Biological studies on Thryssa mystax along the Coast of Maharashtra

The Moustached thryssa Thryssa mystax is one of the important components of by-catch of trawl as well as mini purse seine landings at Ratnagiri. Investigations were carried out on Thryssa mystax with respect to length-weight relationship, morphometrics, feeding and reproductive biology. The length-weight relationship indicated the isometric growth in T. mystax. The qualitative and quantitative analysis of food revealed T. mystax to be carnivore type feeder. Highest GSI value for females were observed during January, December, February and October. Sex ratio showed equal proportion of males and females in most of the months. Studies on reproductive biology showed that T. mystax has got a prolonged spawning season. Fecundity ranged from 3225 to 24225 eggs. Length at sexual maturity has been estimated to be 146 mm. The asymptotic length (L ), growth coefficient (K) and t0 were estimated at 224 mm, 1.0 per year and -0.0036 year respectively.The mortality parameters Z, M and F were estimated at 5.58, 1.03 and 4.55 respectively using FiSAT programme. Length at first capture for T. mystax was found to be 147.5 mm. The present exploitation ratio for the species is 0.81.