Effect of Channel Alteration on Fish Habitat

Abstract

In order to crarify how channel alteration affects fish habitat, fish densities, stream morphology and flow conditions were researched at both altered and unaltered sections in a stream. In the unaltered section the stream bed was very undulating, and differentiation of riffles and pools was clear. Waterflow was affected by morphological factors and became turbulent. In the altered section, the bed shape was flat, differentiation of riffles and pools was not clear, and waterflow was laminary as compared with the former section. The dominant fish was Oncorhynchus masou in the unaltered secion, and Barbatula toni in the altered section. Why the former fish was not dominant in the altered section was discussed in relation to their feeding habit, the flow conditions, multiformity of environment. The low carrying capacity of O. masou in the altered section reflects the uniform environment which was producted by the channel alterations. © 1984, The Japanese Society of Limnology. All rights reserved.