Age determination and growth pattern of temperate seabass Lateolabrax japonicus in Tango Bay and Sendai Bay, Japan

Abstract

The temperate seabass Lateolabrax japonicus is a coastal and partial amphidromous fish that is commercially valuable in Japan. Fish age is an important and sensitive variable for stock structure assessment, and inaccurate aging can result in inappropriate management practices. However, there have been few studies on age determination in this species. By examining monthly changes in marginal increment growth, we validated that otolith increments are formed annually. This information was used to develop an age-determination method using otolith sections. Von Bertalanffy growth models were generated based on standard length and weight data for both sexes in Sendai Bay and Tango Bay, Japan. Differences in standard length- and weight-at-age and growth parameters were observed in both sexes and locations. Females exhibited larger standard lengths and weights at older ages than did males, in both locations. Individuals from Sendai Bay exhibited longer average asymptotic lengths, higher asymptotic weight, higher standard length-at-age and higher weight-at-age compared to their counterparts from Tango Bay. Decreases in growth rates in both Sendai Bay and Tango Bay occurred around the age at maturity, indicating that more energy was allocated to reproduction than growth after reaching maturation. Differences between Sendai Bay and Tango Bay in the age at which the maximum instantaneous growth rate and the asymptotic length are reached were thought to arise from differences in water temperature and biological productivity between the two bays.