Otolith Morphology Reveals Population Connectivity of <i>Siniperca kneri</i> (Garman, 1912) in the Xijiang River

Morphological and morphometric analyses of otoliths are widely used for intraspecific comparisons and fish stock identification. This study examines the stock structure of Siniperca kneri (Garman, 1912), an endemic and economically important carnivorous fish in China, using otolith shape analysis in the Xijiang River. Specimens were collected from three sites in the middle and upper reaches of the river. Traditional shape indices and elliptic Fourier descriptors were used to evaluate otolith morphology after statistically removing the effect of fish size (allometry). After applying corrections for multiple comparisons, no significant differences were found in any of the eight shape indices among groups. Canonical analysis of principal coordinates (CAP) based on elliptic Fourier coefficients also revealed no clear morphological differentiation among the sites. The initial discriminant analysis yielded a raw classification success rate of 61.1%, but a more robust leave-one-out cross-validation reduced the accuracy to 55.6%, indicating substantial morphological overlap. These results suggest that S. kneri in the study area likely constitutes a single phenotypic stock with limited spatial structuring. The absence of strong stock differentiation may be attributed to relatively homogeneous environmental conditions and the potential effectiveness of fish passage facilities that could maintain ecological connectivity. However, these conclusions are tempered by the study’s limitations in sample size. These findings underscore the importance of preserving river connectivity and highlight the urgent need for further studies utilizing otolith microchemistry and genetic tools to validate these findings and support effective conservation management.