About Bonamia ostreae
Bonamia ostreae is a parasite that can kill flat oysters. Overseas, it's had a large effect on flat oysters. However, we don't know the effect it will have here, especially on our species of wild oyster in our unique marine environment.
Bonamia ostreae was found for the first time in the Marlborough Sounds in 2015. In 2017, it was found in Big Glory Bay, Stewart Island.
No food safety risk from bonamia ostreae
Bonamia ostreae is not a food safety risk. Fresh, good quality New Zealand oysters continue to be safe to eat.
How will flat oysters be protected?
On 12 June 2017, the Ministry for Primary Industries (MPI) delivered a notice of direction to flat oyster farmers in Big Glory Bay in Stewart Island and in Marlborough. This notice required the removal of all flat oyster stocks. All farms had been removed by late 2017.
In 2019, the Bonamia programme was established to manage Bonamia ostreae. The overarching objective of the programme is to protect uninfected wild oyster populations from Bonamia ostreae with the following aims:
- Restrict the spread of Bonamia ostreae from existing infected areas.
- Prepare for potential future infections and outbreaks.
- Protect customary, recreational, and commercial fisheries from Bonamia ostreae.
- Protect cultural rights regarding flat oysters.
- Enable future oyster farming opportunities where appropriate.
- Promote biosecurity best practice and improve biosecurity practices in key risk groups to reduce the risk of transmitting Bonamia ostreae.
The Bonamia programme governance group led by Biosecurity New Zealand is in place and oversees the programme. Representatives on the governance group include:
- Aquaculture New Zealand
- Fisheries New Zealand
- Environment Southland
- Awarua Runaka
- Southland District Council
- the Bluff wild oyster fishery.
Stopping the spread
As part of a Controlled Area Notice (CAN), movement controls are in place to reduce the risk of the spread of Bonamia ostreae. The CAN:
- restricts the movement of some shellfish species, and marine farm equipment and craft, into and out of Stewart Island
- stops people moving some shellfish species out of a designated contained zone (Nelson and Marlborough) and into a protected zone (Southland, Otago, and the Chatham Islands)
- covers all life stages of these species, including their spat.
Download the Controlled Area Notice BRC 2021 [PDF, 523 KB]
You may need a permit to move restricted shellfish stock, or marine farm equipment and craft, into or out of zones covered by the CAN.
If you have questions about permits or the CAN, email email@example.com
Early detection of spread
Bonamia ostreae is known to be present in the Marlborough Sounds and Big Glory Bay in Stewart Island (Rakiura). We survey oyster populations twice a year to check for Bonamia ostreae.
Sampling for the Autumn 2022 surveillance was done between April and May 2022. The testing process was completed in late June 2022. Eight oysters were confirmed positive for the presence of Bonamia ostreae at a known infected site in Big Glory Bay, Rakiura. The parasite was not detected at any of the other sites surveyed.
The new detections in Big Glory Bay do not change the risk profile to the wild flat oyster population of Foveaux Strait. It is not unexpected to have new findings of infected oysters from Big Glory Bay where we know the parasite is present.
Report on the Bonamia ostreae Autumn 2022 surveillance [PDF, 3.4 MB]
Biosecurity New Zealand is developing a long-term management plan for Bonamia ostreae and on how flat oyster farming could fit with this.
This approach follows discussions with closely affected parties and feedback on management options through a targeted engagement process. Download the targeted engagement feedback summary:
Biosecurity New Zealand is adopting an "enhanced status quo". This involves a review of the Bonamia ostreae CAN and the development of a flat oyster farming biosecurity policy.
Between November and December 2022, affected and interested parties were consulted on proposed CAN changes and a discussion document on the biosecurity policy. Consultation is now closed. The feedback provided through meetings and in written submissions is being reviewed.
An update on progress will be provided in March 2023.
No changes will be made until the consultation process is completed and all stakeholder input is considered. If you have questions about the consultation, email Bonamia.Liason@mpi.govt.nz
In the longer-term, Biosecurity New Zealand will embed the development of a National Marine Biosecurity Framework into existing work programmes. This was the third option presented in the targeted engagement.
What you can do
Here's how you can help us detect Bonamia ostreae.
Keep an eye out
It can be hard to spot the disease caused by Bonamia ostreae. Common symptoms to look for in oysters are:
- poor condition
- gills that look corroded
- yellow discolouration of the gills and mantle.
Bonamia ostreae can also cause widespread oyster deaths.
The general public, aquaculture farmers, and fishers should keep an eye out for these signs. If you see anything suspicious, contact Biosecurity New Zealand:
- call our Exotic Pest and Disease Hotline – 0800 80 99 66, or
- make a report online
Play your part
There are steps you can take to help prevent the spread of Bonamia ostreae. These are important if you're out on the water, collecting shellfish, or fishing in areas covered by the CAN. The risk of spread increases if any shellfish, or their shells and waste, are moved from one area to another.
To protect our wild oysters from Bonamia ostreae:
- keep your boat's hull clean
- dispose of shells and shellfish waste at home or in a landfill – don't throw them overboard
- return undersized excess shellfish back to where you collected them
- clean your fishing gear after you've finished collecting.
Stay up to date by subscribing to the Bonamia email updates.
If you have questions, email Bonamia.Liason@mpi.govt.nz
Updates, reports, and surveys
Latest stakeholder update – July 2022 [PDF, 148 KB]
Latest surveillance report: Autumn 2022 [PDF, 3.4 MB]
A Technical Advisory Group (TAG) was formed in September 2019. The TAG looked at whether flat oyster farming poses a risk to wild oyster populations and the Bluff oyster fishery. A report was written to give the Bonamia governance group the information they need to recommend if, where, and when flat oyster farming might start again. When the governance group received the TAG report, they made some preliminary recommendations.
Bonamia governance group preliminary recommendations [PDF, 444 KB]
A risk advice document from March 2015 looks at the risk associated with ways Bonamia ostreae can spread (some information has been redacted for privacy or commercial reasons).
Domestic spread of Bonamia – risk advice [PDF, 2.8 MB]
NIWA report of surveys from February 2019 to March 2021
This report includes a summary of surveys and details operations and preliminary testing for surveys 11 to 15.
Following the March 2021 survey, MPI incorrectly reported a positive result for samples from the Foveaux Strait, when the Animal Health Lab's testing had found the tests were inconclusive. The samples were later confirmed as negative through third-party testing by the Geelong CSIRO laboratory. Appendix D in the report outlines the confirmatory process and subsequent negative result.
References in this report to positives in NIWA's screening tests, and NIWA's subsequent conclusions or discussions, are related to preliminary results only and do not reflect the final testing results (some information has been redacted for privacy or commercial reasons).
Report on the re-test of 5 samples from the Otago 2016 surveillance
At the request of stakeholders following the March 2021 Bonamia ostreae response, MPI commissioned NIWA to re-test 5 samples taken from the Otago 2016 surveillance. In 2016, these samples tested positive with NIWA's preliminary screening testing methodology in use at that time. However, confirmatory tests by Biosecurity New Zealand's Animal Health Laboratory yielded negative and one inconclusive final result for Bonamia ostreae.
The samples that were frozen in storage since 2016 have been re-tested using NIWA's current screening methodology. They returned negative results for the presence of Bonamia ostreae.
Note, despite long-term freezer storage and the presence of amplifiable DNA in each sample, sample degradation may still have occurred, influencing the test results reported here. The MPI position on the retesting of older stored samples is that it is not advised, as DNA may degrade over time, influencing results. Test results should be interpreted with caution.