Dam

This report includes results from multiple targeted surveys (TS) conducted throughout Aitkin County in 2025. Bigmouth Buffalo are present throughout Aitkin County. They are most abundant in the Mississippi River but are also common in lakes that have direct or distant connections to the Mississippi River via tributaries and drainage ditches. Bigmouth Buffalo in the Aitkin area have only been recorded during standard surveys and are primarily captured with trap nets due to their low susceptibility to gill nets. However, most Bigmouth Buffalo observations occur in targeted trap net and electrofishing assessments as by-catch and are often not recorded or captured. In 2025, an effort was made to capture, record, and tag any Bigmouth Buffalo by-catch during targeted Walleye, Bass, and panfish assessments. Furthermore, multiple targeted surveys were conducted in 2025 around the Aitkin area to identify locations where Bigmouth Buffalo could consistently be captured for future investigations. Special electrofishing assessments were carried out on parts of Dam Lake (TS 7/23/2025), Sandy River (below Libby dam, TS 7/25/2025), Rice River (TS 6/3/2025), and Ripple River (TS 6/2/2025) targeting Bigmouth Buffalo. Additionally, small mesh trap net (1/4 inch mesh) assessments were done in known spawning grounds of the upper Rice River to target young-of-year (YOY) migrating downstream. Electrofishing was conducted on 6/03/2025 and 7/22/2025 at the confluence of the Rice River and Mississippi River. Zero Bigmouth Buffalo were sampled in the June assessment, and one was sampled in the July assessment. The one fish was an adult and measured 32.5 inches. Other species observed included Channel Catfish, Rock Bass, Shorthead Redhorse, Silver Redhorse, Walleye, and White Sucker. Small mesh trap net (1/4 inch mesh) assessments were executed on 7/22/2025 and 9/19/2025 downstream of known spawning areas in the Rice River to target YOY Bigmouth Buffalo. Zero YOY Bigmouth Buffalo were sampled during these assessments. Other species observed included Black Bullhead, Brown Bullhead, Black Crappie, Bowfin, Hybrid Sunfish, Northern Pike, Rock Bass, Shorthead Redhorse, Tadpole Madtom, White Sucker, and Yellow Perch. Electrofishing was conducted on 6/03/2025 at the confluence of the Ripple River and Mississippi River. Zero Bigmouth Buffalo were sampled. Other species observed included Channel Catfish, Greater Redhorse, Northern Pike, Rock Bass, Shorthead Redhorse, Silver Redhorse, Smallmouth Bass, Walleye, and White Sucker. Electrofishing was conducted on 7/25/25 in the Sandy River below the Libby Dam. Two Bigmouth Buffalo were sampled. One fish was a juvenile that measured 14.9 inches, and the other was an adult that measured 32.6 inches. Other species observed included Channel Catfish, Shorthead Redhorse, Walleye, and White Sucker. Dam Lake was sampled via electrofishing on 7/23/2025. Zero Bigmouth Buffalo were sampled. Fish were observed on forward facing sonar but had a high boat avoidance. Bigmouth Buffalo were observed in other assessments during the 2025 season when targeting Walleye, Bass, and Panfish. Two fish were observed during spring Walleye electrofishing on Hill Lake (see Hill TS 4/21/25), but only one was captured and measured 39.4 inches. Two juveniles were captured in trap nets during a spring panfish assessment on Blind Lake (see Blind TS 5/07/2025), measuring 13.3 and 15.2 inches. One fish was observed during Bass Electrofishing on Rabbit Lake (see field notes Rabbit TS 5/27/25) and estimated to be greater than 35.0 inches. One fish was sampled in Gun Lake with a trap net during an IBI survey (see Gun TS 7/07/2025) and measured 27.9 inches. Three fish were captured during fall Walleye electrofishing on Big Sandy Lake (see Big Sandy TS 10/02/2025), measuring 29.3, 30.3, and 32.8 inches.

