DNA tests may reveal oysters’ battle for survival

SOUTH Africans love their wild oysters, but the delicacy on your plate may not be a local species.

There are at least two indigenous wild oyster species — the Cape rock oyster and a deeper-water species sometimes called the red oyster.

But for years scientists have monitored Japanese oysters farmed locally that have started growing wild in some South African rivers.

Stellenbosch University is conducting DNA tests on oysters along the coast to find out whether the local oyster species are holding off the invader. “We take tiny bits of the oyster tissue and test it in a genetics lab in Stellenbosch,” said Sue Jackson, research associate at the university’s botany and zoology department.

The results will hopefully shed light on oyster dynamics and help the government to set wild oyster quotas.

“We know so little about South African oysters. We don’t know how big their populations are, or if there are different subspecies,” said Jackson.

“We’ve worried for more than 10 years that Pacific [Japanese] oysters might grow wild in South Africa.”

The results so far suggest that the foreign oyster does not last long outside estuaries because of South Africa’s rough but rich coastal waters, in which local species thrive. Oyster farmers rely on the Japanese oyster because of its rapid growth rate. Oysters dished up at restaurants countrywide are therefore more likely to be the foreign variety, given that oyster farms supply the bulk of the trade.

Jackson said oysters were typically farmed in protected West Coast bays where they benefit from the Atlantic Ocean’s nutrient-rich water.

But the Stellenbosch research shows that local wild oysters may also be suitable for aquaculture because of their impressive reproduction rates. Oyster connoisseurs say they taste better too, although opinion differs depending on how much champagne is involved.

Jackson said more research was needed to establish the farming potential of the local oysters.