Life history and ecology of the glowbelly Acropoma japonicum in the Uwa Sea, Japan

Abstract

The life history and ecology of the glowbelly Acropoma japonicum a commercially important fishery resource, were investigated in the Uwa Sea, Japan. Newly settled juveniles (0*) appeared at the end of the breeding season and reached maturity in the next season, i.e. when they became yearlings (1*). The yearlings made a gametic effort comparable to that of older fish. During the breeding season, the somatic conditions were more deteriorated for males than for females. That the deterioration of male somatic conditions was not attributable to a sexual difference in energy gain from feeding suggests that the males incurred higher energetic costs of reproduction despite their relatively low gonadosomatic indices. Such an energy depletion may increase the mortality risk, resulting in female-biased sex ratios in the older age classes. Most of the 1+ fish disappeared in winter following their first breeding. For A. japonicum, the observed precocity and short life span is notable because it is a higher consumer that is generally expected to show later maturation and longer life. As likely. While fishing is one of the most influential factors, the possibility of age-specific migration toward deeper waters remains to be examined.