Coast KZN

The marine science world has been turned up side down by a little filter feeder which they thought they knew.

Oceanographic Research Institute (ORI) senior scientist Dr David Pearton based at Ushaka Marine World said two of his masters students, Jessica Gilmore and Jenna Keightley, recently made a fascinating discovery about these oysters.

“We always thought we only had one species of oyster. Turns out there are actually four species. And the one species we though we knew was a misidentification,” said Pearton, who heads up the reef programme.

“The Natal rock oyster or sun oyster which is seen on exposed intertidal rocks has been identified for years as the Saccostrea cucullata. Our genetic work has shown them to be another Saccostrea species called Saccostrea mordax. This species is still common on beach rocks across KZN, but in many places in the Eastern Cape appears to have been over-exploited by subsistence gathering.”

The Natal Rock Oyster, aka Sun Oyster, has been identified for years as Saccostrea cucullata, but ORI’s genetic work has shown them to be another Saccostrea species called Saccostrea mordax.

Besides this, they have discovered an additional three Saccostrea species which are found in the calmer waters of estuaries all the way down to the Eastern Cape.

“Of these, one appears to be endemic while another is most closely related to a species from South East Asia and the other is most closely related to a species from the Caribbean. This underlines the unique level of biodiversity found in South Africa due, in part, to being on the southern tip of Africa and bordered by both the Indian and Atlantic oceans.”

Meanwhile he said the Pacific oyster, which is a cultivated oyster grown in areas such as Saldanha Bay and is most likely to be found at a restaurant, has now been found in KZN too.

“This species is invasive in most places where it is grown such as Europe, Australia and New Zealand, but in South Africa it was not, until recently. Our genetic work has shown that it is present all the way up into KZN, including Durban harbour, Richards Bay harbour and the Umhlatuze estuary. It is found intermingled with indigenous species and we do not know what the long term ecological effects might be.”

He said the indigenous, sub-tidal oyster that is gathered commercially and recreationally in KZN is called the Cape Rock Oyster or Striostrea margaritace.

“These oysters are governed by a system of permits and rotating collection zones designed by scientists at ORI.”