Seriolina nigrofasciata (Ruppel, 1829), its fishery and biological aspects off south-west coast of India

Abstract

A comprehensive study on fishery, length-weight relationship, trophodynamics and reproductive aspects of the blackbanded trevally Seriolina nigrofasciata (Ruppel, 1829), collected during January 2013 to December 2017 from fishing vessels operating along eastern Arabian Sea off south-west coast of India was conducted. Among the maritime states of the country, Karnataka was the major contributor (53.9%) followed by Kerala (24.1%), Maharashtra (16%) and Tamil Nadu (4.3%). In Karnataka, 99.5% of the blackbanded trevally catch was exploited by trawl net and rest by outboard gillnets (0.5%). The total length ranged from 16.3 to 57.5 cm with fishes in the size range of 24 to 36 cm forming 80.8% of the catch. The length-weight relationship estimated showed a negative allometric growth for both sexes with b values of 2.595 for females and 2.504 for males. The estimated ‘a’ values for females and males were 0.00013 and 0.00021 respectively. In all, fifteen prey items under three major groups (teleosts, cephalopods and crustaceans) comprised the diet, with teleosts (73.23%) being the predominant food item followed by cephalopods (26.53%) and crustaceans (0.24%) in terms of index of relative importance (IRI). Overall sex ratio (male: female) of 1:1.15 indicated a slight dominance of females over males. The length at first maturity was estimated at 25.0 cm for male and 27.0 cm for female. The availability of mature and spent specimens all through the year implied that the species has prolonged spawning period with a peak during the summer season (March-May) and a minor secondary peak in post-monsoon season (October to December).