Stock Assessment of Exploited Populations of Shovel-Nosed Lobster Thenus unimaculatus (Scyllaridae, Burton and Davie, 2007) Along the Indian Coast Using Length-Based Approaches

Abstract

This manuscript presents a detailed investigation into the stock status of Thenus unimaculatus, a commercially valuable lobster species in India. In data-poor fisheries, Bayesian approach offers robust guidance for sustainable sand lobster population management. Utilizing a non-conventional Bayesian approach, the study employed length-based Bayesian biomass (LBB) and length-based Spawning Potential Ratio (LB-SPR) methods to analyze length frequency data collected between 2011 and 2019. In our study using LBB, the current exploited biomass (B/B0 = 0.35) was found to be lower than the biomass capable of producing maximum sustainable yield (B/B_MSY=0.93). Spawning potential ratio was calculated between 28 and 37% using LB-SPR model. The fishing mortality (F/M = 1.5) was slightly above optimal, resulting in low sand lobster biomass due to moderate over-exploitation. This suggests a need for rational slipper lobster catch control. However, with an L_m50/L_c50 ratio close to 1.0, indicates an absence of targeted juvenile fishery, it suggest the need to reduce fishing pressure. . However, implementing measures is challenging because the species forms a by-catch in trawl fisheries.