Stable isotopes in scales of mangrove snapper Lutjanus argentimaculatus as an indicator for origin discrimination

Abstract

Identifying a fish's artificial or natural origin is crucial for stock enhancement assessments. In this study, we collected specimens of hatchery (including the early fry, reared, and released juveniles) and wild mangrove snapper Lutjanus argentimaculatus to explore the feasibility of using delta C-13 and delta N-15 values in scales as a non-lethal alternative to muscle tissues for discriminating between hatchery and wild origins. The results showed scales generally enriched in delta C-13 value and relatively consistent in delta N-15 value compared to muscle. Significant correlations were found between the two tissues for both delta C-13 and delta N-15 values (R-2 = 0.80-0.88). Based on the isotopic composition of the scale core, individuals with different origins could be effectively discriminated, achieving a classification success rate of 77.6%. The random forest analysis revealed that a delta C-13 value of -15.8 parts per thousand could be a reference for determining the hatchery and wild origins of mangrove snapper. This study provides an isotopic approach for assessing the benefit of stock enrichment in mangrove snapper. It highlights the importance of regular sampling and scales analysis to expand fishery management and conservation practices.