Genetic identity and length-weight relationship of Oyster Pompano (Trachinotus anak) at a mariculture site in northern Vietnam

Accurate genetic identification of the Oyster Pompano Trachinotus anak is often impeded by mislabeling of reference sequences as Trachinotus ovatus in nucleotide Basic Local Alignment Search Tool (BLAST) searches within the global GenBank database, highlighting the need for further validation. In this study, mitochondrial cytochrome c oxidase subunit I (COI) sequences were generated from morphologically identified T. anak collected from a single mariculture site in northern Vietnam to resolve this taxonomic ambiguity. The obtained sequences exhibited mean interspecific genetic distances ranging from 5.5% to 17.4% compared with 16 congeners and showed a pronounced genetic divergence (15.2%) from T. ovatus. Both Bayesian Inference and Maximum-likelihood phylogenetic analyses consistently recovered T. anak as a distinct and well-supported lineage, clearly separated from T. ovatus. Furthermore, multiple species delimitation approaches and interspecific haplotype network analyses reinforced species discrimination by identifying distinct Molecular Operational Taxonomic Units (MOTUs) and discrete clustering patterns characterized by a high number of polymorphic sites. In addition, the length–weight relationship analysis from a single mariculture site indicated negative allometric growth, while the regression analysis demonstrated a strong relationship between length and weight, confirming that body length is a reliable predictor of body mass for this species under the studied culture conditions. Collectively, the present research corroborates previous findings and effectively resolves the long-standing species identification dilemma between T. anak and T. ovatus in Asian mariculture systems. This study also provides baseline data on growth patterns of cultured pompano in Vietnam, which will be valuable for fish health monitoring, feed management, harvest optimization, and assessment of overall stock performance in aquaculture operations.