Fishery of elasmobranchs with some observations on the biology and stock assessment of Carcharhinus limbatus (P. Muller & Henle, 1839) exploited along Malabar coast

Abstract

Elasmobranchs are caught in trawls, gillnets and longlines along the Malabar region of Kerala and they are landed almost round the year, accounting less than 1% of the total catch. The catch of elasmobranchs during the period 2001 -2011 has shown a declining trend, but towards the end of this period the fishery has improved marginally. The contribution of trawl, gillnets, longlines and other gears were 43.1%, 31.3%, 21.1%, and 4.5 % respectively. The contribution of sharks, rays and skates were 70.8%, 24.2% and 5.0% respectively. Twenty four species of sharks, 8 species of rays and 2 species of skates were recorded in the catch. Length -weight relationship was estimated for Carcharhinus limbatus and the regression equation for both the sexes was W = 0.00001486L 2.80214 (r=0.9661). The overall F: M ratio was estimated as 1:1.59; females predominated the catches in almost all months. The growth of this species is described by the equation Lt= 302 (1 -e -(0.45)[t -( -1.2)]). The species grows fast during the early stages of its life. The annual average exploitation ratio (E) is estimated as 0.74 which is higher than the optimum exploitation rate estimated. The present study showed that C. limbatus is heavily targeted, hence this species is at risk of being overexploited and is in need of immediate management.