 2011 targeting largemouth bass. A total of 385 largemouth bass were sampled in 11 electrofishing transects, equating to 75.4 bass per hour of on time. Catch rates were similar to the 2009 assessment when 73.2 bass per hour were sampled. These catch rates are above average for area lakes. The size structure of the largemouth bass population in Lake Minnetonka is well balanced and the fish are in good physical condition. The larger fish were in the best condition. Largemouth bass averaged 11.8 inches and 1.04 lbs, which is lower than the 2009 electrofishing assessment when fish averaged 13.5 inches and 1.5 lbs. In 2011, the largest bass sampled was 20.9 inches long and 4.9 lbs. Fish from the 1999 through 2009 year classes were present, indicating consistent reproduction and recruitment. Age-3 bass from the 2008 year class were most abundant (25%), followed by the 2007 (23%) and 2005 (9.4%) year classes. Growth was slower than average compared with other West Metro Area lakes. Largemouth bass reached 14 inches by age 7 and 18 inches by age 11. No smallmouth bass were sampled during the spring elecrofishing assessment.
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\nNumerous bass tournaments are held on the lake every year. Bass tournament are held by permit only and fish data must be turned into the DNR. In 2011, 11 bass tournaments were held. A total of 1,136 tournament anglers caught 3,854 largemouth bass and 38 smallmouth bass. Average size was 2.5 lbs and the largest recorded was 6.9 lbs. Since bass anglers target the largest individuals in a population, it is common for angling results to yield larger size fish, on average, than electrofishing. Additionally, individual tournaments may enact their own minimum size limit, thus only measuring a minimum size of fish. The electrofishing assessment targeted all sizes of bass.
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Introduction
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\nLake Minnetonka is a 14,206 acre lake in Hennepin County, with a maximum depth of 113 feet and an average depth of 30 feet. The lake is comprised of many connected bays, and has a complex shoreline. Multiple public and private boat launches are located around Minnetonka, and the lake is popular with both anglers and recreational boaters. Naturally reproducing populations of Northern Pike and Largemouth Bass are present, and Walleye and Muskellunge populations are maintained by stocking.
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\nA Standard Survey was conducted on Lake Minnetonka June 3 through June 21, 2019. Sampling involved gill netting, trap netting, and water quality sampling. Sampling in Lake Minnetonka is distributed through three basins that differ in their habitat and water quality characteristics. Gill netting and trap netting effectively sample Northern Pike, Walleye, Yellow Perch, Bluegill and Black Crappie. The population trends of those species are described by this survey.
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\nPopulation trends of Largemouth Bass and Muskellunge are not described by this survey, although robust populations of each exist in the lake. Largemouth Bass are sampled by nighttime spring electrofishing, and Muskellunge are sampled by large-frame trap netting during the spring. These sampling methods were not conducted during the 2019 survey.
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\nWater Characteristics
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\nHeavy rainfall during spring 2019 caused high water levels on Lake Minnetonka, and a no-wake regulation within 600 feet of shore was imposed May 31 until June12, 2019. High spring precipitation followed by boating restrictions also occurred in 2014. Water clarity has been improving in Lake Minnetonka over the past several decades. Increasing water clarity can be attributed to improvements in the condition of the watershed. The Northwest Bays are most fertile, primarily because they are the first recipients of the majority of surface runoff from the watershed. The Upper Lakes are intermediate in fertility, while the Lower Lakes are, relatively, the least fertile. The Minnehaha Creek Watershed District more closely monitors water quality in Lake Minnetonka. For more specific, detailed information about Lake Minnetonka water quality, see the District's website (http://www.minnehahacreek.org/data-center).
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\nWalleye
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\nDespite a long history of stocking, Walleye abundance has remained low in Lake Minnetonka. In 2019, the Walleye catch rate of 1.7 fish per gill net was lower than the 3.3 fish/net caught in 2016. Walleye catch rate has dropped throughout all basins. In the Lower Lakes, Walleye catch rate dropped from 3.0 fish/net in 2016, to 1.2 fish/net in 2019. The Upper Lakes saw a drop in catch rate from 3.1 fish/net in 2016, to 1.8 fish/net in 2019. In the Northwest Bays, catch rate decreased from 3.8 to 2.3 Walleye/net.
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\nWalleye in Minnetonka tend to be large. Length of sampled fish ranged from 14.5 to 26.5 inches. Fish averaged 20.3 inches and 3.1 pounds. Average length was similar throughout the basins, being only slightly lower in the Northwest Bays (19.6 inches) than in the Lower Lakes (21.6 inches) and the Upper Lakes (20.1 inches). Walleye grew to 19.1 inches by age-4.
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\nNorthern Pike
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\nThe Northern Pike population in Lake Minnetonka is healthy and naturally reproducing. Abundance has historically been high, and it remained so in 2019. The Lower Lakes held the highest abundance of pike, and the Northwest Bays held the lowest numbers. The Northwest Bays also held the larger fish, where the average length was 27.2 inches. Average length in the Upper Lakes was 22.3 inches and in the Lower Lakes it was also 22.3. The largest Northern Pike in the 2019 survey was 37.1 inches and caught in the Lower Lakes. As part of the North-Central Zone, Northern Pike harvest in Minnetonka is regulated by a possession limit of 10 fish, not more than 2 fish exceeding 26 inches, while respecting a 22-26 inch protected slot.
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\nYellow perch
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\nYellow Perch are important forage in Lake Minnetonka. Compared to similar lakes, perch abundance in Minnetonka was moderately low in 2019. The fish have historically tended to be small in Minnetonka, however, 2019 saw an increase in size structure. Lake-wide, 19% of the sampled Yellow Perch exceeded 8 inches. The increase in size structure was driven by the perch in the Northwest Bays, where 41% of the sampled fish exceeded 8 inches. The largest Yellow Perch sampled in 2019 was 10.9 inches.
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\nMuskellunge
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\nMuskellunge were not targeted during this survey, and only two specimens were sampled. The fish were 44.5 and 45.7 inches in length. Based on other reports, the Muskellunge population remains strong. Fish exceeding 50 inches and approaching 40 pounds are caught in Lake Minnetonka every year.
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\nA research study is currently taking place in Lake Minnetonka comparing the survival of stocked fingerling and yearling Muskellunge. Stocked fish were tagged in 2008, 2009, 2011, and 2012. Muskellunge were tagged with a yellow external tag near the dorsal fin on the fish's left side. These tags are labeled with a six-digit number. Angler reports of captured tagged Muskellunge are essential to the success of this project. If you catch a tagged muskellunge please record the tag number and length of fish and report the catch via the Tagged Fish Reporting page within the MNDNR website ( https://www.dnr.state.mn.us/fisheries/tagged_fish_reporting/index.html ). Please DO NOT remove the tag. Please contact the West Metro Area Fisheries Office with questions.
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\nLargemouth Bass
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\nAlthough electrofishing for bass was not conducting in 2019, the Largemouth Bass population in Lake Minnetonka has a reputation for quality fishing. Numerous bass tournaments are held on the lake every year. In 2019, 12 permitted bass tournaments reported. A total of 1,608 tournament anglers caught 3,530 Largemouth Bass and 160 Smallmouth Bass during these events. Average Largemouth Bass size was 2.57 lb and the largest recorded was 6.99 lb. Since tournament bass anglers target the largest individuals in a population, it is common for angling results to yield larger size fish, on average, than standard sampling. Additionally, individual tournaments may enact their own minimum size limits, thus adding to a larger-fish size bias.
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\nBluegill and Other Fish Species
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\nBluegill and Black Crappie are abundant in Lake Minnetonka. Bluegill averaged 6.3 inches, and the largest individual was 8.3 inches. Black Crappie averaged 8.1 inches, and the largest individual measured 10.6 inches. Consistent natural reproduction of these species have ensured quality angling opportunities.
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\nBlack Bullhead, Brown Bullhead, Common Carp, Green Sunfish, hybrid sunfish, Pumpkinseed Sunfish, Rock Bass, Smallmouth Bass, Yellow Bullhead, White Sucker, and Bowfin were also captured during the 2019 assessment. Smallmouth Bass were sampled only in the Lower Lakes.
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\nInvasive Aquatic Species
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\nEurasian water milfoil and curly leaf pondweed are found in high abundance throughout the lake and in 2010 zebra mussels and flowering rush were first found to be present. Lake Minnetonka receives heavy recreational use, so potential for the spread of invasive species into and out of the lake is high. Anglers and boaters should take the precautions-and follow statewide laws-- necessary to prevent the further spread of all invasive species.
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\nThe shoreline and watershed of Lake Minnetonka is highly developed, which degrades the lake's aquatic habitat. Large docks, boating platforms, and man-made beaches have the potential to destroy vital habitat for fish and wildlife. Environmentally conscious land use practices, such as shoreline buffer strips of natural vegetation and fallen woody debris, are necessary to maintain or improve water quality of Lake Minnetonka. Shoreline development should be a concern to everyone who enjoys lake recreation.
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The 2008 Lake Minnetonka special assessment was conducted June 9th through June 25th. Annual sampling began in 1997 following a 20-year period when the fish community was sampled every five years. Sampling in Lake Minnetonka is divided between aggregations of basins that differ in their habitat and water chemistry. The Northwest bays are most fertile, as they are the first recipients of a majority of surface runoff from the watershed. The Upper Lakes are intermediate in fertility, while the Lower Lakes are least fertile.
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\nSince 1997, special assessments have been conducted to assess trends in growth, condition, relative abundance, reproduction, and size structure of northern pike, walleye, and yellow perch. In order to effectively sample the aforementioned species, twenty-four experimental gillnets were set at 12 historic locations (24 hr sets; 2 net sets at each location with approximately 7-9 days between net sets). The 2008 gillnet assessment revealed a diverse fish community (17 species) dominated (based on lb/gillnet) by northern pike (31.96 lb/net), bluegill (14.48 lb/net), and walleye (9.04 lb/net).
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\nWater Quality
\nWater quality trends in Lake Minnetonka indicated positive change in average Secchi depth (Figure 1, page 7) and anoxic depth (< 2 ppm DO; Figure 2, page 8). The trends in Secchi depth for all three basins are significantly positive (Linear Regression: Lower Lakes: P = 0.015; Upper Lakes: P = 0.002; Northwest Bays: P = 0.035) with the Lower Lakes showing the greatest improvement as evidenced by the highest slope. The same relationship is also true of historical anoxic depths in Lake Minnetonka.
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\nWalleye
\nDespite extensive fingerling stocking effort, walleye abundance, as indicated by gillnet catch per unit effort, has remained at low levels. The 2008 catch of 3.64 fish/net fell below the 2007 catch of 4.3 fish/net and is below the 38-year average of 4.11 fish/net. Since 1970, seventeen surveys have been performed on Lake Minnetonka; nine of which found walleye catch rates below the lower quartile (4.01 fish/net) for class 22 lakes, including 2008. The biennial walleye stocking rate for Lake Minnetonka doubled beginning in 1999 from 1 lb/ littoral acre to 2 lbs/ littoral acre. These increased year-classes would have been recruited to the fishery in 2002. Walleye catch rates post-2002 have been similar to catch rates pre-2002. A comparison of NOP and WAE catch rates suggests WAE catch rates may be inversely related to NOP catch rates. For example, the historically second lowest walleye catch rate (1.5 fish/net) occurred in 2005, three years after the historically second highest NOP catch rate (17.7 fish/net). The high NOP catch rate in 2002 represents a large population of NOP in Lake Minnetonka that could have preyed upon the WAE fingerlings stocked in that year. Since WAE are recruited to gillnets by age-3, this predation was evident three years later (2005) when they were large enough to be sampled. This relationship is also evident 1999 through 2001.
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\nWalleye catch rates were highest in the Lower Lakes (4.3 fish/net), followed by the Northwest Bays (3.5 fish/net) and Upper Lakes (3.1 fish/net). Walleyes are not stocked into the Northwest Bays so immigration into this portion of Lake Minnetonka maintains the fishery there.
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\nWalleye mean weight (2.49 lbs) increased from 2006 (2.38 lbs), and is the fourth highest mean weight observed in 26 years. Walleye mean weight in 2008 exceeded the upper quartile when compared to other class 22 lakes, as has been the case 24 out of the past 26 years. Mean weight was highest within the Northwest Bays (3.3 lbs), followed by the Upper Lakes (2.96 lbs) and the Lower Lakes (1.64 lbs). Walleye mean weight has been the highest in the Northwest Bays in all but one of the previous Lake Minnetonka surveys. This may be the result of lower walleye abundances and the higher yellow perch abundances found in the Northwest Bays. Historically, walleye relative weight in Lake Minnetonka has remained below the value of 100, which indicates the 75th percentile condition or plumpness (above average condition) for the species. Walleye relative weight (91) in 2008 was near the 10-year average relative weight of 92. Walleye relative weight did not change significantly with length.
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\nWalleye averaged 17.96 inches and ranged 8.98 - 27.68 inches. Similar to mean weight, mean length was highest within the Northwest Bays (20.6 inches), followed by the Upper Lakes (19.53 inches) and the Lower Lakes (15.16 inches). Historically, size structure indices have revealed Lake Minnetonka's walleye population consists of larger individuals, and this was again observed in 2008 (N=81, PSD=81, RSD-P=38). PSD was highest within the Northwest Bays (100), followed by the Upper Lakes (92) and the Lower Lakes (58). The largest individual captured was an age-12, 27.7 inch, 8.5 pound female.
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\nAging walleyes using otoliths allowed year-class inferences to be made. Consistent with previous assessments, walleye natural reproduction is limited. Seven out of 76 (9.2%) aged walleye originated from a non-stocked year-class. Five age-3 walleyes and 2 age-5 walleyes, originating from the 2005 and 2003-year-classes, are assumed to be naturally reproduced. One walleye from the 2003 year-class was also sampled in 2007 providing more evidence that some natural recruitment occurred in that year. Past assessments have documented natural recruitment from the 1999 and 1997 year-classes. The 2001, 2004, and 2006 year-classes appear to be strong contributing 66% of the walleye catch. The 2006 year-class may be particularly strong since these fish were only age-2 in 2008 and not fully recruited to the sampling gear.
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\nWalleye growth in Lake Minnetonka was slightly higher compared to all lakes in the West Metro management area and historic walleye growth in Lake Minnetonka particularly for walleyes age 2-4. This increased growth may have been an artifact of recent mild winters and the consequent longer growing seasons. Comparing basins, walleye grew faster in the Northwest Bays.
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\nNorthern Pike
\nConsistent with recent assessments, northern pike displayed relatively high abundance during this assessment. Although slightly down from 2007, gillnet catch rates in 2008 (9.14 fish/net) exceeded the upper quartile as did average weight (3.5 lbs) for class 22 lakes. Northern pike abundances in Lake Minnetonka have been on a steady decline from the historically second highest catch of 17.7 fish/net in 2002 (Figure 4, page 21). Contrary to historical trends, northern pike catch rates in the Lower Lakes (10.4 fish/net) exceeded catch rates in both the Upper Lakes (8.6 fish/net) and Northwest Bays (8.2 fish/net). Previously, northern pike gillnet catch has been highest in the Upper Lakes. The northern pike population averaged 24.53 inches (range: 17.17-34.25) and 3.5 lbs; both increases from the 2007 assessment. Northern pike mean length within each basin was largest in the Northwest Bays (25.68 inches), followed by the Upper Lakes (24.33 inches) and Lower Lakes (24.01 inches). Relative weight (90) was fair and near the historic average (88). The largest individual captured was an age-8, 34.25 inch, 9.25 pound female.
