O'Leary

O'Leary Lake is a 131-acre lake located 13 miles north of Nashwauk in the Mississippi River watershed. O'Leary Lake has a maximum depth of 14 feet and occasionally experiences winterkill. The lake has no defined inlets or outlets and is moderately developed. The 2005 lake management plan listed Black Crappie as the primary management species, with Northern Pike and Largemouth Bass as secondary management species. A standard lake survey was conducted in July 2020 to assess the status of the fish community. The Black Crappie population can generally be described as having high numbers, frequent recruitment, poor to moderate size structure and slow growth. The gill-net catch rate was above average compared to similar lakes, but typical for O'Leary. Size structure was poor. Gill-net sampled crappie ranged from 4.6 to 11.0 inches with an average length of 6.4 inches. The sample contained a high proportion of young fish. Ages 1 through 7 were represented, with a dominant 2018 year class (age 2). Growth was considered slow with crappie averaging 7.5 inches at age 5. Size structure should improve as the abundant smaller fish grow to larger sizes. O'Leary has typically produced moderate numbers of Northern Pike with poor size structure. The 2020 gill-net catch rate was above average compared to lakes with similar habitat. Size structure remained poor; pike ranged from 9.5 to 27.0 inches with an average length of 18.8 inches. Ages 1 through 5 were represented in the sample and growth was considered average. Northern Pike averaged 20.3 inches after 4 years of growth. The trap-net catch rate for Bluegill was typical for the lake and lakes with similar habitat. Bluegill size structure was moderate. Sampled fish ranged from 3.2 to 8.7 inches with an average length of 5.8 inches, and 13% of the sample exceeded 8 inches. Ages 2 through 10 were represented, indicating frequent recruitment. Growth was considered average compared to similar lakes. Bluegill averaged 5.9 inches after 6 years of growth. O'Leary Lake provides fair angling opportunities for Bluegill. The gill-net catch for Walleye was low but similar to previous surveys. Sampled Walleye ranged from 19.8 to 23.5 inches and ages 6 to 8. Walleye had not been stocked in O'Leary since 1996, so it appeared these fish were the result of natural reproduction. Growth was considered average; Walleye exceeded 19 inches after 5 years. Largemouth Bass and Yellow Perch were sampled in low numbers compared to similar lakes. Other species sampled included Golden Shiner, Hybrid Sunfish and White Sucker. In order to maintain or improve fish and wildlife populations, water quality and habitat must be protected. People often associate water quality problems with large-scale agricultural, forestry, urban development or industrial practices in the watershed. In reality, the impact of land use decisions on one lake lot may be relatively small, yet the cumulative impact of those decisions on many lake lots can result in a significant decline in water quality and habitat. For example, removing shoreline and aquatic vegetation, fertilizing lawns, mowing to the water's edge, installing beach sand blankets, failing septic systems and uncontrolled run-off, all contribute excess nutrients and sediment which degrade water quality and habitat. Understanding these cumulative impacts and taking steps to avoid or minimize them will help to insure our quality fisheries can be enjoyed by future generations.

O'Leary Lake is a 131 acre lake located 13 miles north of Nashwauk in the Mississippi River watershed. O'Leary Lake has a maximum depth of 14 feet and occasionally experiences winterkill. O'Leary Lake is managed primarily for panfish and northern pike.Black crappie catch rates were within the normal range and similar to the previous assessment. Black crappie sampled in the 2004 assessment had a modest size structure. Fish in the gill-net sample varied from 4.4 to 11.6 inches in length. Only 15% of the crappie exceeded 10 inches. Black crappie growth rates were below the statewide average.The trap-net catch rate for bluegill (13.7/net) was the highest on record, but still near the lake class average. Bluegill size structure was relatively poor. Trap-net sampled bluegill varied from 2.7 to 8.6 inches in length. Only 4% of the sampled bluegill exceeded 8 inches. Bluegill growth rates were below the lake class average.The northern pike gill-net catch rate in 2004 was within the normal range at 7.5/net. Gill-net catches for pike were above the normal range in the two previous assessments. Northern pike size structure was poor. Gill-net sampled pike varied from 12.7 to 23.4 inches in length. Northern pike growth rates were similar to the statewide average. Five walleye were sampled for a catch rate of 0.8/gill net. This catch rate is below the lake class normal range, but similar to previous assessments on O'Leary. Age analysis indicated the walleye represented the 1994 and 1996 year classes, the last two years of fingerling stocking on O'Leary. Walleye fingerlings were stocked numerous times in the 1980's and early 1990's, but gill-net catch rates never exceeded the first quartile in subsequent assessments.Largemouth bass and yellow perch were sampled in below normal numbers. Other species sampled include: brown bullhead, golden shiner and white sucker.As lakes like O'Leary become increasingly more developed, lakeshore owners will have a larger impact on their future. In order to maintain or improve fish and wildlife populations, water quality and habitat must be protected. Although the effect of land use decisions on one lake lot may seem relatively small, the cumulative impact of many lakeshore owners "fixing up" their property can result in a significant decline in water quality and habitat. For example, removing shoreline and aquatic vegetation, installing sand beach blankets, fertilizing lawns, mowing to the waters edge, uncontrolled run-off and failing septic systems all contribute excess nutrients and sediment which degrade water quality and habitat. Understanding these impacts and taking steps to avoid or minimize them will help to insure our quality fisheries can be enjoyed by future generations.

O'Leary Lake is a northern pike and panfish lake that has also been managed to provide a walleye fishery. Only a few walleye were sampled in this assessment, suggesting that abundance is low. Northern pike were sampled in gill nets at a rate that is above the expected range for this type of lake. Northern pike up to 30.3 inches were sampled, but the mean length was 18.4 inches and the mean weight was 1.6 pounds. Growth appears to be good. Both the gill net and trap net catch rates for black crappie were lower than in any past assessments. The gill net catch rate is still within the expected range while the trap net catch rate is below its range. Black crappie in the gill nets ranged from 5.7 to 11.3 inches in length. Growth appears good. Bluegill were sampled at the highest rate yet seen, but this rate was still within the expected range. These bluegill ranged from 3.0 to 8.8 inches in length. Growth appears to be good. Yellow perch were sampled at a rate within the expected range. They had a mean length of 6.5 inches. White sucker, golden shiner and hybrid sunfish were also sampled. Lakeshore owners and users have the ability to insure that O'Leary Lake will continue to produce a quality fishery by practicing wise use of the land and water to preserve water quality and fish habitat. Anglers might also consider practicing catch and release or selective harvest in order to keep the fishery healthy.

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

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

O'Leary has a maximum depth of 14 feet, per Minnesota DNR data.

The most recent Minnesota DNR survey data for the main sport fish in O'Leary is from 2020.

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