Oyster farming a risk to wild fishery

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An oyster farm in Big Glory Bay, Stewart Island, in 2017. File photo

ANY future flat oyster farming in Stewart Island’s Big Glory Bay will pose an “unacceptable risk” to the wild oyster fishery, a scientific review has cautioned.

The report, from a Technical Advisory Group (TAG) to those managing an introduced parasite outbreak, Bonamia ostreae, says a return to farming in the bay will pose an unacceptable risk to wild (Bluff) oysters in Foveaux Strait; this was based on the positive detection of the parasite in Big Glory Bay in September last year.

“Any attempts to eradicate B. ostreae primary and alternative hosts (if identified) will require extensive surveillance and high biosecurity requirements to prevent its establishment.”

Consultation would take place later this year on the future of flat oyster farming in New Zealand following the release of the review.

Bonamia ostreae was first found in the upper South Island in 2015, then in Big Glory Bay oyster farms in 2017. Later that year, flat oyster farms in Big Glory Bay and in Marlborough were removed to protect wild fisheries.

It was a parasite which could fatally infect flat oysters – overseas, outbreaks of Bonamia ostreae had severely affected wild oyster fisheries, and it could have similar effects here.

Biosecurity New Zealand director of response John Walsh said the report was commissioned to provide a good scientific understanding of the risks presented by flat oyster farming and advice on the feasibility of farming in the future.

“No decisions on the future of the flat oyster farming industry, particularly in Stewart Island waters, could be made without this assessment.”

A governance group comprising Biosecurity New Zealand, the fishing and aquaculture industries, Ngai Tahu and local government agencies would provide recommendations on flat oyster farming to the Ministry for Primary Industries (MPI), but Mr Walsh said no decision would be made without feedback from all affected parties.

Barnes Wild Bluff Oysters general manager Graeme Wright did not want to comment before the consultation period had ended but said it was a process based on scientific evidence.

“It is devastating for the people involved but the decision that will be made will be what it will be I guess… the science will decide what the future is.”

The consultation process later in the year would include meetings in Stewart Island and Marlborough for iwi, wild catch fishers and aquaculture operators and anyone else with an interest.

  • The Technical Advisory Group report, along with preliminary recommendations made by the Governance Group, were available on MPI’s website, www.mpi.govt.nz.
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