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.
