Background. The fishes of the genus Schizothorax, commonly known as snowtrouts, are a group of species that are difficult to distinguish based on external morphological characters. One of them, Schizothorax plagiostomus Heckel, 1838, is a commercially important freshwater fish with wide distribution along the Himalayan foothills. However, recent observations have indicated drastic declines and change in the stock structure of this species in many areas of its range due to the introduction of exotics, water impoundments (dams), and overfishing. Therefore, this study was intended to verify the variation in stock structure of this species in Kashmir Himalaya by using morphological characters generated by truss network analysis. Materials and methods. A total number of 189 specimens of S. plagiostomus were collected from three different water bodies of Kashmir Himalaya. A truss network was constructed by interconnecting 12 landmarks to form a total of 30 distance variables extracted from digital images of samples using tpsDig2 and PAST software platforms. The transformed truss measurements were subjected to principal component analysis, discriminant function analysis, and univariate analysis of variance for identification of different parameters responsible for population discrimination among these water bodies. Results. The principal component analysis generated nine components explaining 86.4% of total variance in samples. The step-wise discriminant function analysis retained two variables that significantly discriminated the populations. These two variables showed significant variation in head region, body depth, and caudal peduncle region of fish. Using these variables, 98.4% of the original groups were classified into their correct samples and 93.7% of cross-validated groups omitting one procedure were classified into their correct samples. Conclusion. This study has provided basic information about morphometric variation of S. plagiostomus, which could be indicative of the underlying stock structure of the species. A clear phenotypic divergence among S. plagiostomus samples revealed the existence of three differentiated groups viz., the Dal Lake population, the Jhelum River, and the Lidder River populations in Kashmir Himalaya. This study should be considered in fisheries management and commercial exploitation of this species and any stock enhancement program.

Schizothorax plagiostomus, landmark method, shape variation, box-truss, Western Himalaya, India