Acetes as a Keystone Species in the Fishery and Trophic Ecosystem Along Northeastern Arabian Sea

Abstract

Diet composition of nine commercially exploited fishery resources which contributes 55–60% of the total fish landings in the northwest coast of India were analyzed in this study. Gut content analysis of the selected fish groups has shown significant variations in the prey composition and predator preference on a prey item. The diet matrix revealed Acetes sp. (32.74%) as a key and common shared prey item, followed by mesopelagic fishes (30.51%), other shrimps (11.00%), digested material (7.42%), crabs (4.03%) and cephalopods (2.77%), etc. In this study, Acetes sp was considered as a proxy for the non-penaeid prawns due to its significant contribution (92%) to the total non-penaeid landings. Targeted exploitation of Acetes sp. has intensified recently (from 0.44 lakh t in 2004 to 1.40 lakh t in 2018) with an average annual growth rate of 11.2% due to the demand from fish meal plants. By considering its ecological and fishery importance, Acetes sp. should be considered as keystone species in the ecosystem. The Schaefer surplus production model was used to calculate the Biological Reference Points (BRPs) and model parameters MSY, FMSY, r, EMSY, and K. The model fit was fair (R2 = 0.630) and significantly positive correlation was observed between CPUEobserved and CPUEmodel. The estimated optimum exploitation limits (p < 0.05) for the fishery were Maximum Sustainable Yield (MSY) as 1.20 lakh t and fishing effort required to harvest MSY (EMSY) as 51.30 lakh fishing hours. However, the recent exploitation yield and fishing effort are beyond the optimum exploitation limits. Further increase in exploitation of the resources may hamper the sustainability of the stocks and may lead to detrimental impact on the trophic interactions of the fishery resources. Technical interventions are needed in the field of post-harvest and value addition for attaining fair economic returns from the harvest which at present forms a low-value high-volume fishery. Sustainable exploitation and management measures need to be introduced and implemented for the Acetes sp. in order to sustain the stocks and to maintain the integrity of the fishery ecosystem.