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Population Dynamics and the Management of the Indo-pacific King Mackerel Scomberomorus Guttatus from the Upper Bay of Bengal Off Bangladesh Coast

H. Rashid
Department of Fisheries Management, Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

M. G. Mustafa
World Fish Center, Bangladesh and South Asia Office, House 22B, Road 7, Block F, Banani, Dhaka-1213, Bangladesh

S. Dewan
Department of Fisheries Management, Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

Abstract/ Executive Summary:

Growth and mortality parameters, exploitation rates, annual recruitment patterns and length-weight relationships were estimated using FiSAT program from monthly length-frequency and weight samples of Indo-Pacific king mackerel, Scomberomorus guttatus, captured mainly by drift gill nets from the upper Bay of Bengal off Bangladesh coast. The aim was to estimate growth parameters, mortality rates, exploitation rate and recruitment pattern of S. guttatus for sustainable management. The von Bertalanffy growth parameters asymptotic length L∞ (cm) and growth constant K (per year) were 73.5 and 0.6, respectively. The L∞ and Z/K estimates provided by Wetherall plot were 73.3 and 2.3 cm. The annual rate of fishing mortality (F = 0.806) was low compared to the relatively high natural mortality (M = 0.994). The exploitation rate (E = 0.45) shows that the species was not over-exploited in the region. About 77.1% of S. guttatus were recruited during May-July and 23.0% during September-October. The growth performance index (φ′) was 3.5. The total length and body weight relationship was W = 0.0101 L 2.8622 suggesting that the growth rate was negative allometric (b<3). The growth parameters derived in the current study are comparable with previous estimates available for the same species.

Keywords: Population dynamics, Management, Indo-Pacific king mackerel Scomberomorus guttatus

Location: Bangladesh Agricultural University, Mymensingh

Start Date: 00-11-1999

End Date: 00-10-2000

Program Area: Socio-economic and Policy

Commodity: Marine fish

Objectives:

To estimate the population parameters and exploitation of S. guttatus, captured mainly by drift gill nets.
To assess the stock status and sustainable management of the species in the upper Bay of Bengal near Cox’s Bazar coast of Bangladesh.

Methodology:

Study area and sample collection: Fish samples were collected monthly from the commercial catches of fishermen, operating mainly drift gill nets, from November 1999 to October 2000. The sampling site was situated at Cox’s Bazar (21.26°N, 91.59°E), southeast Bangladesh, in the Bay of Bengal. Total length (Snout to caudal fin tip) and weight data were measured to the nearest cm and g, respectively, for a total of 2366 specimens of S. guttatus. Identification of S. guttatus from other species of same genus was done according to Collette and Nauen (1983). Estimation of population parameters: For the estimation of population parameters, all the length-frequency data were pooled month-wise and grouped into length classes by 1 cm intervals. Data analysis were based on Electronic Length Frequency Analysis (ELEFAN I and II) computer program incorporated in FAO-ICLARM Stock Assessment Tool (Gayanilo et al., 1994). Asymptotic length (L∞) and growth constant (K) values were estimated by ELEFAN I (Pauly and David, 1981; Saeger and Gayanilo, 1986). Fish growth is conventionally described in fisheries works by the Von Bertalanffy growth equation and in the notation of Beverton and Holt (1956. Length-weight relationships: Total length in centimetres and total weight (calculated weight) in grams were used for estimating length-weight relationships of S. guttatus. The relationship between length and weight was described by the formula: W = a. Lb, where ‘a’ indicates the intercept and ‘b’ indicates slope of the regression line.

Source of Information: The Bangladesh Veterinarian (2010) 27(2) : 82 – 90

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The von Bertalanffy growth parameters asymptotic length L∞ (cm) and growth constant K (per year) were 73.5 and 0.6, respectively. The L∞ and Z/K estimates provided by Wetherall plot were 73.3 and 2.3 cm. The annual rate of fishing mortality (F = 0.806) was low compared to the relatively high natural mortality (M = 0.994). The exploitation rate (E = 0.45) shows that the species was not over-exploited in the region. About 77.1% of S. guttatus were recruited during May-July and 23.0% during September-October. The growth performance index (φ′) was 3.5. The total length and body weight relationship was W = 0.0101 L 2.8622 suggesting that the growth rate was negative allometric (b<3). The growth parameters derived in the current study are comparable with previous estimates available for the same species.

Knowledge Management: Journal