Marine Pests

What does it look like?

The adult Mediterranean fanworm is a tube-dwelling worm. There are many native fanworms that look similar, however, the Mediterranean fanworm is the largest fanworm in New Zealand, with its body measuring up to 20mm wide and from 100 – 800mm long.

It has a prominent single, spiral crown (fan) of feeding tentacles that extend out of the tube and can be 150mm wide. The crown is often banded orange, purple or white. Mediterranean fanworm’s outer tube is leathery, flexible and muddy looking in appearance.

Mediterranean fanworm can live in most artificial and natural habitats in the marine environment but it will not tolerate freshwater. It prefers sheltered, nutrient-enriched waters and is generally found in shallow, subtidal habitats to a depth of 30m. It attaches to a range of solid surfaces including artificial materials (wharf pilings, pontoons, etc.) as well as rocks, wood and benthic organisms (ascidians, mussels, oysters). It is also a common fouling species on moored vessels. Mediterranean fanworm can also be found on soft substrates, generally attached to a small buried fragment of shell or rock.

Why is it a problem?

Mediterranean fanworm can form dense colonies of up to 1000 individuals per square metre that will compete with native species for food and space. As a result, existing species can be squeezed out and new generations prevented from re-establishing. Therefore, Mediterranean fanworm could have a significant impact on our commercial and recreational fisheries, and marine environments such as Pania Reef.

The ability of this species to attach to a wide range of surfaces in varying environmental conditions, its fast rate of growth, and its prolific breeding habits, make it particularly competitive. It has no known predators in New Zealand.

Mediterranean fanworm is spread to new locations primarily through vessel biofouling, although the movement of aquaculture equipment or other marine structures may also contribute to its spread.   

photo credit: NRC

What does it look like?

The Clubbed tunicate has a long, club-shaped body tapering to a short, tough stalk.

The surface is rumpled and knobbly, and the leathery skin ranges in colour from brownish to white. The Clubbed tunicate can grow up to 160mm in length.   By comparison the native species is white to purple with a much longer stalk (two-thirds to three-quarters the overall length of the animal).

The Clubbed tunicate has been found in the low intertidal zone to water up to 40m deep, however, it is most commonly found in water less than 25m deep.

Clubbed tunicate grows on natural and artificial hard marine surfaces, including on rocks, shellfish or shell fragments, wharves, vessel hulls and aquaculture structures.

Why is it a problem?

The Clubbed tunicate is a highly efficient filter feeder which is able colonise a range of hard surfaces and tolerate wide ranges of salinity and temperature. These features enable the clubbed tunicate to form monospecific stands at high densities (up to 500-1000 individuals per square metre) which can outcompete native species. Therefore, Clubbed tunicate could have a significant impact on our commercial and recreational fisheries, and marine environments such as Pania Reef.

Clubbed tunicate is spread to new locations primarily through vessel biofouling, although the movement of aquaculture equipment or other marine structures may also contribute to its spread.   

In 2015, 351 non-indigenous species were identified in New Zealand’s coastal waters and 187 had established a breeding population.  The table below shows some of the marine pests established in New Zealand and the impacts they can have - some of these could have impacts in Hawke’s Bay coastal waters. 

Many other marine pests have already established in New Zealand, and others threaten to invade; to find out about other marine pests check out the marine pest identification guide from MPI.