Vertical distribution of fish larvae in the Kuroshio and Kuroshio-Oyashio transition region in early summer

Vertical distributions of fish larvae were analyzed for samples taken by a MOCNESS and a 130 cm ring net tows at three stations in the Kuroshio and Kuroshio-Oyashio transition region in early summer during 1995 - 1996. A total of 10,467 larvae were identified as 47 families including more than 74 species. Myctophid and engraulid larvae accounted for 44 and 35% of total number of individuals, respectively. Day and night differences in vertical distributions were analyzed for the predominant five species at each station. Vertical migration towards shallower layers during the nighttime was detected in Myctophum asperum, Gonostoma gracile and Sardinops melanostictus. No significant vertical migration was observed in the other species. Maximum distribution depth of Sardinops melanostictus, Engraulis japonicus, and Scomber spp. were observed in the 100- 150m layer at size < 30mm total length. The depths of distribution of warm-water species were limited to the near surface layers in Kuroshio-Oyashio transition region, although they distributed upper 100m layers in the Kuroshio warm water.