O'Brien

A summer trap net survey was conducted in O'Brien Lake by IBI Program staff beginning on June 10, 2024. Nine trap nets were set along the shoreline in locations that encompassed multiple habitat types. Trap net sampling captured 10 species of fish, including 1 species that is intolerant of disturbance (Rock Bass). Bluegill comprised a majority of the catch both by number and by biomass. Pumpkinseed and Yellow Bullhead were also numerous. Bowfin, although few in number, comprised a significant proportion of the catch by biomass. The trap net survey data was combined with a targeted survey of nearshore fish species in O'Brien Lake conducted in August of 2022. Nearshore sampling captured 19 species of fish, including 7 species that are intolerant of disturbance (Banded Killifish, Blackchin Shiner, Blacknose Shiner, Iowa Darter, Least Darter, Rock Bass, and Smallmouth Bass) and 1 species that is tolerant of disturbance (Green Sunfish). The nearshore and trap net data were combined with gill net data from a survey conducted in June of 2019 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. This survey, and the corresponding nearshore and gill net surveys, provide evidence that the fish community in O'Brien Lake is healthy as indicated by an FIBI score that exceeds the exceptional use threshold determined for similar lakes. The survey results will be considered when the biological health of the lake is assessed during the Pine River Watershed assessment process, which will be completed in coordination with MN Pollution Control Agency. O'Brien Lake provides recreational angling opportunities for sunfish, Largemouth Bass, Northern Pike, and Walleye. Although uncommon, Smallmouth Bass are also present in O'Brien Lake. O'Brien Lake provides habitat for the Least Darter, a species of special concern in Minnesota. Least Darters rely on aquatic vegetation and high-quality shoreline habitat to carry out their life cycles. You can help protect the Least Darter and other fish in O'Brien Lake by reducing runoff, maintaining natural shorelines, and preventing the spread of invasive species.

A targeted survey of nearshore fish species in O'Brien Lake was conducted on August 22nd, 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 seine, where possible. Backpack electrofishing was completed at all ten sampling stations, but four stations were sampled from the boat due to site conditions. Similarly, a 50-foot seine was used to sample four stations, a 15-foot seine was used at five stations, and soft sediments with abundant vegetation and deep water prevented the use of seines at one station. Nearshore sampling captured 20 species of fish including seven species that are intolerant of disturbance (i.e., Banded Killifish, Blackchin Shiner, Blacknose Shiner, Iowa Darter, Least Darter, Rock Bass, and Smallmouth Bass) and one species that is tolerant of disturbance (i.e., Green Sunfish). The nearshore data will be combined with trap net and gill net data from a planned 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). 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 O'Brien Lake is healthy as indicated by the presence of several intolerant fish species. Data from this survey will contribute biological information about the health of the fish community to the Pine River Watershed assessment process in coordination with MN Pollution Control Agency.

O'Brien Lake is a 186 acre lake, with a maximum depth of 49', located 31 miles northeast of Brainerd in Crow Wing County. O'Brien is located in the Pine River watershed. A nearshore survey was conducted to assess the populations of both game and non-game fish species. Ten 100' long sampling stations were evenly spaced around the lakeshore. Each station was then sampled by backpack electrofishing, and if conditions allowed with a 15' or 50' 1/8th inch seine. The survey took place on August 23, 2019, with all 10 stations sampled by backpack electrofishing. The 50' 1/8th inch seine was used at 1 station and the 15' 1/8th inch seine was used at an additional 4 stations. Heavy vegetation and/or soft bottom prevented the use of seines at the other 5 sampling sites. Thirteen species were sampled, including 5 species that are intolerant of habitat disturbance: banded killifish, blacknose shiner, Iowa darter, smallmouth bass, and rock bass. This nearshore survey will be used along with the gill net and trap net survey conducted on June 24-27, 2019 to calculate a Fish-Based Index of Biotic Integrity (FIBI) score. The FIBI uses fish community data to measure a lake's health by the types of fish species present and comparing it to what is expected for this type of lake.

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

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

O'Brien has a maximum depth of 49 feet, per Minnesota DNR data.

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

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