Otter Tail River Stressor Identification Report—Lakes

Over the past few years, the Minnesota Pollution Control Agency (MPCA) in coordination with the Minnesota Department of Natural Resources (MNDNR) has substantially increased the use of biological monitoring and assessment as a means to determine and report the condition of the state's lakes. This basic approach is to examine fish communities and related habitat conditions at multiple sites throughout major watersheds. Fish communities are sampled using a combination of trap nets, gill nets, beach seines, and backpack electrofishing. From these data, a fish-based index of biological integrity (FIBI) score can be developed, which provides a measure of overall fish community health. More information about the sampling and assessment process can be found at the MNDNR lake index of biological integrity website. If biological impairments are found, stressors to the aquatic community must be identified. Stressor identification (SID) is a formal and rigorous process that identifies stressors causing biological impairment of aquatic ecosystems and provides a structure for organizing the scientific evidence supporting the conclusions (Cormier et al. 2000). In simpler terms, it is the process of identifying the major factors causing harm to aquatic life. SID is a key component of the major watershed restoration and protection projects being carried out under Minnesota's Clean Water Legacy Act. This report summarizes SID work related to lakes in the Otter Tail River Watershed (OTRW). The OTRW encompasses over 1.2 million acres characterized predominantly as a mix of forested and agricultural land, and includes the cities of Detroit Lakes, Fergus Falls, Pelican Rapids, and Perham. The OTRW also contains numerous lakes, rivers, streams, and wetland complexes.