Exploring otolith phenotypic variability as a marker to discriminate spatial stocks of Mystus vittatus (Bloch, 1794)

Context Mystus vittatus (Bloch, 1794) is an economically significant food and aquarium fish currently experiencing a decline in population, which necessitates the understanding of its potential stock structure. Aim This study aims to delineate the spatial stocks of M. vittatus in the Ganga River by analysing otolith shape and morphometry. Methods The otolith shape variations across four sampling stations along the Ganga River were assessed using wavelet coefficients, otolith morphometric parameters, including size and shape indices. Key results The statistical analyses, including permutational multivariate analysis of variance (PERMANOVA), canonical analysis of principal coordinates (CAP) and ANOVA-like permutation test, showed significant differences in otolith shape among the four populations. Kruskal–Wallis and post-hoc Dunn’s tests confirmed significant differences in most otolith morphometric parameters across the populations. The random forest method achieved a classification accuracy of 64.68% on the basis of otolith shape and 52.04% on the basis of otolith morphometry. Conclusions The observed phenotypic variabilities in otolith morphology among the four populations suggest the presence of heterogeneous stocks. Implications These findings have provided valuable insight for effective fisheries management and conservation strategies aimed at sustaining M. vittatus populations in the Ganga River.