The worm, which was 59cm long, was found under the town wharf at a depth of 5m. The specimen was collected and sent for formal identification.
Environment Southland integrated catchment management acting general manager David Adamson said while no further specimens were detected during follow-up dives, the wharf’s extensive structure meant further surveillance was required to determine the extent of the spread.
"We’re unclear if the marine pest is more widespread in Bluff waters, so we’re planning further surveys to confirm its spread as a part of response planning."
Divers experienced in identifying Mediterranean fanworm will be brought in from outside the region.
Environment Southland is receiving support from Biosecurity New Zealand.
The Mediterranean fanworm is a segmented marine worm that forms dense colonies, displacing native species and threatening fisheries.
It attaches to solid structures such as wharf pilings and aquaculture equipment, potentially increasing harvesting and fuel costs. It competes with mussels and oysters for food, affecting their growth and viability.
The worm has a long, leathery tube that is pale brown with a muddy appearance and extends a spiral fan of yellow-orange filaments to collect food such as plankton.
Environment Southland was asking the public and marine industry to keep an eye out and report any suspected sightings. — APL