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\nSize structure indices revealed a balanced, quality pike population (PSD=78; RSD-P=20) with the best size structure found in the Northwest Bays (PSD=88). The current northern pike population in Lake Minnetonka may offer anglers the best chance at catching northern pike over 24 inches in the West Metro management area. The northern pike population lacks small \"hammer handle\" northern pike with most of the fish sampled between 19-29 inches. Growth rates were above West Metro management area lake averages for the first four years and below average thereafter. On average, northern pike in Lake Minnetonka reach 20 inches at age 2 and 30 inches by age-9. Nine year-classes were sampled with the oldest individual age-10.
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\nYellow Perch
\nYellow perch relative abundance (15.36 fish/net) was below the median level (17.1 fish/net) for class 22 lakes, as historically been the case. Yellow perch gillnet catch increased in Lake Minnetonka each year from 2001 - 2006. However, the 2007 and 2008 gillnet catches were below that of 2006 (16.3 fish/net). Consistent with previous assessments, perch abundance was highest in the Northwest Bays (43.17 fish/net) and relatively low in the Upper (7.88 fish/net) and Lower Lakes (2.0 fish/net) and when compared to class 22 lakes. When comparing perch catch by basins, the Northwest Bays have had the highest gillnet catch since 1970.
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\n Size structure indices (PSD = 4) revealed a population consisting of small individuals (mean length = 6.61 inches). The strong 2004 year-class observed in 2007 also dominated the 2008 catch, averaging 6.71 inches. Yellow perch size structure has been historically small in Lake Minnetonka with an average PSD of 3 since 1992. Yellow perch relative weight (87) was fair in 2008 and has been decreasing from the decade high (102) in 2003. Relative weight decreased significantly with length (Linear Regression: (df = 164; t = -4.783; P < 0.001) indicating a resource bottleneck may be occurring for larger, older individuals. Seven year-classes were sampled in Lake Minnetonka with the oldest individual captured age-8. Yellow perch growth in Lake Minnetonka was slower on average than other lakes in the West Metro management area. Comparing basins, yellow perch grew faster in the Northwest Bays.
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\nLargemouth Bass
\nThe largemouth bass fishery in Lake Minnetonka has a reputation for quality fishing. Numerous bass tournaments have been held on the lake in past years. A Nighttime electrofishing assessment was performed during May in 2008 targeting largemouth bass. Sampling largemouth bass in Lake Minnetonka is difficult due to the abundant docks and marinas. The sandy shorelines of lake Minnetonka also inhibit sampling. Typical largemouth bass habitat in Lake minnetonka consists of submergent vegetation in water deeper than 3 feet. Electrofishing gear does not perfrom well exceeding these depths.
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\nJust over 200 largemouth bass were sampled with an average length and weight of 13.45\" and 1.52 lbs. Forty eight percent of the largemouth bass exceeded 14\", and 13% exceeded 3lbs. Largemouth bass were larger on average in the Lower Lakes (14.11\", 1.88lbs), followed by the Northwest Bays (13.26\", 1.48lbs) and Upper Lakes (12.86\", 1.26lbs). Catch rates expressed as number caught per hour of energized time were also larger in the Lower Lakes (86/hr), followed by the Northwest Bays (72/hr) and Upper Lakes (60/hr). These catch rates are above average for area lakes.
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A targeted survey of nearshore fish species in Lake Minnetonka was conducted during August, 2019 by Index of Biological Integrity (IBI) Program Staff. Sampling sites were evenly spaced around the lake and each was sampled by backpack electrofishing and seining with a 50-foot or 15-foot seine, where possible. Lakewide, backpack electrofishing was completed at 72 sampling stations, but 14 stations were sampled from the boat due to site conditions. Similarly, a 50-foot seine was used to sample 40 stations, a 15-foot seine was used at 18 stations, and site conditions prevented the use of seines at 14 stations. Lakewide, nearshore sampling captured 33 species of fish including nine species that are intolerant of disturbance (Banded Killifish, Blackchin Shiners, Blacknose Shiners, Iowa Darters, Least Darters, Muskellunge, Pugnose Shiners, Rock Bass, and Smallmouth Bass) and two that are tolerant of disturbance (Fathead Minnows and Green Sunfish).
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\nThe nearshore data were combined with trap net and gill net data from a June 2019 survey to describe the fish community and provide a Fish-based IBI (FIBI) score. The FIBI uses fish community data to measure a lake's health, and the types of fish species present can help identify any stressors that may be negatively affecting the lake environment. In Minnesota lakes, certain fish species cannot survive without clean water and a healthy habitat (e.g. Least Darters, Muskellunge, Smallmouth Bass), while other species are tolerant of degraded conditions (e.g. Fathead Minnow and Green Sunfish). The FIBI score, composed of several fish community diversity and composition metrics, indicates the overall health of a lake by comparing it to what is expected for a healthy lake. For additional information on the FIBI, search for \"lake index of biological integrity\" on the mndnr.gov website.
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\nIndividual FIBI scores were calculated for three separate sub-basins of Lake Minnetonka: the North & West Bays, the Lower Lake, and the Upper Lake.
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\nWithin the North & West Bays sub-basin of Lake Minnetonka, backpack electrofishing was completed at 24 sampling stations, but four stations were sampled from the boat due to site conditions. Similarly, a 50-foot seine was used to sample 12 stations, a 15-foot seine was used at five stations, and site conditions prevented the use of seines at seven stations. Nearshore sampling captured 26 species of fish including seven species that are intolerant of disturbance (Banded Killifish, Blackchin Shiner, Blacknose Shiners, Iowa Darters, Least Darters, Muskellunge, and Pugnose Shiners) and four that are tolerant of disturbance (Fathead Minnow, Black Bullhead, Common Carp, and Green Sunfish).
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\nWithin the Lower Lake sub-basin of Lake Minnetonka, backpack electrofishing was completed at 24 sampling stations, but eight stations were sampled from the boat due to site conditions. Similarly, a 50-foot seine was used to sample 12 stations, a 15-foot seine was used at seven stations, and site conditions prevented the use of seines at five stations. Nearshore sampling captured 24 species of fish including seven species that are intolerant of disturbance (Banded Killifish, Blackchin Shiner, Blacknose Shiners, Iowa Darters, Pugnose Shiners, Rock Bass, and Smallmouth Bass) and two that are tolerant of disturbance (Fathead Minnow and Green Sunfish).
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\nWithin the Upper Lake sub-basin of Lake Minnetonka, backpack electrofishing was completed at 24 sampling stations. Similarly, a 50-foot seine was used to sample 16 stations, a 15-foot seine was used at six stations, and site conditions prevented the use of seines at two stations. Nearshore sampling captured 29 species of fish including eight species that are intolerant of disturbance (Banded Killifish, Blackchin Shiner, Blacknose Shiners, Iowa Darters, Least Darters, Pugnose Shiners, Rock Bass, and Smallmouth Bass) and three that are tolerant of disturbance (Black Bullhead, Common Carp, and Green Sunfish).
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\nData from this survey will contribute biological information about the health of the fish community to the Mississippi River - Twin Cities Watershed assessment process in coordination with MN Pollution Control Agency.
The 2010 Lake Minnetonka (27-0133-00) fisheries assessment was conducted June 14th through July 3rd. Annual sampling began in 1997 following a 20-year period when the fish community was sampled every five years. Sampling in Lake Minnetonka is divided between aggregations of basins that differ in their habitat and water chemistry. The Northwest Bays are most fertile, as they are the first recipients of the majority of surface runoff from the watershed. The Upper Lakes are intermediate in fertility, while the Lower Lakes are least fertile.
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\nSince 1997, assessments have been conducted to assess trends in growth, condition, relative abundance, reproduction, and size structure of northern pike, walleye, and yellow perch. In order to effectively sample the aforementioned species, twenty-four experimental gillnets were set at 12 historic locations (24 hr sets; 2 net sets at each location with approximately 7-9 days between net sets). The 2010 gillnet assessment revealed a diverse fish community (17 species) dominated (based on lbs/gillnet) by northern pike (27.1 lbs/net), bluegill (14.1 lbs/net), and walleye (9.2 lbs/net).
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\nWater Quality
\nWater quality trends in Lake Minnetonka indicate a positive change in average Secchi depth and anoxic depth (< 2 ppm Dissolved Oxygen) over time. The trends in Secchi depth for all three basins are significantly positive, with the Lower Lakes showing the greatest improvement. The same relationship is also true of historical anoxic depths.
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\nWalleye
\nLake Minnetonka is stocked with 6,446 pounds of fingerling walleye in even-numbered years. This equates to 1.1 lbs/littoral acre. For more than 30 years, previous management limited walleye stocking locations to the Upper Lake and Lower Lake basins. Starting in the fall of 2010, walleye were and will continue to be stocked into all three basins of the lake. Despite extensive fingerling stocking effort, walleye abundance, as indicated by gill net catch per unit effort, has remained at low levels . The 2010 catch of 2.9 fish/net is the lowest observed since 2006 and is below the previous 39-year average of 3.9 fish/net. Since 1970, 19 surveys have been conducted on Lake Minnetonka; of these, 12 had walleye catch rates below 4.0 fish/net. A comparison of northern pike and walleye catch rates suggest the two may be inversely related . For example, the historically second lowest walleye catch rate (1.5 fish/net) occurred in 2005, three years after the historically second highest northern pike catch rate (17.7 fish/net). The high northern pike catch rate in 2002 represents a large population of northern pike in Lake Minnetonka that could have preyed upon the walleye fingerlings stocked in that year. Since walleye are recruited to gillnets by age-3, this predation was evident three years later (2005) when they were large enough to be sampled. This relationship is also evident 1999 through 2001.
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\nOn an entire lake basis, walleye abundance is lower than previous years; however, catch rates differed by basin. In Upper Lakes, there was an increase of one walleye per net (3.3/ gill net) from 2009 (2.3/gill net). In both Lower Lakes and the Northwest Bays there was a decrease in the number of walleye per net. In Lower lakes catch dropped from 4.3/gill net in 2009 to 3.5 /gill net in 2010. The difference in the Northwest Bays was a decrease in 2 walleye per net from 3.5/gill net in 2009 to 1.5 per gill net in 2010.
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\nWalleye mean weight (3.16 lbs) was similar to 2009 and the highest observed since 1977 (3.27 lbs) . Walleye mean weight in 2010 was high when compared to other similar lakes, and this has been the case 31 out of the past 33 years. Mean weight was highest in the Northwest Bays (4.14 lbs), followed by the Upper Lakes (3.38 lbs), and the Lower Lakes (2.74 lbs). The general trend over time has been for the largest walleyes to be located in the Northwest Bays, followed by Upper Lakes, then Lower Lakes. This is assumed to be related to the productivity of the basins. Historically, the condition of walleye in Lake Minnetonka has been good. A relative weight value of 100 indicates the 75th percentile condition or plumpness (above average condition) for the species. In 2010, walleye relative weight (90) was near the average of the previous 13 years (92). There was no significant relationship with relative weight and fish length.
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\nWalleye averaged 19.9 inches and ranged from 9.3 to 28.5 inches. Similar to mean weight, mean length was highest within the Northwest Bays (22.2 inches), followed by Upper Lakes (20.1 inches), then Lower Lakes (19.1 inches). Historically, size structure indices have revealed Lake Minnetonka's walleye population consists of larger individuals, and this was again observed in 2010. Size structure was highest within the Northwest Bays , and Upper Lakes followed by the Lower Lakes . The largest individual captured was an age-11, 28.5 inch, 9.5 pound female.
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\nAging walleyes using otoliths allowed year-class inferences to be made. Consistent with previous assessments, walleye natural reproduction is limited. In 2010, 11 out of 70 (15.7%) walleye originated from a non-stocked year-class. This was an increase from 2009, where only 5.2 % were determined to be naturally reproduced. Similar to 2009, naturally produced fish from the 2005 and 1999 year classes were present, providing more evidence that some natural recruitment occurred in those years. Past assessments have documented natural recruitment from the 2003 and 1997 year-classes, as was the case again in 2010. The stocked 2004 and 2006 year-classes continue to be strong contributing to 55% of the walleye catch. However, the abundance of walleye in the 2004 year class was not as high as seen in previous years.
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\nIn 2009, a catch curve analysis estimated walleye total annual mortality at 27.5%. Ages 3, 5, and 7-9 were used to calculate the catch curve. Total annual mortality was derived from the slope of a linear regression of the number of fish sampled in each age class. Constant recruitment is one of the major assumptions in catch curve analysis; however, since the walleye population in Lake Minnetonka is dependent upon stocking in alternate years this assumption is violated. To address this problem, the gillnet age frequency data was adjusted to accommodate for the number of walleyes stocked in each age class. For example, 22 walleyes were captured from the 2006 year-class when 125,337 fish were stocked. The gillnet catch of 22 age-3 walleyes was divided by 125,337 (number stocked in that year). The resulting value was then entered into the catch curve analysis for the number of age-3 walleyes sampled.
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\nWalleye growth in Lake Minnetonka was similar to other lakes in the West Metro management area and historic walleye growth in Lake Minnetonka. Walleye reached an average length of 13.5 inches by age 3 and 19.6 inches by age 6. Comparing basins, walleye grew fastest in the Northwest Bays , followed by Lower Lakes, then Upper Lakes .
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\nNorthern Pike
\nConsistent with recent assessments, northern pike were relatively high in abundance (6.9 fish/net) in 2010 compared with other similar lakes. However, northern pike gill net catch has decreased every year since the historical high of 17.7/ net in 2002. Northern pike catch rates in the Lower Lakes (7.8 fish/net) exceeded catch rates in both the Northwest Bays (6.3 fish/net) and Upper Lakes (6.1 fish/net). Possibly due to decreasing abundance, mean northern pike length and weight in 2010 was the highest in recent history. Sampled northern pike averaged 25.4 inches (range: 17.8-34.8 inches) and 3.9 lbs. Northern pike mean length was similar in all three basins (Northwest Bays = 25.5 inches; Upper Lakes = 25.9 inches; Lower Lakes = 25.0 inches). Relative weight (92) was fair and near the historic average (88). The largest individual captured was an age-7, 34.8 inch, 13.23 pound female.
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\nSize structure indices revealed a balanced, quality pike population with the best size structure found in the Northwest Bays. Size structure for the lake as a whole was the highest observed in history. The current northern pike population in Lake Minnetonka may offer anglers the best chance at catching northern pike over 24 inches in the West Metro management area. The northern pike population lacks small \"hammer handle\" northern pike with most of the fish sampled between 20 and 29 inches. Growth rates were near West Metro management area lake averages for the first four years and below average thereafter. On average, northern pike in Lake Minnetonka reach 20 inches by age 3 and 30 inches by age 8. Eight year-classes were sampled with the oldest individual age-9. In 2009, a catch curve analysis estimated northern pike total annual mortality at 36.1%. Ages 3-8 were used to calculate the catch curve.
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\nYellow Perch
\nYellow perch relative abundance (17.3 fish/net) was near the median level (17.1 fish/net) compared with similar lakes in the area. The trend since 2000 has been for increasing yellow perch gillnet catch, with the 2010 catch setting a historical high. Consistent with previous assessments, perch abundance was highest in the Northwest Bays (30.5/net) and lowest in the Lower Lakes (6.1/net). In the Upper Lakes, catch (21.5/net) was the highest since 1998 and three times higher than the 2009 assessment.
