Population Dynamics of Hilsa Shad (Tenualosa ilisha, Clupeidae) in Bangladesh Waters

Abstract

The hilsa shad (Tenualosa ilisha, Clupeidae) is an important migratory species in the Indo-Pak subcontinent and the Persian Gulf region, especially in Bangladesh and India. The population dynamics of the species collected from river and marine environments were studied using length-based methods. The estimated von Bertalanffy growth parameters, L and K were 588 mm and 0.82 yr-1 for river and 610 mm and 0.80 yr-1, for marine populations, respectively. Growth performance indices (Ø′) were 3.45 for the river and 3.47 for the marine populations. The estimated Z, M and F values were 2.38, 1.00 and 1.38 and 2.30, 0.98 and 1.32 yr-1, for river and marine environments, respectively. Optimum length of hilsa at first capture (Lc=L50) was 329 mm TL, and the optimum mesh size for gillnets was 80 mm. The recruitment patterns for both river and marine populations were more or less continuous, but with two major pulses. Present exploitation levels for the hilsa fishery in the river and marine habitats were 0.58 and 0.57, respectively. The hilsa populations in the rivers exhibit tendencies towards overexploitation.