Predatory association of Aeolidiopsis sp. on Palythoa mutuki (Haddon and Shackleton, 1891) along Gujarat coast, India

Abstract

Fishery, population characteristics and stock estimates of grouper with special reference to Epinephelus malabaricus from Tuticorin were carried out during 2015-2017. Among the groupers, E. malabaricus was the dominant resource contributing 42.2%, with an annual average production of 420t along this region. The asymptotic length (L∞), growth coefficient (K) and arbitrary origin of growth (t0) were estimated at 99.75 cm, 0.53 y-1 and 0.18 respectively. The mortality parameters, the instantaneous total mortality rate (Z), fishing mortality (F) and natural mortality rates (M) were estimated at 1.14 y-1, 0.62 y-1 and 0.52 y-1 respectively. The recruitment season was during April to August. The length structured virtual population (VPA) analysis revealed a heavy fishing pressure on length group between 40 and 55cm and there is no sign of recruitment over-fishing in this region. The estimated maximum sustainable yield (MSY) and annual catch were 384 t and 420 t respectively. E. malabaricus was optimally exploited as the exploitation ratio (E) was 0.54 but the study infers that further increase in effort may have a detrimental effect on the stock of this species. The results of this study will serve as baseline information for formulating future management measures for the resource along the coast.