Growth rate-dependent recruitment of Japanese anchovy Engraulis japonicus in the Kuroshio-Oyashio transitional waters

Abstract

Based on the relationship between otolith and somatic growth rates, we examined the effect of growth and developmental rates on survival during larval and early juvenile stages in Japanese anchovy Engraulis japonicus collected in the Kuroshio-Oyashio transition region in the western North Pacific. Mean daily otolith increment width (IW) positively correlated with mean growth and developmental rates in rearing experiments. In the Kuroshio-Oyashio transition region, fastergrowing larvae with larger IWs attained completion of metamorphosis at younger ages than slowergrowing larvae. The minimum IWs in the recruited adults collected in 1999 greatly increased from 4.8 m at 40 d after hatching to 11.0 m at 60 d, while the minimum IWs in the pre-recruits collected in 1998 was less than 5.0 m at 60 d, and accounted for ca. 60% of the total pre-recruit population. Based on the positive relationship between IWs and growth rates in the rearing experiments, an IW of 11.0 m is estimated to correspond to 0.41 mm d -1 in growth rate. It was concluded that pre-recruits with growth rates < 0.41 mm d -1 at 60 d have a negligible probability of survival to recruitment. Mortality dependent on growth and developmental rates occurred in the metamorphosing stage of E. japonicus in the Kuroshio-Oyashio transition region. Since environmental conditions in the transition region are variable, and these conditions affect growth and developmental rates of larvae, the rates in the metamorphosing stage could determine the abundance of recruited 1 yr old E. japonicus in the transition region.