Waikato Regional Council and other marine operators are warning boat owners to clean vessels before introducing them to a new water system to help stop the spread of the Mediterranean Fanworm.

The worm, which is also known as Sabella, has been confirmed in the Coromandel Harbour, while it has also taken hold in several regions around the North Island and is prolific in Auckland.

The regional council is currently working with the Ministry for Primary Industries, Marine Owners Association, plus a newly formed group made up of Northland, Auckland, Bay of Plenty and Gisborne councils, to raise awareness and stop the further spread of Sabella along the eastern seaboard from Coromandel to Gisborne.

Council says vigilance is necessary especially if boaties keep their vessels in infected areas for prolonged periods.

Boaties are being asked to anti-foul vessel hulls if it hasn't been done in the last six months especially if introducing the vessel to a new area.

If a boat should sight the Fanworm or any other unusual looking marine animal they should report it to the Ministry of Primary Industries' pest and diseases hot-line 0800 809966 or call the council on 0800 800 401.