Thompson Lake (Cook County)

Cook County, Minnesota - DNR stocking history, depth and survey data

Minnesota · Minnesota Department of Natural Resources (DNR) · DOW 16016000

DNR records show 15 stocking entries at Thompson Lake (Cook County) since 2016, most recently brown trout fingerlings in 2025 (1,000 fish).

• Thompson Lake (Cook County) has 15 DNR stocking records across 10 years (2016-2025): rainbow trout (10), brown trout (5).
• The most-stocked species by count is rainbow trout: 10,500 fish on record.
• Maximum depth 12 ft, mean depth 8 ft; surface area 18 acres, 18 littoral acres, 0.9 miles of shoreline, per the DNR lake survey.
• Average water clarity (Secchi depth) 8.0 ft.
• Fish species DNR lists here: brown trout, rainbow trout.
• 1 public access on the DNR list.
• Most recent DNR fish survey: October 2, 2024 (standard survey).
• Cook County, nearest town Grand Marais; DNR lake number (DOW) 16016000.

Stocking history

Public accesses

DNR fish survey, 2024

Catch per net (CPUE) is the DNR survey's count per gill net or trap net set; higher means more of that species were sampled, not a fishing forecast. Top species per gear shown; where we have no verified common name for a DNR code, the code itself is shown.

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.

Minnesota DNR survey narrative, October 2, 2024.

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