Thompson

A population assessment was conducted at Thompson Lake in 2013 to monitor the fish community. Prior to the assessment, the lake was primarily managed for Walleye and to a lesser extent for Northern Pike and Yellow Perch. Beginning in 2014, Thompson Lake will be managed as a Walleye rearing pond. A total of 220 Yellow Perch were sampled with gill nets for a catch rate of 110.0/net, which indicated high numbers were present. Historically, catch rates have varied from 0/net to 110.0/net with a average of 34.5/net. In 2013, lengths ranged from 5.5 to 9.4 inches with an average of 7.0 inches. A total of 88 Yellow Perch ranging from 4.8 to 8.9 inches were sampled with trap nets for a catch rate of 11.0/net. Fish from both gears ranged from 1 to 2 years old with 2 year-classes present. A total of 763 Black Bullheads ranging from 4.9 to 13.1 inches long were sampled with gill nets for a catch rate of 381.5/net, which indicated high numbers were present. Historically, catch rates have varied from 6.0/net to 381.5/net with an average of 115.2/net. An additional 251 Black Bullheads were sampled with trap nets for a catch rate of 31.4/net. Black Bullhead numbers remain a large part of Thompson Lake's winterkill-influenced fish community. A total of 25 Common Carp ranging from 12.4 to 24.8 inches long were sampled with trap nets for a catch rate of 3.1/net, which indicated moderate numbers were present. Historically, catch rates have varied from 0.2/net 58.8/net with an average of 10.9/net. An additional 3 Common Carp ranging from 12.8 to 20.0 inches long were sampled with gill nets. Other species sampled in 2013 include Golden Shiner, Green Sunfish, and hybrid sunfish (Lepomis spp.)

Thompson Lake has a shallow basin and can be characterized as having low winter dissolved oxygen concentrations and the potential for frequent winterkill. A pump and baffle aeration system is operated on Thompson Lake and winter oxygen monitoring indicates that the aeration system maintains some area of oxygenated water. However, the effectiveness of the aeration system in preventing or reducing the severity of winterkill is unknown. A fisheries population assessment was conducted in 1995 on Thompson Lake. Bluegill numbers were above the normal range for this lake class. Average length of bluegill was 5.2 inches and most were 1 and 2 year old fish. Largemouth bass were present and spring electrofishing sampled largemouth bass from 10 to 17 inches long. Northern pike were present also and growth was good. All the northern pike sampled were age 2 and average length was 24 inches. Yellow perch may provide the best angling opportunities. The yellow perch sampled ranged in length from 7 to 10 inches with an average length of 8.9 inches. Black bullhead were abundant, but many were too small to attract anglers. Many anglers prefer yellow bullhead and the trapnet catch rate (4.6 per net) for that species was above the normal range for this lake class. Yellow bullhead ranged in length from 6 to 10 inches with an average length of 7.2 inches. The high percentage of age two gamefish sampled indicates that Thompson Lake did have natural reproduction after restocking efforts and that fish were able to survive several winters. Reports indicate that Thompson Lake experienced some fishing pressure during the summer of 1995 and on into the early part of the winter. Anglers apparently had some success fishing for bluegill and yellow perch. However, Thompson Lake again experienced low dissolved oxygen concentrations this winter (1995- 96) and appears to have experienced a severe winterkill.

A lake draw-down and chemical rehabilitation was conducted on Thompson Lake in 1987. A severe drought caused Thompson Lake to become completely dry by the summer of 1989. Water levels returned to normal by the fall of 1991 and Thompson Lake was restocked with fish in the spring of 1992.Thompson Lake has a shallow basin (maximum depth 8 feet) and can be characterized as having low winter dissolved oxygen concentrations and the potential for frequent winterkill. A pump and baffle aerator system was first operated during the winter of 1992-93. However, the effectiveness of the aeration system in preventing or reducing the severity of winterkill is unknown.An assessment netting after ice-out in 1993 indicated that winterkill had occurred. In 1993, Thompson Lake wasrestocked with largemouth bass, bluegill and yellow perch adults and northern pike fingerlings.A high velocity tube was installed downstream of the outlet, prior to lake reclamation to prevent undesirable species from entering the lake. However, high water levels in 1993 may have caused the high velocity tube to be ineffective at preventing fish passage. A fisheries population assessment in July, 1993 revealed the presence of black bullhead and common carp. It is unknown if these species were stocked by anglers or if they entered the lake via the outlet.A fisheries population assessment was conducted on Thompson Lake in 1994. Fish species of particular interest captured in the assessment included black bullhead, bluegill, largemouth bass, northern pike, yellow bullhead and yellow perch.The black bullhead trapnet catch was near the lake class average. Black bullhead ranged in length from 4.4 to 12.2 inches, with an average length of 6.2 inches. Black bullhead may exhibit good growth and provide angling opportunities in the next several years.The bluegill trapnet catch was above the normal range for this lake class. Bluegill ranged in length from 3.1 to 9.3 inches with an average length of 4.6 inches. Adult bluegill were stocked in 1993 and it appears they reproduced successfully. Several age classes of bluegill were present but the catch was dominated by age one fish. Shoreline seining indicated that bluegill natural reproduction occurred this year.Seventeen largemouth bass were sampled in trapnets for a catch rate of 1.9 per net. This is above the normal range for this lake class. All bass sampled were age one. It appears that adults stocked in 1993 reproduced successfully. Growth was good and age one bass ranged in length from 4.4 to 10.3 inches with an average length of 8.5 inches. No largemouth bass were sampled during night electrofishing in the spring and no young-of-year largemouth bass were sampled while shoreline seining.Three northern pike were captured in trapnets for a catch of 0.3 per net. All northern pike were age one and ranged in length from 16.7 to 20.6 inches.Three yellow bullhead were sampled in trapnets for a catch rate of 0.3 per net. This is below the normal range for this lake class. No yellow bullhead were stocked in Thompson Lake after reclamation and the origin of these fish is unknown.Yellow perch trapnet catches were above the normal range for this lake class. The absence of deep water area may have influenced trapnet catches, making them more efficient at sampling yellow perch than in many lakes. Yellow perch adults were stocked in 1993 and it appears they reproduced successfully. All yellow perch sampled were age one and ranged in length from 6.3 to 8.3 inches with an average length of 7.2 inches.Many of the fish species stocked in Thompson Lake after reclamation and winterkill have reproduced successfully. Ifaeration is successful at reducing winterkill, Thompson Lake may provide good angling opportunities within the next several years.

Based on Minnesota DNR survey data, anglers target Northern Pike, Yellow Perch, Largemouth Bass, Green Sunfish, and Bluegill in Thompson. See the full species list above for catch rates, size structure, and quality scores.

Minnesota DNR records list public access for Thompson. Check the DNR LakeFinder page for the launch type and directions before you go.

Thompson has a maximum depth of 8 feet, per Minnesota DNR data.

The most recent Minnesota DNR survey data for the main sport fish in Thompson is from 2013. Surveys this old should be treated with some caution — fish populations change over time.

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