Thomson Reservoir

Thomson is a 339 acre reservoir located immediately north of Thomson, MN. It is operated as a water storage reservoir by Minnesota Power for the Thomson Hydro Station further down stream and is subject to water level manipulation. Maximum depth is 22 feet and 83% of the reservoir is shallower than 15 feet. Access is limited to a carry-down site at the north end of Thomson's main street. Walleye abundance of 4.2 per gillnet lift was above average compared to other Minnesota lakes of similar type. Mean length of walleye was 12.2 inches. Growth was slow, with length at age four of 13.3 inches. Six year-classes were represented from 1995 through 2001, with 82% of the fish from the 2000 and 2001 year-classes. Northern pike abundance of 0.8 per gillnet was below average compared to other Minnesota lakes of similar type. Mean length of northern pike was 19.2 inches. All year-classes were represented from 1998 through 2001. Smallmouth bass abundance of 3.2 per gillnet lift was higher than previous years, but there are no other similar lakes for comparison of catch rates. Mean length of smallmouth bass was 13.5 inches. Growth was fast, with length at age four of 12.0 inches. Seven year classes were represented from 1991 through 2001, with a strong 1998 year-class (44% of the fish). Yellow perch abundance of 2.8 per gillnet lift was below average compared to other Minnesota lakes of similar type. Mean length of perch was 8.6 inches. Growth was extremely fast, with length at age four of 9.4 inches. All year-classes were represented from 1997 through 2001. Eight channel catfish were captured during the assessment, but there are no similar lakes for comparison of catch rates. Channel catfish were large with a mean length of 26.0 inches. Walleye and smallmouth bass should currently provide excellent angling in Thomson Reservoir. Large yellow perch are also available in lower numbers. Other fish sampled included black bullhead, black crappie, rock bass, white sucker and shorthead redhorse.

REPRODUCTIVE SUCCESS IS ADEQUATE FOR ALL SPECIES. WAES ARE OF NORMAL ABUNDANCE, WITH AVERAGE GROWTH. NO FISH OLDER THAN IV WERE SAMPLED. PERCH HAVE A GOOD QUALITY SIZE STRUCTURE, WITH RAPID GROWTH. SMB WERE FEWER IN NUMBER THAN EXPECTED, GIVEN ANGLER REPORTS ABOUT THE RESERVOIR AND RIVER UPSTREAM, SIZE STRUCTURE AND GROWTH RATES ARE AVERAGE. BLGS WERE LARGE, THOUGH ONLY FOUR WERE SAMPLED. WTS ARE VERY ABUNDANT.

Based on Minnesota DNR survey data, anglers target Walleye, Yellow Perch, Rock Bass, Bluegill, and Smallmouth Bass in Thomson Reservoir. See the full species list above for catch rates, size structure, and quality scores.

We don't have a confirmed public access point on record for Thomson Reservoir. Check the DNR LakeFinder page for current access details before you go.

Thomson Reservoir has a maximum depth of 22 feet, per Minnesota DNR data.

The most recent Minnesota DNR survey data for the main sport fish in Thomson Reservoir is from 2002. Surveys this old should be treated with some caution — fish populations change over time.

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

No — Thomson Reservoir has no lake-specific regulations in the 2026 Minnesota DNR regulations, so statewide Minnesota limits apply. The statewide walleye and sauger limit is: 6 combined, not more than one walleye over 20". Verify current rules with the Minnesota DNR before keeping fish.