Ocean floor cleaned as part of Tasman Bay biosecurity operation

27 February 2008

MAF Biosecurity New Zealand (MAFBNZ) is arranging to dredge an area of seabed in Tasman Bay early next week to reduce the risk posed by marine organisms that fell on the ocean floor during the cleaning of an oil rig there late last year.

The rig, the Ocean Patriot, had been directed to remove biofouling species that had been listed as potential pests (including New Zealand's green shell mussel) by the Victorian government in Australia before relocating there. Particularly rough seas meant it carried out this defouling operation within the sheltered waters of Tasman Bay. The actual defouling site where the rig cleaned was approximately 12 nautical miles offshore.

MAFBNZ gave the go-ahead for the defouling in Tasman Bay, as far off shore as possible, based on survey information indicating there were no unwanted organisms on the rig, and the fact that the weather was posing a serious threat to human safety.

Further results of testing on samples taken from the rig during its survey have shown, however, that there may have been small numbers of a potentially invasive South African brown mussel (Perna perna) on the rig structure. Perna perna is classified on a global database as an invasive species, but it is not really known how well this mussel species would establish in the New Zealand environment.

MAFBNZ Incursion Response Manager David Yard says on receipt of the further test results, a check of the clearly defined area was undertaken using robotic cameras and later dredging for samples.

"This dredging of seabed material revealed the presence of living mussels, predominantly blue and green shell mussels which are not a problem in New Zealand. However, two individuals, thought to be Perna perna were also found," says Mr Yard.

"Specialist taxonomists are still formally identifying these individuals, which are easily confused with greenshell mussels. Work will also be undertaken to attempt to determine if any of the mussels retrieved from the seabed had spawned recently, posing a threat of establishment."

In the meantime, clean up operations are scheduled to begin at the defouling site on Monday next week, weather permitting. The affected area will be thoroughly dredged and, apart from some samples taken for further analysis, the materials collected will be disposed of onshore in a landfill. The clean up operation is being largely funded by the oil rig's owners.

MAFBNZ has also held a meeting with industry and iwi representatives in Nelson today to inform local people about the situation as well as to gather important local or marine farming information that may help in any future actions.

For further information, please contact:

Lesley Patston, Phone 029 894 0163

Contact MPI

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