Screening of predatory fish species for larvae of Acanthaster solaris and quantitative analysis techniques of environmental DNA

In the context of ongoing outbreaks of the crown-of-thorns starfish, the outbreak of the South China Sea's crown-of-thorns starfish (Acanthaster solaris) has severely threatened coral reef ecosystems, highlighting the urgent need for research on related control and eradication technologies. Biological control offers environmental friendliness and long-term effectiveness, making research on predator fish species crucial for managing the crown-of-thorns starfish outbreaks. This study investigates the feeding effects of seven common coral reef fish species in the South China Sea on crown-of-thorns starfish larvae, aiming to identify suitable predator fish species for South China Sea reefs. Additionally, the study develops and validates eDNA quantitative detection technology for the most effective predator, providing technical support and data for subsequent stock enhancement, release effectiveness evaluation, and fishery management. The results indicate that Pomacentrus coelestis significantly outperforms other species in terms of both feeding amount and feeding rate on brachiolaria, making it the most optimal predator identified in this study with a consumption rate of 403 larvae/day. There is a significant positive correlation between the density of the P. coelestis and eDNA concentration, with eDNA concentration stabilizing after 96 h of cultivation. The linear function (eDNA concentration = 267,120,000 density − 234,320,000) shows a good fit (R² = 0.985), making it generally effective for assessing the resource levels of P. coelestis in stable water environments.