Mediterranean fanworm is one of the more alarming marine pests to have established itself in New Zealand waters. Capable of colonising at densities of up to 1,000 individuals per square metre, it overwhelms native species simply by crowding them out. Picture that kind of infestation taking hold at one of our most-loved dive sites and the scale of the problem becomes clear.
The species is a filter feeder, drawing in large volumes of water and extracting nutrients and plankton, including the larvae of recreationally important fish species. The damage it does to local ecosystems is compounded by what it can do to your running costs: a hull carrying a significant fouling load of fanworm will be pushing through the water with considerably more drag, and your fuel bill will reflect it.
Known infestations have been confirmed across several regions. In Northland and Auckland, the species has been found in Whangaroa Harbour, Opua, Whangārei Harbour, the Hauraki Gulf including the Waitematā Harbour and Firth of Thames, the Port Fitzroy area and Wairahi Arm at Aotea / Great Barrier Island. On the Coromandel Peninsula it is present on the western side and at Square Top Island. In the South Island, Lyttelton Harbour is also affected. The species has also been recorded at Gisborne.
This location information was accurate at the time of publishing. If you come across Mediterranean fanworm anywhere outside these areas, please report it. For a full and up-to-date list of marine pest locations, visit the Marine Biosecurity Porthole.
