Testicular development of male Sebastolobus macrochir in the Pacific coast of southeastern Hokkaido [Japan]

The annual reproductive cycle of the male kichiji rockfish, Sebastolobus macrochir, was investigated by histological observation of the testes. Spermatogenesis began in late May and gradually progressed until December. In February to May, spermatogenesis was completed and shifted to the functional maturation stage. This indicates the breeding season of this species. It appeared that fish which completed ejaculation immediately resumed proliferation of spermatogonia.The gonad somatic index did not always correspond to the maturity based on histological observation because there are large differences in the testes sizes among males. This indicates that histological evaluation is essential for discrimination of sexual maturity in this species