Skeleton-based morphometric analysis of small yellow croaker (Larimichthys polyactis) in the Southern Yellow Sea and...

Larimichthys polyactis is a transboundary migratory fish species targeted intensively by fisheries in China, Japan and South Korea, and it is currently subjected to substantial fishing pressure. Clarifying population delineation is critical for the sustainable management of overexploited fish stocks such as this species. For skeletal phenotypic analysis, we collected 30 adult specimens from each of six sampling stations in the Southern Yellow Sea and East China Sea during 2017-2018. Discriminant analysis cross-validation yielded an average classification success rate of 74%. Canonical variate and cluster analyses further divided the populations into four distinct units: Group I (West Coast of Korea Group), an independent cluster from the Yellow Sea offshore station; Group II (Northern Yellow-Bohai Group: Haizhou Bay); Group III (Southern Yellow Sea: Yancheng and Lusi); and Group IV (East China Sea: Zhoushan and Xiangshan). Thin-plate spline analysis revealed that L. polyactis from the Southern Yellow Sea exhibited a lower head height and shorter spine length. In contrast, the East China Sea population displayed a higher head height and longer spine length, exhibiting the streamlined morphological characteristics of a "smaller head, slender body". This study provides evidence for the reliability of skeletal morphology in delineating the population structure of L. polyactis. Knowledge of this population structure contributes to resource assessment and effective fishery management.