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\nSize structure indices revealed a population consisting of small individuals (mean length = 6.6 inches). Yellow perch size structure has been historically small in Lake Minnetonka. Yellow perch relative weight (90) was fair in 2010, similar to 2009, but low compared to a high of 102 in 2003. Relative weight decreased significantly with length indicating a resource bottleneck may be occurring for larger, older individuals. Similar to 2009, six year-classes were sampled in Lake Minnetonka with the oldest individual captured age-7. The 2004 year class that remained strong in the 3 previous assessments represented only 11% of the catch in 2010. The 2007 and 2006 year classes comprised 73% of the catch. Yellow perch growth in Lake Minnetonka was slower on average than other lakes in the West Metro management area. Comparing basins, yellow perch grew fastest in the Northwest Bays until age 6, then age 7 and 8 yellow perch grew fastest in the Lower Lakes. In 2009, a catch curve analysis estimated yellow perch total annual mortality at 46.5%. Ages 3-7 were used to calculate the catch curve.
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\nMuskellunge
\nMuskellunge were not targeted during this assessment, but their population remains strong. Fish exceeding 50 inches and approaching 40 pounds are caught in Lake Minnetonka every year. Survival of stocked fingerling muskellunge is assumed to be very low due to the high abundance of largemouth bass and northern pike. Advanced fingerlings and yearlings have been used in recent years to try and improve the survival rate of stocked fish. A research study is currently taking place in Lake Minnetonka investigating the survival of stocked fingerling and yearling muskellunge. Stocked fish were tagged in 2008 and 2009 and will again be tagged in 2011. These fish were tagged with an external spaghetti-type tag near the dorsal fin. These tags are yellow in color and include a six-digit number. Angler reports of captured tagged muskellunge are essential to the success of this project. If you catch a tagged muskellunge please record the tag number and length of fish and report the catch via phone, email or the Tagged Fish Reporting page within the MNDNR website. Please DO NOT remove the tag. Please contact the West Metro Fisheries Office with questions. Practicing CPR (Catch, Photo, and Release) is essential to maintaining the trophy muskellunge fishery found in Lake Minnetonka.
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\nOther Fish
\nBluegill and black crappie are abundant in Lake Minnetonka; however, gill nets are not reliable indicators of their relative abundance. Natural reproduction and high recruitment of these species will ensure quality angling opportunities.
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\nThe largemouth bass fishery in Lake Minnetonka has a reputation for quality fishing. Numerous bass tournaments are held on the lake every year. A nighttime electrofishing assessment was performed during May 2008 targeting largemouth bass. The sandy shorelines and abundant docks and marinas of Lake Minnetonka make sampling challenging. Two hundred four largemouth bass were sampled with an average length and weight of 13.5 inches and 1.5 lbs. Forty-eight percent of the largemouth bass exceeded 14 inches, and 13% exceeded 3.0 lbs. Largemouth bass were largest on average in the Lower Lakes (14.1 inches, 1.9 lbs), followed by the Northwest Bays (13.3 inches, 1.5 lbs) and Upper Lakes (12.9 inches, 1.3 lbs). Catch rates expressed as number caught per hour were also highest in the Lower Lakes (86/hr), followed by the Northwest Bays (72/hr) and Upper Lakes (60/hr). These catch rates are above average for area lakes. Another largemouth assessment is scheduled for spring 2011.
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\nBlack bullhead, bowfin (dogfish), common carp, green sunfish, hybrid sunfish, pumpkinseed sunfish, rock bass, white sucker, and yellow bullhead were also captured in low numbers during the 2010 assessment. Rock bass were only captured in the Lower Lakes. Smallmouth bass are found in Lake Minnetonka, but their numbers remain low.
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\nInvasive Species
\nEurasian water milfoil and curly leaf pondweed are found in high abundance throughout the lake and in 2010 zebra mussels and flowering rush were found to be present for the first time. Lake Minnetonka receives heavy recreational use so the potential for the spread of invasive species into and out of the lake is high. Anglers and boaters should take the precautions necessary to prevent the further spread of all invasive species.
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\nThe shoreline and watershed of Lake Minnetonka is highly developed and puts stress on the lake's aquatic habitat and ecosystem integrity. Large docks, boating platforms, and man-made beaches have the potential to destroy vital habitat for fish and wildlife. Environmentally friendly development practices, such as shoreline buffer strips of natural vegetation, are necessary to maintain the current water quality of Lake Minnetonka. Shoreline development, invasive species, and the fish diseases Viral Hemorrhagic Septicemia (VHS) and Largemouth Bass Virus should be a concern to all Minnesotans who enjoy lake recreation.
\tThe 2011 Lake Minnetonka fisheries assessment was conducted June 13th through 30th. Annual sampling began in 1997 following a 20-year period when the fish community was sampled every five years. Sampling in Lake Minnetonka is divided between aggregations of basins that differ in their habitat and water chemistry. The Northwest Bays are most fertile, primarily because they are the first recipients of the majority of surface runoff from the watershed. The Upper Lakes are intermediate in fertility, while the Lower Lakes are least fertile.
\n\tSince 1997, assessments have been conducted to assess trends in growth, condition, relative abundance, reproduction, and size structure of northern pike, walleye, and yellow perch. To effectively sample the aforementioned species, 24 experimental gillnets are set at 12 historic locations (24-hr sets; 2 net sets at each location with approximately 7-9 days between net sets). Additionally, in May 2011, an electrofishing special assessment was conducted to evaluate the status of the largemouth bass population. The 2011 gillnet assessment revealed a diverse fish community (17 species) dominated (based on lbs/gillnet) by northern pike (19.4 lbs/net), walleye (12.1 lbs/net), and bluegill (9.8 lbs/net).
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\nWater Quality
\n\tWater quality trends in Lake Minnetonka indicate a positive change in average Secchi depth and anoxic depth (< 2 ppm DO) over time. Secchi depths in 2011 were generally shallower than 2010; however, the trends in Secchi depth for all three basins show a positive relationship. The same relationship is also true of historical anoxic depths. The Lower Lakes have the best water quality, followed by the Upper Lakes, then Northwest Bays.
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\nWalleye
\n\tLake Minnetonka is stocked with 6,446 pounds of fingerling walleye in even-numbered years. This equates to 1.1 lbs/littoral acre. Starting in the fall of 2010, walleye were and will continue to be stocked into all three basins of the lake. For more than 30 years, previous management limited walleye stocking locations to the Upper Lake and Lower Lake basins. Despite extensive stocking, walleye abundance, as indicated by gillnet catch per unit effort, has remained at low levels. The 2011 catch of 3.5 fish/net is higher than 2010 (2.9/net), but below the average from 1997-2010 (4.2 fish/net). Since 1970, 20 surveys have been conducted on Lake Minnetonka; of these, 13 (including 2011) had walleye catch rates below the 25th percentile (4.0 fish/net) for Class 22 lakes. On an entire-lake basis, walleye abundance is higher than previous years; however, catch rates differed by basin. In Upper Lakes, there was a decrease from 3.3 walleye per net in 2010 to 2.8 per net in 2011. In both Lower Lakes and the Northwest Bays there was an increase in the number of walleye per net. In Lower Lakes, catch increased by 0.6 fish per net, in the Northwest Bays there was an increase of 2 walleye per net. 2010 appeared to be a low year for walleye abundance in the Northwest Bays but the 2011 catch indicated abundance similar to 2008 and 2009. The average walleye gill-net catch per net from 1997-2010 was 4.2 in the Upper Lakes, 4.9 in the Lower Lakes, and 3.2 in the Northwest Bays.
\n\tA comparison of northern pike and walleye catch rates suggests an inverse relationship. For example, the second lowest walleye catch rate (1.5 fish/net) occurred in 2005, three years after the second highest northern pike catch rate (17.7 fish/net). The high northern pike catch rate in 2002 represents a large population of northern pike in Lake Minnetonka that could have preyed upon the walleye fingerlings stocked in that year. Since walleye are recruited to gillnets by age 3, this predation was evident three years later (2005) when they were large enough to be sampled. This relationship is also evident 1999 through 2001.
\n\tThe size of walleyes was the largest in recent history. The current assessment (2011) was the first where walleye averaged over 20 inches in length. Walleye mean weight in 2011 (3.4 lbs) exceeded the 75th percentile when compared to other Class 22 lakes, and this has been the case since at least 1992. Mean weight was highest in the Upper Lakes (4.6 lbs), followed by the Northwest Bays (4.1 lbs), and the Lower Lakes (2.4 lbs). The general trend over time has been for the largest walleyes to be located in the Northwest Bays, followed by Upper Lakes, then Lower Lakes. This is assumed to be related to the productivity of the basins and the amount of yellow perch available as prey. Historically, the physical condition of walleye in Lake Minnetonka has been good. A relative weight value of 100 indicates the fish is in the 75th percentile for weight, relative to its length (above average condition). In 2011, walleye relative weight (90) was near the average of the previous 14 years (92). There was a significant relationship with relative weight and fish length . As walleye grew older, relative weight decreased.
\n\tWalleye averaged 20.3 inches in length and ranged from 7.3 to 28.5 inches. Similar to mean weight, mean length was highest in the Upper Lakes (22.7 inches), followed by Northwest Bays (22.2 inches), then Lower Lakes (18.0 inches). Historically, size structure indices have revealed Lake Minnetonka's walleye population consists of larger individuals, and this was again observed in 2011. The proportion of walleye 20 inches and larger has increased every year for the last 5 and has doubled since 2006. The proportion of 15-inch and longer fish has fluctuated over the same time period. Size structure was highest in the Northwest Bays, then Upper Lakes , followed by the Lower Lakes.
\n\tAging walleyes using otoliths allowed year-class inferences to be made. Consistent with previous assessments, walleye natural reproduction is limited. In 2011, 13 out of 81 (16.0%) walleye originated from a non-stocked year-class. This was similar to 2010, when only 15.7 % were determined to be naturally reproduced. The stocked 2004 and 2006 year-classes continue to be strong, contributing to 42% of the walleye catch. Three year-olds in the 2008 year class also had a strong presence at 21% of the catch. The largest individual captured was an age-15, 28.5-inch, 8.7-pound male. In 2009, a catch curve analysis estimated walleye total annual mortality at 27.5%.
\nWalleye growth was similar to other lakes in the West Metro Management Area and historic walleye growth in Lake Minnetonka. Walleye reached an average length of 12.8 inches by age 3 and 19.7 inches by age 6. Comparing basins, walleye grew fastest in the Northwest Bays, followed by Upper lakes, then Lower lakes.
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\nNorthern Pike
\n\tConsistent with recent assessments, northern pike were relatively high in abundance in 2011. The 2011 northern pike catch of 6.3 fish/net fell below the 75th percentile for Class 22 lakes for the third time since 1987, the first was 2009. Northern pike gill net catch has decreased every year since the historical high of 17.7/ net in 2002. Northern pike catch rates in the Lower Lakes (7.0 fish/net) exceeded catch rates in both the Northwest Bays (6.3 fish/net) and Upper Lakes (5.4 fish/net). Northern pike average size (mean weight = 3.08 lbs) remained above the 75th percentile for Class 22 lakes. Sampled northern pike averaged 23.0 inches in length, which was smaller than in 2010 (25.4 inches) but was near the average of 22.7 inches, calculated from the previous 15 surveys. Northern pike mean length was similar in all three basins (Northwest Bays = 23.4 inches; Upper Lakes = 23.9 inches; Lower Lakes = 22.2 inches). Relative weight (92) was fair and near the historic average (88). Northern pike condition was similar among all three basins. The largest individual captured was an age-9, 34.7-inch, 9.97-pound female.
\n\tSize structure indices revealed a quality northern pike population consisting of a high proportion of large individuals, with the best size structure found in the Upper Lakes. Size structure for the entire lake was lower in 2011 than 2010 as evidenced by lower mean size and lower size structure indices. The northern pike population in Lake Minnetonka may offer anglers the best chance at catching northern pike over 24 inches in the West Metro management area. The pike population is not overpopulated with small \"hammer handle\" fish, most are between 20 and 29 inches. Growth rates were slightly lower when compared to other West Metro Management Area lakes. On average, northern pike in Lake Minnetonka reached 20 inches by age 3 or 4 and 30 inches by age 7 or 8. Nine year-classes were sampled with the oldest individual age 9. In 2009, a catch curve analysis estimated northern pike total annual mortality at 36.1%. Ages 3-8 were used to calculate the catch curve.
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\nYellow Perch
\n\tYellow perch relative abundance (31.7 fish/net) was high (near the 75th percentile) compared to other Class 22 lakes and the historical average (12.6 fish/net). The trend since 2000 has been for increasing yellow perch gillnet catch, with the 2011 catch setting a historical high. The 2011 catch was nearly twice that of 2010 (17.3 fish/net). Consistent with previous assessments, perch abundance was highest in the Northwest Bays (59.5/net), followed by Upper Lakes (38.0/net) then Lower Lakes (8.7/net). Gill net catch was up in all basins; however the increase was greatest in the Northwest Bays at nearly 100%. In general, it appears there is an inverse trend of increasing yellow perch abundance with decreasing northern pike abundance.
\n \t Size structure indices revealed a population consisting of small individuals (mean length = 6.7 inches). Yellow perch size structure has been historically small in Lake Minnetonka. Despite a small size structure, yellow perch mean length was the highest since 2000. The perch population in the Northwest Bays has a better size structure than the other two basins, where average length (7.06 inches) and weight (0.16 lbs) are greater. Yellow perch relative weight (86) was fair in 2011, but lower than 2010 (90), and lower than the historical average of 90. Relative weight decreased significantly with length, indicating a resource bottleneck may be occurring for larger, older individuals. Seven year-classes were sampled with the oldest individual captured age 8. The 2007 and 2008 year classes were evenly represented, together forming 87% of the population. Yellow perch growth was slower on average than other lakes in the West Metro Management Area. Comparing basins, yellow perch grew fastest in the Northwest Bays, followed by Upper Lakes, then Lower Lakes. In 2009, a catch curve analysis estimated yellow perch total annual mortality at 46.5%. Ages 3-7 were used to calculate the catch curve.
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\nMuskellunge
\n\tMuskellunge were not targeted during this assessment, but their population remains strong. Fish exceeding 50 inches and approaching 40 pounds are caught in Lake Minnetonka every year. Survival of stocked fingerling muskellunge is assumed to be very low due to the high abundance of largemouth bass and northern pike. Advanced fingerlings and yearlings have been used in recent years in attempt to improve survival rates of stocked fish. A research study is currently taking place in Lake Minnetonka investigating the survival of stocked fingerling and yearling muskellunge. Stocked fish were tagged in 2008, 2009, 2011, and will be again in 2012. These fish were tagged with an external spaghetti-type tag near the dorsal fin. These tags are yellow in color and include a six-digit number. Angler reports of captured tagged muskellunge are essential to the success of this project. If you catch a tagged muskellunge please record the tag number and length of fish and report the catch via phone, email or the Tagged Fish Reporting page within the MNDNR website. Please DO NOT remove the tag. Please contact the West Metro Fisheries Office with questions. Practicing CPR (Catch, Photo, and Release) is essential to maintaining the trophy muskellunge fishery found in Lake Minnetonka.
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\nLargemouth Bass
\n\tThe largemouth bass population in Lake Minnetonka has a reputation for quality fishing. A nighttime boat electrofishing assessment was performed during May 2011 targeting largemouth bass. A total of 385 largemouth bass were sampled in 11 electrofishing transects, equating to 75.4 bass per hour of on time. Catch rates were similar to the 2009 assessment when 73.2 bass per hour were sampled. These catch rates are above average for area lakes. The size structure of the largemouth bass population in Lake Minnetonka is well-balanced and the fish are in good physical condition (Relative weight = 95). It appeared the larger fish tended to be in the best condition. Largemouth bass averaged 11.8 inches and 1.04 lbs, which is lower than in 2009 when fish averaged 13.5 inches and 1.5 lbs. The largest bass sampled was 20.9 inches long and 4.9 lbs. Fish from the 1999 through 2009 year classes were present, indicating consistent reproduction and recruitment. Age-3 bass from the 2008 year class were most abundant (25% of the total), followed by the 2007 (23% of the total) and 2005 (9.4% of the total) year classes. Growth was slower than average compared with other West Metro Area lakes. Largemouth bass reached 14 inches by age 7 and 18 inches by age 11. No smallmouth bass were sampled during the spring elecrofishing assessment.
