Size at sexual maturity and annual reproductive cycle of male crimson sea bream Evynnis tumifrons off the southwestern coast of Kyushu, Japan

Abstract

Size at sexual maturity and annual reproductive cycle of male Evynnis tumifrons were investigated off the southwestern coast of Kyushu, Japan. A total of 788 testes were examined histologically. Testis maturity stages were classified into six categories based on the appearance of the most advanced germ cell stage along with the presence of earlier spermatogenic stages, the amount of interstitial tissue, the presence of sperm within lobular lumen and efferent duct, and tunica thickness as follows: immature, developing, early maturing, late maturing, spent, and resting. Males with the testes at developing, early maturing, late maturing, and spent stages were defined as sexually mature, and the size at sexual maturity was estimated as 169 mm in fork length based on 50% maturity size. Monthly changes in the gonadosomatic index and the occurrence of individuals having testes at early maturing or late maturing stages showed that the period when mature fish release sperm was from October to May. Seasonal changes in the condition factor tended to be high from June to October.