Report: Farming in Big Glory Bay poses unacceptable risk to Bluff oysters in Foveaux Strait

Thursday, 23 July 2020

A Government report says returning to flat oyster farming in Big Glory Bay poses an unacceptable risk to the Bluff oyster fishery.

Findings in the report cautioned against future flat oyster farming in the Stewart Island/Rakiura bay because of the threat of the parasite Bonamia ostreae.

The Ministry for Primary Industries made the decision to remove all the farmed oysters from the bay in 2017, after the Bonamia ostreae parasite was detected on oyster farms in the area.

The invasive parasite kills oysters.

Big Glory Bay oyster farmers have been paid out nearly $2.5 million in compensation after being forced to close their businesses, Stuff reported in 2019.

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Southern oyster farmers contacted on Thursday wanted more time to read the report before commenting.

On a separate issue, Barnes Wild Bluff Oysters general manager Graeme Wright said he was unsure how the report would impact on aquaculture overall in the south.

The Southland Aquaculture Working Group is trying to establish ocean salmon farming as a new industry in the south.

Wright said he also needed more time to read the report that was produced by a technical advisory group attached to MPI.

Biosecurity New Zealand director of response John Walsh said consultation on the future of flat oyster farming in New Zealand would take place later in 2020 and include public meetings in Stewart Island and Marlborough.

The technical group was set up in September 2019 to look at whether flat oyster farming posed a risk to wild oyster populations and the Bluff oyster fishery.

Walsh said the group’s report found the level of disease risk posed by the development of flat oyster farming in New Zealand differed by location, but without protective measures, was high and unacceptable in some areas.

Bonamia ostreae was detected in Big Glory Bay in October 2019.

Given that detection, the TAG report concluded a return to flat oyster farming there posed an unacceptable risk to the wild oyster fishery in the Foveaux Strait, Walsh said.

A return to flat oyster farming should not occur without protective measures including further research, ongoing surveillance for the parasite and use of best biosecurity practice, he said.

That included maintaining shellfish stock health and welfare, using pest and disease-free stock, following good cleaning and hygiene, checking farms for anything unusual, reporting abnormalities and having a biosecurity management plan in place, Walsh said.

“It may take many years of research and investment to safely return to flat oyster farming. The report provides a process that can be followed to mitigate the risk posed by farming.”

Bonamia ostreae is a parasite that can fatally infect flat oysters. It is a different type of Bonamia to one that has previously affected Bluff oysters, Bonamia exitiosa.