Investigations on depredation by the deepsea swimming crab Charybdis smithii, during experimental gillnetting along the south-west coast of India

Depredation by crabs can have a negative impact on marine gillnet fishery. Despite this fact, limited studies are attempted to evaluate depredation. The present study is the first attempt to evaluate the qualitative and quantitative effects of crab depredation on marine gillnet fishery. Experimental gillnetting was conducted onboard F V Sagar Harita from February 2017 to January 2018 along the south-west Indian coast. Depredation by the deepsea swimming crab Charybdis smithii caused intentional discard of Indian mackerel (17.59%), kawakawa (14.77%), shrimp scad (10.74%) and horse mackerel (10.02%). Financial loss due to depredation was high for Indian mackerel (19.99%), followed by shrimp scad (19.17%), kawakawa (14.77%) and horse mackerel (14.16%). A total of ₹2554.30 per operation was lost due to crab depredation. C. smithii showed a preference towards scombrids (Indian mackerel and kawakawa) over carangids (shrimp scad and horse mackerel) due to the inherent flavour and texture of scombrids. Incidence of depredation were found exclusively during June to September (monsoon season). Keywords: Crab, Depredation, Economic loss, Fishery, Marine gillnet