Analytical approach to the spawning ground of hilsa Tenualosa ilisha (Ham.) in Bangladesh water

The spawning grounds of hilsa were identified in the areas of Hatia (Moulav ir char) Sandwip (Kalir char) and Bhola (Dhal char and Monpura) in Banglade sh water. Hilsa breeds year after year at the aforesaid areas specially at the lower stretches of the Meghna river of Bangladesh. During September-Oct ober, plenty of fully ripe and oozing males and females hilsa were found an d their ratio was 1:1.6 at the spawning grounds. About 80% females were fou nd in egg releasing condition, some were half spent and some began to lay e ggs just after catch without any pressure on the abdomen. A major spawning occurs during the full moan and new moon in the peak spawning period (Septe mber-October). The essential population characters viz; growth and mortalit y parameters were studied using 2503 specimens of hilsa over years. The asy mptotic length L = 61.5 cm, Curvature parameter K=0.35 Yr(-1), Length at fi rst capture Lc=28 cm, age at first capture, Tc=1.7 Yr, asymptotic weight W =2981 g and average condition factor was Kn=0.0145 g (per cubic cm). The to tal mortality was Z=1.93 Yr(-1), survival rate was calculated as 14.51%, na tural mortality was M=0.57 Yr(-1), fishing mortality F=1.36 Yr(-1) and expl oitation rate E=0.70. Exploitation rate indicates that the hilsa population were in the over exploitation level at the aforesaid spawning grounds.