Union

Union Lake is an 887-acre lake located in south central Polk County. The lake has a history of large fluctuations in water levels, which are influenced primarily by ground water. The most recent water level rises in the late 1990's resulted in the formation of a lake improvement district (LID) made up of riparian owners on both Sarah and Union lakes. The LID facilitated construction of a pumped outlet to the Sand Hill River watershed, following property damage along the lake's shoreline. A standard fisheries survey was conducted in early August 2022 to assess the fish populations at Union Lake. Following a record high abundance of Walleye in 2012, Walleye gill net catch rates have declined in recent years. However, the 2022 catch rate of 6.3 Walleye per gill net is only slightly below the lake's historical average of 6.8 per net. Lengths of sampled Walleye ranged from 7.7 to 30.1 inches with an average of 19.0 inches. The Northern Pike gill net catch rate set a record high in 2022 at 11.9 fish per net. The historic average is 6.1 fish per net. Sampled Northern Pike ranged from 15.1 to 32.0 inches with an average of 21.9 inches. About 23% of the fish sampled were over 24 inches in length. The trap net catch of Bluegill was well below average in 2022 with a catch rate of 8.3 Bluegills per net. The historical average for the lake is 36.6 per net. These fish averaged 6.0 inches in length and ranged from 3.3 to 8.4 inches. Black Crappie abundance increased slightly from recent surveys with trap nets capturing 3.6 per net. Black Crappie sampled in trap nets had an average size of 8.7 inches, but individuals up to 12.1 inches long were encountered. Gill nets caught Largemouth Bass at 1.8 fish per net. Largemouth Bass averaged 11.5 inches long, with Largemouth Bass up to 18.1 inches long measured. Yellow Perch abundance was low in 2022, with fish having an average length of 6.3 inches. Trap net catches of Common Carp were similar to past surveys, but gill nets captured a record number of fish in 2022. Other fish species sampled in 2022 included Black and Brown Bullhead, Pumpkinseed, and White Sucker.

A Targeted Survey was completed on Union Lake on August 14, 2018 to assess the near-shore fish community. This data will be analyzed in conjunction with the Standard Survey that was completed in 2017 to evaluate the biological condition of Union Lake, and contribute to the assessment of the watershed. Fourteen sites within Union Lake were sampled during this survey, using a backpack electrofishing unit and seines. The fish community sampled during this assessment was not diverse, dominated by Bluegill, Largemouth Bass, and Spottail Shiners. Other species sampled inclulded Iowa Darter, Central Mudminnow, Tadpole Madtom, and Yellow Perch. Common Carp and White Sucker were observed, but not sampled. One species intolerant of poor habitat conditions were found (Iowa Darter). The results of this survey suggest that the fish population in Union Lake does not meet expectations for lakes of similar characteristics, suggesting that this lake is likely biologically impaired. Many areas of altered shoreline habitat and vegetation were observed during the survey. A healthy, diverse aquatic plant community, along with adequate shoreline buffers are important to maintain a diverse fishery.

Union is an 887-acre, class 25 lake located in south central Polk County. This lake has a history of large fluctuations in water levels, which are influenced primarily by ground water. The most recent water level rises in the late 1990's resulted in the formation of a lake improvement district (LID) made up of riparian owners on both Sarah and Union lakes. The LID facilitated construction of a pumped outlet to the Sand Hill River watershed, following property damage along the lake's shoreline. A filtered channel from nearby Lake Sarah was also constructed as part of this project to equalize lake levels. The channel was constructed as a filter barrier to prevent Common Carp from migrating from Union Lake to Lake Sarah, where they have not yet been found. The discovery of Eurasian watermilfoil in Union Lake in 2007 had an effect on the future operation of the outflow pump. Initial testing found no signs of Eurasian watermilfoil outside of Union Lake after a series of river inspections and spot checks of the wetland that meanders southwest of Union Lake to the Red River. These findings resulted in the installation of additional filters on the pump to contain the plants so they don't spread downstream into the Sand Hill River and to the Red River, where Eurasian watermilfoil has not been found. Ecological and Water Resources personnel will continue to periodically monitor this outlet. However, because of drier conditions in recent years, the pump has not been operating. In 2017, the mean gill net catch rate of 8.9 Walleyes per net fell from the historical high set in 2012 for Union Lake, but remained above the lake mean. Lengths of sampled Walleyes ranged from 9.7 to 28.3 inches with a mean of 18.8 inches. Currently, Walleye fry are stocked into Union Lake, but some natural reproduction does occur. Two of the three strongest year classes sampled in the 2012 survey came from non-stocked years. Though not as dominant in 2017, Walleye from all non-stocked years were again captured. Future water level fluctuations will undoubtedly impact the success of walleye spawning success and should be monitored in the future. The Northern Pike gill net catch rate nearly met the lake's historic high in 2017 at 10.7 fish per net. The historic average is 6.1 fish per net. Sampled pike ranged from 13.9 to 29.2 inches with a mean of 22.4 inches. The 2017 trap net catch of Bluegill doubled that of 2012, but remained below the historical average. These fish averaged 5.6 inches in length and ranged from 3.0 to 8.3 inches. Black Crappie abundance appeared to be similar to past surveys, with trap nets capturing 2.9 crappie per net. Black Crappie sampled in trap nets had an average size of 8 inches, but individuals almost 12 inches long were encountered. No Largemouth Bass were captured in trap nets, but gill nets caught 1.2 fish per net. Bass had an average size of 11.6 inches long, with bass up to 16 inches long also measured. Yellow Perch catch rates in gill nets was higher than the 2012 survey, but still below the historical average for Union Lake. Common Carp abundance continues to remain low, with a total of nine carp caught in gill nets and two carp caught in trap nets. Other fish species encountered were Black Bullhead, Brown Bullhead, Hybrid Sunfish, Pumpkinseed Sunfish, and White Sucker.

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

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

Union has a maximum depth of 83 feet, per Minnesota DNR data.

The most recent Minnesota DNR survey data for the main sport fish in Union is from 2022.

Yes — Union has confirmed Eurasian watermilfoil and zebra mussel. Clean, drain, and dry your equipment to avoid spreading invasives to other waters.