Portsmouth Mine

Portsmouth Lake is a former open pit iron ore mine pit located in the Cuyuna Country State Recreation Area. Temperature and oxygen conditions suitable for trout occurred from a depth of about 20' down to around 70' in July. Rainbow Trout are stocked annual as yearlings (7,000/year) into Portsmouth. Rainbow Trout provide for a popular fishery, especially early in the season. Rainbow Trout were sampled at 0.8/gill net, with an average length of 12.4". Northern Pike was sampled in low numbers, when compared to similar lakes, at 1.3/gill net. Average length was 20.6" with 13% in the protected 22"-26" slot; 25% were at least 26.0" or larger. Largemouth Bass were sampled in high numbers at 2.2/gill net. Average length was 12.2", with fish up to 18.7" sampled. Bluegills were sampled in low numbers at 7.1/trap net. Most ran on the small side with an average length of 5.0", with 13% at least 7.0" in length. Portsmouth 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. No invasive species have been found in Portsmouth but are in the area. 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.

Portsmouth 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 24 ft down to about 34 ft. The TDO3 value was 5.4 C. Sufficient oxygen for salmonids (> 5 ppm) occurred down to a depth of about 75 ft where the temperature was 5.3 C.

Portsmouth 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 24 ft down to about 34 ft. The TDO3 value was 5.4 C. Sufficient oxygen for salmonids (> 5 ppm) occurred down to a depth of about 75 ft where the temperature was 5.3 C.

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

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

Portsmouth Mine has a maximum depth of 395 feet, per Minnesota DNR data.

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

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