Estimation of habitat potential for Ayu fish by analyzing riffle geomorphology in the Yodo River System

Abstract

Riffle is an important habitat for various lotic animals and its geomorphic variations bear the faunal biodiversity in stream ecosystems. In the present paper, we classified the riffle geomorphology and estimated the habitat potential for Ayu fish, Plecoglossus altivelis (Osmeridae) in the Kizu, Uji, Katsura and Kamo River, in the Yodo River System. Riffle geomorphology was classified into five types based only on plan view pictures: i.e., Traverse type, Widely Diverge type, Narrowly Diverge type, Converge type and Artificial type. Composition and abundance of theses riffle types were distinctively different among the four rivers. Based on these differences, the potential population of Ayu fish was estimated to be 526131 in Katsura River, 688, 795 in Kizu River, 176, 365 in Kamo River, and 356, 005 in Uji River.