Distribution pattern of threadfin breams along North Tamil Nadu and south Andhra coasts

Abstract

Catch rate and biomass of threadfin breams were estimated for north Tamil Nadu - south Andhra coast based on exploratory trawling conducted by M. V. Matsyajeevan and R. V. Cadalmin III. In the entire region explored by M. V. Matsyajeevan, the catch rate was 2.2 kg/hr and the biomass was 0.001 t/km'. In the region explored by R. V. Cadalmin III, the catch rate was 0.7 kg/hr and the biomass was 0.002 t/kml Threadfin breams occurred upto a depth of 220 m and the highest catch rate of 71.7 kg/hr was obtained in 101-110 m depth. Of the 5 species that constituted the threadfin bream catch, Nemipterus japonicus formed 55.1%. Biological studies revealed a positive correlation between depth and length of N. japonicus. About 78% of N. japonicus in 6-10 m depth was immature and the percentage of immature individuals decreased with increasing depth. With increasing depth, the percentage of female with ripe ovary increased. N. japonicus in shallow waters were observed to feed mostly on prawn and those in deeper waters mostly on fish and crab.