\n\tNumerous bass tournaments are held on the lake every year. Bass tournament are held by permit only and fish data must be turned into the DNR. In 2011, 11 bass tournaments were held. A total of 1,136 tournament anglers caught 3,854 largemouth bass and 38 smallmouth bass. Average size was 2.5 lbs and the largest recorded was 6.9 lbs. Since bass anglers target the largest individuals in a population, it is common for angling results to yield larger size fish, on average, than electrofishing. Additionally, individual tournaments may enact their own minimum size limit, thus only measuring a minimum size of fish. The electrofishing assessment targeted all sizes of bass.
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\nOther Fish
\n\tBluegill and black crappie are abundant in Lake Minnetonka; however, gill nets are not reliable indicators of their relative abundance. The consistent natural reproduction and high recruitment of these species will ensure quality angling opportunities. Black bullhead, bowfin (dogfish), common carp, green sunfish, golden shiner, hybrid sunfish, pumpkinseed sunfish, rock bass, smallmouth bass, white sucker, and yellow bullhead were also captured in low numbers during the 2011 assessment. Smallmouth bass and rock bass were found only in the Lower Lakes.
\nInvasive Species
\n\tEurasian water milfoil and curly leaf pondweed are found in high abundance throughout the lake and in 2010 zebra mussels and flowering rush were found to be present for the first time. Lake Minnetonka receives heavy recreational use, so potential for the spread of invasive species into and out of the lake is high. Anglers and boaters should take the precautions necessary to prevent the further spread of all invasive species.
\n\tThe shoreline and watershed of Lake Minnetonka is highly developed and puts stress on the lake's aquatic habitat and ecosystem integrity. Large docks, boating platforms, and man-made beaches have the potential to destroy vital habitat for fish and wildlife. Environmentally friendly development practices, such as shoreline buffer strips of natural vegetation, are necessary to maintain the current water quality of Lake Minnetonka. Shoreline development, invasive species, and the fish diseases Viral Hemorrhagic Septicemia (VHS) and Largemouth Bass Virus should be a concern to everyone who enjoys lake recreation.
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The 2014 Lake Minnetonka fisheries assessment was conducted June 9 through July 1. The current management plan requires assessments on even numbered years (biennially). The goal of the assessment is to describe trends in growth, condition, relative abundance, reproduction, and size structure of Walleye, Northern Pike and Yellow Perch. Sampling these species involves 24 experimental gill-net sets. In May 2011, an electrofishing special assessment was conducted to evaluate the status of the Largemouth Bass population. Those data are included in this report. Sampling in Lake Minnetonka is divided into three aggregations of basins that differ in their habitat and water chemistry characteristics. Data is analyzed as an entire lake and by basin. Overall, the 2014 gill-net assessment revealed a diverse fish community (14 species) dominated by Northern Pike (33.2 lbs/net), Bluegill (6.1 lbs/net), and Walleye (6.0 lbs/net).
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\nWater Quality
\nAccording to the Minnesota State Climatology Office, June 2014 was Minnesota's wettest June, and wettest month of the modern record. This included the preliminary record-setting totals of 11.36 inches for the Minneapolis-St. Paul metropolitan area. Much of the rain came in a few heavy storms that each dropped over 2 inches of rain. The Minnehaha Creek Watershed District measured an all-time high lake level at the Gray's Bay dam of 931.11 ft. on June 23 (929.40 ft. is the ordinary lake level). High water forced boating restrictions, including no-wake for the entire lake June 5-July 24.
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\nThe Northwest Bays are most fertile, primarily because they are the first recipients of the majority of surface runoff from the watershed. The Upper Lakes are intermediate in fertility, while the Lower Lakes are least fertile. Thus, the Lower Lakes have the best water quality, followed by the Upper Lakes, then the Northwest Bays. Water quality trends in Lake Minnetonka show a positive relationship for increasing water clarity, which can be attributed to improvements in the condition of the watershed. Improving water quality was observed before the discovery of zebra mussels in 2010. The Minnehaha Creek Watershed District more closely monitors water quality in Lake Minnetonka. For more a more specific description of the water quality in each bay/basin see the District's website (http://www.minnehahacreek.org/data-center).
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\nWalleye
\nLake Minnetonka is stocked with 6,446 pounds of fingerling Walleye in even-numbered years (approx. 96,000-128,000 fish). Walleye are stocked into all three basins of the lake. Since 2004, most or all of the Walleye fingerlings stocked were purchased from Minnesota-based fish vendors under State contracts. Additionally, in 2013 and 2014, the Westonka Walleye Program (WWP), a privately-funded organization, was issued permits to stock Walleye in the Northwest Bays of the lake. Fundraising events are underway to purchase Walleye for 2015 as well. The goal of the WWP is to stock larger fish that will have higher survival. The permits allow stocking of even-numbered year-classes that coincide with DNR stocking. In the fall of 2013, the WWP stocked 2,502 yearling Walleye (6/lb). In 2014, they stocked 10,500 fingerling Walleye (8-13\" TL, 7/lb). Future assessments will look closely to ascertain changes in Walleye abundances and sizes resulting from these stockings.
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\nDespite extensive stocking, Walleye abundance, as indexed by gill-net catch-per-unit-effort, has remained at a low density. Catch rates since 1977 have ranged from 1.5-8.8/net, averaging 4.0/net. In 2014, Walleye abundance (2.6/net) was lower than the 4.3/net caught in 2012. Lower catch rates were observed in all three basins.
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\nThe size structure of the population was relatively large. The proportion of 15-inch and longer Walleye increased from 78% in 2012 to 90% in 2014 and has averaged 79% over the long term. However; the proportion of Walleye 20 inches and larger decreased from 42% in 2012 to 21% in 2014 and was lower than the long-term average of 34%. Walleye averaged 18.1 inches in length and ranged from 9.7-27.2 inches. Average length was similar in the Northwest Bays (19.8 inches) and the Lower Lakes (19.1 inches) but lower in the Upper Lakes (15.4 inches). Walleye mean weight (2.3 lbs) was large when compared to other similar lakes and this has been the case since the 1992 assessment. Mean weight was highest in the Northwest Bays (3.1 lbs), followed by the Lower Lakes (2.6 lbs), and the Upper Lakes (1.5 lbs). The general trend over time has been for the greatest proportion of larger Walleyes to be located in the Northwest Bays. Growth of Walleye sampled in 2014 was a little faster than in previous assessments. In general, Walleye grew to 13.5 inches by age-3 and 18.8 inches by age-6; however there were gender-related differences. An age-3 female averaged 14.3 inches, while an age-3 male averaged 12.9 inches. Gender-related trends in growth were similar among all three basins, though Walleye grew fastest in the Northwest Bays.
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\nConsistent with previous assessments, Walleye natural reproduction is limited. In 2014, 3 of 57 (3.5%) Walleye originated from a non-stocked year-class. These naturally reproduced Walleye were remnants of the small 1997 and 1999 year classes that have been observed in previous assessments. In recent assessments, few younger Walleye have been sampled in non-stocked year classes. Over the last 5 assessments (2008 through 2012) the number of naturally reproduced fish in a sample has ranged from 5.2 to 16%, averaging 10.5%.
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\nAge-4 Walleye (stocked 2010 year class) were the most abundant in the 2014 sample (65% of the total). These fish averaged 17.2 inches. The 2008 year-class was the second most abundant comprising 12% of the total. Those 6-year-old fish averaged 19.0 inches. The 2008 and 2010 year classes were also the most abundant in the 2012 assessment.
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\nNorthern Pike
\nThe 2014 catch (12.2/net) is high compared to other similar lakes in the state and is higher than the long-term average of 10.6/net. Northern Pike catch rates in the Lower Lakes (15.5 fish/net) exceeded catch in both the Upper Lakes (11.4 fish/net) and Northwest Bays (7.7 fish/net). In the most recent assessments, the Lower Lakes have had higher catch rates of Northern Pike, although among the basins, long-term averages are relatively similar (Upper Lakes = 10.8, Lower Lakes = 10.6, Northwest Bays = 9.5). \t
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\nMean size was relatively large; pike averaged 22.4 inches and 2.73 lbs, which was comparable to 2012 and near the long term average. Mean length was greatest in the Northwest Bays (23.8 inches) followed by Upper Lakes (22.9 inches) then Lower Lakes (21.8 inches). The largest individual captured was an age-7 female at 35.2 inches and 10.7 lbs. Size structure indices revealed a quality Northern Pike population. Fifty-nine percent were 21 inches or longer and 9.6% were 28 inches or longer. The best size structure was found in the Northwest Bays where 78% were 21 inches or longer and 17% were 28 inches or longer.
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\nGrowth rates were similar to other West Metro Management Area lakes. On average, Northern Pike in Lake Minnetonka were 19.6 inches by age-3 and 26.9 inches by age-6, although growth did differ, as expected, by gender. Females reached older ages and consistently grew faster. For example, an age-3 female was 20.3 inches compared to an 18.8-inch male that same age. Based on the length of an age-3 female, growth was fastest in the Northwest Bays (22.0 inches) but similar in both the Upper (20.1 inches) and Lower Lakes (19.9 inches). Nine year-classes were sampled and most fish (83%) were between 3 and 5 years old.
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\nYellow perch
\nYellow Perch abundance (11.6/net) in 2014 was near the long term average of 13.1/gill net and considered moderately low compared to other similar lakes. The Northwest Bays have historically had the highest Yellow Perch abundance and this was again true in 2014. Abundance in the Northwest Bays was 25.3/gill net, 11.8/net in the Upper Lakes, and 3.5/net in the Lower Lakes.
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\nHistorically, Yellow Perch size structure has been small in Lake Minnetonka. In 2014, perch ranged in size from 5.1-8.7 inches; only 2.9% were greater than 8 inches. Mean length (6.4 inches) and weight (0.12 lbs) were similar to 2012 values. The perch population in the Northwest Bays has a better size structure than the other two basins. However, mean size was small (6.5 inches); the largest fish measured 8.7 inches. Six year-classes were sampled with the oldest individual captured age-7. Sixty-eight percent were age-3 or 4. Yellow Perch growth was slower on average and similar in the Upper Lakes and Northwest Bays where perch reached 5.5 inches by age 3. In the Lower Lakes, perch were 5.0 inches at age 3.
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\nMuskellunge
\nMuskellunge were not targeted during this assessment, but, based on other indicators and reports, their population remains strong. Fish exceeding 50 inches and approaching 40 pounds are caught in Lake Minnetonka every year. Survival of stocked fingerling Muskellunge is assumed to be low due to the high abundance of Largemouth Bass and Northern Pike. Advanced fingerlings and yearlings have been used in recent years in attempt to improve survival rates of stocked fish. A research study is currently taking place in Lake Minnetonka comparing the survival of stocked fingerling and yearling Muskellunge. Stocked fish were tagged in 2008, 2009, 2011, and 2012. Muskellunge were tagged with an external spaghetti-type tag near the dorsal fin on the fish's left side. These tags, yellow in color, include a six-digit number. For longer-term tracking, an internal PIT-style tag was also inserted and can only be detected with a specific reader. Angler reports of captured tagged Muskellunge are essential to the success of this project. If you catch a tagged muskellunge please record the tag number and length of fish and report the catch via the Tagged Fish Reporting page within the MNDNR website. Please DO NOT remove the tag. Please contact the West Metro Area Fisheries Office with questions. Practicing CPR (Catch, Photo, and Release) is essential to maintaining the trophy Muskellunge fishery found in Lake Minnetonka.
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\nLargemouth Bass
\nThe Largemouth Bass population in Lake Minnetonka has a reputation for quality fishing. In May 2011, a nighttime boat electrofishing assessment was performed to target Largemouth Bass. A total of 385 Largemouth Bass were sampled in 11 electrofishing transects, equating to 75.4 bass per hour of on-time. Catch rates were similar to the 2009 assessment, when 73.2 bass per hour were sampled. These catch rates are above average for area lakes. The size structure of the Largemouth Bass population in Lake Minnetonka was well-balanced and the fish are in good physical condition. It appeared the larger fish tended to be in the best condition. Largemouth Bass averaged 11.8 inches and 1.04 lbs, lower than in 2009 when fish averaged 13.5 inches and 1.5 lbs. The largest bass sampled was 20.9 inches long and 4.9 lbs. Fish from the 1999 through 2009 year classes were present, indicating consistent reproduction and recruitment. Age-3 bass from the 2008 year class were most abundant (25%), followed by the 2007 (23% of the total) and 2005 (9.4% of the total) year classes. Largemouth Bass reached 14 inches by age 7 and 18 inches by age 11. No Smallmouth Bass were sampled during the spring electrofishing assessment.
\nNumerous bass tournaments are held on the lake every year. These tournaments are by permit only and fish data must be turned into the DNR. In 2014, 8 bass tournaments requiring permits were held. A total of 669 tournament anglers caught 1,744 Largemouth Bass and 6 Smallmouth Bass during these events. Average size was 2.61 lbs and the largest recorded was 6.35 lbs. Since bass anglers target the largest individuals in a population, it is common for angling results to yield larger size fish, on average, than electrofishing. Additionally, individual tournaments may enact their own minimum size limit, thus adding to a larger-fish size bias. The electrofishing assessment targeted all sizes of bass.
\nOther Fish Species
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\nBluegill and Black Crappie are abundant in Lake Minnetonka; however, gill nets are not reliable indicators of their relative abundance. The consistent natural reproduction and high recruitment of these species have ensured quality angling opportunities. Black Bullhead, Brown Bullhead, Green Sunfish, hybrid sunfish, Pumpkinseed Sunfish, Rock Bass, Smallmouth Bass, and Yellow Bullhead were also captured in low numbers during the 2014 assessment. Smallmouth Bass were sampled only in the Lower Lakes.
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\nAquatic Invasive Species
\nEurasian water milfoil and curly leaf pondweed are found in high abundance throughout the lake and in 2010 zebra mussels and flowering rush were first found to be present. Lake Minnetonka receives heavy recreational use, so potential for the spread of invasive species into and out of the lake is high. Anglers and boaters should take the precautions necessary to prevent the further spread of all invasive species.
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\nThe shoreline and watershed of Lake Minnetonka is highly developed which puts stress on the lake's aquatic habitat and ecosystem integrity. Large docks, boating platforms, and man-made beaches have the potential to destroy vital habitat for fish and wildlife. Environmentally friendly development practices, such as shoreline buffer strips of natural vegetation and fallen woody debris, are necessary to maintain the current water quality of Lake Minnetonka. Shoreline development, invasive species, and the fish diseases Viral Hemorrhagic Septicemia (VHS) and Largemouth Bass Virus should be a concern to everyone who enjoys lake recreation.
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Introduction
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\nLake Minnetonka is a 14,206-acre lake in Hennepin County, with a maximum depth of 113 feet and an average depth of 30 feet. The lake is comprised of many connected bays and has a complex shoreline. Multiple public and private boat launches are located around Minnetonka, and the lake is popular with both anglers and recreational boaters. Naturally reproducing populations of Northern Pike and Largemouth Bass are present, and Walleye and Muskellunge populations are maintained by stocking.
