Study on the relation between river water quantity and freshwater fish.

One of the attractive characteristics of rivers is the presence of freshwater fish. The conservation of the fish is an important subject for the river environmental improvement. This study deals with how to decide a necessary river water quantity for the habits of fish.There are about 200 kinds of freshwater fish in Japan. In consequence of investigating the valuable fish in fishery, the important fish on events or festivals, and the widespread fish, 6 kinds of fish are selected as the most essential fish to be considered. Those are ayu, salmon, char, masu trout, carp, and crucian carp. These habitats, life-styles, and the important figures such as velocity and depth for deciding a necessary water quantity are shown in the tables for each 4 periods of the fish growth. It is suggested that seasonal changes of river water quantity must be considered.