Biological characteristics and distribution of the glowbelly Acropoma japonicum, a dominant fish in the Beibu Gulf, China

In the 1990s, a rapid increase in fishing intensity in the Beibu Gulf, disrupted the demersal ecosystem, wherein the dominant species shifted to smaller-sized individuals. Among the smaller-sized species, Acropoma japonicum was the most prominent. We examined the biological characteristics, distribution and environmental factors of this species to better understand its population status and sustained dominance. The dominant body length group was 50-55 mm (18.98%), and the dominant body weight group was 4-5 g (15.69%). The exponent b value was 2.55 for both sexes. The ratio of females to males was 1.33:1. Gonadal maturity was mainly at stages III (20.21%), IV (34.10%) and V (28.27%). Size at first maturity (L50) was 39.40 mm for females and 63.16 mm for males. The mean CPUE and proportion of A. japonicum in the survey catches decreased from 2006 to 2018, but increased thereafter. Redundancy analysis indicated that water depth is the most important factor affecting the species' distribution, followed by bottom water temperature. The overall results indicate that long-term domi-nance by A. japonicum in the Beibu Gulf is likely attributable to early sexual maturity, a high proportion of fe-males and long reproductive time, as well as a suitable environment in the ecosystem.