Reproductive biology of the cardinalfish Apogon lineatus in Tokyo Bay, Japan

Abstract

Reproductive biology of Apogon lineatus in Tokyo Bay, Japan was studied by histological examination of the gonads and measurement of the gonadosomatic indices (GSI). The spawning season occurred during July-October, with both males and females attaining sexual maturity by the end of their first year (60.0 mm TL). It was indicated that A. lineatus is a multiple spawner by the presence of postovulatory follicles and primary-secondary yolk in the same ovaries during the spawning season and the asynchronism of the development of spermatogenesis. Batch fecundity ranged from 7983 to 19 316 eggs for fish of 76.0 mm TL to 106.0 mm TL, respectively, and increased linearly with fish total length. Increases in oocyte diameter were not observed after the tertiary yolk stage, which suggested an adaptation to mouthbrooding, thereby efficiently utilizing the male's restricted buccal cavity to maximize the number of eggs mouthbrooded.