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Availability of Marine Pearl Producing Bivalves in South-eastern Coast of Bangladesh and Development of Pearl Culture Technology

Dr. Md. Enamul Hoq
Chief Scientific Officer
Bangladesh Fisheries Research Institute

Abstract/ Executive Summary:

The present study was conducted during September 2014 to July 2015 to identify the pearl bearing bivalves in south-eastern coast of Bangladesh and culture potentialities of marine oyster in captivity based on field investigation. A total of 7 pearl bearing bivalve species were identified in the coast with a salinity of 18-34 ppt, pH 8.1-8.3 and water depth ranged 0.2-2.0 meter in their habitat. From the collected bivalves, most abundant oyster species windowpane oyster, Placuna placenta (Linnaeus, 1758) was reared in fiber glass tanks with seawater for a period of 6 months. During rearing highest survival rate of 88% was observed in T1 with sandy and gravel substratum and lowest survival rate of 78% was found in T2 with muddy substratum. Average temperature and salinity were varied between 24 °C-25 °C and 21-26 ppt respectively. From the reared oyster, highest 54 nos. small pearls in the month of April and lowest 7 pearls in December from a single P. placenta were obtained. The study proved that pearls can be obtained from the marine oysters in captivity in Bangladesh, and this offers large scale culture potentialities on our coast.

Keywords: Pearl, Placuna placenta, Bay of Bengal, Salinity

Location: South-eastern Coast of Bangladesh

Start Date: 00-09-2014

End Date: 00-07-2015

Program Area: Variety and Species

Commodity: Pearl

Objectives:

To investigate the major pearl producing bivalves in the south-east coast of Bangladesh
To identify the appropriate species for pearl culture by rearing in pond/cistern
To develop culture technology of Placuna placenta (Kortal) by rearing on-station pond as well as coastal channel.

Methodology:

Placuna placenta (kortal) were collected from the coastal river of Moheshkhali and stocked in three fiber glass tanks (500 L) marked as T₁, T₂, T₃ with sand substratum at MFTS, Cox’s Bazar. The stocking density was 100, 125, 150 individuals for T₁, T₂, T₃ respectively with maintaining 35 cm water depth. Average stocking size and weight of kortal were 15.5-11.5 cm and 200-120 g, 13.5-8.7 cm and 150-60 g, 15.6-9.3 cm and 270-90 g, respectively for 3 treatments. P. placenta (kortal) were also stocked in plastic tanks (300 L) marked as G₁, G₂, G₃ with sand substratum. Stocking density were 30, 40, 50 number of individuals respectively maintaining 35 cm water depth. Average stocking size and weight of kortal were 14.8-9.5 cm and 250-130 g, 16.00-9.4 cm and 280-150 g, 14.5-8.8 cm and 210-80 g, respectively.

Source of Information: Annual Report & Journal Publication, Journal of Fisheries 3(3): 293-296.

Article Link (Online Journal):

Funding Source:

1. Government

Budget: 10,00,000

Total Budget (Tk.) : NaN

Achievement/Findings:

Most abundant bivalve species in our coast, Placuna placenta (kortal) were collected from the coastal river of Moheshkhali and stocked in a pond adjacent to Kreju khal, Ukhia, Cox’s Bazar. Net bags were constructed by round shaped iron ring (8 mm diameter) and net. Stocking density of Rope 1, Rope 2 and Rope 3 were 5, 4 and 3 number of individuals, respectively. Average stocking size and weight of Rope 1, Rope 2 and Rope 3 were 14.5-12.5 cm, and 120-250 gm, 11.3-14.6 cm and 90-200 gm, 9-15.5 cm and 80-280 gm. Plastic small cages were also used. The growth performance of P. placenta (kortal) was observed in each three month interval. About 30% of sample was randomly selected to show the growth performance. The initial mean length was 12.25±1.04 cm in July. In the month of October to January the mean length were 12.71±1.06 cm to 13.36±1.05 cm. Final mean length was 13.50±1.14 cm in the month of April. P. placenta show highest length performance from October to January that was 0.65 cm and lowest length performance from January to April was 0.14 cm. During the culture period of kortal in pond, the pearl development in kortal was observed on three month interval. A total 40 number of reared kortal were sampled among them 25 pieces (62.5%) were found pearl inside their body. Maximum number of pearl was found in July that was 26 pieces and lowest amount of pearl found in October was 17 pieces.

Knowledge Management: Journal