Tuesday, November 19, 2019 Information Gateway on Agriculture to Convert "Know How To Do How" മലയാളം
Fisheries > Culture Fisheries > Edible Oysters

Harvesting

Cultured oysters reach marketable size 9-12 months after stocking. Grow-out time depends on initial stocking size. The usual market size is 9-12 cm. Harvesting raft-cultured oysters is easily done by one person. Two persons are required to work the longline, one to remove the oysters from trays and the other to control the boat.

The oysters’ are harvested when the condition is high. Good meat yield is obtained during March-April and August-September. Harvesting is done manually. Oysters kept under moist and cool conditions survive for several days. However, it is desirable that they reach the consumer within three days of harvest. Studies indicate that oysters packed in wet gunny bags are safely transported for 25-30 hrs without mortality and in good condition.

After landing, the harvested oysters should be brushed and any fouling organisms removed. Oysters should be depurated to ensure they are free of bacterial contamination.

Depuration

Oysters, like other filter-feeding bivalves, accumulate pathogenic organisms in their body. The bacteria of concern are Vibrio, Salmonella and Escherichia (Coliform type). Members of the Salmonella group cause typhoid fever, while conforms and vibrios cause gastroenteritis. By depuration the bacterial load is brought down to permissible levels; also faeces, sand particles and silt are removed from the alimentary canal of the oysters.

The oysters are placed for 24 hrs in cleaning tanks under a now of filtered seawater. About 10-20% of the seawater is continuously replaced. At the end of 12 hrs the water in the tank is drained and oysters are cleaned by a strong jet of water to remove the accumulated faeces. The tanks are again filled with filtered seawater and the flow is maintained for another 12 hrs. Then the tanks are drained and flushed with a jet of filtered sea water. The oysters are held for about an hour in 3 ppm chlorinated seawater, and then washed once again in filtered seawater before marketing.

depuration

Small scale depuration unit

Shucking

The removal of the meat from the oyster is called shucking. A stainless steel knife is used for the purpose. To render shucking easy, oysters arc subjected to a wide range of treatments such as exposure to weak hydrochloric acid, heat, cold, vacuum, microwaves and lasers. Freezing the oysters, or immersing them in hot water are the two methods commonly followed.

shucking

Shucking

Top

Admin Login

Copyright © 2019. Developed & Maintained by Centre for E-Learning, Kerala Agricultural University