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Study on Selectivity of Fishing Gears and Its Effects on Fish Biodiversity of Chalan Beel in Natore District

Shakila Jahan
Upazila Fisheries Officer
Department of Fisheries, Dhaka, Bangladesh

Md. Abu Zafar
Department of Aquaculture, Hajee Mohammad Danesh Science and Technology University, Dinajpur-5200, Bangladesh.

Md. Idris Miah
Department of Fisheries Management, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh.

Md. Jasim Uddin
Department of Fisheries Management, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh.

Shankar Majumder
Department of Agricultural Statistics, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh.

Abstract/ Executive Summary:

An investigation was conducted to know the present status of fishing gears used and their species selectivity, length selectivity as well as their effects on fish biodiversity of the Chalan beel in Natore district for a period of 6 months from July to December, 2012. Interview schedules were used in collecting data from different upazilas of Chalan beel. A total 27 types of fishing gears were found including 11 types of nets, 5 types of traps, 4 types of wounding gears, 5 types of hooks and lines and 2 types of Fish Attracting Devices. A total of 53 fish species were identified in the catches of different fishing gears used in the Chalan beel. The mode of operation, fishing duration and season, species and length selectivity of different gears for dominant fish species were determined. Considering the species composition and length selectivity of different fishing gears, seine nets, cast net, lift nets, traps were recorded as non - selective gears both for species and size. Among gill nets, Puti jal an d Batashi jal; traps like Dohair and Bhair; hooks and lines like Daun borshi were recorded as more or less selective fishing gears. Current jal, hooks and lines were regarded as large species gears while Puti jal, Batashi jal, lift nets were found as small species gears. Considering the detrimental effects of different fishing gears it is suggested to restrict the use of these gears for certain period from July to October for effective management and sustainable production of the Chalan beel .

Keywords: Fishing gears, Selectivity, Biodiversity, Chalan beel

Location: Natore Sadar, Singra, Gurudaspur and Baraigram.

Start Date: 00-07-2012

End Date: 00-12-2012

Program Area: Postharvest and Agro-processing

Commodity: Fish

Objectives:

To determine the species and size (length) selectivity of same fishing gears.

Methodology:

To carry out the present study, different spots of Chalan beel were selected considering the fishing spots of the beel and fish landing centre adjacent to the beel. The selected study areas were Natore Sadar, Singra, Gurudaspur and Baraigram. To fulfill the objectives of the study, at first a draft interview schedule was developed. Then it was pre - tested by interviewing to the fish farmers in the study area. After pre - testing a set of final interview schedule was prepared with necessary correct ions and modifications. The survey schedule was elaborated according to the particulars of fishing gears (mesh size, length, breadth, materials etc.), fishing duration, mode of operation, species composition, number of species caught. The study is conducted for a periods of 6 months from July to December, 2012.

Data was collected fortnightly at fish landing centres and fishing grounds in respect to the types and characteristics of the fishing gears used. The particulars of the fishing gears (mesh size, length, breadth, materials, structure etc.) and the catch data were collected from fisherman at the fishing spot through interview. Then detailed description of each and every type of gear was recorded from the fisherman. Catch composition for each type of gear was recorded either by examining the total catch or 10 - 20% in case of large catch randomly.

Various types of models were used in the study to determine the length selectivity curve for most dominant species, L 50% value and selection range (L 25% - L 75% ) for each dominant species. The range of lengths of sample population was divided into 9 to 13 length intervals, depending on the population size. According to the intervals, cumulative frequencies were computed and then transformed to the percentage (relative) cumulative frequencies by using Microsoft Excel Program. The cumulative relative frequencies were transformed to probits. Frequency curves and sigmoid curves were drawn for most dominant species caught by different gears and a linear regression analysis was done between length intervals (independent variable) and the probits (dependent variables) by using SPSS (Statistical Package for Social System) version 16.0. Using the length - probit regression equation, the length at probits which correspond respectively to 25%, 50% and 75% of the percentage frequencies were calculated as L 25%, L 50% and L 75% by the following method.

Source of Information: Journal of Biodiversity and Environmental Sciences, Vol. 8, No. 4, p. 26-38, 2016, ISSN: 2220-6663

Article Link (Online Journal): http://www.innspub.net/wp-content/uploads/2016/04/JBES-Vol8No4-p26-38.pdf

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

From the present study, it can be concluded that people use all possible types of fishing gear, ranging from bare hand to sophisticated seine and gill nets to catch fish and prawn from floodplains for decades. They caught fish indiscriminately which declines the fish production alarmingly. So, the guideline of using fishing gear is a crying need to pass legislation banning the use of harmful gear. Besides, extension program is necessary for the fishermen which will enhance the fish production. Considering the detrimental effects of different fishing gears it is suggested to restrict the use of these gears for certain period from July to October for protection of fish biodiversity of the beel.

Knowledge Management: Journal