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\nA Standard Survey was completed on Lake Minnetonka from June 6 through June 23, 2022. Sampling involved gill netting, trap netting, and water quality sampling. Sampling in Lake Minnetonka is distributed through three basins that differ in their habitat and water quality characteristics. Gill netting and trap netting effectively sample Northern Pike, Walleye, Yellow Perch, Bluegill and Black Crappie. The population trends of those species are described by this survey.
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\nPopulation trends of Largemouth Bass and Muskellunge are not described by this survey. Largemouth Bass are sampled by nighttime spring electrofishing, and Muskellunge are sampled by large-frame trap netting during the spring. These sampling methods were not done during the 2022 survey.
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\nWater Characteristics
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\nWater clarity has been improving in Lake Minnetonka over the past several decades. The Northwest Bays are most fertile, primarily because they are the first recipients of the majority of surface runoff from the watershed. The Upper Lakes are intermediate in fertility, while the Lower Lakes are, relatively, the least fertile. The Minnehaha Creek Watershed District more closely monitors water quality in Lake Minnetonka. For more specific, detailed information about Lake Minnetonka water quality, see the District's website (http://www.minnehahacreek.org/data-center).
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\nWalleye
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\nDespite a long history of stocking, Walleye abundance has remained low in Lake Minnetonka. In 2022, the Walleye catch rate of 2.5 fish per gill net was higher than the 1.7 fish/net caught in 2019. Walleye catch rate has modestly increased throughout all basins. In the Lower Lakes, Walleye catch rate increased from 1.2 fish/net in 2019, to 2.8 fish/net in 2022. The Upper Lakes saw an increase in catch rate from 1.8 fish/net in 2019, to 2.0 fish/net in 2022. In the Northwest Bays, catch rate increased from 2.3 to 2.7 Walleye/net.
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\nWalleye in Minnetonka tend to be large. Length of sampled fish ranged from 10.9 to 26.4 inches. Fish averaged 19.1 inches and 2.6 pounds. Average length varied throughout the basins, with fish averaging smaller size in the Northwest Bays (16.6 inches) than in the Lower Lakes (20.5 inches) and the Upper Lakes (19.1 inches). Walleye grew to 16.2 inches by age-3.
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\nNorthern Pike
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\nThe Northern Pike population in Lake Minnetonka is healthy and naturally reproducing. Abundance has historically been high, and it remained so in 2022. The Lower Lakes held the highest abundance of pike, and the Northwest Bays held the lowest numbers. The Northwest Bays also held the larger fish, where the average length was 24.7 inches. Average length in the Upper Lakes was 22.6 inches and in the Lower Lakes it was 21.2 inches. The largest Northern Pike in the 2022 survey was 35.4 inches and caught in the Lower Lakes.
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\nAs part of the North-Central Zone, Northern Pike harvest in Minnetonka is regulated by a possession limit of 10 fish, not more than 2 fish exceeding 26 inches, while respecting a 22-26 inch protected slot.
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\nYellow perch
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\nYellow Perch are important forage in Lake Minnetonka. Compared to similar lakes, perch abundance in Minnetonka was low in 2022. The fish have historically tended to be small in Minnetonka, however, recently there has been an increase in size structure. Lake-wide, 14% of the sampled Yellow Perch exceeded 8 inches. The increase in overall size structure was driven by the perch in the Upper Lakes, where 25% of the fish exceeded 8 inches, and in the Northwest Bays, where 21% of the sampled fish exceeded 8 inches. None of the perch sampled in the Lower Lakes exceeded 8 inches. The largest Yellow Perch sampled in 2022 was 8.6 inches.
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\nMuskellunge
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\nMuskellunge were not targeted during this survey, but two fish were incidentally sampled in the gill nets. The fish were 35.9 and 50.2 inches in length.
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\nA research study is currently taking place in Lake Minnetonka comparing the survival of stocked fingerling and yearling Muskellunge. Stocked fish were tagged in 2008, 2009, 2011, and 2012. Muskellunge were tagged with a yellow external tag near the dorsal fin on the fish's left side. These tags are labeled with a six-digit number. Angler reports of captured tagged Muskellunge are essential to the success of this project. If you catch a tagged muskellunge please record the tag number and length of fish and report the catch via the Tagged Fish Reporting page within the MNDNR website ( https://www.dnr.state.mn.us/fisheries/tagged_fish_reporting/index.html ). Please DO NOT remove the tag. Please contact the West Metro Area Fisheries Office with questions.
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\nLargemouth Bass
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\nAlthough electrofishing for bass was not done in 2022, the Largemouth Bass population in Lake Minnetonka has a reputation for quality fishing. Numerous bass tournaments are held on the lake every year. In 2022, eight permitted bass tournaments reported their catch. A total of 792 tournament anglers caught 1,681 Largemouth Bass and 29 Smallmouth Bass during these events. Average Largemouth Bass size was 2.58 lb and the largest recorded was 8.00 pounds and 23 inches. Since tournament bass anglers target the largest individuals in a population, it is common for angling results to yield larger size fish, on average, than standard sampling. Additionally, individual tournaments may enact their own minimum size limits, thus adding to a larger-fish size bias.
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\nLake Minnetonka was most recently electrofished for bass in 2016. During that survey, 138 Largemouth Bass were sampled, with an average size of 9.9 inches and 0.66 pounds. The largest fish was 18.7 inches in length.
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\nBluegill and Other Fish Species
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\nBluegill and Black Crappie are abundant in Lake Minnetonka. Trap netted Bluegill averaged 6.2 inches, and the largest individual, caught in a gill net, was 8.9 inches. Black Crappie averaged 8.3 inches, and the largest individual measured 12.0 inches. Consistent natural reproduction of these species have ensured quality angling opportunities.
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\nSmallmouth Bass were sampled only in the Lower Lakes. Four fish were present in the gill nets, ranging in size from 10.1 to 18.3 inches. Average length of Smallmouth Bass was 13.7 inches.
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\nOther species sampled in the 2022 survey include Black Bullhead, Brown Bullhead, Common Carp, Golden Shiner, Green Sunfish, hybrid sunfish, Pumpkinseed Sunfish, Rock Bass, Yellow Bullhead, White Sucker, and Bowfin.
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\nInvasive Aquatic Species
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\nEurasian water milfoil and curly leaf pondweed are found in high abundance throughout the lake and in 2010 zebra mussels and flowering rush were first found to be present. Lake Minnetonka receives heavy recreational use, so potential for the spread of invasive species into and out of the lake is high. Anglers and boaters should take the precautions-and follow statewide laws-- necessary to prevent the further spread of all invasive species.
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\nThe shoreline and watershed of Lake Minnetonka is highly developed, which degrades the lake's aquatic habitat. Large docks, boating platforms, and man-made beaches have the potential to destroy vital habitat for fish and wildlife. Environmentally conscious land use practices, such as shoreline buffer strips of natural vegetation and fallen woody debris, are necessary to maintain or improve water quality of Lake Minnetonka. Shoreline development should be a concern to everyone who enjoys lake recreation.
\n
The 2009 Lake Minnetonka population assessment was conducted June 8th through June 24th. Annual sampling began in 1997 following a 20-year period when the fish community was sampled every five years. Sampling in Lake Minnetonka is divided between aggregations of basins that differ in habitat and water chemistry. The Northwest Bays are most fertile, as they are the first recipients of a majority of surface runoff from the watershed. The Upper Lakes are intermediate in fertility, while the Lower Lakes are least fertile.
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\nSince 1997, annual assessments have been conducted to assess trends in growth, condition, relative abundance, reproduction, and size structure of northern pike, walleye, and yellow perch. In order to effectively sample the aforementioned species, twenty-four experimental gillnets were set at 12 historic locations. The 2009 gillnet assessment revealed a diverse fish community (16 species) dominated (based on lbs/gillnet) by northern pike (24.93 lb/net), walleye (10.64 lb/net) and bluegill (7.86 lb/net).
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\nWater Quality
\nHistoric water quality trends in Lake Minnetonka indicated positive change in average water clarity and anoxic depth (< 2 ppm dissolved oxygen). The trends in water clarity for all three basins were significantly positive with the Lower Lakes showing the greatest improvement. The same relationship is also true of historical anoxic depths in Lake Minnetonka.
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\nWalleye
\nDespite extensive fingerling stocking effort, walleye abundance, as indicated by gillnet catch per unit effort, has remained at low levels. The 2009 catch of 3.42 fish/net fell below the 2007 and 2008 catch and is below the 39-year average of 4.11 fish/net. Since 1970, 18 surveys have been performed on Lake Minnetonka; 10 of which found walleye catch rates below the lower quartile (4.01 fish/net) for class 22 lakes, including 2009. The biennial walleye stocking rate for Lake Minnetonka doubled beginning in 1999 from 1 lb/ littoral acre to 2 lbs/ littoral acre; however, walleye catch rates since the stocking increase have been similar to catch rates pre-increase. Walleye catch rates in the Lower Lakes and Northwest Bays remained unchanged in 2009, but catch rates in the Upper Lakes decreased from 2008. Walleye catch rates were highest in the Lower Lakes (4.3 fish/net), followed by the Northwest Bays (3.5 fish/net) and Upper Lakes (2.25 fish/net). Walleyes are not stocked into the Northwest Bays so immigration into this portion of Lake Minnetonka maintains the fishery there.
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\nWalleye mean weight (3.11 lbs) was the highest observed since 1977 (3.27 lbs). Walleye mean weight in 2009 exceeded the upper quartile when compared to other class 22 lakes, as has been the case 30 out of the past 32 years. Mean weight was highest within the Upper Lakes (3.81 lbs), followed by the Northwest Bays (3.73 lbs) and the Lower Lakes (2.45 lbs). This is only the second survey in Lake Minnetonka where mean weight in the Northwest Bays has not been the highest of the three basins.
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\nWalleye averaged 19.60 inches and ranged from 11.46 to 28.11 inches. Similar to mean weight, mean length was highest within the Upper Lakes (21.5 inches), followed by the Northwest Bays (21.21 inches) and the Lower Lakes (17.97 inches). Historically, size structure indices have revealed Lake Minnetonka's walleye population consists of larger individuals, and this was again observed in 2009. Size structure was highest within the Northwest Bays and Upper Lakes followed by the Lower Lakes. The largest individual captured was an age-10, 27.9 inch, 8.3 pound female.
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\nAging walleyes using otoliths allowed year-class inferences to be made. Consistent with previous assessments, walleye natural reproduction was limited. Four out of 77 (5.2%) aged walleye originated from a non-stocked year-class. Two age-4 walleyes and two age-10 walleyes, originating from the 2005 and 1999-year-classes, are assumed to have been naturally reproduced. Five walleyes from the 2005 year-class were also sampled in 2008 providing more evidence that some natural recruitment occurred in that year. Past assessments have documented natural recruitment from the 1999 and 1997 year-classes. The stocked 2004, and 2006 year-classes continue to be strong, contributing to 71% of the walleye catch.
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\nWalleye growth in Lake Minnetonka was similar to other lakes in the West Metro management area and historic walleye growth in Lake Minnetonka. Walleye reached an average length of 13.5 inches by age 3 and 20.1 inches by age 6. Comparing basins, walleye grew faster in the Northwest Bays.
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\nNorthern Pike
\nConsistent with recent assessments, northern pike displayed relatively high abundance during this assessment. The 2009 northern pike catch rate of 7.58 fish/net fell below the upper quartile for the first time since 1987. Mean weight (3.29 lbs) remained above the upper quartile for class 22 lakes. Northern pike relative abundance in Lake Minnetonka have been on a steady decline from the historically second highest catch of 17.7 fish/net in 2002 (page 23). Contrary to historical trends, northern pike catch rates in the Lower Lakes (10.1 fish/net) exceeded catch rates in both the Northwest Bays (7.83 fish/net) and Upper Lakes (4.25 fish/net). Previously, northern pike gillnet catch has been highest in the Upper Lakes. Sampled northern pike averaged 23.8 inches (range: 11.61-35.91) and 3.3 lbs; both slight decreases from the 2008 assessment. Northern pike mean length within each basin was largest in the Northwest Bays (24.70 inches), followed by the Upper Lakes (23.89 inches) and Lower Lakes (23.31 inches). The largest individual captured was an age-7, 35.91 inch, 10.35 pound female.
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\nSize structure indices revealed a balanced, quality pike population with the best size structure found in the Northwest Bays. The current northern pike population in Lake Minnetonka may offer anglers the best chance at catching northern pike over 24 inches in the West Metro Management Area. The northern pike population lacks small \"hammer handle\" northern pike with most of the fish sampled between 19-29 inches. Growth rates were above West Metro Management Area lake averages for the first six years and below average thereafter. On average, northern pike in Lake Minnetonka reach 20 inches by age 3 and 30 inches by age-10. Ten year-classes were sampled with the oldest individual age-11.
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\nYellow Perch
\nYellow perch relative abundance (16.75 fish/net) was below the median level (17.1 fish/net) for class 22 lakes, as historically been the case. Yellow perch gillnet catch increased in Lake Minnetonka each year from 2001 to 2006. However, the 2007 and 2008 gillnet catches were below that of 2006 (16.3 fish/net). Consistent with previous assessments, perch abundance was highest in the Northwest Bays (52.00 fish/net) and relatively low in the Upper (7.38 fish/net) and Lower Lakes (3.10 fish/net) and when compared to class 22 lakes. When comparing perch catch by basins, the Northwest Bays have had the highest gillnet catch since 1970.
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\nSize structure indices revealed a population consisting of small individuals (mean length = 6.66 inches), as has historically been the case. Yellow perch condition decreased significantly with length indicating a resource bottleneck may be occurring for larger, older individuals. Six year-classes were sampled in Lake Minnetonka with the oldest individual captured age-7. The 2004 year-class dominated the catches of 2007 and 2008, and remained strong in 2009. Recruitment appears to have been consistent during 2004-2006. Yellow perch growth in Lake Minnetonka was slower on average than other lakes in the West Metro management area. Comparing basins, yellow perch grew faster in the Northwest Bays.
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\nMuskellunge
\nMuskellunge were not targeted during this assessment, but their population remains strong. Fish exceeding 50 inches and approaching 40 pounds are caught in Lake Minnetonka every year. Survival of stocked fingerling muskellunge is assumed to be very low due to the high abundance of largemouth bass and northern pike. Advanced fingerlings and yearlings have been used in recent years to try and improve the survival rate of stocked fish. A reserach study is currently taking place in Lake Minnetonka investigating the survival of stocked fingerling and yearling muskellunge. Stocked fish were tagged in 2008 and 2009 and will again be tagged in 2011. These fish were tagged with an external spaghetti-type tag near the dorsal fin. These tags are yellow in color and include a six-digit number. Angler reports of captured tagged muskellunge are essential to the success of this project. If you catch a tagged muskellunge please record the tag number and length of fish and report the catch via phone, email or the Tagged Fish Reporting page within the MNDNR website. Please DO NOT remove the tag. Please contact the West Metro Fisheries Office with questions. Practicing CPR (Catch, Photo, and Release) is essential to maintaining the trophy muskellunge fishery found in Lake Minnetonka.
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\nOther Fish
\nBlack bullhead, bowfin (dogfish), common carp, green sunfish, hybrid sunfish, pumpkinseed sunfish, rock bass, white sucker, and yellow bullhead were also captured in low numbers during the 2009 assessment. Rock bass and green sunfish were only captured in the Upper Lakes. Smallmouth bass are found in Lake Minnetonka, but their numbers remain low. Smallmouth bass reproduction has been severly reduced due to the loss of submerged wood and rocky habitats.
