Species of Rastrelliger in the Java Sea, their taxonomy, morphometry and population dynamics

Rastrelliger is a mackerel genus which inhabits the Indo-Pacific Regions. This genus is characterized by long, numerous and featherlike gill rakers, and anal fin without spines. Two species, Rastrelliger braahysoma and R. kanagurta, are recognized. These are identified by the differences in the ratios of the greatest body depth and the length of intestine to fork length, and the appearance of the cephalic lateral line canal systems. Synonymies, descriptions and morphometric ranges are given. The morphometric characters of the two species exhibit some intraspecific differences due to sexual dimorphism and strong allo-metric growth, R. braahysoma exhibits intraspecific geographical variation in its dorsoventral depth, greatest body depth, and inter-orbital distance; while R. kanagurta exhibits variation only in its dorsoventral depth and head depth. Both species attain their maximum growth increments before they reach sexual maturity. The vital parameters for yield prediction are as follows: the coefficient of growth rate K=0.19, 0.23; the length-weight exponent b=2.88, 3.19; the maximum length L=22.92 cm, 23.89 cm; the natural mortality coefficient M=0.38, 0.37; and the total mortality coefficient Z=0.82, 1.20 for R, braahysoma and R. kanagurta respectively. Rastrelliger fisheries in the Java Sea have not yet reached maximum exploitation which suggests the possibility of increasing production by increasing fishing intensity.Science, Faculty ofZoology, Department ofGraduat