Fishery, growth, and mortality of threatened Asian Sunfish, Horabagrus brachysoma (Gu¨nther 1864) in five rivers of Western Ghats hotspot, India

Abstract

Community-based data monitoring (CBM) systems in small-scale inland fisheries provide insights into the catch patterns of diverse fish species over extended periods. In this study, a participatory approach was employed to ascertain the fishery, demography, and exploitation patterns of Asian Sun fish catfish, Horabagrus brachysoma, across five river systems within the Western Ghats biodiversity hotspot of India. H. brachysoma (Gu¨nther 1864) is a commercially important food fish that is heavily exploited from rivers of Kerala state, India and is listed as ‘Vulnerable’ on the IUCN red list. The monthly catches of this species from various landing centres across the Western Ghats' rivers varied between 303 kg to 631 kg annually. These fish typically measured between 11.00 and 41.10 cm in Total Length (TL) and weighed between 26.00 g to 470.00 g in Total Weight (TW). Using the annual length frequency data provided by local fishers, the estimated growth parameters of H. brachysoma are estimated as; asymptotic length ((L_∞) between 316.05 and 421.05 mm, growth coefficient (K) between 0.58 and 1.10 yr^− 1 from different rivers. The total mortality (Z) was calculated to range between1.25 yr^− 1 and 2.91 yr^− 1 while the fishing mortality (F) was estimated between 0.62 yr^− 1 and 2.09 yr^− 1. The fishing mortality rate of H. brachysoma in the Periyar River, at 2.09 yr⁻¹, appears to be one of the highest recorded for this species. This rate suggests a potentially indiscriminate level of exploitation by local fishers in this area. The calculated exploitation rate (E) ranging from 0.49 to 0.72 yr⁻¹ exceeds the anticipated optimum exploitation levels (0.5). This suggests that the populations of H. brachysoma in the river systems of the Western Ghats are experiencing overexploitation. This approach includes measures such as implementing fishing closures during spawning seasons, imposing restrictions on mesh sizes, non-fishing zones and establishing quota systems for local fishermen. These strategies collectively aim to promote sustainable practices and preserve the population of H. brachysoma.