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 such as kuku/kūtai (mussels), tio (oysters), and tipa/tupa (scallops).

Fanworm tubes can attach to vessels or equipment used for underwater farming. This increases harvesting and fuel costs, clogs fishing gear and dredges, and impacts fishing operations.

This pest spreads mainly through hull fouling on vessels but can also be transported by 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 around the country, and has been detected in Otago and Bluff Harbours.

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: This tube-dwelling worm usually reaching between 10–50 centimetres but can grow up to 80 centimetres on occasion.
• Appearance: Tubes are leathery and flexible with a muddy appearance. A prominent spiral crown of feeding tentacles that extend sout of the tube.
• Distinctive features: A single large spiral of feeding tentacles, often banded in bright colours such as 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 centimetres) 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 10 centimetres deep in soft substances.

Late summer to autumn (February to April). 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).

www.orc.govt.nz/fanworm