High-value fish species (Actinopterygii) in Tam Giang Lagoon, Vietnam: Biological traits and ecological insights

The Tam Giang Lagoon in central Vietnam is one of the largest coastal lagoon ecosystems in Southeast Asia, playing a role in maintaining regional fish biodiversity and supporting local fisheries. However, knowledge about the ecological adaptation and genetic structure of key fish species in this system remains limited. This study investigated the morphological variation, trophic ecology, and mitochondrial genetic diversity of three ecologically and economically important species Terapon jarbua (Forsskål, 1775); Acanthopagrus latus (Houttuyn, 1782); and Oxyurichthys ophthalmonema (Bleeker, 1856). Morphometric and meristic analyses revealed clear interspecific differentiation in body depth, fin configuration, and scale counts, reflecting adaptive divergence across distinct habitat zones within the estuarine–lagoon continuum. Dietary analyses, based on gut morphology and nutritional composition, indicated feeding strategies ranging from omnivory to carnivory. Terapon jarbua exhibited a generalist omnivorous habit exploiting both planktonic and benthic resources, A. latus showed predominantly benthic feeding behavior, whereas O. ophthalmonema displayed strong carnivory, consuming mainly small fishes and crustaceans. Mitochondrial COI and CR analyses revealed high haplotype diversity and distinct nucleotide composition patterns among species, suggesting lineage-specific evolutionary trajectories. Phylogenetic analyses showed that individuals from each local population clustered into monophyletic clades, with several unique haplotypes particularly within T. jarbua and A. latus. Overall, the integration of morphological, ecological, and genetic data highlights species-specific adaptations to lagoon habitats and provides valuable insights for monitoring, management, and conservation of fish biodiversity under increasing environmental pressures in central Vietnam.