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Selectivity of Fishing Gears and Their Effects on Fisheries Diversity of Rabnabad Channel of Patuakhali District in Bangladesh

Md. Bokthier Rahman
Department of Fisheries Technology, Faculty of Fisheries, Patuakhali Science and Technology University, Dumki, Patuakhali, Bangladesh

Md. Sazedul Hoque
Department of Fisheries Technology, Faculty of Fisheries, Patuakhali Science and Technology University, Dumki, Patuakhali, Bangladesh

Md. Mahmudul Hasan
Department of Geo-information Science and Earth Observation, Faculty of Disaster Management, Patuakhali Science and Technology University, Dumki, Patuakhali- 8602, BANGLADESH

Abstract/ Executive Summary:

The Rabnabad is a marine channel, harbor of plentiful aquatic resources, situated at southern district of Patuakhali in Bangladesh. An investigation has been carried out on three different selected spots (S1, S2 and S3) of Rabnabad channel to identify fishing gears used for fishing and their potential effects on available fisheries diversity for a period of 8 months from February 2015 to September 2015, employing a prepared questionnaire. The study explored total 21 fishing gears under 8 major groups of net. In total, 54 species of fishes were identified belongs to 10 orders and 27 families in the catches of these gears. The order basis percentage analysis of the fish species executed the highest occurrence belongs to the order Perciformes (31.48%) and lowest for five ordersviz., Aulopiformes, Beloniformes, Osteoglossiformes, Pleuronectiformes and Tetraodontiformes were found in the percentage as 1.85% (for each) of the total fish community. Out of 54 species, 7, 2 and 7 species was recorded as endangered, critically endangered and vulnerable, respectively. Calculated Shannon- Weiner index (H), Gibson’s evenness (E), Simpson’s dominance index (D), Simpson’s index of diversity (1-D) and Margalef’s index (d) of fishes ranges between 3.22-3.30, 0.54-0.59, 0.04-0.05, 0.95-0.96 and 5.67-6.10, respectively. It is worse that numerous non-selective and restricted fishing gears are used which lead to unsorted catches, consequently, diversity of fish fauna are decreasing from the channel. For sustainability of these resources, proper management and conservation is crucial to guard the species diversity.

Keywords: Conservation status, Fish biodiversity, Fishing gears, Rabnabad channel

Location: Patuakhali District

Start Date: 00-02-2015

End Date: 00-09-2015

Program Area: Conservation and Biodiversity

Commodity: Fish

Objectives:

To identify fishing gears with their mesh size and catch composition of respective fishing gears and their effects on fish diversity in Rabnabad channel of Patuakhali district in Bangladesh.

Methodology:

Location of study area: The study site i.e., Rabnabad channel, also recognized as Patua River or Patuakhali River, situated at southern district of Patuakhali in Bangladesh and falls between 21°52'37" N latitude and 90°16'55" E longitude. To obtain higher number of specimens of fishes sampling stations were divided into three different spots including Dhulasar (S1), Lalua (S2) and Dhankhali (S3).The investigation was conducted for a period of 8 months from February 2015 to September 2015. Gears surveyed: The fishing gears including their mesh size, price and catch composition of respective fishing gear were surveyed following a prepared questionnaire from the fishers fishing in the three dissimilar spots of Rabnabad channel. The fishing gears were categorized under different major groups followed by Ahmed N.(1971).Freshly caught unsorted samples of different gears was collected and measured using a digital balance (up to 0.01 g) as well as pan balance and numerical data were expressed in kg. Fish specimen collection: Fish specimens were collected from three different selected spots (S1, S2 and S3) of Rabnabad channel. Nine fishermen were hired temporarily three from S1, three from S2 and three from S3 to carry out specimen collection process. Specimens were collected using current jal, jagat ber jal and badha jal under the group of gill net, seine net and fixed purse net, respectively as these nets are popular throughout the channel. Diversity of fishes were observed following lunar periodicity (full moon and new moon) as during these periods higher abundance of fishes were reported by the fishermen and fish vendors. Fish samples were also collected from the local fish landing centers and fish markets from previously contacted fishermen. Total numbers of individual species were counted in each sampling day from these three stations. Laboratory analysis: Immediately photographs were taken using a digital camera (Canon, IXUS 155) earlier to preservation since formalin decolorizes the fish color on long preservation. For laboratory study, 20% of the total catch was taken from each station in each sampling day and preserved in 10% buffered formalin solution in a previously leveled plastic jars according to size and species. In the laboratory, the collected specimens were identified to species level with the help of standard taxonomic keys. Biodiversity indexes: Species diversity was assessed using five indices viz., species richness, Shannon–Wiener index, Evenness and Dominance Indices. The Shannon - Weiner index and Gibson’s evenness was measured to evaluate species diversity. The dominance index like Simpson’s dominance index and Simpson’s index of diversity was calculated to determine whether or not particular species dominate in a particular aquatic system. Conservation Status: Bangladesh conservation status and population trend were detected. Data analysis: For the analysis of present findings statistical analyses were carried out using Microsoft Excel 2007 and Statistical Packages for Social Sciences (SPSS) version 16.0.

Source of Information: Academic Research International Vol. 6(6) November 2015, 184-196 ISSN: 2223-9944, e ISSN: 2223-9553

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

In total, 54 species of fishes were identified belongs to 10 orders and 27 families in the catches of these gears. The order basis percentage analysis of the fish species executed the highest occurrence belongs to the order Perciformes (31.48%) and lowest for five ordersviz., Aulopiformes, Beloniformes, Osteoglossiformes, Pleuronectiformes and Tetraodontiformes were found in the percentage as 1.85% (for each) of the total fish community. Out of 54 species, 7, 2 and 7 species was recorded as endangered, critically endangered and vulnerable, respectively.

Knowledge Management: Journal