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Undaria monitoring success

Environment Southland recently completed monitoring of sites around Rakiura/Stewart Island. The invasive seaweed had previously been found in Broad Bay, Easy Harbour and other anchorages on the southern coast, and removed in previous years. No Undaria was found in Broad Bay and the small amounts of regrowth found elsewhere were removed.

Environment Southland biosecurity operations manager Ali Meade said all Undaria was removed and no further expansion of the population was identified.

“The reduced number of plants and density is a good sign that our work to eliminate the incursion is on track. Follow-up removal efforts will be required to ensure elimination from the site.”

“This is a great result and shows what can happen with quick efforts to remove the invasive species. Further surveillance will be required to confirm complete elimination over the next few years but it looks promising.”

The final aspect of the dive trip was to survey key anchorages around the southern coast of Rakiura and within Port Pegasus for Undaria, carpet sea squirt and other marine pests.

“No Undaria was found at the sites inspected around the southern coast or in Port Pegasus. Some sea squirts were found in very low numbers but were not positively identified as the invasive species, carpet sea squirt.”

Photographs of the ascidians will be sent away for identification, but they are most likely native, Ali Meade said.

Boaties should keep an eye out for undaria in harbours and notify their local council or send in photos via the Find-A-Pest app is they see anything unusual.


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