Reproductive aspects of the Japanese threadfin bream, Nemipterus japonicus (Bloch, 1791) in the Southern Java waters (FMA-RI 573)

Abstract

This study describes the reproductive biology of the Japanese threadfin bream, Nemipterus japonicus (Bloch, 1791) captured from the Southern Java Waters (FMA-RI 573). Fish monthly sampling collection was conducted from July to December 2022 at three fish landing ports: PPI Ciwaru, PPN Palabuhanratu, and PPI Binuangeun. Overall, 951 individuals consisting of 469 males (49.32%) and 482 females (50.68%), with a size range of 92-300 mm and a weight range of 10–344 g were collected. The sex ratio is balanced (1:1.10), with fecundity ranging from 10,079 to 82,650 eggs. The length at first maturity is 146 mm for males and 141 mm for females. The Japanese threadfin bream is a total spawner. Spawning occurs throughout the sampling period, with a peak in October-November. The length-based spawning potential ratio (LBSPR) measures the sustainability of fish stocks, indicating that Japanese threadfin bream in southern Java is in an overexploited condition.