Abstract
The relationship between fish fauna and physical environmental factors was studied in the reach including a dam, in the Katsuura River, eastern Shikoku Island, Japan. We set five investigational stations: three in regulated low-flow portion below Masaki Dam and two in unregulated portion in the river. The first station of unregulated portion was located upstream of the dam reservoir. The second station of unregulated portion was located below the outlet of the hydroelectric power plant settled at 8 km downstream from the dam. Each station consists of 20-31 transverse lines to observe the occurrence of fishes and to measure the environmental factors.
In total 17 species were recognized in five investigational stations. We attempted to examine the species diversity, and both combination and diversity of six environmental types classified by 17 environmental factors on the transverse lines in each station. The tendency of low species diversity was observed in the regulated portion, corresponding to the low environmental diversity. Furthermore, the abundance of certain environmental types and low species diversity in certain environmental types also corresponded to the low species diversity in the regulated portion. These two findings suggest that the species diversity of stream fishes was affected by both the environmental diversity and the species diversity subsisted in each environmental type.
