Patterns in the Distributions of Stream Fishes in Michigan’s Lower Peninsula

–We examined distribution and abundance patterns of 69 commonly occurring fishes at several hundred sites in Lower Michigan streams. We used cluster analysis to group fishes that commonly occurred together at stream sites. These seventeen clusters explained about 39% of the variation in species abundances among the stream sites, providing a reasonable, albeit simplified picture of general associations of fishes in Lower Michigan streams. Known ecological differences among species and further analyses suggested that a single measure of cluster abundance should not be used to predict abundances of its constituent species. We used measures of stream size and hydrology as landscape-scale, habitat axes (a “macrotemplate”) for comparing streams. We identified catchment area (CA) and low-flow yield (90% exceedence flow divided by catchment area) as key driving variables that linked features of the landscape to multiple, site-scale characteristics of stream habitat (e.g. temperature, velocity, and depth) important to fishes. As a measure of groundwater loading to streams, low-flow yield (LFY) integrates geology, landform, and soil characteristics of catchments, reaching its highest values in basins with highly permeable soils and relatively steep topography. In Lower Michigan streams, high LFY values were generally associated with: greater portions of coarse-textured glacial deposits in catchments; higher stream gradients; coarser stream substrates; and cooler and less variable predicted July weekly temperatures. High CA values were generally associated with lower stream gradients, and warmer and less variable predicted July weekly temperatures.