Fishery and population dynamics of the sand lobster Thenus unimaculatus (Burton & Davie, 2007) landed by trawlers at Sakthikulangara Fishing Harbour in the south-west coast of India

Abstract

The average annual landing of Thenus unimaculatus from trawlers at Sakthikulangara during 2005-2010 was 19 t forming 0.73% of the total marine fish landings. Males slightly outnumbered females in the catch (1:0.9) and peak fishery was observed from November to February. Total length varied between 61-230 mm in males and 46-250 mm in females. Length at recruitment (Lr) was 48 mm. Carapace length-weight relationship was not significantly different (p>0.05) between the sexes, The parameters of the length-weight relationship were estimated as: a = 0.00237, b = 2.64, r2 = 0.95 for males and a = 0.00156, b = 2.758, r2 = 0.96 for females. Growth parameters estimated by von Bertalanffy’s growth equation were: L∞ = 240 mm, K (monthly) = 0.042 for males and L∞ = 260 mm, K (monthly) = 0.05 for females. Exploitation rate was found to be higher in males (0.86) than in females (0.78). The length at 50% capture (Lc50) was 147 mm for males and 153 mm for females which corresponded to an age (tc) of 1.9 and 1.6 years, respectively. Absolute fecundity varied from 14750 to 33250 mature eggs.