Thistledew

A targeted survey of nearshore fish species in Thistledew Lake was conducted on July 7th-8th, 2025, by Lake Biological Monitoring and Assessment Program staff. Sampling sites were evenly spaced around the lake, and each was sampled by backpack electrofishing and seining with a 50-foot seine, where possible. Backpack electrofishing was completed at all ten sampling stations. Similarly, a 50-foot seine was used to sample eight stations, a 15-foot seine was used to sample one station, and site conditions (i.e., dense aquatic vegetation and soft substrate) prevented the use of a seine at one station. Nearshore sampling captured 13 species of fish including three species that are intolerant of disturbance (i.e., Blackchin Shiner, Iowa Darter, and Rock Bass) and no species that are tolerant of disturbance. The nearshore data was combined with gill net and trap net data from an August 2024 survey to describe the fish community and provide a Fish-based IBI (FIBI) score. The FIBI uses fish community data to measure a lake's health, and the types of fish species present can help identify any stressors that may be negatively affecting the lake environment. In Minnesota lakes, certain fish species cannot survive without clean water and a healthy habitat (e.g., Blackchin Shiner, Iowa Darter, and Rock Bass), while other species are tolerant of degraded conditions (e.g., Green Sunfish). The FIBI score, composed of several fish community diversity and composition metrics, indicates the overall health of a lake by comparing it to what is expected for a healthy lake. For additional information on the FIBI, search for "lake index of biological integrity" on the mndnr.gov website. Results from this survey provide evidence that the fish community in Thistledew Lake is healthy as indicated by a FIBI score that exceeds the exceptional use threshold determined for similar lakes. These results are similar to previous findings, which indicated that Thistledew Lake is fully supporting aquatic life. The survey results will be considered when the biological health of the lake is assessed during the Little Fork River Watershed assessment process, which will be completed in coordination with MN Pollution Control Agency. You can help protect the fish community in Thistledew Lake by reducing runoff, maintaining natural shorelines, and preventing the spread of invasive species.

Thistledew Lake is a 318-acre lake located five miles southwest of Togo, MN in the Little Fork River watershed. A state-administered boat access and campground are located at the north end of the lake. All the land surrounding the lake is in State of Minnesota ownership and is generally undeveloped except for a Department of Corrections facility located on the east side of the lake between Thistledew and Moose Lakes. Thistledew Lake has relatively low fertility and clear water. Water clarity has ranged from 12 to 25 feet in past surveys. Thistledew is in ecological lake class 23. Other area lakes in this class include Clubhouse, Hatch and Ruby lakes. The Fisheries Lake Management Plan (LMP) was last updated in 2021. Walleye are the primary management species and are actively managed via annual fry stocking with a goal of maintaining population size typical for lakes like Thisledew. Northern Pike are a secondary management species with a goal of maintaining a moderate population density with individuals larger than 28 inches present. A standard lake survey (gill nets and trap nets) was conducted in early August 2024 to evaluate the Walleye stocking plan and update information on the fishery. Walleye were captured at a rate typical for Thisledew and met the management goal. Size structure was favorable with Walleye ranging from 16.5 to 24.6 inches and having an average length of 19.3 inches. Twenty-five percent of Walleye exceeded the angler-preferred length of 20 inches. Age 3 and 5 fish made up nearly the entire sample. Growth was fast with Walleye averaging 17.6 inches at age 4. Thistledew Lake appears to provide good fishing opportunities for Walleye. Thistledew Lake has historically produced low to moderate numbers of Northern Pike with moderate size structure. The 2024 gill-net catch was average for the lake and met the LMP goal. Size structure was favorable. Pike ranged from 21.1 to 33.7 inches with an average length of 26.1 inches. Twenty-five percent of the sample exceeded 28 inches; meeting the management goal. Ages 3-8 were represented with ages 5 and 6 the most abundant. Northern Pike averaged 25.1 inches at age 5. Thistledew Lake provides good angling opportunities for Northern Pike with a chance to catch fish exceeding 30 inches. The Bluegill population has generally had low to average catch rates and size structure. The 2024 trap-net catch was below the normal range for lakes with similar habitat. Size structure was modest; Bluegill ranged from 3.2 to 8.8 inches with an average length of 6.1 inches. Only 6% of Bluegill exceeded 8 inches. Age and growth information was not collected in this survey, but previous surveys showed average growth rates. Like many northern Minnesota lakes, net catches for Black Crappie in Thistledew have been low in mid-summer surveys. Sample size in 2024 was too low to draw meaningful conclusions about size and age structure, but the limited sample indicated several year classes were present. Sampled Black Crappie ranged from 4.7 to 13.0 inches. Black Crappie populations are better evaluated by spring trap netting and will be considered for future surveys. Largemouth Bass were captured in relatively high numbers from gill nets, above the normal range for similar lakes. Size structure was modest; with bass ranging from 5.4 to 15.5 inches with an average length of 11.4 inches. Largemouth Bass are not sampled well with standard netting, so recent observations suggest they are an important component of the fishery. Fair angling opportunities appear to exist for bass, at least for numbers of smaller-sized fish. Yellow Perch are an important prey species in Minnesota lakes. Catch rates in Thistledew have generally declined over time which corresponds to statewide trends. The 2024 gill-net catch was below the normal range for this type of lake but equaled the previous survey. Perch were generally too small to be of interest to anglers, ranging from 5.8 to 6.7 inches. Other species sampled included Hybrid Sunfish, Pumpkinseed, Rock Bass and White Sucker.

