Oyster culling and harvesting

Culling

Culling reduces the spatfall that may have accumulated on an oyster's shell and helps grade oysters into various sizes.

Regular inspections are necessary and the culling process can be very time-consuming and labour-intensive. Some recent advances have involved covering the oysters in a special coating that prevents spat and unwanted species from attaching to the oyster's surface.

A more common practice is immersing oysters in a hot water bath of 82°C for 3 seconds. The aim is to kill off all small spat that cannot tolerate high temperatures because of their smaller size and thin shell. This method is easily performed on aquaculture farms that use the BST longline system, trays and even sticks. In many cases, it can be done on the water - an immersion tank is placed on the barge and pre-heated to 82°C. Oysters are removed from the longline or racks, placed directly in the hot water, and then returned to their original positions.

Harvesting

Oysters are generally large enough to market in 2-3 years.

The qualities that determine the grade of an oyster are size and condition of the meat. Rock oysters are marketed as 'bottle size' at 29-40g (whole weight) and as 'plate size' at 40-67g. Oysters less than 5cm are returned to banks or trays for further growth.

Bottled oysters are 'shucked' (opened) with a knife and the body of the oyster removed by cutting the muscles joining it to the shell. The oysters are rinsed in fresh water and are bottled in clean fresh water with salt added.

Plate oysters are sold either in full or half shell. Shells are cleaned of silt and any surface growth prior to sale using a scrubbing brush or some form of tumbler.

Also consider...

• You will need to discuss technical and licensing aspects of any proposed aquaculture venture with staff from Fisheries Queensland and the Department of Environment and Science before proceeding with site selection, design and, where applicable, land purchase.
• Read our policy for maximising rock oyster production.
• The oyster industry management plan for Moreton Bay Marine Park supports the sustainable development of the commercial oyster industry in Moreton Bay.
• Download the latest report to farmers for aquaculture industry statistics and production data.