Coffin Bay OystersOyster farming
The Coffin Bay oyster is farmed either on a rack and rail system (the original method) or a long line system (the more recent method) both of which produce excellent oysters.
Techniques and equipment
There are a number of different methods used for intertidal oyster growing in South Australia. These methods have been developed to best suit the physical factors of the site as well as the size of oysters transferred on to the farm. Each grower has the option of using either of these methods to grow their oysters.
Intertidal racks and baskets
The rack and basket method of oyster culture has been used since the inception of oyster farming in SA.
Rectangular shaped baskets, handmade from tough polypropylene mesh, are secured to the racks by two wooden sticks (approximately 1m length). The oyster racks are made of wooden posts (uprights) which are drilled vertically into the seabed and act as the main supporting structure. Attached to these are more wooden posts which run parallel to the seabed and hold up the baskets.
Farmers position the posts and oyster baskets according to the water depth and tides experienced at the farm site.
Intertidal racks and trays
Spat, straight from a hatchery need greater protection than adult oysters when on the farm site. For this reason trays are generally used for spat smaller than 10mm. Trays allow good water exchange but also protect them from excessive currents which can cause the spat to fall out.
An oyster tray used to hold oyster spat. They are made of wooden frames with mesh covering secured to racks. They are usually separated into compartments to prevent oysters "clumping" up at one end.
Intertidal Long-lines
A more recent and more popular method being used quite widely is intertidal longlines and bags to on-grow oysters. The bags are made of polypropylene mesh; cylindrical in shape, 90cm length x 15cm diameter, and hung on a wire suspended by wooden uprights. The benefit of this system is that the height of the wire can be adjusted so the oyster bags can be lowered or raised depending on the tide and water temperature.
The intertidal bag method. Similar to baskets, these bags are made of various mesh sizes according to the size of the oysters. The bags are designed to hang on a wire and move with the water currents. This rumbles the oysters and removes excess shell growth and improves meat to shell ratio.
Subtidal Long-lines
In some parts of SA, farmers have access to sub-tidal sites where sub-surface or surface longlines are used to suspend a series of stacked trays (approximately 1.5 x 1.5m). These longlines are moored to the sea-bed and supported by buoys.
Check out the Coffin Bay Attractions website for more information