Dam Lake is a moderate sized lake located about ten miles east of the City of Aitkin. There is a state-owned public access with a concrete log ramp on the west side of the lake. Fish habitat is diverse with a good amount of emergent vegetation (bulrush), areas with floating-leaf plants (waterlilies), a variety of submerged plant beds, as well as open water areas. In addition to providing excellent fish and wildlife habitat, emergent plants help stabilize sediments and protect shorelines from erosion by breaking wave action. This lake is part of the Quality Sunfish Initiative where the limit is 10 fish. Walleye stocking began with regularity around 1950, with fingerlings having been stocked at a variety of rates and frequencies in the past. More recently experimental fry stocking with supplemental fingerling stocking in alternate years was tried for a period of years with no measurable increases in the Walleye population. The current management plan for the lake was amended in 2018 and current stocking plans call for stocking fingerling Walleye annually. Also, when available surplus fish may be stocked but no more than every other year. This was a change from annual fry with alternate year fall fingerling stocking contingent upon low electrofishing catches. Catch rates for Walleye were slightly below the management abundance objective for this lake (3/net) the previous five assessments going back to 2009, although age class objective of at least 4-year classes has been met regularly. The current stocking regime will continue and will be evaluated on a regular basis. The lake is also known for its Black Crappie, Bluegill, and Largemouth Bass populations. Black Crappie abundance had been decreasing since 2015, but abundance improved in the 2022 survey. Size structure remained good with 20% larger than 10 inches and a maximum length of 12.4 inches. Bluegill abundance in 2022 (5.9/trap net) was a decrease from the previous survey. The average size was 5.9 inches and ranged from 2-11 years old with 7-year old's being the most abundant. Only a few fish over 8 inches were sampled. Dam Lake is considered a good bass lake for the area with a respectable size structure as fish up to 19 inches and beyond are usually sampled. Typically, spring night electrofishing is a method used to gauge the abundance and size structure of Largemouth Bass populations, but in lakes where they are abundant, they will also show up in gill nets. There were 1.4 bass caught per net in 2022. Abundance of Northern Pike as measured by gill net catch rates decreased slightly between 2019 (8.6/net) and 2022 (5.0/net). Catches have been reasonably stable over survey history, with a long-term average of around 4/net. Average size was down in this survey with an average size of 19.9 inches and 1.6 pounds. No fish larger than 30 inches were sampled. Anglers are encouraged to release larger pike, thereby multiplying opportunities for anglers to catch big fish through recycling, as well as helping to maintain a better size distribution in this keystone predator. Yellow Perch abundance (0.6/gill net) has bounced all over the place and showed a decrease in the previous two surveys. Yellow Perch catches have varied greatly in previous surveys from less than 1 to over 24 per gill net. Yellow Perch continue to provide invaluable forage for Northern Pike and Walleye populations but are currently at a low level of abundance. Tullibee have declined steadily since the late 1990's and only 4 have been caught in the previous 4 surveys. This cold-water species has sensitive requirements for oxy-thermal regime and recent weather patterns may be contributing to their decline. Anglers are reminded to follow current MN-DNR Aquatic Invasive Species guidelines as described in the MN fishing regulations handbook to prevent the spread of unwanted invasive species.

A targeted survey of nearshore fish species in Dam Lake was conducted on July 5, 2022 by Aitkin Area Fisheries Staff. Sampling sites were evenly spaced around the lake and each was sampled by backpack electrofishing and seining with a 50-foot or 15-foot seine, where possible. Backpack electrofishing was completed at all fourteen sampling stations. Similarly, a 50-foot seine was used to sample seven stations and a 15-foot seine was used at seven stations. Nearshore sampling captured 18 species of fish including six species that are intolerant of disturbance (i.e., Banded Killifish, Blackchin Shiner, Blacknose Shiner, Burbot, Mimic Shiner and Rock Bass) and none that were tolerant of disturbance. The nearshore data were combined with trap net and gill net data from a July 2022 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., Iowa Darter and Rock Bass), while other species are tolerant of degraded conditions (e.g., Green Sunfish and Black Bullhead). 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 the fish community of Dam Lake is in good health as indicated by an FIBI score above the impairment threshold for aquatic life use determined for similar lakes. Data from this survey will contribute biological information about the health of the fish community to the Mississippi River-Grand Rapids Watershed assessment process in coordination with MN Pollution Control Agency.

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

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

Dam has a maximum depth of 48 feet and a mean depth of 19 feet, per Minnesota DNR data.

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

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