Big Swan

A targeted survey of nearshore fish species in Big Swan Lake was conducted on July 14- 16, 2025, by Lake Biological Monitoring and Assessment Program (LBMA) 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 14 sampling stations. Similarly, a 50-foot seine was used to sample eight stations, and a 15-foot seine was used at two stations. Four stations were not seined due to deep water and soft substrate. Nearshore sampling captured 27 species of fish including eight species that are intolerant of disturbance (i.e., Banded Killifish, Blackchin Shiner, Blacknose Shiner, Iowa Darter, Least Darter, Logperch, Pugnose Shiner, and Rock Bass) and two that are tolerant of disturbance (i.e., Fathead Minnow and Green Sunfish). A concurrent summer trap net survey was also conducted by LBMA staff. Twelve trap nets were set along the shoreline in locations that encompassed multiple habitat types. Trap net sampling captured 12 species of fish, including one that is intolerant of disturbance (i.e., Rock Bass) and two species that are tolerant of disturbance (i.e., Common Carp and Green Sunfish). Bluegill comprised a majority of the catch by number, whereas Yellow Bullhead and Common Carp comprised a majority by 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., Green Sunfish and Common Carp). 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 Big Swan Lake is healthy as indicated by an FIBI score above the general use impairment threshold for aquatic life use determined for similar lakes. These results are similar to previous findings, which indicated that Big Swan Lake is fully supporting aquatic life. The survey results will be considered when the biological health of the lake is assessed during the Mississippi River Brainerd watershed assessment process, which will be completed in coordination with the MN Pollution Control Agency. You can help protect the fish community in Big Swan Lake by reducing runoff, maintaining natural shorelines, and preventing the spread of invasive species.

Temperature and dissolved oxygen (DO) measurements were collected from the deepest basin in Big Swan Lake on August 15th, 2024, to evaluate the quantity and quality of cold, oxygenated water (i.e., oxythermal habitat) available to Cisco, also known as Tullibee, the most sensitive coldwater species present in this lake. During the summer, Cisco require a layer of oxythermal habitat that contains water temperatures below 21.2 degrees C (70.2 degrees F) and dissolved oxygen concentrations above 3.0 mg/L. Based on the profile from the deepest basin (maximum sampled depth 44.9 feet), the water temperature decreased below 21.2 degrees C (70.2 degrees F) at 21.0 feet and the dissolved oxygen concentration decreased to 3.0 mg/L at 26.6 feet at the time of sampling. The thickness of this layer of water in the water column was 5.6 feet, indicating that oxythermal habitat was present for Cisco. Further, the temperature at which dissolved oxygen decreased to 3.0 mg/L (i.e., TDO3, a single variable to characterize oxythermal habitat) was 20.9 degrees C (69.6 degrees F). TDO3 values near than 21.2 degrees C (70.2 degrees F) indicate that oxythermal conditions were present, but marginal for Cisco at the time of the survey. However, data collected by the Minnesota Department of Natural Resources during the late summer period of maximum oxythermal stress (July 26th to Aug 24th) in 4 years, between 1981-2016, indicate unsuitable oxythermal habitat in most years when surveyed, with the least favorable conditions recorded in 2016 when the suitable oxythermal habitat layer was 0 feet thick. Additionally, 5 surveys completed outside of the period of maximum oxythermal stress (i.e., 1986, 1991, 1996, 2000, and 2020) also indicated unsuitable oxythermal habitat. When inadequate oxythermal habitat is available, Cisco are squeezed into unfavorable, warmer water conditions and experience higher levels of stress.

Temperature and dissolved oxygen (DO) measurements were collected from the deepest basin in Big Swan Lake on August 15th, 2024, to evaluate the quantity and quality of cold, oxygenated water (i.e., oxythermal habitat) available to Cisco, also known as Tullibee, the most sensitive coldwater species present in this lake. During the summer, Cisco require a layer of oxythermal habitat that contains water temperatures below 21.2 degrees C (70.2 degrees F) and dissolved oxygen concentrations above 3.0 mg/L. Based on the profile from the deepest basin (maximum sampled depth 44.9 feet), the water temperature decreased below 21.2 degrees C (70.2 degrees F) at 21.0 feet and the dissolved oxygen concentration decreased to 3.0 mg/L at 26.6 feet at the time of sampling. The thickness of this layer of water in the water column was 5.6 feet, indicating that oxythermal habitat was present for Cisco. Further, the temperature at which dissolved oxygen decreased to 3.0 mg/L (i.e., TDO3, a single variable to characterize oxythermal habitat) was 20.9 degrees C (69.6 degrees F). TDO3 values near than 21.2 degrees C (70.2 degrees F) indicate that oxythermal conditions were present, but marginal for Cisco at the time of the survey. However, data collected by the Minnesota Department of Natural Resources during the late summer period of maximum oxythermal stress (July 26th to Aug 24th) in 4 years, between 1981-2016, indicate unsuitable oxythermal habitat in most years when surveyed, with the least favorable conditions recorded in 2016 when the suitable oxythermal habitat layer was 0 feet thick. Additionally, 5 surveys completed outside of the period of maximum oxythermal stress (i.e., 1986, 1991, 1996, 2000, and 2020) also indicated unsuitable oxythermal habitat. When inadequate oxythermal habitat is available, Cisco are squeezed into unfavorable, warmer water conditions and experience higher levels of stress.

Based on Minnesota DNR survey data, anglers target Walleye, Rock Bass, Black Crappie, Largemouth Bass, and Pumpkinseed in Big Swan. See the full species list above for catch rates, size structure, and quality scores.

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

Big Swan has a maximum depth of 45 feet and a mean depth of 18 feet, per Minnesota DNR data.

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

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