The Distribution of the Oceanic Sea Skaters, Halobates inside and outside the Kuroshio

The purpose of this study was to clarify the distribution of oceanic Halobates in the area of the Kuroshio flowing near the southern shore in the direction of 100° - 120°, and also to compare the population density of Halobates between the area within or outside the area of the Kuroshio and also among seasons. This study was carried out during 8 cruises by R/V TANSEIMARU. The Kuroshio area south of the southern Japan coast (30°00'N - 35°00'N, 130°25'E - 141°04'E) was dominated by H. sericeus, and the averaged population-density of this species was significantly higher inside the Kuroshio than outside this current. On the Kuroshio, H. sericeus was dominant with the population density of 16,396.4 km-2 ± 66,138.4 [26] (Mean ± SD [n]), whereas the density of H. germanus was 8,581.9 km-2 ± 24,443.2 [26]. The two oceanic sea skaters, H. sericeusand H. germanus showed significant seasonal variation in the population density, with significantly higher density in October than other months, whereas there was no such significant October peak in the cosmopolitan oceanic sea skater, H. micans. The results of this study may suggest that H. sericeus could use the Kuroshio as a transportation tool to distribute a wide latitude area of from 10°N to 40°N in the western tropical, subtropical and temperate area in the Pacific Ocean.