Suitability analysis of stocking waters of Plectropomus leopardus based on fish growth characteristics and nutrient composition

Global marine fishery resources are declining due to the effects of overfishing, climate change, and environmental pollution. Stock enhancement is considered to be an effective means of increasing the number of biological populations and promoting the sustainable development of fisheries. However, the effectiveness of stock enhancement is affected by many factors. Among of them, the habitat conditions at the releasing waters directly affect the survival rate and growth rate of the released fish. Therefore, before the fish were released in large numbers, it is important to evaluate the suitability of this water area. At present, the research on the evaluation of the suitability of the release waters is mainly to carry out the background investigation of the proposed releasing waters by sampling before releasing, including water quality, food organisms, fishery resources and other aspects. However, this investigation method is expensive. To develop a method for evaluating the suitability of fish releasing waters, in this study, a small batch of Plectropomus leopardus was first released to the waters, and then recaptured them. The growth characteristics and muscle nutrients of the recaptured P. leopardus and the farmed P. leopardus were compared to evaluate whether the waters are suitable for the growth of released fish. The results showed that the allometric growth factor b value of the recaptured and farmed populations of P leopardus was close to 3, showing an isokinetic growth state. The growth condition factor a value of recaptured P. leopardus was greater than that of farmed P. leopardus, and the condition factor K value was also greater than that of farmed P. leopardus. There were no significant differences in moisture, ash, crude protein, crude fat, essential amino acid content, and total amino acid content in the muscles of the recaptured and farmed P. leopardus. The contents of monounsaturated fatty acids, C20:4n6, C20:5n3 and C22:6n3 in muscle of recaptured P. leopardus were significantly higher than those in farmed P. leopardus. There were no significant differences in other elements except manganese and selenium in the muscle of recaptured and farmed P. leopardus. The content of lead in the muscle of recaptured P. leopardus was significantly lower than that of farmed P. leopardus, and there were no significant differences in other heavy metals. In short, this study indicated that the habitat conditions of the releasing waters could ensure the balance and accumulation of various nutrients to meet the growth and development needs of the P. leopardus. This study verified the feasibility of evaluating the suitability of fish releasing waters based on the fish growth characteristics and nutrient composition and formed the evaluation process. It can provide a new insight for evaluating the suitability of fish releasing waters in the future, and can also be used to other aquatic species.