Thompson

Thompson Lake is a small, 18-acre lake with a maximum depth of 12 ft and is located approximately 9 miles northwest of Grand Marais. There is a small carry-in access located off Cook County Road 57 (Devil Track Road). Thompson Lake is a designated stream trout lake and has been actively stocked with brown trout and rainbow trout since 1988. In 2024, a standard survey was conducted using trap nets to assess the current fish community and evaluate the success of stocking efforts. Rainbow trout are the primary management species within Thompson Lake and are stocked annually in the spring with 1,050 yearlings. Rainbow trout catches have been declining slowly since 2012 but remain above management goals. Rainbow trout ranged from 9.6 to 15.8 inches with an average length of 12.9 inches. Three age classes were present during the survey, indicating successful stocking efforts from 2022, 2023, and 2024. Growth rates were average for Grand Marais area lakes, taking fish approximately three years to reach 15.0 inches. Habitat (temperature and dissolved oxygen) continues to be adequate and support rainbow trout in Thompson Lake. Anglers should be able to catch good numbers of small to medium sized rainbow trout on Thompson Lake by fishing from shore in the spring and fall. Brown trout are the secondary management species within Thompson Lake and are stocked in the fall during odd-numbered years with 1,000 fingerlings. Brown trout catches from the 2024 survey were low and did not meet management goals. Only one fish was caught during the survey and the fish measured 12.0 inches. The fish was aged at 3 years old, indicating that it was from the 2021-year class. Brown trout growth and survival has been poor over the last couple of surveys so anglers should not expect good brown trout fishing. Minnesota Lakes within Cook County continue to be susceptible to aquatic invasive species introductions. Invasive species have the potential to significantly alter fish communities and overall lake health. Anglers should clean watercraft and fishing gear, drain all water, and dispose of unused bait in the trash to prevent accidental introductions to these pristine waters within this part of the state.

Thompson Lake is a designated stream trout lake, and has been managed for trout since at least 1952. Since March 2005 it has been managed as a trophy trout lake, under a suite of special regulations. It is closed to winter fishing. During the open water season, it is open for catch-and-release fishing only, and anglers are limited to artificial lures and flies only, with a single hook. This was the third of what was to have been three standard surveys scheduled in the 2008 lake management plan to determine whether management goals could be met with the current stocking regime, and under the existing special regulation. The first survey (2009) could not be completed, but the 2012 survey was done as planned. Rainbow Trout were apparently abundant in Thompson Lake in the fall of 2015, and they were above-average in size. Survey results from 2012 and 2015 clearly indicate Rainbow Trout catch and size goals have been met by the current stocking plan and the special regulation. The 2015 Rainbow Trout catch was well above the goal of 0.75 fish/set, and most of the fish collected were over 12 inches in length. Several fish had survived to three years of age, unusual in an accessible lake like Thompson, and most likely attributable to the special regulation. Rainbow Trout growth had been about average for the area; fish reached a mean length of 11.9 inches by the end of their second year, compared to an area average of 11.6 inches. No Brown Trout were taken in 2015; however, low catches have been common in this lake, and they may simply have been missed in this survey. Brown Trout have been regularly stocked, and fish over 16 inches in length have been seen in most past surveys. No undesirable fish species were found in 2015. Thompson Lake is not connected to any other waters, so no natural routes exist for new species to enter the lake. This lake is infested with Chinese Mystery Snail, so users should take special care to clean all equipment used in the lake before moving to other waters.

Thompson Lake is a designated stream trout lake, and has been managed for a variety of trout species since it was first stocked in 1953. The lake was rehabilitated for stream trout management in 1988, and has since been stocked only with rainbow trout and brown trout. Since 2005 Thompson Lake has been one of eight "trophy trout" lakes in the Grand Marais area. As such, it is closed to winter fishing. Only catch-and-release fishing is allowed during the open-water season, and only artificail lures and flies, with a single hook, may be used. No bait is allowed. The 2008 management plan for Thompson Lake established goals for the rainbow trout population consisting of a minimum trap net catch of 0.75 fish/set, with 50% of those fish exceeding 12 inches in length. The goal for brown trout was a minimum trap net catch of 0.68 fish/set, with 40% of those fish exceeding 16 inches in length. The 2012 assessment was the second of three scheduled in the 2008 plan to determine whether long range goals for the lake would be met with increased rainbow trout stocking and reduced brown trout stocking called for in that plan. The first assessment (in 2009) was canceled due to a shortage of staff and funding. The management plan will be reviewed and revised in March 2017, following completion of the final assessment scheduled for 2015. The 2012 rainbow trout trap net catch, and the mean weight for rainbow trout taken in trap nets, were the highest seen in Thompson Lake since it was last reclaimed. Catch and size goals for the species from the 2008 plan were met. The trap net catch, and the mean weight for rainbow trout, exceeded normal ranges for fall assessments of stream trout lakes in this area (0.30-2.10 fish/set and 0.47-0.82 lb/fish, respectively). Rainbow trout as old as three years were collected, although one- and two-year-old fish made up the bulk of the catch. Growth had been about average; two-year-old fish reached an average length of 11.3 inches at the end of their second year, compared to an area average of 11.4 inches. Survival through two full seasons seemed to have been relatively high, suggesting that mortality in the catch-and-release fishery was not excessive. The brown trout catch in 2012 was within the normal range for a fall assessment in this area (0.20-1.25 fish/set), while the mean weight for brown trout taken in trap nets exceeded the normal range (1.05-2.87 lb/fish). The catch fell just short of the goal for the species, but the size goal established in the 2008 plan was met. Most of the brown trout taken were three-year-old fish from a 2009 fingerling stocking. Growth had been relatively fast; three-year-old fish reached an average length of 15.3 inches at the end of their third year, compared to an area mean of 13.4 inches. No undesirable fish species were found in 2012. Thompson lake is known to be infested with chinese mystery snails, and anglers and other visitors should carefully drain and clean their equipment before moving to another lake.

Based on Minnesota DNR survey data, anglers target Brook Trout and Rainbow Trout 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 12 feet and a mean depth of 7.6 feet, per Minnesota DNR data.

The most recent Minnesota DNR survey data for the main sport fish in Thompson is from 2024.

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.