Viewing Streams As a Habitat Mosaic; Implications for Riverscape Ecology and Stream Conservation

Here, we develop a riverscape-scale, habitat-mosaic approach for quantifying how human impacts and climate change influence freshwater fish biodiversity. If mosaics create different patterns of biodiversity than traditionally-measured isolated habitat patches, extant approaches to examining organism-habitat relationships will be unable to address larger scale conservation threats. To develop and test the mosaic approach, we sampled fish and habitat along ten 3-km stretches of river within the Upper Neosho and Cottonwood Rivers, KS, from May-October 2013. Four results illustrate our mosaic approach to habitat-biodiversity relationships. First, mesohabitats (pool, riffle, run, glide) formed distinct habitat categories based on physical characteristics (depth, flow velocity, substrate size). Second, complex mosaics of individual mesohabitats were present at all 3-km sample sites. Third, empirically determined fish species guilds and multivariate techniques confirmed isolated mesohabitat-fish associations. Fourth, biodiversity in the connected riverscape mosaic differed from biodiversity in isolated mesohabitat-patches. For example, riffles were the limiting mesohabitat (< 5% of the total proportion of sampled area), but native species richness was significantly higher within 3-km mosaics with higher riffle densities. Thus, our focus on a mosaic view of streams revealed unique patterns of stream habitat and biodiversity that must be considered to understand and conserve threatened aquatic ecosystems.