Impacts of environmental variability on the growth and survival of larval sardine and anchovy in the Kuroshio and its extension

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In order to clarify growth and survival processes of Japanese sardine and Japanese anchovy in areas around the Kuroshio and its extension, larval sampling, otolith microstructure analyses, observations of environmental condition, and numerical experiments were conducted. During the period from 2006 to 2012, larval density fluctuated interannually, reflecting the fluctuations of the abundances of whole stock level of each species. However, spatial distribution showed large variations that were related to the structure of the path of the Kuroshio. The results of particle tracking experiments suggested that short-term variations of the path of the Kuroshio drastically changed the transport and growth rates of larvae. While the growth rates showed positive correlation with temperature for both of the two species, there were significant differences when the samples were divided by years. Survival processes were suggested to be the important factors affecting these relationships.