Abstract
The South China Sea (SCS) is one of the world’s main centers for coral reef diversity, with more than one-third of all reef fish species being found in this area. Some indications of overfishing have appeared in typical coral reefs of the SCS, as fish diversities have declined and the average body lengths of dominant fish species have decreased. However, only few assessments of coral reef fish stocks have been conducted, due to insufficient available data. In this study, we applied a newly developed length-based Bayesian biomass (LBB) estimation method to assess 10 dominant coral reef fish species from three main reefs (Yongshu Reef, Zhubi Reef, and Meiji Reef) of the Nansha Islands, SCS. Simulations indicated the estimated parameters were not sensitive to sample sizes (more than 100) using the LBB method. Our results showed that the relative biomass levels (B/BMSY) of Cephalopholis spiloparaea, Cephalopholis urodeta, Lutjanus gibbus, Gnathodentex aureolineatus, Pentapodus caninus, and Cheilinus fasciatus were between 0.16 and 0.45, suggesting an overfishing status; the relative biomass levels of Epinephelus merra, and Parupeneus crassilabris were 0.98 and 1.1, respectively, indicating that they were fully exploited; and the relative biomass levels of Lutjanus kasmira and Melichthys vidua were 1.3 and 2.5, respectively, indicating the populations were in good conditions. The estimates of Lc/Lc_opt were less than one for seven stocks, suggesting that the stocks were suffering from growth overfishing. Therefore, we emphasize the need to reduce fishing mortality and increase the mesh size of the coral reef fishery in the Nansha Islands, to achieve a sustainable yield and biomass.
Highlights
Coral reefs are distinguished by their tremendous diversity and the ecosystem services they provide to coastal tropical and subtropical nations (Hughes et al, 2003; Spalding and Brown, 2015)
The results suggest a pressing situation for the coral reef fishery, as 60% of the dominant fish species were overexploited and 20% were fully exploited
Growth overfishing occurs when fish are harvested before they reach their optimum size, reducing fishery yields (Nadon et al, 2015)
Summary
Coral reefs are distinguished by their tremendous diversity and the ecosystem services they provide to coastal tropical and subtropical nations (Hughes et al, 2003; Spalding and Brown, 2015). For the coral reef fishery, most studies have focused on biology and catchable body size (Li, 2010; Zhang J. et al, 2020), species composition and taxonomic diversity (Arai, 2015; Li et al, 2020), and risk assessment of contaminants in reef fishes (Pan et al, 2018; Nie et al, 2019). Only limited research has been undertaken assessing the stocks of coral reef fisheries in the SCS. Despite this lack of research, some indications of overfishing have appeared, such as declines in the fish diversity of typical reefs (Li et al, 2020), and decreases in the average body lengths of dominant fish species (Zhang J. et al, 2020). It is necessary to carry out effective stock assessments and pay more attention to the sustainable use of coral reef fishes
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