Opening Door To Nth. Auckland Bluff Oyster Fishery

Research Collaboration Opens Door To Bluff Oyster Fishery North Of Auckland

A favourite with oyster-eaters worldwide, the Bluff oyster, could soon be farmed commercially in the warm waters north of Auckland following a successful collaboration between researchers at The University of Auckland’s School of Biological Sciences and the marine farming industry.

The Bluff oyster is acknowledged as one of the best eating oysters in the world, but overfishing of the wild fishery in the Foveaux Strait and a disease epidemic (Bonamia) has reduced wild stock by about 95 percent.

Professor Rufus Wells, head of The University of Auckland Experimental Marine Biology research group said that after two years of experimentation north of Auckland the results so far were remarkable.

“The growth rate is much higher than expected given the origins of the species in the cold southern waters of Foveaux Strait. Bluff oysters are growing to the size of a fifty-cent coin in less than four months, which compares well with the Pacific Oyster.

“Just as importantly, we are able to grow the species in the north without the major disease problems that plague the wild stock at Bluff.”

“Farmed Bluff oysters would also overcome another practical problem. Wild Bluff oysters are always marketed without their shells because the shells are unattractive and infested with parasites and overgrowth. International gourmands insist on oysters being sold in the shell. Therefore aquaculture of the bluff oyster will allow the sale of intact oysters.

Professor Wells and Brendon Dunphy, a postgraduate student funded by a Technology New Zealand scholarship, have developed new technologies to enable the development of the fishery. with assistance from BioMarine Ltd, Warkworth, Pakahi Marine Farms in Clevedon and Kia Ora Seafoods from Manakau City.

“The first step has been to develop new spat collecting methods for the Bluff oyster,” Professor Wells said. “Spat has been collected from Bluff oysters that have drifted north on oceanic currents during the larval phase and settled on the mudflats of the Manukau Harbour. Unlike Pacific oysters, the mother Bluff oyster retains eggs and broods them throughout larval development prior to release and settlement.

“The team has also trialled a range of surfaces to find the one best suited for encouraging oyster settlement, growth and survival. Scientific research has also been undertaken to discover the ideal conditions for the Bluff oyster’s growth, such as plankton supply, temperature, salinity, oxygen levels,” he said.

Professor Wells said that the Bluff oyster looks like a good candidate for aquaculture in the North. “The future work will come in securing an artificial supply of spat for growing, determining the cultivation methods for on-growing oysters at optimum rate and quality, finding a suitable location on west Kaipara or east Mahurangi, and testing the market.”

“There are still several hurdles to jump, but this research offers real hope to add new value and greater security to New Zealand’s oyster fishery,” he concluded.

New Zealand has approximately 2200 hectares in farmed Pacific oysters worth $45 million p.a.

ENDS

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