Grave

A targeted survey of nearshore fish species in Grave Lake was conducted on July 11-13, 2023, 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 14 sampling stations, but three stations were sampled from the boat due to site conditions. Similarly, a 50-foot seine was used to sample 10 stations, a 15-foot seine was used to sample one station, and site conditions prevented the use of a seine at three stations. Nearshore sampling captured 20 species of fish including six species that are intolerant of disturbance (i.e., Banded Killifish, Blackchin Shiner, Blacknose Shiner, Iowa Darter, Mottled Sculpin, and Rock Bass) and one species that is tolerant of disturbance (i.e., Black Bullhead). A concurrent summer trap net survey was also conducted by IBI Program Staff. Nine trap nets were set along the shoreline and in shallow offshore locations that encompassed multiple habitat types. Bluegill comprised a majority of the trap net catch by number and Bluegill and Bowfin catch by biomass. The number of Bluegill sampled per net was above the 25% quartile for similar Lake Class 25 lakes and the average length was 5.3 inches, with 18% over 7 inches. The nearshore and trap net data were combined with gill net data from an August 2021 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, Fathead Minnow, and 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. Data from this survey indicates Grave Lake is in good health as indicated by an exceptionally high FIBI score well above the impairment threshold for aquatic life use determined for similar lakes. These results are similar to previous survey findings, which indicated that Grave Lake is an exceptional lake. Data from this survey will contribute biological information about the health of the fish community to the Big Fork River Watershed assessment process in coordination with MN Pollution Control Agency. IBI Program staff also conducted an assessment of lakeshore habitat on May 26, 2023, following the Score the Shore survey protocols. The assessment consisted of 62 survey sites evenly spaced 100 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 88.1 (+/- 1.8) out of 100 possible. Approximately 30 percent of the sites were developed with a mean score of 79.0 (+/- 4.5), while undeveloped sites had a mean score of 92.1 (+/- 1.3).

A targeted survey of nearshore fish species in Grave Lake was conducted on July 11-14, 2022, 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 14 sampling stations, but two stations were sampled from the boat due to site conditions. Similarly, a 50-foot seine was used to sample eight stations, a 15-foot seine was used to sample one station, and site conditions prevented the use of a seine at five stations. Nearshore sampling captured 17 species of fish including five species that are intolerant of disturbance (i.e., Banded Killifish, Blackchin Shiner, Blacknose Shiner, Iowa Darter, and Rock Bass). A concurrent summer trap net survey was also conducted by IBI Program Staff. Nine trap nets were set along the shoreline and in shallow offshore locations that encompassed multiple habitat types. Bluegill comprised a majority of the trap net catch by number and Bluegill and Bowfin catch by biomass. The number of Bluegill sampled per net was above the 25% quartile for similar Lake Class 25 lakes and the average length was 6.4 inches, with 21% over 7 inches. The nearshore and trap net data were combined with gill net data from an August 2021 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, Fathead Minnow, and 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. Data from this survey indicates Grave Lake is in good health as indicated by an exceptionally high FIBI score well above the impairment threshold for aquatic life use determined for similar lakes. Data from this survey will contribute biological information about the health of the fish community to the Big Fork River Watershed assessment process in coordination with MN Pollution Control Agency.

Grave Lake is located south of Marcell, MN, has one public access and moderate shoreline development. The 2015 lake management plan indicated Bluegill and Walleye as the primary management species with Largemouth Bass and Northern Pike as secondary species. A targeted survey using 9 gill net sets was conducted in 2021 to determine the status of select gamefish populations and evaluate Walleye fry stocking. An additional targeted survey was conducted in June to evaluate the Bluegill population. That survey continued to describe a quality fishery that included opportunities for large sunfish. Data from that survey can be found in a separate report. The Grave Lake Walleye fishery is primarily maintained with annual fry stocking. Lakes with similar habitats typically produce modest Walleye populations. The 2021 catch was below average for Grave Lake. Although the catch remained within the typical range for similar lakes, it failed to meet the management objectives. In 2021, the sampled fish ranged from 15 to 25.7 inches and had a mean length of 18.6 inches. It appears modest angling opportunities continue to exist, though numbers may have declined in recent years. Northern Pike catches have fluctuated but have occasionally been high compared to similar lakes. High pike numbers are undesirable and often result in poor size quality and slow growth. The 2021 catch rate was typical compared to similar lakes but size quality remained poor. The sampled fish ranged from 14.1 to 33.6 inches and had a mean length of 19.7 inches. Only 6% of sampled pike exceeded 28 inches. Grave Lake is in the North-central zone regulation for Northern Pike. Anglers may keep up to 10 pike but all fish from 22-26 inches must be released and only two pike exceeding 26 inches may be possessed. Anglers can help improve the size quality on Grave Lake by keeping more pike under 22 inches and releasing pike over 26 inches. Yellow Perch are an important prey species on Grave Lake. Perch catches have varied but have occasionally been high compared to similar lakes. The 2021 survey resulted in sufficient perch numbers to maintain the current pike and Walleye management. Perch were generally too small to interest anglers as sampled fish ranged from 4.8 to 9.3 inches and averaged 6.9 inches. Tullibee are another important prey species but have declined across much of Minnesota. Lakes with similar habitats rarely produce large Tullibee populations. Though the 2021 catch was low, it was near the long-term average for Grave and typical for lakes with similar habitats. The sampled fish ranged from 9.2 to 19.2 inches, suggesting that multiple year classes are present. Largemouth Bass are difficult to sample using standard summer netting methods because they tend to avoid the nets. Although night electrofishing is a more effective sampling tool for Largemouth Bass it was not conducted in 2021 because the population does not warrant the additional effort on a regular basis. Only two fish were sampled in gill nets. Like many northern Minnesota lakes, Black Crappie catches on Grave have varied due to inconsistent year class production and angler harvest. Black Crappie were sampled in gill nets at a rate comparable to lakes with similar habitats, but above average for Grave Lake. Lengths from the gill net sample ranged from 5.4 to 12.3 inches and 55% exceeded 10 inches. The catch and size distribution suggests moderate opportunities exist for catching nice crappie. Other species observed during the gill-net only targeted survey assessment included Bluegill, Bowfin, Brown Bullhead, Hybrid Sunfish, Pumpkinseed Sunfish, Rock Bass, White Sucker and Yellow Bullhead.

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

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

Grave has a maximum depth of 39 feet, per Minnesota DNR data.

The most recent Minnesota DNR survey data for the main sport fish in Grave is from 2023.

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