Fishmouth

A targeted survey of nearshore fish species in Fishmouth Lake, was conducted on July 14 - July 15, 2025, by Lake Biological Monitoring and Assessment Program staff. Nearshore sampling sites were evenly spaced around the lake, and each was sampled by backpack electrofishing, mini-fyke nets, and seining with a 50-foot or 15-foot seine, where possible. Backpack electrofishing and 1/8" mesh mini-fyke net sampling were completed at six sampling stations, however one mini-fyke net was severely damaged by beaver and the was not included in the catch analysis. Additionally, a 15-foot seine was used at three stations. Three stations were not seined due to site conditions such as dense vegetation, depth, or rocky substrate. Nearshore sampling captured six species of fish, including three species that are intolerant of disturbance (i.e., Iowa Darter, Blacknose Shiner, and Mimic Shiner) and no species that are tolerant of disturbance. The nearshore data along with gill net and standard trap net data will be used to develop fish community models for Minnesota's Boreal Shield lakes to measure lake health in this region. These models may function similarly to fish index of biological integrity (IBI) models developed for lakes across much of the rest of the state. For additional information, search for "lake index of biological integrity" on the mndnr.gov website. Fishmouth Lake, located within Voyageurs National Park, can be protected by visitors using designated access points, avoiding disturbance of shoreline vegetation, and cleaning, draining, and drying gear to prevent the spread of invasive species.

Fishmouth Lake is a small (32 acre) lake located within the Interior of Voyageurs National Park. The lake is only accessible via an unimproved portage trail from the west shore of Peary Lake or by going cross country from Browns Bay of Rainy Lake. Fishmouth exhibits very low productivity; total alkalinity was 7 ppm and the total dissolved solids was 25. Secchi disk visibility was 11.5 feet indicated moderately clear water. The shoreline is dominated by boulder and ledgerock and the surrounding watershed is heavily forested. Currently, boats are not allowed on Fishmouth due to the concern for the spread of invasive species to the Interior. However, the lake is largely accessible by shore fishing. Northern pike abundance has varied considerably in Fishmouth since the first survey was conducted in 1971. During this investigation, we caught 8.25 pike/net, however, in 1983, abundance was 18.60 fish/net. Lengths of pike have improved however. In 1983, the average length was 20.6 inches and the average weight was 1.75 pounds. In 2009, the average length was 23.9 inches and the average weight was 2.7 pounds. The largest pike caught during our survey was 27.0 inches long and weighed 4.00 pounds. The only other species caught in Fishmouth were yellow perch and two species of shiners.

Based on Minnesota DNR survey data, anglers target Northern Pike and Yellow Perch in Fishmouth. See the full species list above for catch rates, size structure, and quality scores.

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

Fishmouth has a maximum depth of 28 feet, per Minnesota DNR data.

The most recent Minnesota DNR survey data for the main sport fish in Fishmouth is from 2009. Surveys this old should be treated with some caution — fish populations change over time.

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