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Some Population Dynamics Aspect of Catla Catla (hamilton) in the Sylhet Basin, Bangladesh

A. K. Yousuf Haroon
Bangladesh Fisheries Research Institute, Riverine Station Chandpur-3602, Bangladesh

Abstract/ Executive Summary:

Population parameters of Catla catla (Hamilton) were estimated using FiSAT software with length-frequency data collected from different areas of Sylhet basin, north-eastern part of Bangladesh. The von Bertalanffy growth parameters L∞and K for the species were 93.95 cm and 0.53/year respectively. The annual rate of natural (M) and fishing mortality (F) were found to be 0.84 and 0.85, respectively. The mean length at first capture (Lc) was estimated as 11.29 cm. The rate of exploitation (E) was estimated as 0.503. Recruitment of this species into the fishery takes place during May to July. Peak recruitment occurred during the month of May. Emax was found to be 0.41. Their total length-total weight relationship was found to be W = 0.012TL3.04.

Keywords: Population dynamics, Catla catla, Bangladesh

Location: Different landing sites around Sylhet district

Start Date: 00-01-1998

End Date: 00-12-1998

Program Area: Resource Development and Management

Commodity: Carp fish

Objectives:

To estimate the key parameters of stock assessment and its population dynamics like asymptotic length (Lc.), growth coefficient (K), total mortality (Z), natural mortality (M), fishing mortality (F), exploitation rate (E), recruitment pattern, relative yield per recruit, relative biomass per recruit, and virtual population analysis (VPA), etc.

Methodology:

Length-frequency data of C. catla were collected fortnightly from the commercial catches at different landing sites around Sylhet district from January 1998 to December 1998. Samples of C. catla were mainly caught by purse sine net. Random samples of 823 specimens were collected. Total length was measured in cm by a meter scale (1 ±mm) of sizes ranging from 21.0 to 93.0 cm. The weight was measured in g by a Salter spring balance from 823 random samples ranging in weight from 111.50 -4, 200 g with corresponding length. The data were then pooled month-wise from different landing sites and subsequently grouped in to classes of three cm intervals. The data were analyzed using the FiSAT (FAO-ICLARM Stock Assessment Tools) as explained in detail by Gayanilo Jr. et al. (1995) in the computer software package. Asymptotic length (L∞) and growth coefficient (K) of the von Bertalanffy equation for growth in length were estimated by means of ELEFAN-I (Pauly and David, 1981; Saeger and Gayanilo, 1986). Additional estimate of L.. and Z/K value were obtained by plotting "mean length" minus "limit of the first length class used in computing a value" of on "mean length" (Wetherall, 1986 as modified by Pauly, 1 986).

Fishing mortality (F) was obtained by subtracting M from Z and exploitation rate (E) was obtained from F/Z [E = F/Z = F/ (F+ M)] (Gulland, 1971). Recruitment patterns was obtained by backward projection on the length axis of a set of length-frequency data as described in the FiSAT routine. Relative yield per recruit (Y/R) and biomass per recruit (R/8) values as a function of E were determined from the estimated growth parameters and probability of capture by length (Pauly and Soriano, 1986). The calculations were carried out using the complete FiSAT software package. An estimated length structured VPA of C. catla was carried out. L∞= 93.95, K = 0.53/Yr, M = 0.84, F = 0.85, a =0.012 and b =-3.04 were used as input to a VPA. The t_o value was taken as zero.

Source of Information: Pakistan Journal of Biological Sciences 2 (4): 1188-1192,1999

Article Link (Online Journal): http://www.oalib.com/paper/2126375#.Vu91wHqeXIU

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The C. catla is a moderate sized fish having perfect growth rate. Recruitment pattern of the fish revealed that it recruits in to the fishery almost round the year and peak recruitment occurs in May. Its fishing pressure (F=0.85) is high and need to be reduced for getting more sustained production. Some fishing restriction should be imposed to get higher fish yield from that basin.

Knowledge Management: Journal