Thistledew Lake is a 318-acre lake in northeastern Itasca County located 30 miles north of Nashwauk, MN. A state administered public access is located at the north end of the lake on Thistledew Rd. (County 551) off Highway 65. The access has a cement ramp with parking for four rigs. Thistledew Lake has a maximum depth of 45 ft and 23% of the lake is 15 ft or less. The lake has low fertility. The water is clear to light brown, resulting in visibility to a depth of 23 ft in mid-summer. The depth of water at which oxygen levels limit fish presence was 26 ft in mid-summer. One inlet on the western shore flows from Little Dew Lake while one outlet on the southwest shore flows into Moose Lake. Other area lakes with similar habitat include Bluewater, Bello, Hartley, Loon, and Ruby. The 2020 survey was the 13th survey of the fish community since 1958. Surveys occur to monitor for changes in species composition, number, length distribution, and growth. Gamefish species that are best suited for the lake are Walleye, Northern Pike, and Black Crappie. No special regulations are present. The Walleye population had a below average catch rate, an average length distribution, and above average growth. Gill net catches were below average for the lake (1.9/net) and low compared to lakes with similar habitat. The sampled Walleye ranged from 10 to 24 inches and averaged 16 inches. The length distribution was average, as only 41% of Walleye exceeded 15 inches. However, 29% exceeded 20 inches, and Walleye 25 to 27 inches have been sampled in six surveys. Walleye ranged from age 2 to 11. Growth rates were above the statewide average. On average, Walleye took four years to exceed 15 inches. Walleye have been stocked for many years because natural reproduction is limited, particularly in recent decades. Twelve of the 17 Walleye sampled in 2020 were from stocked year classes, which is consistent with previous surveys. The Walleye stocking guidelines recommend discontinuing stocking if it fails to produce a viable fishery supporting a catch rate of 2.0/gill net and perch catches are below 8/gill net. Future of Walleye management will be considered based on these recommendations and data. The Northern Pike population had a low catch rate, average length distribution, and above average growth. Gill net catches were below average for the lake and low compared to lakes with similar habitat. However, higher catches are undesirable because they are usually associated with higher density populations having poor size structure and slow growth. The sampled pike ranged from 13 to 31 inches and averaged 21 inches. The length distribution was average, as 44% of pike exceeded 21 inches and 6% exceeded 28 inches. However, pike over 30 inches were sampled in six surveys. The largest fish sampled was a 38-inch fish in 2016, indicating the potential exists for producing larger pike. Pike ranged from age 1 to 7. Growth rates exceeded the statewide average. On average, pike took four years to exceed 21 inches. The pike population may interest anglers and spearers due to its length distribution. However, due to the lake's small size, anglers are encouraged to release pike over 26 inches and harvest up to 10 less than 22 inches to help maintain and improve size structure. Spearers are encouraged to harvest smaller pike also. Thistledew Lake is in the North-central Zone for pike management, which may contribute to modest improvements in size quality. The Black Crappie population had low catch rates and an above average length distribution. Gill net catches were above average for the lake and low compared to lakes with similar habitat. Only two crappie were sampled in 2020, which were 11 and 13 inches. Only twice have the total number of crappie sampled by all gears exceeded eight fish. Ten-inch fish were sampled in eight surveys, while 12-inch fish were sampled in three. Therefore, the potential exists for producing larger crappie. Growth rates from previous surveys were above average. On average, crappie took four years to exceed eight inches. Although the crappie population was lower in 2020, fish over 10 inches that interest anglers have been sampled in 62% of surveys. The Largemouth Bass population had an