Disease outbreaks in Ulva Island-Te Wharawhara Marine Reserve
IntroductionWhat disease outbreaks have occurred in Ulva Island-Te Wharawhara Marine Reserve?
A microscopic parasite, Bonamia ostreae, was found in farmed oysters in Big Glory Bay (3.5 km from the marine reserve) in May 2017. The parasite spreads through the water or via infected oysters and can kill 80–90% of the oysters in a wild or farmed population. It infects flat, dredge or Bluff oysters (Ostrea chilensis) but not Pacific oysters (Crassostrea gigas) and there is no known treatment for the parasite.
In an attempt to prevent the parasite spreading to the wild Bluff oysters in nearby Foveaux Strait, all the farmed oysters in Big Glory Bay were removed and culled. A closely related species, Bonamia exitiosa, has been present in the Bluff oyster populations since the early 1960s. It wiped out about 95% of the total population in 2001 and 2002.
Oysters were not reported in the marine reserve in DOC’s 2014 habitat survey.
More information about the parasite Bonamia ostreae is available from the Ministry for Primary Industry’s website.
In late 1989, several salmon farmers in Big Glory Bay noticed that some of their fish were dying. Eventually all the farms were severely affected and fish began to die in increasing numbers. The organism responsible was identified as the microalga Heterosigma akashiwo, which is known to cause algal blooms around the world.
This event was the first record of this organism in New Zealand. It is not known if it affected fish in the marine reserve. An industry funded phytoplankton monitoring programme was set up as a result of the bloom.
- Toxic and noxious phytoplankton in Big Glory Bay, Stewart Island, New Zealand. By
Lincoln MacKenzie, Cawthron Institute, 1991.