Mahnomen, Alstead & Arco Mine

Mahnomen Lake is a complex of former open pit iron ore mines located in the Cuyuna Country State Recreation Area. The Mahnomen complex includes (from east to west) the Mahnomen No. 1, Louise, Mahnomen No. 2 and 3, Arco, and Alstead mines. Temperature and oxygen conditions suitable for trout occurred from a depth of about 20' down to around 70'. Rainbow Trout were first stocked in 1982 and are stocked annual as yearlings (15,000/year) into the Mahnomen complex and connected Pennington. Rainbow Trout provide for a popular fishery, especially early in the season. Rainbow Trout were sampled at 4.6/gill net which was the highest catch to date. Average length was 10.9". Lake Trout were first stocked in Mahnomen in 2019 and are stocked biennially as yearlings (1,670/year). No Lake Trout were sampled in this survey, although there are reports of anglers catching a few. Tullibee (Cisco) were also stocked in 2019 to provide forage for the Lake Trout. Tullibee (Cisco) were sampled in low numbers, when compared to similar lakes, at 0.6/gill net. Northern Pike were sampled in low numbers at 1.0/gill net. Average length was 21.6", with 8% in the protected 22"-26" slot, and 50% at least 26.0" in length. Northern Pike up to 31.7" were sampled. Largemouth Bass were sampled in average numbers, when compared to similar lakes, at 1.3/gill net. Average length was 12.0", with fish up to 20.5" sampled. Smallmouth Bass were also sampled in average numbers at 0.3/gill net. Average length was 17.2". Mahnomen is a designated stream trout lake. Designated stream trout lakes have additional angling regulations. Be sure to consult the current Minnesota Fishing Regulations book for regulations, seasons, and possession limits before fishing designated trout waters. Zebra mussels are present in Mahnomen Lake. Before and after launching lake users are required to inspect and remove any aquatic plants and animals from their watercraft and trailers as well as pull the plug and drain all water from the watercraft, including bilges, livewells and baitwells.

Mahnomen Mine Pit Lake is a former open pit iron mine that is a designated stream trout lake presently managed for rainbow trout. The dissolved oxygen and temperature profile was measured on August 22, 2011 to monitor habitat for trout. Optimal conditions for rainbow trout (11-19 C, greater than or equal to 5 ppm DO) occurred in about 11 vertical ft from a depth of about 21 ft down to about 31 ft. The TDO3 value was 4.5 C. Sufficient oxygen for salmonids (> 5 ppm) occurred down to a depth of about 82 ft where the temperature was 4.4 C. Water temperatures actually warmed from a depth of 82 ft by 0.4 C to 4.8C at 92 ft.

Mahnomen Mine Pit Lake is a former open pit iron mine that is a designated stream trout lake presently managed for rainbow trout. The dissolved oxygen and temperature profile was measured on August 22, 2011 to monitor habitat for trout. Optimal conditions for rainbow trout (11-19 C, greater than or equal to 5 ppm DO) occurred in about 11 vertical ft from a depth of about 21 ft down to about 31 ft. The TDO3 value was 4.5 C. Sufficient oxygen for salmonids (> 5 ppm) occurred down to a depth of about 82 ft where the temperature was 4.4 C. Water temperatures actually warmed from a depth of 82 ft by 0.4 C to 4.8C at 92 ft.

Based on Minnesota DNR survey data, anglers target Northern Pike, Black Crappie, Rainbow Trout, Largemouth Bass, and Smallmouth Bass in Mahnomen, Alstead & Arco Mine. See the full species list above for catch rates, size structure, and quality scores.

Minnesota DNR records list public access for Mahnomen, Alstead & Arco Mine. Check the DNR LakeFinder page for the launch type and directions before you go.

Mahnomen, Alstead & Arco Mine has a maximum depth of 525 feet, per Minnesota DNR data.

The most recent Minnesota DNR survey data for the main sport fish in Mahnomen, Alstead & Arco Mine is from 2022.

Yes — Mahnomen, Alstead & Arco Mine has confirmed zebra mussel. Clean, drain, and dry your equipment to avoid spreading invasives to other waters.

Yes — the 2026 Minnesota DNR regulations list 1 special rule for Mahnomen, Alstead & Arco Mine, covering lake trout. Special regulations override the statewide limits; see the fishing regulations section on this page. Verify current rules with the Minnesota DNR before keeping fish.