Blue

Blue Lake is a 263-acre lake in southwest Isanti County located five miles northeast of Zimmerman and is within the Rum River watershed. It has a maximum depth of 31 feet and 51 percent of the lake is less than 15 feet deep (134 acres). Water clarity in May and June can be 6 to 9 feet; however, it becomes low in summer and ranges from 3 to 5 feet as algal blooms become present. An aquatic vegetation survey in 2021 indicated vegetation was present in depths up to 15 feet, but most common in depths from 1 to 9 feet. Blue Lake was found to have a low diversity of aquatic plants, with 10 submergent and 4 floating leaf species sampled lake wide. The diversity of aquatic plants has declined throughout the nine surveys that have occurred since 2004. Boat navigation during early summer can be affected by dense stands of Curly leaf pondweed in shallow areas, which is a non-native species. The most common shoreline substrate is sand, followed by gravel and muck, which results in abundant spawning habitat for bluegills and crappies. There are two public accesses located on the lake, one in the middle of the eastern shore and one on the northwestern shore. Parking is limited at both accesses. The lake is well developed and popular with local pleasure boaters. Past standard lake surveys on Blue Lake have occurred in August. Warm summer water temperatures typically result in crappies suspending in open water, which decreases their sampling efficiency. No prior crappie or bluegill spawning surveys have occurred on Blue Lake until 2024. In 2024 a survey targeting spawning bluegills was conducted which included trap netting from May 14 -17 when water temperatures ranged from 62 to 65 degrees. In the 2024 targeted bluegill survey, a total of 172 Black Crappie were sampled for a catch rate of 6.6/net. Black crappie lengths ranged from 4.0 to 10.8 inches with an average length of 7.4 inches. Ten percent of crappies sampled were greater than 10 inches. The 2024 survey demonstrated a good crappie population was present; however, aging structures were not taken. Therefore, to include Blue Lake in the statewide crappie research project, electrofishing was used in 2025 to sample known crappie areas efficiently. In the spring of 2025, a targeted Crappie survey was done to assess the crappie population and occurred in conjunction with a statewide crappie research study. Fish were collected using an electrofishing boat on May 12th with a water surface temp of 64 degrees. A total of 264 Black Crappies were caught. Shocking was done along the shoreline intermittently and stations were not standardized so catch rate comparisons from this survey are not appropriate. Crappies ranged from 3.7 to 11.4 inches, with an average length of 9.0 inches. Thirty-six percent of crappies were 10 inches or greater. A total of 110 of the crappies were aged using otoliths. All fish sampled were between ages 2 and 6, except one age-10 fish. The 2020-year class was the most frequently sampled (age-5), comprising 48% of the sample.

Blue Lake is a 263-acre lake in southwest Isanti County located five miles northeast of Zimmerman, MN, and is within the Rum River watershed. It has a maximum depth of 31 feet and 51 percent of the lake is less than 15 feet deep (134 acres). Water clarity is moderate ranging from 3 to 5 feet with algal blooms present as summer progresses. An aquatic vegetation survey in 2021 indicated vegetation was present in depths up to 15 feet, although was most common in depths from 1 to 9 feet. Blue Lake was found to have a low diversity of aquatic plants, with 10 submergent and 4 floating leaf species sampled lakewide. The diversity of aquatic plants has declined throughout the nine surveys that have occurred since 2004. Boat navigation during early summer can be affected by dense stands of Curlyleaf pondweed in shallow areas, which is a non-native species. The most common shoreline substrate is sand, followed by gravel and muck. There are two public accesses located on the lake, one in the middle of the eastern shore and one on the northwestern shore. The lake is well developed and popular with local pleasure boaters. Past surveys on Blue occurred in August and have indicated the lake has a moderate to high density Bluegill population, consistent recruitment, with 8.5 to 9.0 inch fish present. Recent interest in quality sized Bluegill have led to efforts to obtain additional information on the size structure of this population. No prior Bluegill spawning survey has occurred on Blue Lake. In 2024 a survey targeting spawning Bluegills was conducted which included trap netting from May 14 -17. This survey was completed using 9 trap nets prior to Bluegill spawning, with water temperatures that ranged from 62 to 65 degrees. Blue Lake has a quality population of Bluegill with numbers and lengths of interest to anglers. A total of 480 Bluegill were sampled for a catch rate of 19/net. Lengths ranged from 2.6 to 9.0 inches with an average length of 6.1 inches. Nearly 12 percent of the Bluegill caught were greater than 8 inches. Other species sampled in this survey were Black Crappie, Pumpkinseed, Hybrid Sunfish, and Green Sunfish. A total of 172 Black Crappie were sampled for a catch rate of 6.6/net. Lengths ranged from 4.0 to 10.8 inches with an average length of 7.4 inches. Fifty Pumpkinseed were sampled for a catch rate of 1.9/net. Pumpkinseed lengths ranged from 3.5 to 8.3 inches with an average of 7.2 inches. Forty Hybrid Sunfish were sampled for a catch rate of 1.5/net. Hybrid sunfish lengths ranged from 5.3 to 8.8 inches with an average length of 7.5 inches.

Blue Lake is a 309 acre lake in southwest Isanti County. There are two public accesses located on the lake. Water clarity is moderate with algal blooms present as summer progresses. Blue Lake is managed primarily for Walleye and Largemouth Bass; the lake is stocked biennially with 134 pounds of Walleye fingerlings. In 2021 a fisheries survey was conducted which included trap netting and gillnetting from August 2-5. Six gill net sets and nine trap nets were used during the assessment. The previous assessment on Blue Lake was conducted in 2013. Both numbers and sizes of Black Crappies and Bluegills have increased since the 2013 assessment. The abundance of Black Crappie was found to be above the normal range for this lake type, with lengths extending from 3.0 to 10.8 inches and an average of 7.8 inches. Just over 62% of the crappie sampled were greater than 8.0 inches in length. Bluegill numbers were within a normal range for this type of lake. Measured Bluegill ranged from 3.2 to 7.9 inches, with an average of 7.1 inches. Spring night electrofishing found good numbers of Largemouth Bass that had an average size of 1.1 pounds. Lengths ranged from 6.4 to 19.2 inches with an average length of 11.7 inches. Anglers can expect to catch good numbers of moderate sized Largemouth Bass on Blue Lake. Walleye catch rates were 5.3 fish per net which is above average for this type of lake in Minnesota. Sampled Walleye ranged from 13.2 to 26.6 inches with a 19.2 inch average. Northern Pike catch rates were 1.7 fish per net which is below average for this type of lake in Minnesota. Pike ranged from 21.5 to 31.2 inches with a 26.6 inch average. Both Northern Pike and Walleye growth were normal.

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

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

Blue has a maximum depth of 31 feet, per Minnesota DNR data.

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

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