Demographics of threatened Malabar mahseer, Tor malabaricus in a small-scale fisheries of Western Ghats hot spot in India

The Western Ghats region of India, a segment of the Western Ghats-Sril Lanka biodiversity hotspot, is renowned for its abundant fish diversity and endemism. Tor malabaricus, commonly known as Malabar mahseer, is a large growing, threatened cyprinid having restricted distribution in fast-flowing streams of the southern region of the Western Ghats. The absence of demographic and exploitation data regarding threatened freshwater fish in this region is a barrier to sustainably managing and conserving the species. This study focused on assessing the growth patterns, mortality rates, and the extent of exploitation faced by the Malabar mahseer from a small-scale fishery in Chalakudy River, WG, India, with the help of tribal fishers. The growth parameters for T. malabaricus were estimated as asymptotic length (L?) = 657.3 mm and growth rate (K) = 0.19 year^-1. The study revealed a potential longevity (t_max) of 15.78 years and a length at first capture (L_c) of 201.54 mm. The fishing mortality (F= 0.26 year^-1) of T. malabaricus was observed to exceed the natural mortality (M = 0.23 year^-1), indicating an unsustainable level of exploitation for the species within the study area. The current exploitation rate (E = 0.53) exceeding the E₅₀ threshold indicates a potentially uncertain future for the stock under the current level of exploitation. Employing an integrative conservation approach such as fishing closures during spawning seasons, mesh size regulations, and establishing quota systems for local tribes and fishermen for fishing can effectively promote sustainable harvesting practices for the species within the Western Ghats hotspot.