average catch rate and length distribution in gill nets. However, only seven bass were sampled with in 2020. The most effective method to evaluate a bass population is spring night electrofishing, which has only occurred in 2016. Electrofishing catches were twice the average for Grand Rapids area lakes. The 97 bass sampled with electrofishing ranged from 3 to 17 inches and averaged 11 inches. The length distribution was average, as 45% of bass exceeded 12 inches and 9% exceeded 15 inches. The largest fish ever sampled was an 18-inch fish in 2016. Bass ranged from age 1 to 9. Growth rates were below the statewide average. On average, bass took six years to exceed 12 inches. Due to the lake's small size, anglers are encouraged to release bass exceeding 15 inches to help maintain or improve size structure. The Bluegill population has consistently had low to average catch rates, length distributions, and growth. Only 16 Bluegill were sampled in gill nets in 2020. Bluegill populations are evaluated better with spring trap netting. However, surveys on Thistledew Lake have occurred in August. This timing likely results in lower trap net catches. Trap net catches have been lower than those observed on lakes with similar habitat. Length distributions from trap nets indicate the population has below average proportions of fish over 6 and 8 inches. Growth was below the statewide average. On average, Bluegill took six years to exceed six inches. Due to the lake's small size, anglers are encouraged to release Bluegill exceeding 8 inches to help maintain or improve size structure. The Yellow Perch population had a low catch rate. The gill net catches were the lowest observed (1.1/net) and declined in each of the last three surveys. Declining perch numbers are consistent with statewide trends that have occurred since the 1970s. Reasons for statewide declines include increased predation by gamefish, higher Bluegill numbers resulting in perch having to share food resources, and loss of woody habitat along shorelines due to removal by property owners. Lower perch numbers can limit the number of gamefish the lake can support. The ten perch sampled ranged from 6 to 7 inches. While 8-inch perch were sampled in the first eleven surveys, none were sampled in the last two. Ten-inch perch have not been sampled since 1985. Statewide Walleye stocking guidelines recommend discontinuing stocking if perch gill net catches fall below 8/net. Other species sampled included Pumpkinseed Sunfish and Rock Bass. In order to maintain or improve fish and wildlife populations, water quality and habitat must be protected. People often associate water quality problems with large-scale agricultural, forestry, urban development or industrial practices in the watershed. In reality, the impact of land use decisions on one lake lot may be relatively small, yet the cumulative impact of those decisions on many lake lots can result in a significant decline in water quality and habitat. For example, removing shoreline and aquatic vegetation, fertilizing lawns, mowing to the water's edge, installing beach sand blankets, failing septic systems and uncontrolled run-off, all contribute excess nutrients and sediment which degrade water quality and habitat. Understanding these cumulative impacts and taking steps to avoid or minimize them will help to insure our quality fisheries can be enjoyed by future generations. Anglers and boaters are reminded to help slow the spread of invasive species by removing all aquatic plants from boats, trailers, and equipment. All drain plugs must be removed and live and bait wells must be drained before leaving the access. Anglers and boaters are encouraged to power wash and thoroughly dry all equipment prior to use in another water body.

Based on Minnesota DNR survey data, anglers target Largemouth Bass, Northern Pike, Black Crappie, Walleye, and Hybrid Sunfish in Thistledew. See the full species list above for catch rates, size structure, and quality scores.

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

Thistledew has a maximum depth of 45 feet, per Minnesota DNR data.

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

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