Impact of Small-Scale Dams on Fishes of the Willamette River, Oregon and an Evaluation of Fish Habitat Models

摘要

Two aspects of the potential effects of small-scale hydroelectric dams on fish communities in the Willamette River were examined. The first study was to determine whether or not models of habitat assessment based solely upon physiological tolerances would be suitably accurate for prediction of impact. It was found that ecological processes such as interspecific competition greatly limit the accuracy of habitat models based solely on physical variables. Also, distributional patterns of fishes differed among streams, presumably due to different limiting factors which shift fish behavior. A multivariate approach was developed to define habitat selection, by denoting habitat availability and habitat occupation based on microhabitat characteristics. The second study was to determine physical and ichthyofaunal characteristics for unimpounded streams and for streams impounded by various types of small-scale dams. Also, the types of impacts of small-scale dams were identified and the predictive capacity of habitat suitability models was evaluated.