Willmert (main bay)

A targeted survey of the nearshore fish community in Wilmert Lake was conducted by Fisheries Index of Biological Integrity (IBI) Program Staff starting June 24, 2019. Ten sampling sites were evenly spaced around the lake and each was sampled by backpack electrofishing and seining with a 50-foot seine. Nearshore sampling captured 9 native species of fish. None of these species are intolerant of disturbance and four species are tolerant of disturbance (Bigmouth Buffalo, Black Bullhead, Fathead Minnow, and Orangespotted Sunfish). Data from this targeted nearshore survey is combined with trap net and gill net data from an August 2018 standard survey to describe the fish community and provide a Fish-based Index of Biological Integrity (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., Iowa Darter and Rock Bass), while other species are tolerant of degraded conditions (e.g., Black Bullhead and Fathead Minnow). 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. Data from this survey will contributed biological information about the health of the fish community in Wilmert Lake to the Blue Earth River Watershed assessment of surface waters process completed in coordination with MN Pollution Control Agency.

Wilmert Lake is a 362-acre lake located 5 miles south of the City of Fairmont in Martin County. Wilmert Lake has a relatively small watershed, as the watershed-to-lake ratio is 10 to 1. Historically, Wilmert Lake has been susceptible to winterkills, however; recent mild winters have reduced winterkill frequency and severity. Wilmert Lake is managed primarily for Northern Pike and secondarily for Yellow Perch, Walleye, and Black Crappie. A standard survey was conducted the week of August 27, 2018, to monitor fish populations using two gill nets and nine trap nets. Northern Pike have occurred in very low abundance in Wilmert Lake, less than 0.3 per gill net dating back to 1993. The trend was similar in 2018 as no Northern Pike were sampled in gill nets or trap nets. Given the less frequent winterkills in this lake, top predator management could be switched from Northern Pike to Walleye, which have a stable population in Wilmert Lake. If you are fishing for Northern Pike, remember there is a new regulation. The limit in the southern Northern Pike zone is now two Northern Pike and both need to be 24 inches or longer. Any Northern Pike under 24 inches must be returned to the lake immediately. Since 1993, Walleye catch rates have averaged 8.3 per gill net, varying from 0.0 per gill net in 2001 to 11.8 per gill net in 1997. In 2018, the Walleye catch rate was 9.5 per gill net, which is within the expected range of catch rates for similar lakes (2.3 to 18.1 per gill net). Five year classes of Walleye were sampled including year classes from 2013, 2014, 2015, 2016, and 2017. The 2013 and 2016 year classes do not correspond to fry stocking events, suggesting that some natural reproduction occurred or Walleye are moving into Wilmert Lake from another waterbody. Lengths of Walleye ranged from 9.1 to 24.1 inches and averaged 15.2 inches. Average length at age 1 was 9.1 inches, age-2 was 12.5 inches, age-3 was 14.7 inches, age-4 was 17.7 inches and age-5 was 18.5 inches, indicating normal growth. Since 2001, Yellow Perch catch rates have declined from 140.0 per gill net in 2001 to 83.0 per gill net in 2010, to 14.5 per gill net in 2018. Despite the decrease, the 2018 catch rate of 14.5 per gill net is within the expected range of catch rates for similar lakes (2.7 to 25.0 per gill net). Yellow Perch lengths ranged from 5.6 to 9.2 inches and averaged 7.1 inches (PSD=35). The Black Crappie and White Crappie catch rates in 2018 were 25.7 per trap net and 13.6 per trap net, both exceeding their expected range of catch rates for similar lakes (Black Crappie (1.2 to 20.5 per trap net; White Crappie 0.3 to 6.0 per trap net). Lengths of Black Crappie ranged from 6.0 to 11.1 inches and averaged 8.7 inches. Lengths of White Crappie ranged from 3.4 to 11.8 inches and averaged 7.6 inches. The Freshwater Drum catch rate decreased from 121.0 per gill net in 2010 to 52.0 per gill net in 2018. The Black Bullhead catch rate increased from 11.0 per gill net in 2010 to 64.5 per gill net in 2018. Lengths of Black Bullhead ranged from 6.4 to 10.9 inches and averaged 8.8 inches. Other species sampled included Bigmouth Buffalo, Common Carp, and White Sucker.

Wilmert Lake is a 362-acre lake located 5 miles south of the City of Fairmont in Martin County. Wilmert Lake is a class 43 lake with a maximum depth of 8.0 feet and is managed primarily for northern pike and secondarily for walleye and yellow perch. Wilmert Lake was stocked with Lower Mississippi strain Walleye fry in the spring of 2017, due to surplus production of this strain. The Lower Mississippi strain was last stocked decades ago, but has persisted in several area lakes despite extensive stocking of Mississippi strain Walleye. A daytime electrofishing survey was conducted on September 13, 2017 to determine if the fry stocking was successful. Young-of-the year Walleye were captured at a rate of 33.8 per hour electrofishing, which indicates that the fry stocking was somewhat successful. Fin clip samples were collected up to 50 age-0 walleye for genetic analysis. Over 88% of those fish were a byproduct of stocking. In stocked years, the goal is to attain 30.0 per hour electrofishing. Lengths of Walleye ranged from 5.4 to 6.9 inches and averaged 6.1 inches.

Based on Minnesota DNR survey data, anglers target Walleye, Black Crappie, White Crappie, Yellow Perch, and Bluegill in Willmert (main bay). See the full species list above for catch rates, size structure, and quality scores.

Minnesota DNR records list public access for Willmert (main bay). Check the DNR LakeFinder page for the launch type and directions before you go.

Willmert (main bay) has a maximum depth of 8 feet, per Minnesota DNR data.

The most recent Minnesota DNR survey data for the main sport fish in Willmert (main bay) is from 2019.

No invasive species are on record for Willmert (main bay) in Minnesota DNR data. Always clean, drain, and dry your equipment to help keep it that way.