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

Abstract

The spawning grounds of hilsa were identified in the areas of Hatia (Moulavir char) Sandwip (Kalir char) and Bhola (Dhal char and Monpura) in Bangladesh water. Hilsa breeds year after year at the aforesaid areas specially at the lower stretches of the Meghna river of Bangladesh. during September-October, plenty of fully ripe and oozing males and females hilsa were found and their ratio was 1: 1.6 at the spawning grounds. About 80% females were found in egg releasing condition, some were half spent and some began to lay eggs just after catch without any pressure on the abdomen. A major spawning occurs during the full moon and new moon in the peak spawning period (September-October). The essential population characters viz; growth and mortality parameters were studied using 2503 specimens of hilsa over years; The asymptotic length L =61.5 cm, Curvature parameter K=0.35 Yr^-1, Length at first 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 total mortality was Z=1.93 Yr^-1, survival rate was calculated as 14.51%, natural mortality was M=O.57 Yr^-1, fishing mortality F= 1.36 Yr^-1 and exploitation rate E=O.70. Exploitation rate indicates that the hilsa population were in the over exploitation level at the aforesaid spawning grounds.