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Loss of Aquatic Fauna During Collection of Penaeus Monodonpost Larvae in Tidal Water of Mongla River, Bagerhat

M. S. Islam
Department of Coastal and Marine Fisheries, Sylhet Agricultural University, Sylhet-3100

M. M. RahmanK
Research Station, Bangladesh Fisheries Research Institute, Bagerhat-9300

K. U. Ahmed
Research Station, Bangladesh Fisheries Research Institute, Bagerhat-9300

Md. Motaher Hossain
Department of Fisheries Technology & Quality Control, Sylhet Agricultural University, Sylhet-3100

P. P. Barman
Department of Aquatic Resource Management, Sylhet Agricultural University, Sylhet-3100

Abstract/ Executive Summary:

The study was carried out in Mongla tidal river of Bagerhat district from May 2012 to April 2013 to ascertain the abundance of black tiger shrimp (Penaeus monodon) post larvae (PL) and to quantify the damage of different aquatic fauna during collection of P. monodon PL. It was found that around 1650 larvae of other shrimp species, 1562 fin fishes and 6787 other macrozooplankton were cruelly damaged at the time of collection just for single PL of P. monodon. During the survey period about 0.18 million man days/year were calculated to be engaged in shrimp PL collection and on average 6.5 million of P. monodon PL were collected annually from the studied area. It was also ascertained from the present study that about 29,988 million of other shrimp species, fin fishes and macrozooplankton were destroyed annually by the shrimp seed collection activities in Mongla river. The results of the study reveals that present seed collection practice caused severe damage of other valuable aquatic fauna, which directly affect the biodiversity of neritic and offshore fauna, natural productivity of tidal waters and ecological balance of coastal and marine environment.

Keywords: Penaeus monodon post larvae, Aquatic fauna, Tidal water

Location: Bagerhat district, Bangladesh

Start Date: 00-05-2012

End Date: 00-04-2013

Program Area: Animal Health and Management

Commodity: Plankton, Fish

Objectives:

To assess the abundance and catch composition of the drag/push net used for collecting PL of P. monodon and to quantify the damage caused to different shrimp species, fin fishes and zooplankton larvae while collecting PL of tiger shrimp.

Methodology:

Samples were collected from three different sites/spots of Mongla tidal river of Bagerhat district from May 2012 to April 2013. Monthly sampling was done by a fine meshed (0.3 mm) push net made of nylon with bamboo split frame (1.6 m x 0.6 m) locally called "Tana jal". The net was manually operated in shallow water against the current. Each hauling time was only 10.0 minutes. Sampling was done twice in a day during low and high tides. After each hauling, samples were stored in plastic pots and preserved with 5% buffered formalin solution. After return to the laboratory, samples were segregated and penaeid shrimp larvae were identified upto species level following Muthu (1978) and Motoh and Buri (1980). Macrozooplankton including other shrimp and fin fishes were identified as major taxonomic groups following George (1969) and Fischer and Witchead (1974). Salinity of water was estimated using a portable refractometer (AT AGO, Hand-Held Refractometer). Water temperature and pH were measured using an alcohol thermometer and a digital pH meter, respectively.

Source of Information: J. Asiat. Soc. Bangladesh, Sci. 41 (I): 95-103, June 2015

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The findings of the above mentioned studies and also the this study revealed that there has been a trend of gradual decreasing in the abundance of other shrimps, fin fishes and other zooplankton larvae in neritic and offshore. This might be associated with over fishing with smaller mesh sized nylon nets and indiscriminate killing of zooplankton and other shrimps that hinder the normal recruitment pattern to the original mother stock. Therefore, appropriate measures should urgently be taken to stop such massive destruction and to grow awareness among the seed collectors to release back the unwanted organisms into the waterbodies without any damage. These initiatives would help to conserve the biodiversity of aquatic fauna and to keep in a congenial environment of coastal as well as marine waters.

Knowledge Management: Journal