Mediterannean fanworms can form dense beds of up to 1000 individuals per square metre. They can outcompete native species, including filter-feeding organisms, for food and space and can threaten commercially and culturally important kaimoana species like kuku/kūtai (mussels), tio (oysters), and tipa/tupa (scallops).

Fanworm tubes can attach to aquaculture equipment or vessels, increasing harvesting and fuel costs, clogging fishing gear and dredges, and impacting on fishing operations.

This pest spreads mainly through hull fouling on vessels but can also be transported by aquaculture equipment and marine structures.

The Mediterranean fanworm is native to the Mediterranean Sea and parts of the North-Eastern Atlantic coast.

The Mediterranean fanworm was first detected in 2008 in Lyttelton Harbour, where it is now well established. Since then, it has spread to both the top of the North Island and South Island, and has been recently detected in Otago Harbour.

We are working to prevent the establishment of Mediterranean fanworm in Otago and help prevent its spread into pristine environments and neighbouring areas such as Fiordland.

• Size: Tube-dwelling worm, usually reaching between 10–50 cm but can grow up to 80 cm on occasion.
• Appearance: Tubes are leathery and flexible with a muddy appearance. Prominent spiral crown of feeding tentacles that extend out of the tube. The spiral crown is often banded orange, purple or white.
• Similar species: It can often be mistaken for similar looking native species, however, native Sabellid and Serpulid tubeworms are smaller (<20 cm) and have two fans. For more information visit this identification guide from marinebiosecurity.niwa.co.nz.
• Habitat: It attaches to a wide variety of hard surfaces including rocks, wood, steel, concrete, shellfish and artificial materials, but can also be buried up to 10cm deep in soft substances.

Late summer to autumn (February to April in Southern Hemisphere). During this period, individuals are more conspicuous due to their extended feeding plumes, making them easier to spot. Warmer temperatures often encourage growth and reproduction, increasing their presence.

It is an offence to breed, knowingly communicate, exhibit, multiply, propagate, release, or sell, an unwanted organism (Biosecurity Act 1993).

ORC is currently developing a marine biosecurity programme and needs to obtain more information on species distributions before pursuing management options. If you think you have spotted clubbed tunicate, please let us know by calling 0800 474 082 or emailing biosecurity@orc.govt.nz