Unnamed

Unnamed water (31-1225) is known locally as O'Brien Reservoir #4 and is located about two miles east of Nashwauk, MN in the Mississippi River watershed. There is a city-administered park, including a beach and fishing pier with an access on the east side of the impoundment. The reservoir was created as a water supply for mining in 1977-1978 by impounding O'Brien Creek, but has since been abandoned. The lake management plan (LMP) was last updated in 2014. Black Crappie and Northern Pike were listed as primary management species while Bluegill, Largemouth Bass and Walleye were secondary management species. A standard lake survey was conducted in August 2023 to update information on the fishery. Only three Black Crappie were sampled for a catch rate of 0.3/trap net, well below average for the lake and lakes with similar habitat. Sampled crappie varied from 7.0 to 9.5 inches. While catch rates for crappie have varied considerably, previous surveys mention they are targeted by anglers with good success at times. The gill-net catch for Northern Pike was typical for the lake and lakes with similar habitat. Size structure was poor. Lengths ranged from 13.2 to 30.2 inches with an average length of 19.9 inches. Ages 1 through 4, 6 and 8 were represented in the sample with average growth rates. Pike averaged 20.8 inches after 4 years of growth. The Bluegill population has typically had low to moderate numbers and poor size structure. The 2023 trap-net catch was below the typical range for comparable lakes but similar to the previous survey on O'Brien. Size structure remained poor; sampled Bluegill ranged from 3.1 to 7.8 inches with an average length of 4.4 inches. Ages 2 through 6 were represented in the sample. Growth was average with Bluegill exceeding six inches after five years of growth. The Walleye gill-net catch was above average for O'Brien Reservoir and lakes with similar habitat. Size structure was favorable; Walleye ranged from 11.7 to 21.8 inches with an average length of 15.8 inches. Five year-classes from ages 2 to 9 were represented in the sample. Walleye have been stocked at various times since 1983, but only twice since the previous survey in 2013. Five of the eleven Walleye corresponded to a fry-stocked year (2019), with the remaining fish attributed to natural reproduction. Growth was similar to the statewide average with Walleye exceeding 17 inches after five years of growth. The gill-net catch for Yellow Perch was below the typical range for comparable lakes and below average for O'Brien Reservoir. Some larger perch were present as fish up to 12.6 inches were sampled. Largemouth Bass were sampled in low numbers with one fish exceeding 17 inches. A previous survey employing electrofishing showed O'Brien Reservoir contains good numbers of moderate-sized bass. Other species sampled in test-nets included Black Bullhead, Pumpkinseed Sunfish, Rock Bass and White Sucker.

Unnamed water (31-1225) is known locally as O'Brien Reservoir #4 and is located about two miles east of Nashwauk, MN. There is a city administered park, including a beach and fishing pier, along with an access on the east side of the impoundment. The reservoir was created as a water supply for mining in 1977-1978 by impounding O'Brien Creek, but has since been abandoned. Walleye have been stocked at various times since 1983. Black crappie and northern pike were listed as primary management species while bluegill, largemouth bass, and walleye were secondary management species. Only one black crappie was sampled, below the range for lakes similar to O'Brien. This was down from the previous historically high catches observed in gill nets and trap nets. Angler reports suggest crappie were frequently targeted with good success at times. Northern pike were the most numerous fish sampled in gill nets, sampled at the lake class average and similar to the previous assessment. Size structure was poor. Lengths ranged from 14.1 to 30.0 inches with an average of 20.4 inches. Scale and bone analysis identified ages 1 to 5 suggesting relatively consistent recruitment. Growth was similar to the statewide average for all ages. Northern pike averaged 21.4 inches by age 4. Walleye were sampled at a rate exceeding the lake class average and above the previous assessment. Lengths ranged from 14.5 to 20.8 inches with an average length of 16.8 inches. Scale and bone analysis identified ages 3, 4, and 8. Age 3 comprised 67% of the sample, which correlates to the 2010 stocking. Growth was similar to the statewide average for all ages. Walleye averaged 17.4 inches by age 4. Largemouth bass were actively sampled by electrofishing at a rate of 94.2/on-time, double the previous assessment (42.6/on-time). Size structure was moderate. Lengths ranged from 4.9 to 19.3 inches with an average length of 9.6 inches. Scale analysis identified ages 2 to 9, indicating consistent recruitment. Growth was slow early, but similar to the statewide average by age 3. Largemouth bass averaged 15.2 inches by age 6. Yellow perch were sampled at a rate lower than expected and below the previous assessment. Size structure was surprisingly favorable. Lengths ranged from 5.2 to 12.4 inches with an average length of 9.0 inches. Scale and otolith analysis identified ages 3 to 9 in the sample and growth appeared average. Perch averaged 10.3 inches by age 6. Bluegill were sampled at a rate lower than expected and the previous assessment. Size structure was poor, as lengths ranged from 2.9 to 7.5 inches with an average length of 4.2 inches. Scale analysis identified ages 2 to 4, 6, and 7 present in the sample. Growth was similar to Ecological Lake Class 28 averages. Other species sampled include brown bullhead, hybrid sunfish, pumpkinseed sunfish, white sucker, and yellow bullhead. As part of IBI (Index of Biotic Integrity) near shore sampling, Iowa darter, blacknose shiner, bluegill, green sunfish, and yellow perch were sampled in one 15 foot seine haul. Backpack electrofishing sampled Iowa darter, Johnny darter, black crappie, bluegill, bluntnose minnow, central mudminnow, golden shiner, green sunfish, hybrid sunfish, largemouth bass, tadpole madtom, and yellow perch at 10 stations.

Index of biological integrity data was collected in 2013 in conjunction with Minnesota Pollution Control Agency watershed sampling.

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

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

Unnamed has a maximum depth of 41.5 feet, per Minnesota DNR data.

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

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