Pacific Oyster

(Crassostrea gigas)

1. What is it?

Pacific oysters (Crassostrea gigas) are invasive, filter feeding species with white/ off-white shells. Larvae often settle on the shell of adults and great masses of oysters grow together to form oyster reefs. After introduction into South Africa, this species managed to form naturalised populations in the wild, but have not displaced or competed with native species in the 40 years of repeated introductions through the aquaculture industry. Stock status is unknown.

2. How was it caught or farmed?

Pacific oysters are farmed in sheltered bays in the sea attached to ropes or rafts floating in the water column. Oysters are filter feeders and therefore farming is managed as a completely natural system with no input of chemicals or feed. Due to difficulties in inducing predictable spawning and subsequent setting under South African conditions, “disease free” certified oyster spat is imported and hatchery based. This results in very few impacts on the environment apart from localised damage due to the waste discharged into the surrounding environment.

3. Where is it from?

South Africa

Pacific oysters can be found along coastlines throughout the Pacific and are grown locally at specialised oyster farms. Management is largely effective through strict environmental assessments and a very good legal framework. At present there is no third party audit of the bivalve farming industry.

Imported - China

Pacific oysters can be found along coastlines throughout the Pacific Ocean. They are grown in China on specialized oyster farms and imported to South Africa. China has some regulatory measures in place to protect the surrounding ecosystems but the effectiveness of these measures is unknown. There are also some issues surrounding enforcement of these measures on a local scale.