Length-weight relationship of six species of Thryssa with emphasis on the biology ofThryssa mystax from Indian waters

The length-weight relationships (LWRs) of six species of the genus Thryssa (Cuvier, 1829) with special reference to the relative condition factor, sex ratio, and fecundity of Thryssa mystax (Bloch and Schneider, 1801) are reported from Indian water based on two years (2020-2022) study.Six species of Thryssa (N = 2023) were analysed, Thryssa malabarica (Bloch, 1795), Thryssa setirostris (Broussonet, 1782), Thryssa vitrirostris (Gilchrist and Thompson, 1908), which showed positive allometry while, T. mystax, Thryssa dussumieri (Valenciennes, 1848) and Thryssa polybranchialis (Wongratana, 1983) had negative allometry.The r 2 value of these six species varied from 0.8 to 0.99.Fulton condition factor for T. mystax at different months varied between 0.5-0.82indicating poor health condition.The sex ratio of male to female T. mystax was 1:0.98, which was slightly biased towards the male.Overall sex ratios were found to be non-significant.The fecundity of T. mystax ranged from 1219 to 19782 eggs.This study provides basic biological information on the commercially important genus Thryssa from Indian waters as a valuable tool to assist fishery management studies.