Variations in the fish community of the Beibu Gulf (South China Sea) following fishery resources protection measures

Abstract

The Beibu Gulf is a resource–rich bay in the northwestern South China Sea; however, its fishery resources have been in decline owing to overfishing and other factors. To rebuild the depleted fish stocks, China has implemented a series of fishery resources conservation and management measures; the most influential of these is possibly the summer fishing moratorium, in effect since 1999. This study used data from bottom–trawl surveys conducted in spring and autumn from 1998 to 2020 to analyze variations in the fish community of the Beibu Gulf following implementation of the fishery resources protection measures. The data analysis indicated improvements in fish species richness, diversity, and mean trophic level, but further declines in fish abundance and biomass since 1998. The composition of dominant species, except for the small–sized glowbelly Acropoma japonicum, changed obviously from 1998 to 2020, although still mainly composed of small–sized demersal and pelagic species. Abundance–biomass comparison curves indicate that the disturbance level affecting fish in the Beibu Gulf remained unchanged and that it is still in a heavily disturbed state. These findings suggest that the current fishery resource conservation policies are inadequate for reversing the trend of declining fishery resources. China’s marine fishery resources management measures should be refined by incorporating more–precise conservation measures consistent with the characteristics of the local resources. In particular, relevant measures are needed to control the fishing output, such as the quota fishing system currently being piloted.