Blackduck

Minnesota DNR Fisheries IBI program staff conducted an assessment of lakeshore habitat on Blackduck Lake on August 21st, 2025, following the Score the Shore survey protocols. The assessment consisted of 106 survey sites evenly spaced 200 meters around the lake. Assessments were made in three habitat zones: Shoreline Zone (the shore-water interface to the top of the natural bank), Shoreland Zone (land-ward from shoreline to development structure or 100 feet), and Aquatic Zone (lake-ward 50 feet of shoreline). The average lakewide habitat score was 80.2 (+/- 1.6) out of 100 possible. A score of 80.2 indicates the lakewide shoreline condition is Moderately High (80-84.9). However, developed sites generally had poor habitat quality. Approximately 33 percent of the sites were developed with a mean score of 63.1 (+/- 3.4) indicating shoreline habitat quality of developed sites is Poor (50-65.9), while undeveloped sites had a mean score of 88.6 (+/- 0.5) with High (85-91.9) habitat quality.

A targeted survey of nearshore fish species in Blackduck Lake was conducted over several days, including August 20-21 and August 27-28, 2024, by Index of Biological Integrity (IBI) Program staff. Sampling sites were evenly spaced around the lake, and each was sampled by backpack electrofishing and seining with a 50-foot or 15-foot seine, where possible. Backpack electrofishing was completed at all 24 sampling stations. Similarly, a 50-foot seine was used to sample 12 stations, a 15-foot seine was used to sampled five stations, and site conditions (e.g., dense aquatic vegetation, soft substrate, and deep water) prevented the use of a seine at seven stations. Nearshore sampling captured 19 species of fish including five species that are intolerant of disturbance (i.e., Banded Killifish, Blacknose Shiner, Burbot, Iowa Darter, and Rock Bass) and two species that are tolerant of disturbance (i.e., Fathead Minnow and Black Bullhead). A concurrent summer trap net survey was also conducted by IBI Program Staff. Fifteen trap nets were set along the shoreline and in shallow offshore locations that encompassed multiple habitat types. Trap net sampling captured ten species of fish, including one that is intolerant of disturbance (i.e., Rock Bass) and one that is tolerant of disturbance (i.e., Black Bullhead). Yellow Perch, Bluegill, and Pumpkinseed comprised a majority of the trap net catch by number and Freshwater Drum comprised a majority by biomass. The nearshore and trap net data were combined with gill 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., Black Bullhead and Fathead Minnow). 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 Blackduck Lake may be adversely impacted by stressors, as indicated by an FIBI score near the general use impairment threshold for aquatic life use determined for similar lakes. These results are lower than the August 5th, 2024, survey but similar to previous assessment findings indicated that Blackduck Lake was vulnerable to impairment when last assessed. The survey results will be considered when the biological health of the lake is assessed during the Upper/Lower Red Lake River Watershed assessment process, which will be completed in coordination with MN Pollution Control Agency. You can help protect the fish community in Blackduck Lake by reducing runoff, maintaining natural shorelines, and preventing the spread of invasive species.

Blackduck Lake is a 2,711-acre lake with a maximum depth of 28 feet. The lake is located 1 mile west of the city of Blackduck in Beltrami County. Public access sites are located on the east shore of the lake off County Road 30 and on the southwest shore off County Road 31. A special regulation consisting of a reduced bag limit of 5 sunfish per day is in effect. Statewide regulations apply to all other species found in the lake. Blackduck Lake is managed primarily for Walleye, with Northern Pike, Yellow Perch and Bluegill managed as secondary species. Blackduck Lake is a popular and consistent Walleye fishing lake. The Walleye population is maintained through fry stocking although some reproduction occurs in the lake. The 2024 survey had a Walleye gillnet catch rate (14.3 per net) well above the statewide average for similar lakes. Walleye captured in 2024 had an average size of 16.5 inches in length and 1.7 lbs./fish. The largest Walleye captured in the survey measured just short of 28 inches. The 2024 Northern Pike catch rate of 7.5 fish per net was higher than the statewide average for similar lakes. One pike exceeding 31 inches in length was captured, but overall only 12% of pike exceeded 26 inches. There is currently an abundance of fish directly below the 22-26 inch protected slot limit which are available to anglers interested in taking advantage of the north-central zone's 10 fish bag limit. Yellow Perch are important as a forage species in the lake as well a popular species with anglers, particularly during winter. Blackduck has traditionally been known as one of the better perch fisheries in the Bemidji area, but quality has recently declined. Only three percent of Yellow Perch caught were greater than 9 inches in length in 2024, which is down considerably from 10% in 2021 and 21% of the catch in the 2018 survey. Blackduck Lake has been known to produce large Bluegill exceeding 10 inches in length; however, they are few and far between. Low abundance and excellent size potential on Blackduck led to a special regulation for a reduced sunfish bag limit of 5 fish which was implemented in 2006. Trap nets in 2024 captured 34 Bluegills with several exceeding the 10-inch mark while the largest reached just under 11 inches. An impressive 76% of Bluegills captured were over 8 inches in length.

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

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

Blackduck has a maximum depth of 28 feet, per Minnesota DNR data.

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

Yes — Blackduck has confirmed faucet snail and starry stonewort. Clean, drain, and dry your equipment to avoid spreading invasives to other waters.