On the Food of the Salmonoid Fish, Ayu (Plecoglossus altivelis Temminck & Schlegel)

Abstract

A number of Ayu we e obtained from several rivers of Gihu Prefecture during a period from summer to autumn of 1935. Each lot of the fish caught at the same time at the same station was examined with a view to determine the difference of food of the fish in accordance with the difference of its size.
The authors' observations show that the food of larger size of Ayu chiefly consisted of abundant quantity of diatoms and bluegreen algae, and moreover the kinds of these algae were not so many. On the other han ??, the smaller size of Ayu ate some green algae besides those above mentioned algae, all of which were poor in quantity but referable to pretty many kinds of species, and also took some quantity of sand grains and animal matters such as chironomid larvae and pupae as usual.