South Twin

A targeted survey of nearshore fish species in South Twin Lake, was conducted on June 30th and July 1st, 2025, by Lake Biological Monitoring and Assessment (LBMA) 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 10 sampling stations. Similarly, a 50-foot seine was used to sample 10 stations. Nearshore sampling captured 13 species of fish including six species that are intolerant of disturbance (i.e., Banded Killifish, Blackchin Shiner, Blacknose Shiner, Iowa Darter, Mimic Shiner, and Rock Bass) and no species that are tolerant of disturbance. A concurrent summer trap net survey was also conducted by LBMA Program Staff. Nine trap nets were set along the shoreline and in shallow offshore locations that encompassed multiple habitat types. Trap net sampling captured eight species of fish, including one that is intolerant of disturbance (i.e., Rock Bass). Bluegill comprised a majority of the trap net catch by number and biomass. The nearshore and trap net data were combined with gill net data from a July 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. In addition to fish sampling, LBMA program staff conducted an assessment of lakeshore habitat on South Twin Lake on June 14th, 2025, following the Score the Shore survey protocols. The assessment consisted of 32 survey sites evenly spaced 150 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 87.3 (+/- 2.9) out of 100 possible. A score of 87.3 indicates the lakewide shoreline condition is High (85-91.9). Approximately 38 percent of the sites were developed with a mean score of 76.7 (+/- 6.4) indicating shoreline habitat quality of developed sites is Moderate (70-79.9), while undeveloped sites had a mean score of 93.7 (+/- 1.2) with Excellent (92+) habitat quality. Results from this survey provide evidence that the fish community in South Twin Lake is healthy as indicated by an FIBI score that exceeds the exceptional use threshold determined for similar lakes. These results are similar to previous findings. The survey results will be considered when the biological health of the lake is assessed during the Mississippi River-Headwaters watershed assessment process, which will be completed in coordination with MN Pollution Control Agency. You can help protect the fish community in South Twin Lake by reducing runoff, maintaining natural shorelines, and preventing the spread of invasive species.

South Twin Lake is a 222-acre lake, located 20 miles northeast of Bemidji in Beltrami County. A targeted survey was completed on South Twin Lake by Bemidji Area Fisheries staff during July of 2024 to assess the nearshore fish community and overall health of the lake. In this survey, 10 nearshore sites (100-foot) were evenly spaced along the lakeshore to sample a variety of aquatic habitat types and collect a representative sample of the nearshore fish community. Depending on the habitat conditions at each site, backpack electrofishing and shoreline seining were attempted where possible. All 10 sites were sampled with seine and backpack electrofishing. A total of 11 species were sampled, which included 5 species (Banded Killifish, Blacknose Shiner, Iowa Darter Mimic Shiner, and Rock Bass) captured that are intolerant to disturbance or poor water quality. Nearshore fish community data was analyzed with information collected from the standard survey in 2024 to calculate a Fish-based Index of Biotic Integrity (FIBI) score to measure the biological condition and overall health of South Twin Lake. In Minnesota, certain fish species cannot survive without clean water and healthy habitat (e.g. Blacknose Shiner, Mimic Shiner, Tullibee (cisco), and Mottled Sculpin), while other species are tolerant of degraded conditions (e.g. Black Bullhead, Fathead Minnow, and Green Sunfish). The combination of fish species present may identify stressors negatively affecting the lake environment. The FIBI score is composed of several fish community diversity and composition metrics to indicate the overall health of a lake by comparing it to what is expected for a healthy lake. For additional information on FIBI search for "lake index of biological integrity" on the Minnesota Department of Natural Resources website (www.mndnr.gov). Results of this survey indicate South Twin is in great health with a FIBI score above the exceptional threshold for aquatic life use determined for similar lakes. In coordination with the Minnesota Pollution Control Agency, data from this survey will contribute biological information about the health of the fish community to the Mississippi River (Headwaters) Watershed assessment.

South Twin Lake is a 222-acre lake located in southern Beltrami County, approximately 20 miles northeast of Bemidji, MN in the Chippewa National Forest. South Twin has 3 miles of lightly developed shoreline and a maximum depth of 45 feet. A US Forest Service public water access is in the southeastern bay of the lake with enough space for 3 vehicle/boat trailers. A standard survey was completed on South Twin Lake in 2024 to assess the fish community. Gamefish species targeted by anglers in this lake include Bluegill, Black Crappie, Largemouth Bass, Walleye, and Northern Pike. Bluegill abundance decreased from 2016 but was still within the normal range for this lake. Bluegill lengths averaged 7 inches, with a few Bluegill over 10 inches captured. The Bluegill population appears healthy with ages ranging from 2 to 12 years old. With the statewide regulation, it is recommended to keep smaller sunfish and release the majority of larger sunfish to maintain a balanced population. Spring electrofishing for Largemouth Bass was completed in early June to adequately sample the bass population. Largemouth Bass abundance increased from the 2016 survey and was close to the lake's average. Largemouth Bass lengths ranged 6 to 19 inches and averaged about 12 inches. The large sample size was expected based on previous targeted surveys. A total of 17 year-classes of Bass were represented and ages ranged from 2 to 20 years old. A special regulation consisting of a 14-20 inch protected slot with only one over 20 inches allowed is in effect on this lake. Black Crappie abundance was similar to the previous survey and considered normal for this lake type. Black Crappie lengths ranged from 4 to 12 inches in length and averaged 8 inches. The majority of the Black Crappie captured were 2 to 4 years old, indicating recent recruitment, with a few up to 8 years old. Walleye abundance was below average but within the typical range for lakes with similar morphological characteristics. Length of teh 11 Walleye caught ranged from 19 to 26 inches. Walleye fingerlings are stocked in odd years to account for inconsistent natural reproduction. No fish were sampled under five years old, indicating poor recruitment in recent years. Northern Pike remain moderately abundant and are near the upper end of the typical range for similar lakes in Minnesota. Northern Pike ranged from 11 to 34 inches and averaged 20 inches. Ninety-four percent of Northern Pike captured in gill nets were outside the North Central Zone protected size range of 22-26 inches, giving anglers a good opportunity to catch harvestable size fish. Yellow Perch abundance has consistently decreased since 2006 and was below the historical average for the lake. Yellow Perch ranged 5 to 11 inches and averaged 9 inches. Yellow Perch are an important forage species for large predators like Walleye, Northern Pike, and Largemouth Bass. Other species sampled during the survey included hybrid sunfish, Pumpkinseed, and Rock Bass. Currently, South Twin Lake is not infested with any aquatic invasive species (AIS). AIS can be transferred by anglers and boats from infested to non-infested waterbodies. To avoid spreading AIS, lake users are required to remove all aquatic plants and animals from their watercraft and drain all water from their boat before leaving the access. Please follow the current AIS regulations to avoid spreading to other lakes.

Based on Minnesota DNR survey data, anglers target Black Crappie, Largemouth Bass, Muskellunge, Rock Bass, and Bluegill in South Twin. See the full species list above for catch rates, size structure, and quality scores.

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

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

The most recent Minnesota DNR survey data for the main sport fish in South Twin is from 2025.

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