Year-class strength and growth rates after metamorphosis of Japanese sardine (Sardinops melanostictus) in the western North Pacific Ocean during 1996–2003

Abstract

Growth trajectories during larval to early juvenile stages in Japanese sardine ( Sardinops melanostictus ) were backcalculated based on the widths of otolith daily increments from 1996 to 2003 in the nursery grounds, Kuroshio–Oyashio transitional waters. Planktonic larvae hatched near Kuroshio have been transported northeastward from the Kuroshio waters to the transitional waters. We show that the somatic growth rates sharply increased after metamorphosis to the early juvenile stage, whereas previously, others showed that growth rate decreases during the larval stage. Otolith growth rates were more variable during the juvenile stage than the larval stage. Interannual variations in the otolith growth rate after metamorphosis explained more than 80% of variation in abundances of recruits (ca. 8–10 months old) in the Pacific coastal waters, whereas no correlation was found between the growth rate during the early larval stage and abundance. Our result was consistent with the hypothesis of growth rate-dependent recruitment success in the Kuroshio–Oyashio transitional waters.