More oysters to go

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    REMAINING flat oysters in the Marlborough Sounds are now being removed to protect the Foveaux Strait fishery after a bid by the aquaculture industry to retain some stock for a parasite resilience breeding programme failed.

    A Ministry for Primary Industries (MPI) spokesman said it had been guided by expert scientific advice and had declined the request for a resilience breeding programme.

    Work to remove the remaining oysters in the Marlborough Sounds had restarted, but there was no time frame for its completion at this stage, he said.

    The industry requested MPI consider retaining some stock in the Marlborough Sounds which had survived Bonamia ostreae mortality events for a selective breeding programme. It was proposed the programme could future-proof and rebuild wild oyster fisheries so in the event of future incursions flat oysters would be more able to survive infection.

    Bonamia ostreae is a parasite lethal to flat oysters which was found in two oyster farms in Big Glory Bay, Stewart Island, in May. The parasite has been present in the Marlborough Sounds and Nelson since 2015, but this was the first time it had been found in another area in New Zealand.

    In response to the aquaculture industry’s request, MPI commissioned a Technical Advisory Group (TAG), comprising seven world experts, to advise on the feasibility, biosecurity risks and requirements for a Bonamia resilience breeding programme for flat oysters.

    The group’s report, released last month, recommended any in-water resilience breeding programme would increase the risk of the parasite spreading to uninfected wild oyster populations, including Foveaux Strait, and remaining oysters should be removed as soon as possible.

    TAG’s recommendation was if a Bonamia ostreae resilience breeding programme was to be established it should be conducted in a biosecure land-based facility. It estimated the cost of establishing a breeding programme would be more than $20 million.

    Oyster cull to continue to protect fishery

    “THE flat oyster aquaculture industry would need to expand rapidly and reach a size much larger than it was prior to the detection of Bonamia ostreae to recoup the investment in a breeding programme and/or become economically viable.”

    Bluff Oyster Management Company operations manager Graeme Wright said he “100%” supported TAG’s recommendations. “I am only an office boy, not a scientist.

    “We have to hang our hat on the science. If the science did support it, we would have to go with the flow.”

    There had been two incursions with large mortality in the Marlborough Sounds in recent years, he said.

    “I am a great fan of aquaculture and there is huge potential for growth of the economy, but it needs to be better regulated to minimise the biosecurity risk.”

    MPI had completed its operation to cull all farmed flat oysters from Big Glory Bay following the discovery of the parasite, and a revised surveillance plan had been implemented.

    Surveillance of remaining flat oyster farms on Stewart Island would occur monthly and surveillance of the Foveaux Strait fishery would occur every three months. Previously it had been carried out every six months.

    MPI completed another survey in Stewart Island’s Big Glory Bay and Paterson Inlet, Foveaux Strait and Bluff Harbour in September-October.

    The MPI spokesman said the test results would be finalised by the end the month.

    The investigation into how the parasite was introduced into the Big Glory Bay farms was ongoing, he said.

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