Lake Conservation Webinar Series: Development of dissolved oxygen, temperature, and nutrient thresholds to protect cold water fish species in Minnesota lakes
Minnesota’s current water quality standards framework for lakes provide protections for lakes that support or are managed for trout, but these standards do not specifically protect other cold water fish species such as Cisco and Lake Whitefish. Many cold water fish species populations are threatened, because these species require oxygenated, cool water which is negatively impacted by a warming climate and eutrophication. The Minnesota Department of Natural Resources and Minnesota Pollution Control Agency are collaborating to inventory lakes that support Cisco, Lake Whitefish, and Lake Trout, and to develop water quality standards that specifically protect these species. This effort includes the development of protective thresholds, which combine dissolved oxygen and temperature requirements (i.e., oxythermal habitat) for these fish species. In addition, thresholds for total phosphorus and chlorophyll-a have been determined that link to conditions needed to maintain protective levels of dissolved oxygen. These analyses and previous research have indicated that each species has different requirements, which necessitates species-specific standards. Designating Minnesota’s lakes that support cold water fish and documenting which cold water fish species occur in these lakes will allow the application of species-specific standards. The resulting framework will provide standards, which will be used to protect these threatened fish species and to protect or restore these important resources.