Growth rates of larval stage of Japanese anchovy <i>Engraulis japonicus</i> and environmental factors in the Kuroshio Extension and Kuroshio-Oyashio transition regions, western North Pacific Ocean

Abstract

Recent studies of Japanese anchovy Engraulis japonicus have shown that they are distributed and spawn widely off the Pacific coast of eastern Honshu, Japan, with increasing stock size. Larvae are considered to be transported offshore and migrate, influenced by physically complicated process with warm and cold waters derived from the Kuroshio and Oyashio currents respectively. Survival mechanism during early life history stages in such offshore waters could be a missing link for population dynamics of Japanese anchovy. In this study, we examined the growth rates of larval stage of Japanese anchovy, which were collected in the Kuroshio Extension and Kuroshio-Oyashio transition regions, western North Pacific Ocean, by sagittal otolith microstructure analysis. Our objectives are to determine the principal environmental factor affecting larval growth rates and to find out a survival mechanism in relation to transport and migration of larvae.