Species composition and spatio-temporal variation of bycatch from mid-water trawlers operating in the Arabian Sea along north-west coast of India

The mid-water multiday trawl fishery along the north-west coast of India generally targets adult largehead hairtail, Trichiurus lepturus. Bycatch landed by the commercial mid-water multiday trawlers operated from Veraval harbor during August 2017–December 2019 was investigated by analyzing catch composition with respect to its spatial and temporal patterns. A total of 834 bycatch sample observations from mid-water trawl fishery were examined. Bycatch comprises of 123 species and account for 53.36% of the total catch. Highest composition in bycatch comprises of teleosts (62.09%), cephalopods (35.88%), crustaceans (1.47%) and elasmobranchs (0.56%) respectively. Uroteuthis duvaucelii, Sepia elliptica, Nemipterus japonicus, Otolithes cuvieri, S. pharaonis, Priacanthus hamrur, Sepiella inermis and Saurida tumbil were the dominant species with high annual average catches; and together contributed 50.30% of total bycatch. Discards formed 6.32% of total catch and consisted of 62 species belonging to 29 families. The most common discards were juveniles of S. tumbil, N. japonicus, Platycephalus indicus, O. cuvieri, Johnius glaucus and T. lepturus. CPUE of bycatch differed significantly between the seasons with the lowest being in summer and highest in post-monsoon period. Minimum bycatch rates were observed in the offshore waters than inshore waters. Endangered, Threatened and Protected (ETP) species listed in CITES as well as IUCN were also observed. The present study revealed that quantities of bycatch landed off northwest coast of India in the Arabian Sea were relatively higher than that landed by mid-water trawlers operating in other parts of the world. Hence the mid-water trawl fishery operating in north-west coast of India and targeting largehead hairtail needs to be closely monitored to mitigate and reduce the quantity of bycatch landed by them.