Mediterranean fanworm (Sabella spallanzanii) was found at the multipurpose wharf at Port Otago, during routine winter surveillance carried out by Niwa staff, from August 26-30.
Now boat owners and water users across Otago’s coastline are being asked to check their vessels' hulls and moorings for any sign of the pest.
If boaties think they have seen Mediterranean fanworm, they are urged to contact the Otago Regional Council immediately so specialists could be brought in to remove it.
Otago Regional Council environmental implementation manager Libby Caldwell emphasised the importance of public vigilance.
"We’re urging all boat owners, commercial and recreational, to be vigilant.
"Reporting any sightings early is a simple yet crucial step in preventing the spread of this invasive species and protecting Otago’s marine environment.
"It attaches itself to hard surfaces such as boat hulls, wharf piles and rocky reefs, where it can out-compete native species for food and space, disrupting local marine life and impacting aquaculture and fisheries."
The species was illegal to move around or remove without a permit.
She urged boaties not to try to remove it themselves because it could spread the pest.
"It is very important that people do not attempt to remove this species from their boat or mooring without contacting Otago Regional Council."
It is believed to have been brought into the harbour by a vessel, but it was not known what type.
Environment Canterbury also recently detected Mediterranean fanworm at new sites in Lyttelton Harbour.
"These recent findings underline the continued risk of reintroduction of this pest, especially given the high level of vessel traffic in Otago Harbour," Mrs Caldwell said.
It is not the first time it has been detected in Port Chalmers.
In 2019, a small number of Mediterranean fanworms were detected and removed.
The ORC is working with Port Otago and Biosecurity New Zealand, and will look at partnering with mana whenua, to ensure a co-ordinated response to the latest discovery.
"Further surveys will likely be conducted to determine whether other Mediterranean fanworms are present," she said.
