Portage

Temperature and dissolved oxygen measurements were collected from the deepest basin in Portage Lake on July 30th, 2025. This was done to evaluate the quantity and quality of cold, oxygenated water (i.e., oxythermal habitat) available to Cisco, also known as Tullibee, the most sensitive coldwater species present in this lake. Cisco require a layer of oxythermal habitat that contains water temperatures below 21.2 degrees C (70.2 degrees F) and dissolved oxygen concentrations above 3.0 mg/L. Based on data collected from the deepest basin (maximum sampled depth was 44.6 feet), the water temperature decreased to 21.2 degrees C (70.2 degrees F) at 11.5 feet and the dissolved oxygen concentration decreased to 3.0 mg/L at 23.4 feet at the time of sampling. This layer in the water column was 11.9 feet, indicating oxythermal habitat for Cisco was present. Further, the temperature at which dissolved oxygen decreased to 3.0 mg/L (i.e., TDO3, a single variable to characterize oxythermal habitat) was 7.7 degrees C (45.9 degrees F). TDO3 values cooler than 21.2 degrees C (70.2 degrees F) indicate that oxythermal conditions were suitable for Cisco at the time of the survey. Data collected by the Minnesota Department of Natural Resources during the period of maximum oxythermal stress (July 26th to Aug 24th) in 2024 also indicated suitable oxythermal habitat. When adequate oxythermal habitat is not available, Cisco are squeezed into unfavorable, warmer water conditions and experience higher levels of stress.

Temperature and dissolved oxygen (DO) measurements were collected from the deepest basin in Portage Lake on July 30th, 2024, to evaluate the quantity and quality of cold, oxygenated water (i.e., oxythermal habitat) available to Cisco, also known as Tullibee, the most sensitive coldwater species present in this lake. During the summer, Cisco require a layer of oxythermal habitat that contains water temperatures below 21.2 degrees C (70.2 degrees F) and dissolved oxygen concentrations above 3.0 mg/L. Based on the profile from the deepest basin (maximum sampled depth 45.9 feet), the water temperature decreased below 21.2 degrees C (70.2 degrees F) at 12.1 feet and the dissolved oxygen concentration decreased to 3.0 mg/L at 19.8 feet at the time of sampling. The thickness of this layer of water in the water column was 7.7 feet, indicating that oxythermal habitat was present for Cisco. Further, the temperature at which dissolved oxygen decreased to 3.0 mg/L (i.e., TDO3, a single variable to characterize oxythermal habitat) was 10.7 degrees C (51.3 degrees F). TDO3 values cooler than 21.2 degrees C (70.2 degrees F) indicate that oxythermal conditions were suitable for Cisco at the time of the survey. This is the first Minnesota Department of Natural Resources temperature and dissolved oxygen survey completed on Portage Lake during the late summer period of maximum oxythermal stress (July 26th to Aug 24th). When inadequate oxythermal habitat is available, Cisco are squeezed into unfavorable, warmer water conditions and experience higher levels of stress.

Temperature and dissolved oxygen (DO) measurements were collected from the deepest basin in Portage Lake on July 30th, 2024, to evaluate the quantity and quality of cold, oxygenated water (i.e., oxythermal habitat) available to Cisco, also known as Tullibee, the most sensitive coldwater species present in this lake. During the summer, Cisco require a layer of oxythermal habitat that contains water temperatures below 21.2 degrees C (70.2 degrees F) and dissolved oxygen concentrations above 3.0 mg/L. Based on the profile from the deepest basin (maximum sampled depth 45.9 feet), the water temperature decreased below 21.2 degrees C (70.2 degrees F) at 12.1 feet and the dissolved oxygen concentration decreased to 3.0 mg/L at 19.8 feet at the time of sampling. The thickness of this layer of water in the water column was 7.7 feet, indicating that oxythermal habitat was present for Cisco. Further, the temperature at which dissolved oxygen decreased to 3.0 mg/L (i.e., TDO3, a single variable to characterize oxythermal habitat) was 10.7 degrees C (51.3 degrees F). TDO3 values cooler than 21.2 degrees C (70.2 degrees F) indicate that oxythermal conditions were suitable for Cisco at the time of the survey. This is the first Minnesota Department of Natural Resources temperature and dissolved oxygen survey completed on Portage Lake during the late summer period of maximum oxythermal stress (July 26th to Aug 24th). When inadequate oxythermal habitat is available, Cisco are squeezed into unfavorable, warmer water conditions and experience higher levels of stress.

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

We don't have a confirmed public access point on record for Portage. Check the DNR LakeFinder page for current access details before you go.

Portage has a maximum depth of 45 feet, per Minnesota DNR data.

The most recent Minnesota DNR survey data for the main sport fish in Portage is from 1979. Surveys this old should be treated with some caution — fish populations change over time.

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