Geometric Morphometric Analysis of Phenotypic Population Structure in Hatchery and Wild Stocks of Ompok pabda From Bangladesh

ABSTRACT Population structure is important for broodstock management and conservation of Ompok pabda . This study evaluated phenotypic shape variation among three hatchery populations from Bogura (Kahalu), Dinajpur (Sadar) and Mymensingh (Muktagacha) and one wild population from Arial Beel , Munshiganj, using 15 landmark geometric morphometrics. After data‐quality screening and generalised Procrustes analysis, a small but significant common within‐group allometric effect explained 2.28% of shape variation (permutation p = 0.0413) and was removed before multivariate analysis. Principal component analysis of allometry‐adjusted Procrustes coordinates showed that PC1 and PC2 explained 48.08% and 18.19% of the variation, respectively (66.27% cumulative). MANOVA detected a strong population effect on shape (Wilks' λ = 0.0393, F (33, 257.02) = 15.57, p < 0.001). Canonical variate analysis showed that CV1 and CV2 accounted for 65.19% and 22.18% of the canonical discriminatory variation, respectively. Discriminant function analysis using 11 PCs that retained 95.27% of allometry‐adjusted Procrustes shape variance achieved 87.13% overall leave‐one‐out cross‐validated classification accuracy with equal prior probabilities. All pairwise Mahalanobis and Procrustes distances were significant, while UPGMA based on complete mean‐shape Procrustes distances grouped Bogura most closely with Arial Beel and identified Mymensingh as the most distant population. Thin‐plate spline visualisations localised major variation around the head and ventral pelvic‐anal region. The results demonstrate significant phenotypic structuring, but the unbalanced wild sample and absence of molecular data require caution when inferring genetic stock boundaries.