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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.

Longtail tuna Thunnus tonggol (Bleeker, 1851) is the major tuna resource in the neritic realms of the northern Arabian Sea and forms considerable fishery in the coastal nations in the region. Gujarat, on the north-west coast is the major province landing longtail tuna in India. The paper attempts to add to the hitherto sparse knowledge base on biology of the longtail tuna fished along the north-west coast of India, through a study spanning from 2011 to 2015. Reproductive biology, spawning, food and feeding dynamisms of the species were investigated. Sex ratio of the species was estimated as 1:2.1 and depicted an increase in male preponderance as the size increased. The fish attains maturity at 607 mm and it spawns during summer months starting from May. The fish is typically a non-selective feeder and over 22 taxa comprising of fishes, cephalopods and crustaceans formed the diet at varying rates over the year. Variation in feeding intensity at different reproductive stages is discussed besides the constraint posed by the large presence of unidentifiable, partially digested gut content.