Trout

Temperature and dissolved oxygen measurements were collected from the deepest basin in Trout Lake on August 5th, 2025. This was done to evaluate the quantity and quality of cold, oxygenated water (i.e., oxythermal habitat) available to Lake Trout, the most sensitive coldwater species present in this lake (Cisco, also known as 'Tullibee', are also present). Lake Trout require a layer of oxythermal habitat that contains water temperatures below 8.8 degrees C (47.8 degrees F) and dissolved oxygen concentrations above 3.0 mg/L. Based on data collected from the deepest basin (maximum sampled depth was 85.3 feet), the water temperature decreased to 8.8 degrees C (47.8 degrees F) at 59.0 feet and the dissolved oxygen concentration stayed greater than 3.0 mg/L for the entire sampled depth. This layer in the water column was 26.2 feet, indicating oxythermal habitat for Lake Trout was present. Further, the temperature at which dissolved oxygen decreased to 3.0 mg/L (i.e., TDO3, a single variable to characterize oxythermal habitat) was never reached because dissolved oxygen remained above 3.0 mg/L throughout the sampled depths. In this case, the minimum temperature, 7.9 degrees C (46.2 degrees F), was substituted as TDO3. TDO3 values cooler than 8.8 degrees C (47.8 degrees F) indicate that oxythermal conditions were suitable for Lake Trout at the time of the survey. Data collected by the Minnesota Department of Natural Resources during the period of maximum oxythermal stress (July 26th to Aug 24th) in 4 years during 2006-2023 indicated unsuitable oxythermal habitat in most years surveyed, with unfavorable conditions recorded in 2006, 2008, 2010 when there was no suitable oxythermal habitat layer. When adequate oxythermal habitat is not available, Lake Trout are squeezed into unfavorable, warmer water conditions and experience higher levels of stress. Despite the low values for oxythermal habitat since 2006, the latest three fisheries surveys, in 2014, 2018, and 2022, caught moderate numbers of Lake Trout in deewater nets.

Trout Lake is located nine miles north of Tower and just north of Lake Vermilion but is entirely within the Boundary Waters Canoe Area Wilderness (BWCAW). It has a number of portages to nearby lakes, but the main lake access is via a motor portage from Lake Vermilion. The lake is 7,425 acres and although it is entirely within the BWCAW, 25 hp and under outboards are permitted. Motor use permits are required from the US Forest Service. The lake has a maximum depth of 98 feet and clear water. There are several small to moderate sized inlets mostly on the lakes east and north sides. Only one outlet exists which flows out the southernmost point and into Lake Vermilion. Trout Lake is a prototypical northern Minnesota/Canadian shield water body with shorelines covered in tall pines, areas of granite ledge rock, and exceptionally clear water. Lake bottom substrates along the shoreline are mostly boulder and ledgerock with some areas of rubble and cobble. A few bays have soft bottoms but vegetation is fairly sparse. Additionally, a few bays are quite sandy and make for great swimming areas. On July 17, 2022, the dissolved oxygen profile showed thermal stratification with a surface temperature of 74 F and bottom temperature 46 F. The water temperatures suitable for lake trout were reached around 33 feet. Oxygen levels suitable for lake trout were sustained throughout the water column. The overall deep water gillnet catch rate for all fish combined was 39.3 fish/net which was below average for the lake. Yield was 21.0 lbs/net which was right at the lake's historic average. Fish species sampled in deep water gill nets were cisco, lake trout, and walleye. The overall shallow water gillnet catch rate for all fish combined was 10.8 fish/net which was the lowest on record for the lake. Yield was 16.3 lbs/net which was also the lowest on record for the lake. Fish species sampled were rock bass, walleye, northern pike, yellow perch, white sucker, smallmouth bass, bluegill, and pumpkinseed. The deep water gillnet catch for lake trout in 2022 was 1.3 fish/net which was better than the average for past surveys of Trout Lake. Lengths ranged from 13 to over 33 inches with an average of just over 25 inches. The average weight was very impressive at nearly 6.5 lbs/fish. Of the fish that were aged, ages ranged from 4 to 19 years. Lake trout growth was fairly fast with the average fish taking 8 years to reach 22 inches long. Six-hundred-eighty-one cisco were caught in deep water gill nets for a catch rate of 37.8 fish/net. This was below average compared to past surveys on Trout Lake but still quite good when compared to other cisco lakes in the Tower area. Sizes were 6.5 to nearly 16 inches with an average of just over 9 inches. Sizes appear to have remained fairly consistent throughout the years. Thirty-seven walleye were sampled in the shallow water gill nets for a catch rate of 3.1 fish/net. This catch rate was the lowest on record for Trout Lake. Lengths ranged from 8.5 to just over 24 inches with an average of nearly 19 inches. Average weight was 2.5 pounds. Growth rates were quite good when compared to other similar lakes and other walleye populations in the Tower area. Ages ranged from 1 to 23 years old with the strongest year class coming in 2017. The northern pike shallow water gillnet catch was 1.3 fish/net which was on par with previous surveys of Trout Lake. Lengths ranged from 20.5 to just over 35 inches with an average of 25.5 inches. Sizes were similar to previous surveys. The average weight was nearly four pounds. Eight smallmouth bass were sampled in shallow water gill nets for a catch rate of 0.7 fish/net which was the lowest catch rate on record since smallmouth were first sampled in 1977. The average weight was just over a pound per fish. Lengths ranged from 11 to just over 16 inches with an average of just over 13 inches. Growth was somewhat slow compared to other smallmouth lakes in the area. The average smallmouth was eight inches long at four years old. Ages ranged from 4 to 12 years.

