Undaria discovered in Subantarctic Islands, DOC to consider eradication

Date:  07 December 2006

The Department of Conservation is investigating the discovery of a small population of undaria for potential eradication at one of the Subantarctic Islands.

A DOC dive team recently found the invasive seaweed undaria had established on a section of two lines at the fishing boat mooring in Ho Ho Bay at the Snares Islands with a small number of plants spreading onto the surrounding rocks.

Southern Islands Area Manager Andy Roberts said a team would be returning to the Snares to remove more plants, survey how widespread the plants were and gather more information to determine if eradication was feasible.

He expected the team would leave, weather permitting, on December 8 and return around the 15th.

While undaria would undoubtedly have an impact on the environment, to what extent was unknown.

“We do know that in many cases undaria has been shown to permanently and irreversibly diminish the natural character and reduce biodiversity of the marine environment,” Mr Roberts said.

He said discovery of undaria in the Snares highlighted the challenges Southland faced with both vessels and equipment being a vector for invasive marine species.

It was believed the pest weed was brought to the Snares by the line being infected with tiny undaria cells prior to arrival or, alternatively, undaria was transferred to the line from a boat hull infected with mature plants. The mooring line was probably modified with a new section of rope sometime within the last 18 months.

“Even if eradicated from the Snares, the risk of reintroduction cannot be eliminated and this is something that needs to be taken into consideration when considering an eradication programme” Mr Roberts said.

Assessment of eradication possibilities would be based around the need to remove undaria plants each six weeks in their growth season before they release spores, and the number of years a programme would need to be run for. In addition an accurate assessment of the re-invasion potential is required.

Mr Roberts said the dive team would survey the surrounding area and neighbouring bay of the infected site, remove as many plants as could be found, investigate the plants’ maturity states and, through DNA testing, determine where the plants were transferred from.

END OF STATEMENT

For more information please contact Department of Conservation Southern Islands area manager Andy Roberts, +64 3 211 2400 or email aroberts@doc.govt.nz

Additional information:

• Undaria is a fast growing invasive seaweed that was accidentally introduced to New Zealand around 1987.
• Undaria was first found in Wellington Harbour in 1987
• It is native to Japan, China and Korea.
• The main way it is spread is by its spores sticking to the hulls of boats and hitch-hiking to a new place or onto another vessel’s hull or by infesting lines or other gear that are moved from one site to another. .
• Undaria can permanently change underwater ecosystems and fouls mussel and salmon farms and boats.

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