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INFLUENCE OF HUMAN ACTIVITIES ON LANDSCAPE AND HABITAT FACTORS CONTROLLING PACIFIC NORTHWEST COASTAL STREAM FISH ASSEMBLAGES
Citation:
Kaufmann, P R. AND R M. Hughes. INFLUENCE OF HUMAN ACTIVITIES ON LANDSCAPE AND HABITAT FACTORS CONTROLLING PACIFIC NORTHWEST COASTAL STREAM FISH ASSEMBLAGES. Presented at American Fisheries Society meeting, Madison, WI, August 22-26, 2004.
Description:
Fish assemblages in the Oregon-Washington coast range consist primarily of coldwater taxa of salmonids, cottids, dace, and Pacific giant salamander. This region has a dynamic natural disturbance regime, where mass failures, debris torrents, fire, and tree-fall are driven by climate and weather but subject to alteration by human activities. The major land uses in the region are logging, dairy farming, and related road building. There is considerable controversy concerning the effects of these activities on habitat and fish assemblages. To examine potential influences on habitat and fish, we examined associations among physical habitat, land use, geomorphology, and fish assemblages in data from the USEPA's EMAP regional surveys. In general, these data show that much of the variation in fish assemblage composition, and in habitat characteristics such as residual pool volume and substrate size appeared to be predetermined by drainage area, channel slope, and basin lithology. However, once the deterministic influences of these geomorphic controls were factored out, associations with human activities became apparent. Streambed fining was associated with riparian disturbance and road density. In turn, lower abundances of salmonids and other coldwater and sediment-intolerant taxa were associated with excess streambed fines, bed instability, road density, riparian disturbance, and lack of large pools and cover complexity.