A Classification System for Large U.S. Reservoirs and Its Application to the Midwest

In order to prioritize conservation efforts, the Reservoir Fisheries Habitat Partnership needs information regarding the condition of reservoir fish habitats, and reservoir classification provides a framework within which to assess fish habitat condition.  Using a combination of ecologically-based spatial partitioning and cluster analysis, we developed a classification system for large U.S. reservoirs.  First, we conducted a survey of fisheries biologists to evaluate habitat of reservoirs ≥100 ha in the U.S. Questions covered numerous habitat attributes – including availability, water quality, water regime, and degradation processes – as well as selected aspects of the fish community and recreational fishery.  A total of 1,302 useable responses were received.  Second, we examined several extant systems of spatial partitioning reflecting ecological differences among regions (i.e., Omernik’s Level I and II ecoregions, EPA Wadeable Streams Assessment [WSAs], and Landscape Conservation Cooperatives).  Using habitat variables from the survey, we conducted cluster analysis within each region of each partitioning system.  Our goal was to balance recognition of inherent ecological differences and recognition of natural groups within the data.  Our final classification system utilized WSAs and yielded 24 unique reservoir classes that showed various types and levels of habitat impairment.  Reservoir class characteristics for the Midwest are presented.