Abstract
It has been pointed out that the preservation of fish fauna in paddy field regions requires the maintenance of a water zone network connecting paddy fields, small streams, agricultural waterways, and rivers. In this research, a survey was conducted on the migration of Japanese dace (Ugui) in an aquatic network consisting of fish ways including the Yagawa stream, the Kugohan canal, the Uchikawa stream, and the Nishi Kinugawa river in the Nishi Kinugawa river district of Tochigi Prefecture to study the significance of building the network. As a result, the migration of individuals into the Yagawa stream from the other waterways was confirmed to infer that the network built had contributed to the conservation of Japanese dace populations in the Yagawa stream. In addition, many individuals besides the migrant individuals were found to reproduce in artificial spawning grounds and many non-migrant individuals inhabited the Yagawa stream. Hence, many individuals were inferred to inhabit the Yagawa stream permanently. From the above contemplation, it was judged that fish preservation in agricultural waterways requires the construction of a water zone network and the conservation of individuals inhabiting the agricultural waterways permanently.
