SURVIVAL AND GROWTH OF SARDINE LARVAE IN THE OFFSHORE SIDE OF THE KUROSHIO

After 1984 the major spawning of the Japanese sardine, Sardinops melan ostictus, has been observed to occur in the offshore waters, where the survival of early-stage larvae (4-10 mm in length) is questionable. T he main objective of this study is to estimate the growth and survival rates of the early-stage larval cohort in the offshore side of the Ku roshio Current. A radar-reflecting buoy with a surface drogue was laun ched to tag a patch of larvae, and the patch was traced for 3 days in March 1991. The survival rate of the early-stage larval cohort was cal culated from the change in density during the survey. The range of the instantaneous mortality rate was from 0.83 to 1.11 day(-1), a surviva l rate of 32-44% day(-1). The mean density of the smaller larvae (4-6 mm in length) decreased more rapidly than that of the larger larvae (6 -10 mm in length) during the sampling period. The survival rate of the first-feeding larvae in the offshore region seemed to be lower than t hat of the post-first-feeding larvae. However, the growth rates of the first-feeding larvae's survivors in the region were higher than those of the post-first-feeding larvae's survivors. The first-feeding larva e in the offshore region seemed to survive when the growth rate of the larvae was high.