Lake information report

Name: Minnetonka

Nearest Town: Mound Primary County: Hennepin Survey Date: 06/11/2007 Inventory Number: 27013300

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Public Access Information

Fishing Regulations:

Lake Characteristics

Fish Sampled for the 2007 Survey Year

Length of Selected Species (Trapnet, Gillnet) Sampled for the 2007 Survey Year

Fish Stocking Activity

Fish Stocked by Species for the Last Ten Years

Fish Consumption Guidelines

These fish consumption guidelines help people make choices about which fish to eat and how often. Following the guidelines enables people to reduce their exposure to contaminants while still enjoying the many benefits from fish.

Pregnant Women, Women who may become pregnant and Children under age 15

General Population

DOWID - MN DNR, Divion of Waters' lake ID number.

Contaminants listed were measured at levels high enough to warrant a recommendation to limit consumption.

Listing of consumption guidelines do not imply the fish are legal to keep, MN DNR fishing regulations should be consulted.

Dioxin
Mercury
PCBS - Polychlorinated biphenyls
PFOS - Perfluorooctane sulfanate

Status of the Fishery (as of 06/11/2007)

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).

Walleye Despite 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.

Walleye 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.

Walleye 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.

Walleye 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.

Aging 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.

Lake 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.

Northern Pike Consistent 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.

Size 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.

Yellow Perch Yellow 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.

Size 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.

Bluegill Bluegill 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.

Eight 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.

Black Crappie The 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.

Nine 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.

Largemouth Bass The 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.

Just 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.

Other Fish Black 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.

Eurasian 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. ?

For more information on this lake, contact: Area Fisheries Supervisor 9925 Valley View Rd Eden Prairie, MN 55344 Phone: (952) 826-6771 Internet: West Metro Fisheries E-Mail: MetroWest.Fisheries@state.mn.us	Lake maps can be obtained from: Minnesota Bookstore 660 Olive Street St. Paul, MN 55155 (651) 297-3000 or (800) 657-3757 To order, use B0122 for the map-id.
For general DNR Information, contact: DNR Information Center 500 Lafayette Road St. Paul, MN 55155-4040 TDD: (651) 296-6157 or (888) MINNDNR Internet: www.dnr.state.mn.us E-Mail: info.dnr@state.mn.us	Turn in Poachers (TIP):     Toll-free: (800) 652-9093