Abstract
The population of far eastern catfish Silurus asotus has been dwindling due to reduction of the places for spawning in temporary waters. In this study, in order to clarify catfish life history from spawning to growth of juvenile, field investigation was conducted in consolidated paddy fields in Utsunomiya city, Tochigi prefecture. Preliminary field observation found several catfish gathering for spawning in one farm drain, and hence detail investigation was carried out for that farm drain from May to June 2012. Although the farm drain is made of concrete flumes and has several hydraulic drops, large portion of the bottom of the ditch was covered with muddy sediment and occasional heavy rain could realize the continuity of water body over the drops. This condition enabled the farm drain to become reproductive area for catfish despite some disadvantages. Besides, the young catfish grew by 2.6 times in total length for a month. They moved to downstream in the farm drain and finally migrated to the river connected with the ditch. Thus, this habitat served as a nursery area for juveniles. The abundance of feed organism for the juveniles and presence of mud substratum in the farm drain were considered to provide good conditions for it.
