Fishery and stock assessment of the three-spot swimming crab Portunus sanguinolentus (Herbst, 1783) off Veraval, Gujarat

The fishery and stock characteristics of Portunus sanguinolentus was studied during 2009-2010 from Veraval waters. The average annual landing was 322 t, which constituted about 40% of the total edible crab landings at Veraval. Length-weight relationship showed isometric growth. L∞, K and t0 estimated were 178.7 mm, 1.2 yr-1 and -0.08 yr, respectively. Total mortality rate (Z), fishing mortality rate (F) and natural mortality rate (M) were estimated to be 4.69 yr-1, 2.85 yr-1 and 1.84 yr-1, respectively. The estimated length at capture (L50) and length at maturity (LM50) were 101.33 mm and 96.89 mm, respectively, indicating that the crabs enter into peak exploitation phase after attaining sexual maturity. The species is a continuous spawner and shows peak recruitment during May and August. The current exploitation rate (Ecur) was found to be 0.61 which is equal to E0.1 estimated by Beverton and Holt yield per recruit analysis. Thompson and Bell bio-economic analysis showed that species can be exploited at the present level to maintain the revenue from the fishery at economic level