Trout Lake is located approximately 7 miles NW of Tower and is entirely within the BWCAW. Outboard motors up to a maximum of 25 hp are allowed. Snowmobile use is prohibited. Other BWCAW rules and regulations apply when visiting this lake. The most common access is via 1/2 mile portage from Lake Vermilion where a concessionaire will transport your watercraft by ATV and trailer to Trout Lake. There are several other portages surrounding the lake for addtional access options. Designated USFS campsites are common around the lake for overnight and day use. The 2018 survey of Trout Lake was focused on the deepwater fish community, in particular the survival of stocked lake trout. Twenty-seven lake trout were sampled in 2018 and cisco dominated the catch (94%). Northern pike, smallmouth bass and walleye were incidentally sampled in low relative abundances. Lake trout numbers in 2018 (1.5/gill net) were slightly above the historical average (0.8/gill net) for this lake. Eight stocked trout were sampled and all but one of them were under 9 inches long and from stocking in the prior spring. The only other stocked lake trout sampled was 19.5 inches. As we have seen in previous surveys, the stocked lake trout rarely acheive large size indicating that their survival is poor. Naturally reproduced lake trout ranged from 12 to 28 inches long. Overall, the lake trout average length was 15 inches which is smaller than the historic average length of 21 inches. This average was lowered by the number of small stocked fish in 2018, which typically were not caught in past surveys. Fin-clipped yearling lake trout were stocked in even years in Trout Lake through 2018. Cisco are an important forage fish for lake trout. Numbers in 2018 (37.3/gill net) were below the historic average (50.4/gill net). Cisco average length was 9.3 inches which is slightly larger than the historic average length of 8.9 inches. Cisco sizes ranged from 5.4 inches up to 17.4 inches.

Based on Minnesota DNR survey data, anglers target Walleye, Northern Pike, Smallmouth Bass, Lake Trout, and Rock Bass in Trout. 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 Trout. Check the DNR LakeFinder page for current access details before you go.

Trout has a maximum depth of 98 feet, per Minnesota DNR data.

The most recent Minnesota DNR survey data for the main sport fish in Trout is from 2022.

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