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\nEurasian water milfoil is found in high abundance throughout Lake Minnetonka. Although milfoil is a common occurrence in most metro lakes, anglers and boaters should take precautions to prevent the spread of milfoil and other invasive species. Lake Minnetonka receives heavy recreational use so the potential for the spread of invasive species into and out of the lake is high. The shoreline and watershed of Lake Minnetonka is highly developed and puts stress on the lakes aquatic habitat and ecosystem integrity. Large docks, boating platforms, and man-made beaches have the potential to destroy vital habitat for fish and wildlife. Environmentally friendly development practices, such as shoreline buffer strips of natural vegetation, are necessary to maintain the current water quality of Lake Minnetonka. Shoreline development, Eurasian water milfoil, curly leaf pondweed, zebra mussels, rusty crayfish, and the fish disease VHS should be a concern to all Minnesotans who enjoy lake recreation.
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The 2012 Lake Minnetonka (27-0133-00) fisheries assessment was conducted June 18th through 28th. Annual sampling began in 1997 following a 20-year period when the fish community was sampled every five years. Sampling in Lake Minnetonka is divided into three aggregations of basins that differ in their habitat and water chemistry characteristics. The Northwest Bays are most fertile, primarily because they are the first recipients of the majority of surface runoff from the watershed. The Upper Lakes are intermediate in fertility, while the Lower Lakes are least fertile.
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\nSince 1997, assessments have been conducted every year to assess trends in growth, condition, relative abundance, reproduction, and size structure of northern pike, walleye, and yellow perch. Sampling of these species typically involves 24 experimental gill net sets at 12 historic locations (24-hr sets; 2 net sets at each location with approximately 7-9 days between net sets. However, due to budget and staffing constraints, only one circuit of 12 net sets was completed in 2012. In May 2011, an electrofishing special assessment was conducted to evaluate the status of the largemouth bass population. That year-old data is included in this report. The 2012 gill net assessment revealed a diverse fish community (14 species) dominated (based on lbs/gillnet) by northern pike (32.3 lbs/net), walleye (11.4 lbs/net), and bluegill (6.1 lbs/net).
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\nWater Quality
\nWater quality trends in Lake Minnetonka indicate a positive change in average Secchi depth and anoxic depth (< 2 ppm dissolved oxygen) over time. Secchi depths in 2012 were generally shallower than 2011 in the Upper Lakes and Northwest Bays; however, the trends in Secchi depth for all three basins show a positive relationship for increasing water clarity. The same positive relationship is also true of historical anoxic depths. The Lower Lakes have the best water quality, followed by the Upper Lakes, then Northwest Bays.
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\nWalleye
\nLake Minnetonka is stocked with 6,446 pounds of fingerling walleye in even-numbered years. This equates to 1.1 lbs/littoral acre. Starting in the fall of 2010, walleye were and will continue to be stocked into all three basins of the lake. For more than 30 years, previous management limited walleye stocking locations to the Upper Lake and Lower Lake basins. Since 2004, most or all of the walleye stocked were purchased from Minnesota-based fish farmers.
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\nDespite extensive stocking, walleye abundance, as indicated by gill net catch per unit effort, has remained at low levels. Since 1977, 20 surveys have been conducted on Lake Minnetonka; of these, 12 had walleye catch rates below 4.0 fish/net. The 2012 catch of 4.3 fish/net is higher than that of 2011 (3.5/net), and for the first time since 2007, is near the long term average (4.2/net; 1997-2011). On an entire-lake basis, walleye abundance was higher than the previous 4 years; however, catch rates differed by basin. In Upper lakes, walleye catch rate increased from 2.9 to 3.5 per net since 2011. In the Northwest Bays, catch increased from 3.5 to 5.7 walleye per net. In Lower Lakes, no considerable change in walleye abundance (4.0/net) was observed from 2011. The long-term (1997-2010) average walleye gill net catch per net for Upper Lakes is 4.1, 4.8 in Lower Lakes, and 3.3 in the Northwest Bays. Walleye catch rate in the Northwest Bays has been increasing since 2010 and in 2012 it was the highest observed in 12 years. This may be related to the increased distribution of stocked fish into those bays of the lake.
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\nA comparison of northern pike and walleye catch rates suggests an inverse relationship. For example, the second lowest walleye catch rate (1.5 fish/net) occurred in 2005, three years after the second highest northern pike catch rate (17.7 fish/net). The high northern pike catch rate in 2002 represents a large population of northern pike in Lake Minnetonka that could have preyed upon the walleye fingerlings stocked in that year. Since walleye are recruited to gill nets by age 3, this predation was evident three years later (2005) when they were large enough to be sampled. This relationship was also evident from 1999 through 2001. However, northern pike numbers have been decreasing since 2002 (with the exception of 2012) and show no relationship with relative walleye abundance. During that same time period (2002-2012), walleye abundance also showed no relationship with yellow perch abundance.
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\nWalleye mean weight in 2012 (2.7 lbs) exceeded the 75th percentile (1.9 lbs) when compared to other similar lakes, and this has been the case since at least 1992. Mean weight was highest in the Upper Lakes (3.3 lbs), followed by the Northwest Bays (2.9 lbs), and the Lower Lakes (2.1 lbs). The general trend over time has been for the largest walleyes to be located in the Northwest Bays, followed by Upper Lakes, then Lower Lakes. This is assumed to be related to the productivity of the basins and the amount of yellow perch available as prey. Historically, the physical condition of walleye in Lake Minnetonka has been good. A relative weight value of 100 indicates the fish is in the 75th percentile for weight, relative to its length (above average condition). In 2012, walleye body condition was above the average of the previous 15 years and was similar among all three basins of the lake.
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\nAfter walleye mean length exceeded 20 inches for the first time ever in the 2011 assessment, mean length decreased in 2012 to a value more similar to other recent assessments. Walleye averaged 18.6 inches in length and ranged from 11.0 to 24.4 inches. Following the same trend as mean weight, mean length was highest in the Upper Lakes (20.1 inches), followed by Northwest Bays (19.0 inches), and Lower Lakes (17.2 inches). Historically, size structure indices have revealed Lake Minnetonka's walleye population consists of larger individuals and this was again observed in 2012; however, values were lower than those of recent years. The proportion of walleye 20 inches and larger had increased every year for the last 5 until the 2012 assessment. Forty-two percent were 20 inches or larger in 2012, which is lower than the 2011 value, but still higher than the long-term (1997-2011) average of 34%. The proportion of 15-inch and longer walleye has fluctuated over the same time period and has averaged 80% in the last 15 years. In 2012, the highest proportion of larger fish was in the Upper Lakes, followed by the Lower Lakes, then the Northwest Bays.
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\nAging walleyes using otoliths (bones within the skull) allowed year-class inferences to be made. Consistent with previous assessments, walleye natural reproduction is limited. In 2012, 3 of 46 (6.5%) walleye originated from a non-stocked year-class. This was lower than 2011, when 16.0 % were determined to be naturally reproduced. The two most abundant year classes were 2008 (age-4) and 2010 (age-2); each was equally present and together constituted 52% of the walleye catch. The strong 2004 (age-8) and 2006 (age-6) year classes observed in 2011 were still present, representing 15 and 9% of the catch, respectively. The oldest walleye sampled was a 19- year old fish that was a 23.4-inch, 4.6-lb male.
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\nGrowth of walleye sampled in 2012 was similar to that of previous assessments. In general, walleye grew to 11.6 inches by age-3 and 18.2 inches by age-6, however there were gender-related differences. Males grew slower, but reached older ages. An age-3 female averaged 13.6 inches, while an age-3 male averaged 10.9 inches. Trends in growth were similar in all three basins, although young walleye (age-1 and 2) grew fastest in the Northwest Bays and older ages grew fastest in the Lower Lakes.
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\nNorthern Pike
\nConsistent with recent assessments, northern pike were relatively high in abundance in 2012. On an entire-lake basis, the 2012 northern pike catch of 11.2/net ended a streak of 9 consecutive years showing decreasing relative abundance (6.3/net in 2011). The current assessment was the first time since 2008 that relative abundance was above 7.9/net, where it had consistently been between 1987 and 2008.
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\nNorthern pike catch rates in the Lower Lakes (14.8 fish/net) exceeded catch rates in both the Northwest Bays (10.3 fish/net) and Upper Lakes (7.3 fish/net). Northern pike average size (2.89 lbs) was similar to 2011 (3.08 lbs). Northern pike averaged 22.8 inches in length, which was similar to 2011 (23.0 inches) and was at the long-term average of 22.8 inches (1992-2011, spanning 16 surveys). Northern pike mean length was similar in all three basins (Northwest Bays = 23.9 inches, Upper Lakes = 23.5 inches, Lower Lakes = 22.1 inches). Relative weight (90) was good and near the historic average (89). Northern pike condition was similar among all three basins. The largest individual captured was an age-7 female (33.7 inches, 10.8 lbs).
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\nSize structure indices revealed a quality northern pike population. Fifty-one percent were 21 inches or longer and 10% were 28 inches or longer. The best size structure found in the Northwest Bays where 52% were 21 inches or longer and 13% were 28 inches or longer. Growth rates were similar to other West Metro Management Area lakes. On average, northern pike in Lake Minnetonka were 20.7 inches by age-3 and 26.8 inches by age-6, although growth did differ, as expected, by gender. Females reached older ages and consistently grew faster. For example, an age-6 female was 28.0 inches compared to a 21-inch male that same age. Growth was similar among the basins. Nine year-classes were sampled, with most fish (80%) between 2 and 5 years old.
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\nYellow Perch
\nAfter a historical high of 31.7 yellow perch/net in 2011, the 2012 catch (13.4/net) returned to near the long-term (1997-2011) average of 14.2/net. Yellow perch relative abundance (13.4/net) in 2012 was moderate compared to other similar lakes. Despite a drop in 2012 (lowest since 2004), the overall trend since 2000 has been for increasing yellow perch gill-net catch. In most previous surveys, yellow perch abundance was highest in the Northwest Bays, but in 2012, the highest catch was in the Upper Lakes (25.5/net), followed by the Northwest Bays (18.7/net), then the Lower Lakes (0.6/net). Gill-net catch was down in all three basins. Over time, there has been an inverse relationship between yellow perch and northern pike abundance. Recently, this appears to be evident as yellow perch gill-net catch peaked in 2011, and in 2012 northern pike abundance increased for the first time since 2002.
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\nSize structure indices revealed a population consisting of small individuals, and this has historically been the case. Yellow perch mean length (6.7 inches) and weight (0.14 lbs) were similar to 2011. The perch population in the Northwest Bays has a better size structure than the other two basins. In 2012, however, the largest mean size was in the Upper Lakes (6.8 inches, 0.14 lbs).
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\nYellow perch relative weight (86) was fair and the same as 2011, but lower than the historical average of 90. Seven year-classes were sampled with the oldest individual captured age-8. Recruitment seemed consistent as ages 2 through 5 were relatively evenly represented. Yellow perch growth was slower on average than other similar lakes in the West Metro Management Area. Comparing basins, yellow perch grew fastest in the Northwest Bays, followed by Lower Lakes, then Upper Lakes. Yellow perch averaged 5.4 inches by age 3, and 7.5 inches by age 6.
\n
\nMuskellunge
\nMuskellunge were not targeted during this assessment, but based on other measures and reports, their population remains strong. Fish exceeding 50 inches and approaching 40 pounds are caught in Lake Minnetonka every year. Survival of stocked fingerling muskellunge is assumed to be low due to the high abundance of largemouth bass and northern pike. Advanced fingerlings and yearlings have been used in recent years in attempt to improve survival rates of stocked fish. A research study is currently taking place in Lake Minnetonka comparing the survival of stocked fingerling and yearling muskellunge. Stocked fish were tagged in 2008, 2009, 2011, and 2012. These muskellunge were tagged with an external spaghetti-type tag near the dorsal fin on the fish's left side. These tags are yellow in color and each includes a unique six-digit number. Angler reports of captured tagged muskellunge are essential to the success of this project. If you catch a tagged muskellunge please record the tag number and length of fish and report the catch via the Tagged Fish Reporting page within the MNDNR website. Please DO NOT remove the tag. Please contact the West Metro Fisheries Office with questions. Practicing CPR (Catch, Photo, and Release) is essential to maintaining the trophy muskellunge fishery found in Lake Minnetonka.
\n
\nLargemouth Bass
\nThe largemouth bass population in Lake Minnetonka has a reputation for quality fishing. In May 2011, nighttime boat electrofishing was performed to assess the largemouth bass population. A total of 385 largemouth bass were sampled in 11 electrofishing transects, equating to 75.4 bass per hour. Catch rates were similar to the 2009 assessment, when 73.2 bass per hour were sampled. These catch rates are above average for area lakes. The size structure of the largemouth bass population in Lake Minnetonka is well-balanced and the fish are in good physical condition. It appeared the larger fish tended to be in the best condition. Largemouth bass averaged 11.8 inches and 1.04 lbs, which is lower than in 2009 when fish averaged 13.5 inches and 1.5 lbs. In 2011, 52% were 12 inches or longer, 24% were 15 inches or longer, and 1% were 20 inches or larger. The largest bass sampled was 20.9 inches long and 4.9 lbs. Fish from the 1999 through 2009 year classes were present, indicating consistent reproduction and recruitment. Age-3 bass from the 2008 year class were most abundant (25%), followed by the 2007 (23% of the total) and 2005 (9.4% of the total) year classes. Growth was slower than average compared with other West Metro Area lakes.
\nLargemouth bass reached 14 inches by age 7 and 18 inches by age 11. No smallmouth bass were sampled during the spring electrofishing assessment.
\n
\nNumerous bass tournaments are held on the lake every year. These tournaments are held by permit only and fish data must be turned into the DNR. In 2012, 10 bass tournaments were held. A total of 869 tournament anglers caught 1,989 largemouth bass. Average size was 2.73 lbs and the largest recorded was 6.25 lbs. Since bass anglers target the largest individuals in a population, it is common for angling results to yield larger size fish, on average, than electrofishing. Additionally, individual tournaments may enact their own minimum size limit, thus only measuring larger size fish. The electrofishing assessment targeted all sizes of bass.
\n
\nOther Fish Species
\nBluegill and black crappie are abundant in Lake Minnetonka; however, gill nets are not reliable indicators of their relative abundance. The consistent natural reproduction and high recruitment of these species have ensured quality angling opportunities. Black bullhead, green sunfish, hybrid sunfish, pumpkinseed sunfish, rock bass, smallmouth bass, white sucker, and yellow bullhead were also captured in low numbers during the 2012 assessment. Smallmouth bass and rock bass were found only in the Lower Lakes.
\n
\nInvasive Aquatic Species
\nEurasian water milfoil and curly leaf pondweed are found in high abundance throughout the lake and in 2010 zebra mussels and flowering rush were first found to be present. Lake Minnetonka receives heavy recreational use, so potential for the spread of invasive species into and out of the lake is high. Anglers and boaters should take the precautions necessary to prevent the further spread of all invasive species.
\n
\nThe shoreline and watershed of Lake Minnetonka is highly developed and puts stress on the lake's aquatic habitat and ecosystem integrity. Large docks, boating platforms, and man-made beaches have the potential to destroy vital habitat for fish and wildlife. Environmentally friendly development practices, such as shoreline buffer strips of natural vegetation, are necessary to maintain the current water quality of Lake Minnetonka. Shoreline development, invasive species, and the fish diseases Viral Hemorrhagic Septicemia (VHS) and Largemouth Bass Virus should be a concern to everyone who enjoys lake recreation.
\n
Introduction
\nThe 2016 Lake Minnetonka (27-0133-00) Standard Survey (new term effective 2015; gears and methods same as previous terms of Population Assessment and Lake Survey) was conducted June 13 through June 29. Annual fish sampling began in 1997 following a 20-year period of sampling once every five years. Annual sampling continued through 2012; however the frequency of sampling changed after that survey. The current management plan now requires surveys on even-numbered years (biennially).
