Portage (main bay)

A targeted survey of nearshore fish species in Portage Lake was conducted on August 8-9, 2023, by Index of Biological Integrity (IBI) Program staff. Nine 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 ten sampling stations. Similarly, a 50-foot seine was used to sample six stations, a 15-foot seine was used at three stations, and site conditions prevented the use of seines at one station. Nearshore sampling captured fourteen species of fish including six species that are intolerant of disturbance (i.e., Banded Killifish, Blackchin Shiner, Blacknose Shiner, Iowa Darter, Mimic Shiner, and Smallmouth Bass) and zero that are tolerant of disturbance. A concurrent summer trap net survey was also conducted by IBI Program staff. Nine trap nets were set along the shoreline in locations that encompassed multiple habitat types. Trap net sampling captured eight species of fish. Bluegill comprised a majority of the catch by number, whereas Largemouth Bass, Bluegill, and Yellow Bullhead comprised a majority by biomass. The nearshore and trap net data were combined with 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., Blackchin Shiner, Least Darter, and Rock Bass), while other species are tolerant of degraded conditions (e.g., Black Bullhead and Green Sunfish). 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. Results from this survey indicate that the fish community in Portage Lake is healthy as indicated by an FIBI score that exceeds the general use threshold determined for similar lakes. These results will be considered when the biological health of the lake is assessed during the Redeye River Watershed assessment process, which will be completed in coordination with MN Pollution Control Agency. In addition to the fish survey, Minnesota DNR Fisheries IBI program staff conducted an assessment of lakeshore habitat on Portage Lake on Sep 22 2023, following the Score the Shore survey protocols. The assessment consisted of 28 survey sites evenly spaced 150 meters around the lake. Assessments were made in three habitat zones: Shoreline Zone (the shore-water interface to the top of the natural bank), Shoreland Zone (land-ward from shoreline to development structure or 100 feet), and Aquatic Zone (lake-ward 50 feet of shoreline). The average lakewide habitat score was 75.4 (+/- 4.3) out of 100 possible. A score of 75.4 indicates the lakewide shoreline condition is Moderate, but a large difference was noted in shoreline condition between undeveloped and developed sites. Undeveloped sites had a mean score of 94.4, and excellent shoreline condition. However, developed sites were in poor condition with a mean score of 58.9.

Portage Lake is a 269-acre mesotrophic (moderately fertile) lake located in east-central Otter Tail County approximately one mile east of Ottertail, MN. Portage Lake is part of the Redeye River Watershed. There are no inlets or outlets connected to Portage Lake. The immediate watershed is composed primarily of hardwood woodlots. The maximum depth is 49 feet; however, 55% of the lake is less than 15 feet in depth. The secchi disk reading during the 2022 survey was 12.5 feet. Previous secchi disk readings have ranged from 8.5 to 16.0 feet. The majority of the shoreline of Portage Lake remains undeveloped. A DNR owned concrete public water access is located off of County Road 61 along the east shoreline of the lake. Shoal water substrates consist primarily of sand and gravel. Stands of hardstem bulrush, common cattail, and wild rice are limited to the north shoreline of the lake. Emergent aquatic plants such as wild rice cattail, and bulrush provide valuable fish and wildlife habitat, and are critical for maintaining good water quality. They protect shorelines and lake bottoms, and can actually absorb and break down polluting chemicals. Emergent plants provide spawning areas for fish such as Northern Pike, Largemouth Bass, and panfish. They also serve as important nursery areas for all species of fish. Because of their ecological value, emergent plants may not be removed without a DNR permit. Portage Lake can be ecologically classified as a Walleye-bass-panfish type of lake and this is reflected in the assemblage of the fish community. Walleye, Largemouth Bass, and Bluegill are the dominant gamefish species in the fish community of Portage Lake. Walleye abundance has historically remained high. Walleyes ranged in length from 9.2 to 24.7 inches with an average length and weight of 13.8 inches and 1.0 pounds. The 2019 year class is very strong and should provide excellent Walleye angling for several years. Walleyes attain an average length of 14.9 inches at four years of age. Largemouth Bass abundance has also historically remained high. Age data indicate that Largemouth Bass reproduction is consistently good. Largemouth Bass ranged in length from 5.4 to 17.7 inches with an average length and weight of 11.0 inches and 0.8 pounds. Largemouth Bass attain an average length of 13.4 inches at five years of age. A moderate to high density Bluegill population exists. Bluegill reproduction is consistently good; however, size structure is poor. Only 2% of the Bluegills were 8.0 inches or greater in length and only 7% were 7.0 inches or greater in length. Bluegill growth rates are slow with an average length of 7.5 inches at eight years of age. Anglers can maintain the quality of fishing by practicing selective harvest. Selective harvest encourages the release of medium to large-size fish while allowing the harvest of more abundant smaller fish for table fare. Releasing the medium to large fish will ensure that the lake will have enough spawning age fish on an annual basis and will provide anglers with more opportunities to catch large fish in the future. Portage Lake is not listed as an infested water. Aquatic invasive species are threatening Minnesota waters. Aquatic invasive species can potentially harm water quality, water recreation, aquatic habitat, native species, and fish populations. Anglers can help prevent the introduction and spread of invasive species by following watercraft transportation laws.

A targeted survey of nearshore fish species in Portage Lake was conducted on July 8, 2022 by Fergus Falls 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. Electrofishing was completed at all ten sampling stations, but one station was moved a short distance due to site conditions and one station was sampled by boat electrofishing. A 15-foot seine was used at seven stations, a 50-foot seine was used at two stations and soft sediments and abundant vegetation prevented the use of seines at one station. Nearshore sampling captured 13 species of fish including five species that are intolerant of disturbance (i.e., Banded Killifish, Blackchin Shiner, Blacknose Shiner, Iowa Darter and Mimic Shiner) and zero species that are 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., Banded Killifish, Blackchin Shiner, Blacknose Shiner, Iowa Darter and Mimic Shiner), while other species are tolerant of degraded conditions (e.g., Green Sunfish). 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. Results from this survey indicate Portage Lake is in good health as indicated by an exceptionally high FIBI score well above the impairment threshold and above the exceptional 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 Redeye Watershed assessment process in coordination with MN Pollution Control Agency.

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

Minnesota DNR records list public access for Portage (main bay). Check the DNR LakeFinder page for the launch type and directions before you go.

Portage (main bay) has a maximum depth of 49 feet, per Minnesota DNR data.

The most recent Minnesota DNR survey data for the main sport fish in Portage (main bay) is from 2023.

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