IDENTIFICATION
Oysters, like mussels, are bivalves, soft bodied animals protected by a pair of shell valves. The lower valve of oysters is cemented to the rocky substrate. The main oyster harvested in KwaZulu-Natal is the Cape Rock oyster, a large heavy oyster with a deep cup-shaped lower valve. These oysters occur low on the shore in the infratidal and subtidal and are in great demand for their succulent flesh. Higher up the shore, sun oysters (Saccostrea cuccullata) are found, often occurring in a dense band. This species is smaller, has a shallower lower valve and has a ribbed margin.

DISTRIBUTION
Rock oysters extend from Cape Point northwards to central Mozambique. They are common on rocky reefs from the low tide mark to depths of about 5 m.

FEEDING
Like mussels, oysters are filter feeders, sieving small particles of dead matter and plankton from the water column.

GROWTH
Although oysters reach maturity early, approximately 4 months after settling onto the rocks, they then grow fairly slowly, taking two years and nine months to reach a size at which they can be sold- about 60 mm. Oysters can reach an age of 25 years.

REPRODUCTION
Rock oyster breed all year round but release the most eggs in summer. Fertilisation is external and there is a short larval stage. Then the young oysters, like juvenile mussels, prefer to settle and grow on other adults.
The short larval stage limits the ability of the larvae to move to adjacent shore and deep-water stocks must be protected to sustain inshore fisheries.

FISHERY
Oysters are the only intertidal invertebrates in KwaZulu-Natal that are also harvested commercially. Recreational collectors gather between 70 000 and 300 000 oysters each year whereas about 500 000 oysters are commercially harvested annually. In Maputaland, subsistence collectors gather far less.

MANAGEMENT
The KZN oyster fishery is managed by a rotational harvesting system, different zones are used for commercial or recreational harvesting in some years and then lie fallow for 3 years so that stocks can recover. There are gear limitations for collectors and divers may not gather oysters to ensure that populations in deeper water are protected and can supply juvenile oysters to shallower water. The rights of subsistence fishers to collect intertidal invertebrates have now been recognised and new management plans are being formulated. Subsistence harvesters will be permitted and managed with their own set of regulations.
You may see small teams of women using crowbars to gather oysters for commercial operators. When complaints of denudation of reefs by such harvesters were investigated, low by-catch of other species was found. This report states that the spacing of oysters ensures that total clearance of the substratum does not occur. Recreational permits will be endorsed with the area where harvesting is permitted. Oysters which are removed from the rocks cannot re-attach and harvesters should only remove those they intend to keep.

ECOLOGY
Oysters, mussels and redbait often compete for space on shallow rocky reefs but oysters are most tolerant of sand inundation. All three are filter feeders and are responsible for capturing particulate matter and plant plankton from the water column. Oysters are eaten by fish such as spotted eagle ray and Natal stumpnose and by drilling gastropods (snails). Oysters provide habitat for many other species and gaps in oyster beds provide small animals with refuge from predators.