Observations on some aspects of biology and population dynamics of the Scad Decapterus Russelli (Ruppell)(Carangidae) in the trawling grounds off Kakinada

Decapterus russelU (Ruppell)* is abundaat in relatively deeper waters and forms 80-90 % of carangid \t \ncatches by trawlers. The von Bertalanffy growth parameters are estimated as Loe =• 232.3 mm, K =-\t \n1.08 per year and to =» —0.08 year. The length-weight relationship can be described by the equation \t \nlog W (g) = —5.93433+3.40764 log L (mm). The length and age at first maturity are estimated as \t \n150mmand0.88 year respectively. This species spawns offKakinada during December-August. The \t \ndifferent mortality rates are estimated as Z = 6.65, M «= 1.90 and F = 4.75 and the length and age \t \nat first capture as 158 mm and 0.98 year respectively. The yield per recruit analysis shows that: with \t \nt« above 0.6 the Yw/R increases with increased F without reaching maximum. The highest Yw/R, \t \nhowever, is obtained with tc at 0.6 only.