The distribution and life history of the catadromous cottid fish, Trachidermus fasciatus were studied in rivers discharging into Ariake and Yatsushiro Sounds, west Kyushu, Japan. The fish were found to inhabit rivers located between the Yabe River of Fukuoka Prefecture and the Honmyo River of Nagasaki Prefecture. Juveniles were found in May pointing upstream just below dams which were located at the lowest point in the rivers. Until their first autumn, the fish remained in small areas below the dams. Most of the dams were located at the upper end of the tidal reaches of the rivers. We did not find T. fasciatus inhabiting areas above the lowest dam. Their present distribution, which is restricted down-stream and confined to unnaturally small areas, is thought to be caused by the construction of the dams. The fish do not appear to migrate as far upstream as previously reported. The fish mature and migrate downstream in their first autumn or winter, when they are about 150 mm in total length. No age 2 fish were found in the rivers surveyed. Juveniles smaller than 19mm in total length mainly fed on copepods, and their main food changed from aquatic insects to fish after their upstream migration.
We surveyed fish fauna at 3 boulder sites in Uchiumi Bay, Shikoku Island, Japan. Numbers of fish species and individuals of each species were recorded along 2 lines (50 and 100m) at each site, using SCUBA in September 1992. A total of 126 species were recorded; about 66% of them were tropical or subtropical fishes. Number of temperate species was similar among the 3 sites (26-28 spp.). Numbers of tropical or subtropical species (30-60 spp.) was greater at the sites where the coral coverage was higher (4-37%). The location in the bay and the strength of water current in each site are also suggested to affect recruitment and density of tropical fishes transported by the Kuroshio Current. The fish fauna of Uchiumi Bay was compared with those of 16 localities of southern Japan. The number of species common to Uchiumi Bay was relatively high in Kushimoto, Kagoshima Bay and Shirahama; all the 4 localities are situated near the border between the warm temperate region and the subtropical region.