Mary

A targeted survey of nearshore fish species in Mary Lake was conducted beginning on July 22nd, 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 10 sampling stations. Similarly, a 50-foot seine was used to sample 7 stations, and a 15-foot seine was used at 3 stations. Nearshore sampling captured 11 species of fish including two species that are intolerant of disturbance (Iowa Darter and Least Darter) and one that is tolerant of disturbance (Green Sunfish). A concurrent summer trap net survey was also conducted by IBI Program staff. Nine trap nets were set along the shoreline in locations that encompassed multiple habitat types. Trap net sampling captured 12 species of fish, two considered to be tolerant of disturbance (Green Sunfish and Common Carp). Bluegill and Pumpkinseed comprised a majority of the catch by number and the majority by biomass. A concurrent summer gill net survey was conducted on July 22nd to July 25th, 2024, by IBI Program Staff. Six gill nets were set in offshore locations that encompassed deeper littoral habitat. Black Crappie and Bluegill comprised a majority of the gill net catch by number, and Northern Pike, Walleye, and Bluegill comprised a majority of the catch by biomass. The number of Northern Pike sampled per net (3.3 /net) was near the 50% quartile for Lake Class 24 lakes (3.7/net) with an average length of 26.8 inches; and the number of Walleye sampled per net (3.0 /net) was above the 50% quartile for Lake Class 24 lakes (2.8/net) with an average length of 19.9 inches. Data from all gears were combined 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., Iowa Darter), 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 Mary Lake is adversely impacted by stressors, as indicated by an FIBI score below the general use impairment threshold for aquatic life use determined for similar lakes. The survey results were consistant with previous assessments and will be considered when the biological health of the lake is assessed during the North Fork Crow River watershed assessment process, which will be completed in coordination with MN Pollution Control Agency. You can help protect the fish community in Mary Lake by reducing runoff, maintaining natural shorelines, and preventing the spread of invasive species.

A targeted survey of nearshore fish species in Mary Lake was conducted beginning on July 22nd, 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 10 sampling stations. Similarly, a 50-foot seine was used to sample 7 stations, and a 15-foot seine was used at 3 stations. Nearshore sampling captured 11 species of fish including two species that are intolerant of disturbance (Iowa Darter and Least Darter) and one that is tolerant of disturbance (Green Sunfish). A concurrent summer trap net survey was also conducted by IBI Program staff. Nine trap nets were set along the shoreline in locations that encompassed multiple habitat types. Trap net sampling captured 12 species of fish, two considered to be tolerant of disturbance (Green Sunfish and Common Carp). Bluegill and Pumpkinseed comprised a majority of the catch by number and the majority by biomass. A concurrent summer gill net survey was conducted on July 22nd to July 25th, 2024, by IBI Program Staff. Six gill nets were set in offshore locations that encompassed deeper littoral habitat. Black Crappie and Bluegill comprised a majority of the gill net catch by number, and Northern Pike, Walleye, and Bluegill comprised a majority of the catch by biomass. The number of Northern Pike sampled per net (3.3 /net) was near the 50% quartile for Lake Class 24 lakes (3.7/net) with an average length of 26.8 inches; and the number of Walleye sampled per net (3.0 /net) was above the 50% quartile for Lake Class 24 lakes (2.8/net) with an average length of 19.9 inches. Data from all gears were combined 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., Iowa Darter), 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 Mary Lake is adversely impacted by stressors, as indicated by an FIBI score below the general use impairment threshold for aquatic life use determined for similar lakes. The survey results were consistant with previous assessments and will be considered when the biological health of the lake is assessed during the North Fork Crow River watershed assessment process, which will be completed in coordination with MN Pollution Control Agency. You can help protect the fish community in Mary Lake by reducing runoff, maintaining natural shorelines, and preventing the spread of invasive species.

Mary Lake is a 180 acre lake located four miles southeast of the City of Howard Lake in southern Wright County. It has a maximum depth of 46 feet and a small watershed dominated by open water, row crops, and pasture. Mary Lake has an access at the south end of the lake which is owned by the Winsted Sportsman's Club and open to public use. Mary Lake is managed for Northern Pike and Largemouth Bass and was last surveyed in 2011. Anglers can expect good fishing for Northern Pike, Largemouth Bass, and Walleye. Very little emergent vegetation was found. Submerged vegetation was abundant but not surveyed. In the 2011 survey, the most common submerged species included: coontail, bushy pondweed, flatstem pondweed, and Illinois pondweed. Water clarity was good; Secchi depth was six feet in early August and MPCA data show an average of almost ten feet over the last ten years. Dissolved Oxygen was adequate to support fish to 19 feet in early August. Northern Pike numbers were somewhat low compared to other lakes like Mary and similar to 2011 results, but the average size has increased. Only 12 pike were caught during the survey and ranged in length from 21.7 to 36.3 inches with an average length and weight of 26.2 inches and 4.1 pounds. Largemouth Bass were sampled by daytime electrofishing on May 24. The catch rate of 77/hr was higher than the Sauk Rapids area daytime average of 43/hour and identical to 2011 (77/hr), but size increased. Lengths ranged from 5.4 to 19.3 inches with an average length of 11.3 inches. Of catchable size fish (>8 inches), 11% were longer than 15 inches. Walleye fingerlings have been stocked by the lake association for many years. The Walleye catch was similar to 2011 and within the expected range of values for lakes like Mary. Lengths ranged from 10.8 to 27.2 inches with an average length and weight of 16.1 inches and 1.5 pounds. Ages ranged from two to ten years old and growth was fast, reaching 18 inches in four years. Most Walleye were two years old with an average length of 13 inches. Bluegill numbers were higher than 2011, but still within the expected range of values for similar lakes. Lengths ranged from 1.4 to 8.0 inches with an average length of 4.7 inches. Black Crappie numbers were similar to 2011 and within the expected range of values. Crappie lengths ranged from 3.3 to 13.0 inches with an average length of 8.2 inches. Summer surveys likely underrepresent panfish abundance and size; targeted surveys near shore around spawning time would provide a better assessment of Bluegill and Black Crappie numbers and size. Yellow perch numbers were low and declined from 2011. Lengths ranged from 4.9 to 7.6 inches with an average length of 6.1 inches. Other species sampled included: Golden Shiner, Green Sunfish, Hybrid Sunfish, Pumpkinseed, White Sucker, and Yellow Bullhead.

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

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

Mary has a maximum depth of 46 feet and a mean depth of 17.8 feet, per Minnesota DNR data.

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

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