The use of artificial temporary streams with and without shelters by Japanese dace Tribolodon hakonensis
In order to know how fish use temporary streams, we set up artificial temporary streams with and without shelters and investigated the fish that colonized there from connected permanent streams. A total of 220 fish belonging to six species were captured over four sampling periods from May to September, with Japanese dace Tribolodon hakonensis being the most abundant (75%). More Japanese dace colonized the stream with shelters than without shelters. The standard length and condition of Japanese dace tended to be greater in the stream with shelters than without shelters. Foraging behavior and area of Japanese dace differed significantly between the two streams; more Japanese dace employing drift feeding near the entrance of the shelterless stream. Japanese dace predominantly fed upon chironomid larvae, which became abundant in stream mud in July. However, in August and September, Japanese dace rarely preyed upon chironomid larvae and their digestive canal fullness was low, probably because most chironomid larvae had been consumed. This tendency was more prominent in the stream with shelters. The use of temporary waters by Japanese dace changed dynamically in response to the abundance of chironomid larvae and the presence or absence of shelters.