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Presented at the NABS Annual meeting, Vancouver, British Columbia, 2004
in Fish Ecology 1
Natural and human factors structuring fish assemblages in West Virginia wadeable streams
D.M. Walters1 and F.H. McCormick2. 1US EPA Ecological Exposure Research Division, 26 W. MLK Dr., Cincinnati, OH 45220, 2USFS, Olympia Forestry Sciences Laboratory, 3625 93rd Ave. SW, Olympia, WA 98512
We surveyed fishes and environmental variables in 119 stream basins to identify natural and anthropogenic factors structuring fish assemblages. We collected fishes and physico-chemical variables using standardized EPA methods and compiled basin characteristics (e.g., land cover) from digital coverages. Nonmetric multidimensional scaling, NMS, analysis identified two axes that explained 70% of among-site variation in fishes. Axis 1 (31%) positively correlated with pH and basin area and corresponded with a shift from tolerant to sensitive species as pH increased. Axis 2 (39%) strongly correlated with temperature, elevation, and slope. High elevation, cold, steep streams were dominated by salmonids, cottids, and Rhinichthys spp. that gradually changed to diverse assemblages of cyprinids, percids, catostomids, ictalurids, and centrarchids at lower elevations. Land cover variables were weakly correlated with NMS axes but were significantly correlated with changes in water quality (e.g., conductivity, SO4, and NO2/NO3 increased with mining and urbanization). Our findings suggest that land use effects may be difficult to detect in systems characterized by strong abiotic controls on assemblage structure and that changes in stream chemistry precede gross changes in fish assemblages. Although this work was reviewed by EPA and approved for publications, it may not necessarily reflect official Agency policy.
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