Life history and stock status of the critically endangered Smoothback Guitarfish in the Northwestern Bay of Bengal

Dash, Swatipriyanka Sen and Dash, Gyanaranjan and Kizhakudan, Shoba Joe and Thomas, Sujitha and Zacharia, P U and Ghosh, Shubhadeep and Pradhan, Rajesh Kumar and Das, Madhumita and Dash, Biswajit (2025) Life history and stock status of the critically endangered Smoothback Guitarfish in the Northwestern Bay of Bengal. Journal of Coastal Conservation, 29 (19). pp. 1-25. ISSN 1874-7841

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Abstract

The present study was envisaged to generate prime information on the life history, biological characteristics, and stock status of the critically endangered smoothback guitarfish (Rhinobatos lionotus) that forms a fishery along the northwestern Bay of Bengal using length-based methods. The stock was predominantly represented by the females (Male: Female = 1:1.71). The species exhibited sexual dimorphism, where females grew bigger (Lmax = 79.0 cm) and matured at a larger size (LM50 = 43.71 cm) than males (Lmax = 61.0 cm, LM50 = 34.93 cm). Growth was allometric, where females were heavier compared to males. The life history characteristics, i.e., L∞, K, t0, M, and LC50 were 84.31 cm, 0.43 y−1, − 0.45 yr, 0.88 y−1, and 35.31 cm, respectively. The LBB analysis showed that the current biomass (B/B0 = 0.39) exceeded the level needed for maximum sustainable yield (BMSY/B0 = 0.35). The Lmean and LC50 were lower than the Lopt and LCopt, indicating growth overfishing. A sensitivity analysis revealed that the outputs of the Thompson and Bell model are highly influenced by uncertainties associated with L∞, followed by LC50, M, and K. The Thompson and Bell model revealed that the Fcurrent has depleted the SSB to a 35% level and therefore should be reduced by 18–19% to circumvent growth-overfishing (F0.1) and recruitment-overfishing (F0.4), respectively. Considering the multi-species nature of the fisheries in the region, focusing on spatial and temporal closures and strict implementation of by-catch reduction devices in the trawls are advised for the conservation and sustainable management of the species.

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