\n
\nThis survey describes trends in growth, condition, relative abundance, reproduction, and size structure of three native sportfish species having long timelines of sample data: Walleye, Northern Pike and Yellow Perch. Sampling these species involved 24 experimental gill-net sets at 12 historic locations (24-hr sets; 2 net sets at each location with approximately 7-9 days between net sets. Springtime night electrofishing was also conducted this survey, to evaluate Largemouth Bass. Eleven electrofishing stations were sampled over four nights. In 2016, trap netting was also included in the survey, providing information on Bluegill relative abundance and size structure. Sampling in Lake Minnetonka is divided into three aggregations of basins that differ in their habitat and water chemistry characteristics. Data is analyzed as an entire lake and by basin. Overall, the 2016 gill-net assessment revealed a diverse fish community (18 species) dominated by Northern Pike (36.5 lb/net), Bluegill (5.2 lb/net), and Walleye (8.0 lb/net).
\n
\n
\nWater Characteristics
\nWater clarity, as indicated by Secchi-depth values, has been improving in Lake Minnetonka over the past several decades. The Northwest Bays are most fertile, primarily because they are the first recipients of the majority of surface runoff from the watershed. The Upper Lakes are intermediate in fertility, while the Lower Lakes are, relatively, the least fertile. Increasing water clarity can be attributed to improvements in the condition of the watershed. Increased water clarity was observed before the 2010 discovery of zebra mussels. The Minnehaha Creek Watershed District more closely monitors water quality in Lake Minnetonka. For more a more specific, detailed information of Lake Minnetonka water quality, see the District's website (http://www.minnehahacreek.org/data-center).
\n
\nWalleye
\nLake Minnetonka management, as of this report write-up, includes stocking 6,446 pounds of fingerling Walleye in even-numbered years (approx. 96,000-128,000 fish). This equates to 1.1 lb/littoral acre. Starting in the fall of 2010, Walleye were and will continue to be stocked into all three basins of the lake. For more than 30 years prior to 2010, previous management limited Walleye stocking locations to the Upper Lake and Lower Lake basins. Since 2004, most or all of the Walleye fingerlings stocked were purchased from Minnesota-based fish vendors under State contracts.
\n
\nIn 2013, 2014, 2015 and 2016 the Westonka Walleye Program (WWP), a privately-funded organization, received permits to stock Walleye in the Northwest Bays of the lake. Fundraising events are underway to purchase Walleye for 2017 as well. The goal of the WWP is to stock larger fish that will have higher initial survival. The permits allow stocking of even-numbered year-classes that coincide with DNR stocking (so any natural reproduction can be better tracked). In the fall of 2013, the WWP stocked 2,502 yearling Walleye (6/lb). In 2014, they stocked 10,500 fingerling Walleye (8-13\" TL, 7/lb). In 2015, WWP stocked 12,964 yearling Walleye (7fish/lb) and in 2016, they stocked 32,000 fingerling Walleye (7.6/lb). Future assessments will look closely to ascertain changes in Walleye abundances and sizes resulting from these stockings.
\n
\nDespite extensive recent stockings, Walleye abundance, as indexed by gill-net catch-per-unit-effort, has remained at a low density. Since 1977, 22 fisheries assessments have been conducted on Lake Minnetonka; of these, 14 had Walleye catch rates below the first quartile (4.0 fish/net) of Class 22 lakes. Catch rates during this time ranged from 1.5-8.8/net, averaging 4.0/net (median = 3.6/net). In 2016, Walleye abundance (3.3/net) was higher than the 2.6/net caught in 2014. Slightly higher catch rates were observed in the Northwest Bays and the Uppers Lakes. Walleye catch rate dropped in the Lower Lakes, from 3.6/net in 2014, to 3.0/net in 2016. In Upper Lakes, Walleye catch increased from 2.4 to 3.1/net. In the Northwest Bays, catch increased from 1.2 to 3.8 Walleye/net. The long-term (1997-2016) average Walleye gill-net catch per net for Upper Lakes is 4.0 (median=3.5), 4.7 (median = 4.3) in Lower Lakes, and 3.4 (median=3.5) in the Northwest Bays.
\n
\nHistorically, size structure indices have shown Lake Minnetonka's Walleye population consists of larger individuals; this was again observed in 2016. Walleye averaged 18.3 inches in length and ranged from 8.1-27.8 inches. Average length was lower in the Northwest Bays (17.4 inches) and in the Lower Lakes (17.6 inches) and higher in the Upper Lakes (19.4 inches). Walleye mean weight in 2016 (2.5 lb) exceeded the third Lake Class quartile (75th percentile) when compared to other Class 22 lakes, and this has been the case since the 1992 assessment. Mean weight was highest in the Upper Lakes (3.0 lb), followed by the Lower Lakes (2.3 lb), and the Northwest Bays (2.1 lb). The general trend had once been for the greatest proportion of larger Walleyes to be located in the Northwest Bays. That changed in the 2016 survey, suggesting an influence of the Westonka Walleye stocking on the size structure of the fish in the Northwest Bays. Growth of Walleye sampled in 2016 was a little faster than in previous assessments. In general, Walleye grew to 13.6 inches by age-3 and 20.6 inches by age-6.
\n
\nAging Walleyes using otoliths allowed year-class inferences to be made. Consistent with previous assessments, Walleye natural reproduction is limited. In 2016, 2 of 78 (3 percent) Walleye originated from a non-stocked year-class. In recent assessments, few younger Walleye have been sampled in non-stocked year classes. Age-4 Walleye (stocked 2012 year class) were the most abundant in the 2016 sample (37 percent of the total). These fish averaged 17.9 inches. The 2010 year-class was the second most abundant comprising 31 percent of the total catch. Those 6-year-old fish averaged 20.6 inches.
\n
\nNorthern Pike
\nFrom 2002 to 2011, gillnet catch of Northern Pike had decreased every year, from a high of 17.7/net to a low of 6.3/net. However, recent surveys (2012, 2014, and 2016) show an increasing trend to values greater than 10/net. The 2016 catch (13.8/net) is high (above 75th percentile) compared to other Class 22 lakes in the state and is higher than the long-term average of 10.8/net (1977-2016). Northern Pike catch rates in the Lower Lakes (16.0 fish/net) exceeded catch in both the Upper Lakes (15.7 fish/net) and Northwest Bays (5.8 fish/net). \t
\n
\n
\nIn 2016, Northern Pike average size (2.65 lb) was similar to that found in 2014 (2.73 lb). Mean weight was near the 75th percentile for Class 22 lakes. In the current survey, these fish averaged 21.8 inches in length, which was comparable to 22.4 inches in 2014. Northern Pike mean length was greatest in the Northwest Bays (25.9 inches) followed by Upper Lakes (22.3 inches) then Lower Lakes (20.4 inches). The largest individual captured was an age-7 female at 34.7 inches. Forty-three percent were 21 inches or longer and 15 percent were 28 inches or longer. The largest size structure was found in the Northwest Bays, where 83 percent were 21 inches or longer and 39 percent were 28 inches or longer.
\n
\nGrowth rates were similar to other West Metro Management Area lakes. On average, Northern Pike in Lake Minnetonka were 20.1 inches by age-3 and 27.8 inches by age-6. Nine year-classes were sampled and most fish (89 percent) were between 2 and 6 years old.
\n
\nThis survey was the first since a wintertime spearing ban (enacted winter 1987-88) was rescinded in December 2015. The 2015-16 winter was mild, with thinner ice, so impacts of re-opening winter Northern Pike spearing were likely less than expected and/or delayed. Future surveys could show influences of this regulation change on the species' abundances and size structures.
\n
\nYellow Perch
\nYellow Perch abundance (11.1/net) in 2016 was moderately low compared to other Class 22 lakes. The Northwest Bays have historically had the highest Yellow Perch abundance and this was again true in 2016. Abundance in the Northwest Bays was 31.2/gill net, 7.4/net in the Upper Lakes, and 2.0/net in the Lower Lakes.
\n
\nYellow Perch size structure has been historically small in Lake Minnetonka. In 2016, size structure indices revealed a population consisting of small individuals that ranged in size from 4.9 - 8.6 inches; only 3.3 percent were greater than 8 inches. Mean length (6.5 inches) and weight (0.12 lb) were similar to 2014 values.
\n
\nSeven year-classes were sampled with the oldest individual captured age-10. Seventy-two percent were age-2 or 3. Yellow Perch growth was similar to other Class 22 lakes in the West Metro Management Area. Growth was consistent among basins; fish reached an average of 6.8 inches by age 3.
\n
\nMuskellunge
\nMuskellunge were not targeted during this survey, and onlytwo individuals were sampled. One fish, measuring 14.9 inches, like originated from the 2015 stocking. The second individual measured 48.4 inches and weighed 29.61 pounds. Based on angler reports, Minnetonka's Muskellunge population remains strong. Fish exceeding 50 inches and approaching 40 pounds are caught in Lake Minnetonka every year. Survival of stocked fingerling Muskellunge is assumed to be low due to the high abundance of Largemouth Bass and Northern Pike. Advanced fingerlings and yearlings have been used in recent years in an attempt to improve survival rates of stocked fish.
\n
\nA research study is currently taking place in Lake Minnetonka comparing the survival of stocked fingerling and yearling Muskellunge. Stocked fish were tagged in 2008, 2009, 2011, and 2012. Muskellunge were tagged with an external spaghetti-type tag near the dorsal fin on the fish's left side. These tags, yellow in color, include a six-digit number. For longer-term tracking, an internal PIT-style tag was also inserted and can only be detected with a specific reader. Angler reports of captured tagged Muskellunge are essential to the success of this project. If you catch a tagged Muskellunge please record the tag number and length of fish and report the catch via the Tagged Fish Reporting page within the MNDNR website. Please DO NOT remove the tag. Please contact the West Metro Area Fisheries Office with questions. Practicing CPR (Catch, Photo, and Release) is essential to maintaining the trophy Muskellunge fishery found in Lake Minnetonka.
\n
\nLargemouth Bass
\nThe Largemouth Bass population in Lake Minnetonka has a reputation for quality fishing. In May 2016, a nighttime boat electrofishing assessment was performed to target Largemouth Bass. A total of 138 Largemouth Bass were sampled in 11 electrofishing transects, equating to 49.9 bass per hour of on-time. The size structure of the Largemouth Bass population in Lake Minnetonka is well-balanced and the fish are in good physical condition. Largemouth Bass averaged 9.9 inches and 0.65 lb, lower than in 2014 when fish averaged 11.8 inches and 1.04 lb. The largest bass sampled was 18.7 inches long and 3.7 lb. Fish from the 2004 through 2015 year classes were present, indicating consistent reproduction and recruitment. Age-2 bass from the 2014 year class were most abundant (24 percent), followed by the 2013 (21 percent of the total) and 2012 (14 percent of the total) year classes. Largemouth Bass reached 14 inches by age 8 and 18 inches by age 11. No Smallmouth Bass were sampled during the spring electrofishing assessment.
\n
\nNumerous bass tournaments are held on the lake every year. Larger tournaments require DNR permits that include submission of some fish-related data. In 2016, 11 permitted bass tournaments reported totals of 1,058 tournament anglers, 3,947 Largemouth Bass and 197 Smallmouth Bass during these events. The number of Smallmouth Bass reported in 2016 was quite large compared to previous years. Average Largemouth Bass size was 2.34 lb and the largest recorded was 6.69 lb. Since tournament bass anglers target the largest individuals, and tournaments usually apply minimum size requirements, results typically show larger size fish, on average, than electrofishing sampling, where all Largemouth Bass sampled are used for analyses.
\n
\nBluegill and Other Fish Species
\nBluegill and Black Crappie are abundant in Lake Minnetonka and thus are not of enhanced management focus. Bluegill were sampled by trap netting in 2016, as part of a statewide study of the ecological impacts of Muskellunge stocking. The fish were caught at a rate of 72.9 fish per trap net, which is very high for this type of lake. Bluegill averaged 5.9 inches and 0.17 pounds; the largest individual was 8.3 inches. Caught at a rate of 7.4 per gill net, Black Crappie are highly abundant and modestly sized. Black Crappie averaged 6.8 inches and 0.17 pounds, with the largest individual measuring 10.4 inches. Consistent natural reproduction and high recruitment of these species have ensured quality angling opportunities.
\n
\nBlack Bullhead, Brown Bullhead, Green Sunfish, hybrid sunfish, Pumpkinseed Sunfish, Rock Bass, Smallmouth Bass, Yellow Bullhead, Common Carp, Golden Shiner, and Bowfin were also captured in low numbers during the 2016 assessment. Smallmouth Bass were sampled only in the Lower Lakes.
\n
\nInvasive Aquatic Species
\nEurasian watermilfoil and curlyleaf pondweed are found in high abundance throughout the lake and in 2010 zebra mussels and flowering rush were first found to be present. Lake Minnetonka receives heavy recreational use, so potential for the spread of invasive species into and out of the lake is high. Anglers and boaters should take the precautions-and follow statewide laws- to prevent the further spread of all invasive species.
\n
\nThe shoreline and watershed of Lake Minnetonka is highly developed, which puts stress on the lake's aquatic habitat and ecosystem integrity. Large docks, boating platforms, and man-made beaches have the potential to destroy vital habitat for fish and wildlife. Environmentally conscious land use practices, such as shoreline buffer strips of natural vegetation and fallen woody debris, are necessary to maintain or improve water quality of Lake Minnetonka. Shoreline development, invasive species, fish disease potential (such as Viral Hemorrhagic Septicemia [VHS] and Largemouth Bass Virus) should be a concern to everyone who enjoys lake recreation.
\n
\n
\n
Electrofishing 11 sites over 3 nights resulted in the capture of 212 largemouth bass. Sites were located in Grays Bay, Halstead's Bay, North Arm, Maxwell Bay, Phelp's Bay, Preists Bay, Seton Channel, Tanager Lake, West Arm, a small back bay in Crystal Bay and in the channel that divides Big Island. Minnetonka LMB averaged 13.2 inches and 1.46 pounds, PSD=62, RSD16=26, RSD18=7. Electrofishing rates were as follows: # per hour on-time=69.68, lbs per hour on-time =102.02. Growth was slow for fish ages 1-3, but improved to average for ages 4-9. Individuals from every yearclass from 2006-1997, age 2 to age 11, were sampled. Age 2-4 fish comprised 49% of the sample. While ages 5-8 and ages 9-11 accounted for 45% and 7%, respectively.
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\nDISCUSSION AND STATUS OF THE FISHERY
\n
\n\tThe 2006 Lake Minnetonka (27-0133) special assessment was conducted June 5th to June 23rd. Annual sampling began in 1997 following a 20-year period when the fish community was sampled every five years. Since 1997, special assessments have been conducted to assess trends in growth, condition, relative abundance, reproduction, and size structure of northern pike, walleye, and yellow perch. In order to effectively sample the aforementioned species, twenty-four experimental gill nets were set at 12 historic locations (24 hr sets; 2 net sets at each location with approximately 7-9 days between net sets). The 2006 gill net assessment revealed a diverse fish community (17 species) dominated (based on lb/gill net) by northern pike (40.4 lb/net), bluegill (9.8 lb/net) and walleye (7.2 lb/net).
