Population dynamics of an endemic and threatened Yellow Catfish Horabagrus brachysoma (Günther) from Periyar River, southern Western Ghats, India

Abstract

Based on the annual length frequency data collected from three major fish landing centres along the River Periyar, draining the southern Western Ghats, the von Bertalanffy growth function (VBGF) estimates of Horobagrus brachysoma were worked out as asymptotic length (La) = 422mm total length, growth co-efficient (K) = 0.55 yr-1 and growth performance index (ø) = 4.99. The total mortality rate (Z) was estimated at 5.64 yr-1, natural mortality rate (M) at 1.04 yr-1, fishing mortality (F) at 4.60 yr-1, and exploitation rate (E) at 0.82 yr-1. Yield per recruit (expected lifetime yield per fish recruited in the stock at a specific age) analysis showed an excessive fishing effort. Using the analysis of probability of capture of each length class, the length at first capture (Lc) of H. brachysoma was estimated to be 110mm. An indication of both growth and recruitment fishing is provided by the dominance of year 1 class in the exploited population and the capture of immature individuals below first maturity. Management of H. brachysoma fishing should include setting of a minimum mesh size limit of 160–180 mm for gill nets as well as a closed season starting from the month of May till August aimed at protecting the spawning stock. This study on H. brachysoma, an endemic and threatened catfish of peninsular India, provides hard evidence that species targeted by artisanal fishermen, in small-scale tropical riverine fisheries, are vulnerable to overexploitation.