Mediterranean fanworm

Sabella spallanzanii

Mediterranean fanworm

Mediterranean fanworm

Legal Status: Unwanted Organism - MFish
Status in New Zealand: Established
Organism: Water snails, crabs, shellfish, starfish, and other aquatic

(Photo right: S. Wilkens, NIWA)

This pest is an unwanted organism and is present in New Zealand. It has become established in Lyttelton Port, the wider Waitemata Harbour/inner Hauraki Gulf in Auckland and in Whangarei Harbour. There are ongoing elimination programmes underway in the Coromandel, Tauranga, Gisborne and Nelson harbours where this pest has been detected; also Picton and Tutukaka marinas where Sabella has been recently detected (November 2014 and March 2015, respectively).

For suspected finds anywhere else in New Zealand (apart from Lyttelton, the wider Waitemata and Whangarei harbours) please call MPI on 0800 80 99 66.

Marine pests such as the fanworm are easily transported to new locations on dirty boat hulls, inside sea chests, emergency fire intakes and other niche areas.

If you are the owner/operator of a moored boat, you can help prevent the spread of this marine pest by ensuring your boat's hull is clean and well antifouled. It is especially important that your boat's hull is clean before setting out from Auckland, as this region has high densities of fanworms in many places and there is a very high risk of spreading this marine pest to other areas in New Zealand.

worker cleaning fanworms from boat hull  large Mediterranean fanworms on boat hull
Above: A recreational boat which is heavily fouled with Mediterranean fanworm. Because of their size, these large fanworms probably spawned before the vessel was slipped. It's important that boat hulls are kept regularly cleaned to prevent fanworms from establishing and spreading.
Photos: H. Lass, Bay of Plenty Regional Council.

Owners of commercial vessels are also asked to ensure their vessels are regularly maintained with good effective antifouling in place. It’s also important that sea chests and other niche areas are regularly maintained. Having clean hulls will also improve fuel efficiency.

Mediterranean Fanworm
Sabella spallanzanii worm with fan extended from its tube.
Photo: G. Read, NIWA


The Mediterranean fanworm is a marine animal that is typically found in harbours and estuaries, living in depths of anywhere between one to 30 metres.

It consists of a segmented worm living inside a tube which is usually fixed to a hard surface. The worm has a single spiral fan (radiole) which extends out of the top of the tube. The tube is tough and flexible and often muddy in appearance. It can often have other organisms growing on the surface.

Mediterranean fanworms can grow to over 40 cm high. The fans are white, banded with brown and orange, and the central stem is orange.

This particular fanworm looks different to New Zealand native fanworms in that it is larger and it has the single fan. Fanworms with two spiral fans are NOT this pest.


The Mediterranean fanworm (Sabella spallanzanii) forms dense colonies that could affect native species by competing for food and space. Recent studies have indicated impacts on the establishment of new generations of some species, and on nutrient flow.

The presence of dense colonies of this species could also change the underwater scenery of an area, potentially impacting on dive tourism activities.

While they have not yet been recorded to have had significant impacts on fisheries in New Zealand, they could become a nuisance to recreational and commercial fishers by clogging dredges and fouling other fishing gear when in high densities. This fanworm has been detected on some mussel farms in the Hauraki Gulf and Coromandel region recently. Because mussels and fanworms are filter feeders, the productivity of mussels may be affected if the fanworm infestations become high.

fanworm growing among green lip mussels
Above: A heavy infestation of Mediterranean fanworm growing amongst green lip mussels on the hull of a barge. Photo: MPI

Mussel dropper lines that have become heavily infested with Mediterranean fanworm
Above: Mussel dropper lines that have become heavily infested with Mediterranean fanworm. Photo: K. Walls, MPI.

Initial MPI efforts to eliminate Mediterranean fanworm in Lyttelton Port and Waitemata Harbour, Auckland, 2008 and 2009

When this fanworm species (Sabella spallanzanii) was first detected in New Zealand (in Lyttelton Port) in May 2008, MAFBNZ (now MPI) embarked on a $3.5 million, five-year local programme to attempt elimination of the pest.

The elimination work involved control of the fanworm by diver search and removal and regular monitoring to detect any hidden populations. An educational awareness programme was also undertaken to encourage the owners of moored vessels to keep their boat hulls clean to avoid spreading the pest.

In 2009 the elimination programme was extended to treat what was thought to be a small population of the fanworm in Auckland's Viaduct Basin. In January 2010, the fanworm was, however, found in large numbers on structures and vessels in the upper Waitemata Harbour. Consequently in June 2010 a decision was made to cease the elimination programme as it was no longer feasible to attempt eradication of the fanworm from New Zealand.

Since 2010, MPI has focused on working with and supporting regional councils where new incursions of Sabella have been detected in an effort to prevent new populations establishing in new areas.  MPI is also developing a domestic marine pathways management approach to help prevent Sabella being spread by the movement of vessels around the country.

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Page last updated: 15 December 2016