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Population Dynamics of Male and Female Hilsa, Tenualosa Ilisha of Bangladesh

G.C. Haldar
Aquatic Resources Development, Management and Conservation Studies of the Fourth Fisheries Project, Sena Kalyan Bhaban (7th Floor), 195 Motijheel C/A, Dhaka-1000, Bangladesh.

S.M. Nurul Amin
Assistant Professor
Institute of Marine Sciences, University of Chittagong, Chittagong-4331, Bangladesh.

Abstract/ Executive Summary:

Population dynamics of male and female T. ilisha in Bangladesh water were studied using the length frequency based analysis of FiSAT software to evaluate the growth parameters, mortality rates, exploitation levels, Maximum Sustainable Yield (MSY) and the corresponding fishing mortality. The study reveals that the fishes are harvested at a level than the optimum fishing mortality. The fishing pressure should be reduced to about 1.08/year, i.e. 9% reduction from the present level of mortality per year for obtaining MSY, 235,130 tones.

Keywords: Population dynamics, Tenualosa ilisha, Bangladesh

Location: Chandpur, Barisal, Bhola and Kuakata

Start Date: 00-01-2002

End Date: 00-12-2002

Program Area: Resource Development and Management

Commodity: Hilsa

Objectives:

To assess the stocks in the Bangladesh waters and make appropriate management recommendations.

Methodology:

Length-based stock assessment method was used for the present study. For this purpose, length-frequency data of male and female T. ilisha were collected monthly from the commercial catches at different landing sites (Chandpur, Barisal, Bhola and Kuakata) between January to December 2002. To avoid gill net selectivity different landing sides were selected as different mesh of gill nets are used to catch different size group of fishes on their availability. Total length and weight of the specimens were measured in em and g by a meter scale and a spring balance, respectively. The data from different landing sites were then pooled month-wise and subsequently grouped into length classes by 2 cm interval. Then the data were analyzed using the FiSAT (FAO-ICLARM Stock Assessment Tools) software. Asymptotic length (L.) and growth coefficient (K) of the von Bertalanffy's growth equation were estimated by means of ELEF AN-I_{[19, 20].}

Source of Information: Pakistan Journal of Biological Sciences 8 (2): 307-313, 2005; ISSN 1028-8880

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The problem of over exploitation of this species, resulting in gradual decline of catches in the inland sector, is mainly because of heavy exploitation of its juveniles. Measures need to be taken to minimize juvenile Hilsa catching as far as possible. Banning of nets, specially operated for catching juveniles and through creating mass awareness amongst the fishers and providing alternative source of employment to them during the period of juvenile fishing (December to April) would greatly help to minimize juvenile Hilsa catching. This would substantially decrease the present level of over exploitation and also help to increase the fishable number of adults during subsequent years. Further increase of existing fishing level/exploitation will most likely results in a reduction in the yield-per-recruit and thereby hampering the MSY.

Knowledge Management: Journal