The invasive Mediterranean aquatic pest has spread to Tauranga Harbour.
Bay of Plenty Regional Council confirmed a single specimen of the invasive aquatic pest Mediterranean fanworm (Sabella spallanzanii) had been found at Pilot Bay in Tauranga Harbour.
The regional council's natural resource operations general manager Warwick Murray said it was extremely disappointing the unwanted organism had appeared in Bay of Plenty waters.
"It's most likely the organism was brought here on the hull of a boat. Boat owners must remember to regularly clean their boat hull, keep their anti-fouling paint in good order, and ensure the hull is clean before they travel to a new region."
Currently only a single specimen had been discovered, however Tauranga Harbour would be surveyed to establish if more existed.
A University of Waikato diver found the fanworm growing from a rock near the bathing sheds at Pilot Bay on September 13.
The Ministry for Primary Industries confirmed it was the invasive aquatic pest.
The Mediterranean fanworm can grow in dense, thick mats which compete with native plants and animals for nutrients and space.
It can interfere with boat equipment and aquaculture, and affect recreational activities like diving by changing the underwater character.
Once well established, it's very hard, or even impossible, to eradicate.
The Mediterranean fanworm is also found in Auckland, Whangarei and Lyttelton Harbours, and was discovered on two barges in Coromandel Harbour earlier this year.