Reproductive cycle of yellow sea bream Dentex tumifrons in Wakasa Bay, the Sea of Japan off central Honshu

Abstract

To determine the spawning season and reproductive cycle of the yellow sea bream, Dentex tumifrons, in Wakasa Bay, in the Sea of Japan off central Honshu, seasonal change in the gonadosomatic index (GSI) was examined and histological observations of both ovaries and testes were conducted. The female GSI gradually increased from May, maintained a high level between that vitellogenesis began from May and developed until September. Spent fish began to be observed in October and all the fish collected in December were spent. There was only one peak in the seasonal change in GSI of males and females in Wakasa Bay. Thus, yellow sea bream spawn only in autumn in Wakasa Bay. Differences in the reproductive cycle and number of spawning seasons were found between the two different latitudinal areas, Wakasa Bay and the East China Sea (low latitudinal area) where the spawning seasons were spring and autumn. An increase in water temperature is an important factor to initiate gonadal maturation (recrudescence) and is terminated by the short day-length in Wakasa Bay.