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Location-wise Seasonal Catch Assessment of Shark and Trawl Fisheries in Bangladesh

Mr. Ehsanul Karim
Scientific Officer
Marine Fisheries & Technology Station, Bangladesh Fisheries Research Institute, Cox's Bazar

Md. Shahzad Kuli Khan
Scientific Officer
Marine Fisheries & Technology Station, Bangladesh Fisheries Research Institute, Cox's Bazar

Abstract/ Executive Summary:

A total of 26 elasmobranch species were identified from the landing data of artisanal fisheries, among them Carchariniformes was 14-18%, Rhinobatiformes was 4-7% and Mylobatiformes, Torpediniformes was 75-80%. Total catch percentage of true sharks varied from 14% to 18%, skates from 4% to 8% and rays from 73% to 80%. Among 26 identified species, length-weight regressions were presented for 24 species. The parameter b ranged from 2.71 for dog shark (Scoliodon laticaudus) to 3.50 for sharp nose guitar fish (Rhyncobatus granulatus) with a mean value of 3.138+0.02 and the median value ranged between 3.06 and 3.34. The coefficient of determination (r2) ranged from 0.890 for black spotted electric ray (Narcine teimlei) to 0.990 for dwarf sting ray (Himuntura walga). Sixteen species had r2 values between 0.95 and 0.98 while seven r2 values were less than 0.95. All regressions were highly significant (p<0.001). Again ten species showed positive allometric growth, five showed negative allometric growth and nine showed isometric growths. It indicates different growth status of different species in different months and also indicates the proper growth of maximum species.

Keywords: Catch assessment, Shark and trawl,

Location: Cox's Bazar

Start Date: July 2010

End Date: June2013

Program Area: Variety and Species

Commodity: Aquatic animal

Objectives:

Monthly location-wise catch assessment of shark fisheries in Bangladesh; assessment of abundance, species diversity and population study of sharks, skates and rays; time series catch assessment for each of the fishing grounds for each type of trawlers; improvement of the data recording of the trawl catch by motivation and hands-on training; formulation of the future data recording, resources assessment and management strategies.

Methodology:

The study was conducted in the important shark landing sites throughout the coastal belt of Bangladesh including Cox’s Bazar, Chittagong, Kuakata and Dubla Island areas. The catch of fish, in numbers or in weight, taken by a defined unit of fishing effort is catch per unit effort (CPUE). The landing sites were visited fortnightly in all the seasons considering lunar cycle and all species were recorded together with their respective catch in weight and size in length. Samples were identified and taxonomical study was also conducted with greater efforts. Then the collected information was assessed to evaluate the lunar and seasonal impact. Finally, the annual catch for each of the species were assessed for each of the landing sites.

Source of Information: Annual Research Program 2012-13. BFRI, Mymensingh.

Article Link (Online Journal):

Funding Source:

1. Government

Budget: Twenty lakh ninety thousand

Total Budget (Tk.) : Twenty lakh ninety thousand

Achievement/Findings:

A total of 26 species of sharks, skates and rays were identified, of which 11 species were sharks, 02 species were skates and the remaining 13 species were rays. The 26 identified elasmobranch species belong to 10 families under 4 orders. Carchariniformes contributed14-18%, Rhinobatiformes contributed 4-7% and Mylobatiformes, Torpediniformes contributed about 75-80% of the total catch percentage. The parameters of length-weight relationships, particularly a, may vary daily, seasonally, and/or between habitats, unlike the parameters b, which does not vary significantly throughout the year (Bagenal and Tesch 1978). Although sampling was not conducted seasonally in the present study, more fish were sampled during spring season. However, the estimated parameters in this study should be considered composites across the whole year rather than representing a particular season as the analysis is based on all data collected during the year. This study seems to be the first information on length-weight relationships for 24 elasmobranch species of the Bay of Bengal, Bangladesh.

Knowledge Management: Report/Proceedings