Evidence of multiple stocks of catfish, Rita rita (Hamilton), from the Ganges Basin on the basis of an integrated analysis of truss morphometrics, otolith microchemistry, and otolith shape

Context. Management of Rita rita (Hamilton) in India is hampered by a lack of understanding of possible stock structure. Aim. To investigate possible spatial stock structure of Rita rita in the Ganges Basin. Methods. Independent analyses of landmark-based truss morphometry, otolith elemental analysis and otolith shape were conducted to investigate the stock structure of the catfish (Rita rita) from the Ganga River and its tributaries Yamuna and Ramganga. Key results. Each of the stock-delineation approaches, namely, truss morphometrics, otolith elemental composition and otolith shape, showed significant differences among the fish groups from three sampling locations (P = 0.003). Despite these differences, reclassification analyses showed variable (although all greater than random) reclassification rates (truss morphometry: 78%, otoliths elemental data: 98%, otolith shape: 50%). Conclusions. An integrated view of the three analyses suggested spatial structuring and that there may be multiple stocks of Rita rita in the Ganges Basin. Implications. Future investigations should consider possible variations in demographic parameters that may affect fisheries management. The multiple-lines-of-evidence approach taken in this study can serve as a template for studies of other species in any region.