Bertha

Temperature and dissolved oxygen profiles were collected in the deepest basin in Bertha Lake on August 14, 2024, to evaluate the quantity and quality of cold, oxygenated water (i.e., oxythermal habitat) available to Lake Whitefish, the most sensitive coldwater species present in this lake (Cisco are also present). Lake Whitefish require a layer of oxythermal habitat that contains water temperatures below 17.2 degrees C (63.0 degrees F) and dissolved oxygen concentrations above 3.0 mg/L. Based on the profile from the deepest basin, the water temperature decreased to below 17.2 degrees C (63.0 degrees F) at 24.5 feet and the dissolved oxygen concentration decreased to 3.0 mg/L at 23.7 feet at the time of sampling. The water column did not contain a layer of water with sufficient temperature and dissolved oxygen for Lake Whitefish. Further, the temperature at which dissolved oxygen decreased to 3.0 mg/L (i.e., TDO3, a single variable to characterize oxythermal habitat) was 17.9 degrees C (64.3 degrees F). TDO3 values near 17.2 degrees C (63.0 degrees F) indicate that oxythermal conditions were unsuitable for Lake Whitefish at the time of this survey. Data collected by the Minnesota Department of Natural Resources in 2011-2023 during the late summer thermal stress period, indicate suitable oxythermal habitat in all years surveyed, in contrast with 2024. When inadequate oxythermal habitat is available, Lake Whitefish are squeezed into unfavorable, warmer water conditions and experience higher levels of stress.

Temperature and dissolved oxygen profiles were collected in the deepest basin in Bertha Lake on August 14, 2024, to evaluate the quantity and quality of cold, oxygenated water (i.e., oxythermal habitat) available to Lake Whitefish, the most sensitive coldwater species present in this lake (Cisco are also present). Lake Whitefish require a layer of oxythermal habitat that contains water temperatures below 17.2 degrees C (63.0 degrees F) and dissolved oxygen concentrations above 3.0 mg/L. Based on the profile from the deepest basin, the water temperature decreased to below 17.2 degrees C (63.0 degrees F) at 24.5 feet and the dissolved oxygen concentration decreased to 3.0 mg/L at 23.7 feet at the time of sampling. The water column did not contain a layer of water with sufficient temperature and dissolved oxygen for Lake Whitefish. Further, the temperature at which dissolved oxygen decreased to 3.0 mg/L (i.e., TDO3, a single variable to characterize oxythermal habitat) was 17.9 degrees C (64.3 degrees F). TDO3 values near 17.2 degrees C (63.0 degrees F) indicate that oxythermal conditions were unsuitable for Lake Whitefish at the time of this survey. Data collected by the Minnesota Department of Natural Resources in 2011-2023 during the late summer thermal stress period, indicate suitable oxythermal habitat in all years surveyed, in contrast with 2024. When inadequate oxythermal habitat is available, Lake Whitefish are squeezed into unfavorable, warmer water conditions and experience higher levels of stress.

Temperature and dissolved oxygen profiles were collected in the deepest basin in Bertha Lake on August 14, 2024, to evaluate the quantity and quality of cold, oxygenated water (i.e., oxythermal habitat) available to Lake Whitefish, the most sensitive coldwater species present in this lake (Cisco are also present). Lake Whitefish require a layer of oxythermal habitat that contains water temperatures below 17.2 degrees C (63.0 degrees F) and dissolved oxygen concentrations above 3.0 mg/L. Based on the profile from the deepest basin, the water temperature decreased to below 17.2 degrees C (63.0 degrees F) at 24.5 feet and the dissolved oxygen concentration decreased to 3.0 mg/L at 23.7 feet at the time of sampling. The water column did not contain a layer of water with sufficient temperature and dissolved oxygen for Lake Whitefish. Further, the temperature at which dissolved oxygen decreased to 3.0 mg/L (i.e., TDO3, a single variable to characterize oxythermal habitat) was 17.9 degrees C (64.3 degrees F). TDO3 values near 17.2 degrees C (63.0 degrees F) indicate that oxythermal conditions were unsuitable for Lake Whitefish at the time of this survey. Data collected by the Minnesota Department of Natural Resources in 2011-2023 during the late summer thermal stress period, indicate suitable oxythermal habitat in all years surveyed, in contrast with 2024. When inadequate oxythermal habitat is available, Lake Whitefish are squeezed into unfavorable, warmer water conditions and experience higher levels of stress.

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

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

Bertha has a maximum depth of 64 feet, per Minnesota DNR data.

The most recent Minnesota DNR survey data for the main sport fish in Bertha is from 2024.

Yes — Bertha 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 Bertha, covering crappie and sunfish. Special regulations override the statewide limits; see the fishing regulations section on this page. Verify current rules with the Minnesota DNR before keeping fish.