\n\t
\nWalleye
\nDespite extensive fingerling stocking effort, walleye abundance has sustained levels below the lower quartile (4.01/gill net) for class 22 lakes for the fourth consecutive year. Significantly higher than the 2005 walleye CPUE of 1.5/gill net (Paired t-test, p=0.02), walleye averaged 2.71/gill net (95% CI: 1.66-3.76) in 2006. Overall, walleye numbers have generally decreased since an all-time high of 8.8/net in 1999. Additionally, nine out of fifteen surveys performed since 1970 have revealed walleye catch rates below the lower quartile. Apparently, increased stocking since 2001 has not translated into higher walleye gill net catches.
\nWalleye catch rates increased across all basins from 2005 to 2006. Upper lake walleye catch rates increased from 1.6/net in 2005 to 2.0/net in 2006. Similarly, lower lake catch rates nearly doubled from 1.8/net in 2005 to 3.0/net in 2006. Although no walleyes are stocked into the northwest bays, catch rates (3.2/net) increased by a factor of four while boasting the highest catches of all basins. Walleye migration into the northwest bays is likely occurring due to increased forage availability (i.e., above average perch numbers).
\nAlthough average weight (2.7 lb) is slightly down from the 2005 assessment (2.9 lb), mean weight still exceeded the upper quartile when compared to other class 22 lakes. Sampled walleye (N = 65) averaged 18.6 inches with the largest fish measuring 28.6 inches. Size structure indices (N=65, PSD=87, RSD-P=33) revealed a population consisting of larger individuals. Walleye relative weight (93) is up from the 2005 assessment (91) and slightly above the 10-year average of 92. A value of 100 indicates 75th percentile condition or plumpness (above average condition) for the species.
\nAging walleyes using otoliths allowed year class inferences to be made (pg 19; Stocking History and Walleye Year Class Strength from 2006 Gill Net Sample). Consistent with previous assessments, walleye natural reproduction is limited. No walleyes aged in 2006 originated from non-stocked year classes. The 2000, 2001, and 2002 year-classes all appear to be weak. This inference can be made due to the 1998 year-class (12 individuals) contributing similar numbers to the 2006 sampled population when compared to the 2001 (12 individuals) and 2002 (14 individuals) year-classes. The 1998 year-class should be weaker based on natural mortality and 3-4 more years of angling pressure. Additionally, the 2001 year- class should be strong given 11,608 lb (329,318 fingerlings; 19,051 yearlings) of walleyes were stocked in 2001. Predation by a high-density pike population may be limiting stocked year classes from growing to quality sizes. Length limits aimed at decreasing pike numbers (e.g., protected pike slot limits) or increasing walleye numbers (e.g., walleye minimum length limit) may positively influence walleye year class strength. Although not fully recruited to the sampling gear, the 2004 year-class contributed 10 individuals to the sampled population. The 2007 population assessment should further assess the contribution of the 2004 fingerling stocking to the overall walleye population.
\n
\nNorthern Pike
\nConsistent with the 2005 assessment, northern pike displayed relatively high abundance during this assessment. Gill net catch rates (catch per unit effort; CPUE = 11.5/gill net) exceeded the upper quartile while average weight increased nearly 0.25 lb and exceeded the upper quartile for class 22 lakes. Following historical trends, upper lake catch rates (16.4/gill net) exceeded pike catch rates in both the lower lake (7.6/gill net) and the northwest bays (11.3/gill net). The entire pike population averaged 24.1 in (range: 14.8-35.3) and 3.5 lb (both increases from the 2005 assessment). Based on assessments dating back to 1970, pike gill net catch rates may be related to yellow perch abundance (i.e., gill net catch rates; refer to pg.15).
\nSize structure indices revealed a pike population (PSD=73; RSD-P=21) dominated by a strong 2001 year-class. PSD is slightly down from 77 in 2005 while RSD-P increased from 17 to 21. Pike RSD-P (proportion of 15 inch fish that also exceed 28 inches) increased for the fourth consecutive year, and likely will continue to increase as the strong 2001 (age-5) year class grows and progresses through the population. Additionally, the percentage of the population over 30 inches increased from 5% in 2005 to 11% in 2006. Relative weight increased (89 in 2005 to 92 in 2006) throughout the entire lake. Growth rates were above lake class 22 averages for the first three years and below average thereafter. Consistent with previous assessments and high-density pike populations, six consecutive strong year classes were evident after age analysis.
\n
\nYellow Perch
\n\tAlthough 2006 yellow perch relative abundance (16.3/gill net) was slightly below the median level (17.1/gill net) for class 22 lakes, perch numbers have increased for the fourth consecutive year. Consistent with previous assessments, perch abundance was high in the northwest bays (42.3/gill net) and relatively low in the lower (6.9/gill net) and upper (8.5/gill net) basins when compared to class 22 lakes. Size structure indices revealed a population (PSD = 4) consisting of a strong 2001 year class that averaged 7.1 inches at time of capture. Additionally, consistent perch year classes following the strong 2001 (age-5) year class should provide additional forage for the predators of Lake Minnetonka.
\n
The 2007 Lake Minnetonka population assessment was conducted June 11th through June 28th. Annual sampling began in 1997 following a 20-year period when the fish community was sampled every five years. Since 1997, special assessments have been conducted to assess trends in growth, condition, relative abundance, reproduction, and size structure of northern pike, walleye, and yellow perch. West Metro fisheries identified a need to asses bluegill and black crappie populations in Minnetonka, and in 2007 a population assessment was conducted. The 2007 gill net assessment revealed a diverse fish community (15 species) dominated (based on lb/gill net) by northern pike (33.24 lb/net), walleye (10.10 lb/net), and bluegill (8.39/net). Trap nets sampled 14 species and catches were dominated by bluegill (20.75 lb/net).\n\nWalleye\nDespite extensive fingerling stocking effort, walleye abundance, as indicated by the number of walleyes caught per gillnet, has sustained at low levels. The 2007 catch of 4.25/gill net is the first time in 4 years that the gill net catch has exceeded 4 walleyes per net. Although walleye gill net catch increased in 2007, the gill net catch has generally decreased since an all-time high in 1999. Additionally, nine out of fifteen surveys performed since 1970 have observed walleye catch rates below 4 walleyes per net. The walleye stocking rate for Minnetonka doubled in 2001 from 1 lb/ littoral acre to 2 lbs/ littoral acre. Despite the increased gill net catch in 2007 compared to the previous 4 years, the 2007 catch rate was comparable to catch rates observed prior to the increased stocking rate, indicating the increased stocking rate has not increased the overall walleye population in Lake Minnetonka.\n\nWalleye catch rates in the Upper Lakes basin more than doubled in 2007 from 2006 and were the highest recorded since 2002. Similarly, catch rates in the Lower Lakes increased in 2007 and were also the highest recorded since 2002. Alternatively, catch rates in the Northwest Bays decreased in 2007. Walleyes are not stocked into the Northwest Bays and the higher catch in 2006 was assumed to be the result of walleye migrating into the Northwest Bays due to above average abundance of yellow perch. \n\nWalleye mean weight (2.4lbs) continues to drop from the 25 year high of 2.9 lbs observed in 2005, but is the fourth highest mean weight observed in 25 years. Walleye mean weight in 2007 was high when compared to other lakes in the same lake classification as Lake Minnetonka, as has been the case 23 out of the past 25 years. Mean weight was highest within the Northwest Bays, followed by the Upper Lakes and Lower Lakes. Historically, walleye relative weight in Lake Minnetonka has remained below the value of 100, which indicates the 75th percentile condition or plumpness (above average condition) for the species. Walleye relative weight (91) in 2007 was near the 10-year average. Relative weights within each of the three Lake Minnetonka basins were quite similar to the lake average. Walleye condition did not change significantly with length. \n\nWalleye averaged 17.9 inches and ranged from 7.1 - 27.3 inches. Similar to mean weight, mean length was highest within the Northwest Bays (21.8 inches), followed by the Upper Lakes (18.0 inches) and the Lower Lakes (16.9 inches). Historically, size structure indices have revealed Lake Minnetonka's walleye population consists of larger individuals, and this was again observed in 2007. \n\nAging walleyes using otoliths (ear bones) allowed year class inferences to be made. Consistent with previous assessments, walleye natural reproduction is limited. One out of 102 (0.98%) sampled walleye originated from a non-stocked year class. The age 4 walleye, captured in the Upper Lakes, originated from the 2003-year class and was assumed to be naturally reproduced. The 2004-year class (age 3) of walleyes appears to be strong, and contributed 35% of the walleye gill net catch in 2007. The 1996-year class (age 11) appears to have also been a large year class as 7 individuals were captured in 2007. This year class was also strong in previous surveys. The oldest individual captured was a 16 year old, 24.1-inch, male.\n\nLake Minnetonka walleyes grew to catchable size (>13 inches) at age 3. Walleye growth in Lake Minnetonka was slow compared to all lakes in the West Metro management area. Walleyes averaged 0.99 (range: 0.64 - 1.59) inches smaller at age as compared to all lakes in the management area (comparisons are for ages 1 - 8). Comparing basins, walleye grew faster in the Northwest Bays. \n\nNorthern Pike \nConsistent with the 2005 and 2006 assessments, northern pike displayed relatively high abundance during this assessment. Although slightly down from 2006, the gill net catch rate in 2007 was high when compared to other lakes in the same lake classification as Lake Minnetonka, as was average weight. Contrary to historical trends, Lower Lake catch rates exceeded catch rates in both the Northwest Bays and the Upper Lakes. Previously, northern pike gill net catch has been highest in the Upper Lakes. The northern pike population averaged 23.3 inches (range: 13.0-33.9) and 3.07 lb. Northern pike mean length within each basin was largest in the Northwest Bays, followed by the Upper Lakes and Lower Lakes.\n\nSize structure indices revealed a pike population dominated by fish in the 19 - 24 inch range. Northern pike condition decreased slightly in 2007, but has remained fair. Growth rates were above West Metro management area lake averages for the first four years and below average thereafter. On average, northern pike in Lake Minnetonka reach 20 inches at age 3. Northern pike grew faster in the Northwest Bays. Consistent with previous assessments and high-density pike populations, five consecutive strong year classes were evident after age analysis. \n\nYellow Perch\nYellow perch relative abundance was below the median level for similar lakes, as historically been the case. Yellow perch gill net catch increased in Lake Minnetonka each year from 2001 - 2006. However, the 2007 gill net catch was below that of 2006. Consistent with previous assessments, perch abundance was high in the Northwest Bays and relatively low in the Lower and Upper Lakes. When comparing perch catch by basins, the Northwest Bays has had the highest gill net catch since 1970.\n\nSize structure indices revealed a population of small individuals consisting of a strong 2004 year class that averaged 6.3 inches. Yellow perch size structure has been historically small in Lake Minnetonka. Yellow perch condition was fair in 2007 and has been decreasing from the decade high in 2003. Yellow perch condition decreased significantly with length indicating a resource bottleneck may be occurring for larger, older individuals. Yellow perch growth in Lake Minnetonka was slower on average than other lakes in the West Metro management area, with the fastest growth observed in the Northwest Bays. \n\nBluegill\nBluegill relative abundance was seven fold higher in 2007 when compared to the median value of similar lakes. Bluegills averaged 5.89 inches (range: 0.63-8.15) and 0.18 pounds in trap nets. Size structure indices revealed a population consisting of small individuals with most fish between 5.5 and 7.5 inches. Bluegills are near poor condition in Lake Minnetonka, and condition did not change significantly with length.\n\nEight year classes were represented in the bluegill catch. Consistent year class contribution was observed from the 2000-2004 year classes (ages 3-7) with a particularly strong year class in 2002. Bluegill growth in Lake Minnetonka was slower than other lakes in the West Metro management area. Bluegills age 5 and younger were about 1 inch smaller at age, and bluegills older than age 6 were about 0.5 inches smaller at age. Comparing basins, bluegill grew faster in the Northwest Bays. The high abundance and occurrence of Eurasian water milfoil in Lake Minnetonka may be negatively affecting the bluegill population. High densities of milfoil have been shown to limit predation upon bluegills as well as hinder bluegill foraging efficiency. This may result in a high abundance of bluegills that must compete for the available forage. A high abundance of bluegills can also result in slower growth of the population and the apparent \"stunting\" anglers are familiar with.\n\nBlack Crappie\nThe crappie trap net catch fell at the median value for similar lakes. Trap nets sampled slightly larger individuals than gill nets on average (7.89 inches, 7.36 inches respectively). Black crappie mean was 0.22 lbs. Black crappie condition was fair, and condition decreased significantly with length. \n\nNine year classes were represented with the oldest individual captured age 11. Sixty-three percent of the crappies captured were from the 2004 and 2005 year classes (ages 2 and 3). Although one old individual was captured in 2007, the bulk of the Lake Minnetonka crappie population appears to be from younger, age 2 and 3 fish. Black crappie growth is slower than other lakes within the West Metro management area.\n\nLargemouth Bass\nThe largemouth bass fishery in Lake Minnetonka has a reputation for quality fishing. Numerous bass tournaments have been held on the lake in past years. A Nighttime electrofishing assessment was performed during May in 2008 targeting largemouth bass. Sampling largemouth bass in Lake Minnetonka is difficult due to the abundant docks and marinas. The sandy shorelines of lake Minnetonka also inhibit sampling. Typical largemouth bass habitat in Lake minnetonka consists of submergent vegetation in water deeper than 3 feet. Electrofishing gear does not perfrom well exceeding these depths.\n\nJust over 200 largemouth bass were sampled with an average length and weight of 13.45\" and 1.52 lbs. Forty eight percent of the largemouth bass exceeded 14\", and 13% exceeded 3lbs. Largemouth bass were larger on average in the Lower Lakes (14.11\", 1.88lbs), followed by the Northwest Bays (13.26\", 1.48lbs) and Upper Lakes (12.86\", 1.26lbs). Catch rates expressed as number caught per hour of energized time were also larger in the Lower Lakes (86/hr), followed by the Northwest Bays (72/hr) and Upper Lakes (60/hr). These catch rates are above average for area lakes. \n\nOther Fish\nBlack bullhead, bowfin (dogfish), common carp, green sunfish, hybrid sunfish, largemouth bass, muskellunge, pumpkinseed sunfish, rock bass, white sucker, yellow bullhead were also captured in low numbers during the 2007 assessment. Rock bass and green sunfish were only captured in the Upper Lakes. Smallmouth bass are found in Lake Minnetonka, but their numbers remain low. Smallmouth bass reproduction has been severly reduced due to the loss of submerged wood and rocky habitats. Muskellunge were not targeted during this assessment, but their population remains strong. Fish exceeding 50 inches and approaching 40 pounds are caught in Lake Minnetonka every year. Survival of stocked fingerling muskellunge is assumed to be very low due to the high abundance of largemouth bass and northern pike. Advanced fingerlings and yearlings have been used in recent years to try and improve the survival rate of stocked fish. Practicing CPR (Catch, Photo, and Release) is essential to maintaining the trophy muskellunge fishery found in Lake Minnetonka.\n\nEurasian water milfoil is found in high abundance throughout Lake Minnetonka. Although milfoil is a common occurrence in most metro lakes, anglers and boaters should take precautions to prevent the spread of milfoil and other invasive species. Lake Minnetonka receives heavy recreational use so the potential for the spread of invasive species into and out of the lake is high. The shoreline and watershed of Lake Minnetonka is highly developed and puts stress on the lakes aquatic habitat and ecosystem integrity. Large docks, boating platforms, and man-made beaches have the potential to destroy vital habitat for fish and wildlife. Environmentally friendly development practices, such as shoreline buffer strips of natural vegetation, are necessary to maintain the current water quality of Lake Minnetonka. Shoreline development, Eurasian water milfoil, curly leaf pondweed, rusty crayfish, and the fish disease VHS should be a concern to all Minnesotans who enjoy lake recreation.\n
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