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Marine Pests

Marine pests can have a significant impact on our natural coastal environment, and we can all take steps to help prevent them establishing in Hawke’s Bay waters.

Why are marine pests a problem?

Marine pests compete with and prey on native species, modify natural habitats, affect marine industries, and alter ecosystem processes. Once here, they are difficult and expensive to get rid of.

Hawke’s Bay Regional Council is part of the North Marine Biosecurity Partnership with 6 other regional and unitary councils, sharing knowledge and expertise.

In early 2019 Hawke’s Bay Regional Council commissioned a survey by divers of the underwater structures in Napier’s Inner Harbour to look for Mediterranean fanworm and Clubbed tunicate. This recent survey showed that the harbour is clear of these pests, and the survey will be carried out in another 2 years.  The previous diver survey in 2016 also showed these pests were not present. 

Also early in 2019 regional council biosecurity staff held a well-attended workshop to discuss marine pest issues with local boating and harbour interests.

In November 2017 Hawke’s Bay Regional Council staff worked with the Mana Ahuriri Trust to remove 219 tonnes of invasive marine tubeworm (Ficopomatus enigmaticus) from Ahuriri estuary. Read more about that project.

Staff have an important advisory role for landowners and work to raise awareness.


How do they enter and spread?

Boat hulls are considered the main way marine pests are spread. A restricted number of harbours and vessels entering Hawke’s Bay presents an opportunity to manage the main domestic vector pathway of marine pests entering Hawke’s Bay waters.

What to look out for

Two  marine pests - Mediterranean fanworm (Sabella spallanzanii) and Clubbed tunicate (Styela clava) - are  classified as exclusion pests in the Regional Pest Management Plan.  Neither of these pests are known to be established in Hawke’s Bay but are established in some other areas of New Zealand.  We want to keep our marine environment free of these invasive pests.

What does it look like?

Fanworm in water 2 credit NRC

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?clubbed tunicate

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 Ministry for Primary Industries' marine pest identification guide.

Marine Species


Impact and History

Asian date (bag) mussel

Arcuaatula senhousia

Small, thin-shelled mussel that lives in estuaries

  • Modifies native habitats
  • Established in Auckland in 1970’s

Asian paddle crab

Charybdis japonica

Large, aggressive swimming crab

  • Predator of native species
  • First recorded in Auckland region in 2000

Australian droplet tunicate

Eudistoma elongatum

Sea squirt that forms long, white cylindrical tubes

  • Smothers beaches, rocks and tide pools and a pest to aquaculture
  • First reported in Northland in 2005

Greentail (greasyback) prawn

Metapenaeus bennettae

Prawn that grows to about 13cm in length

  • Estuarine deposit feeder
  • First recorded in Waitemata Harbour in 2009

Mediterranean fanworm

Sabella spallanzanii

Very large, fast-growing worm that builds long, flexible tubes up to 1m in length.

  • Modifies natural habitats
  • Displaces native and fisheries species
  • Affects cycling of nutrients within natural ecosystems
  • Establishment date not recorded

Clubbed tunicate

Styela clava

Rapid growing sea squirt that forms dense colonies

  • Displaces native and fisheries species
  • Establishment date not recorded

Fragile clam

Theora lubrica

 Small bivalve (shellfish with two hinged shells)

  • An indicator of marine pollution
  • Present since 1970’s


Undaria pinnatifida

Fast-growing brown kelp

  • Pest of aquaculture and other industries
  • First reported in New Zealand in 1987
  • Established in Hawke’s Bay

Pyura sea squirt

Pyura praeputialis

Sea squirt that inhabits the mid intertidal zone to the shallow intertidal zone

  • Potential to significantly alter the structure and composition of intertidal communities
  • First recorded in Northland in 2007


Didemnum vexillum

Grows on hard surfaces from the intertidal zone down to 65m

  • Displaces other organisms by growing over them
  • Hinders larval settlement through the production of chemical compounds

Visit our Pest Hub to find more information about specific marine pests

What can I do?

You can help prevent the spread of marine pests by:

  • Keeping a vigilant eye out for Mediterranean fanworm and clubbed tunicate in Hawke’s Bay waters and reporting them immediately

  • Ensuring your vessel's hull is clean and free of fouling before you travel to a new area

  • Regularly cleaning your vessel’s hull – keeping fouling growth to no more than a slime layer and/or goose barnacles

  • Applying a thorough coating of antifouling paint and keep it in good condition

  • Cleaning and drying any marine equipment (e.g. ropes, lines and pots) before using in a new area

  • Inspecting areas on your boat that retain water for signs of marine life

  • Checking for aquatic weeds tangled around anchors, trailers and other equipment

  • Keeping your haul out/antifoul receipts onboard to provide as evidence of recent treatment or lift and wash

  • Make use of haul out facilities in the upper North Island

Marine pest rules for Hawke’s Bay

Under the Biosecurity Act 1993, operators of a vessel must abide by this rule:

The operator of a vessel entering the waters of the Hawke’s Bay Regional Council must ensure the hull (includes hull area, niche areas and wind and water line) or any structure or navigation aid of any origin, is sufficiently cleaned and antifouled so that there is no more than a slime layer and/or goose barnacles.

International Vessels

International commercial shipping is governed by international rules about ballast and hull cleaning.

International vessels that stay in New Zealand waters for up to 20 days and are only visiting approved Places of First Arrival, remain under and must abide by the rules of the Craft Risk Management Standard (CRMS): Biofouling.

International vessels staying for 21 days or more, or visiting non-approved Places of First Arrival, must abide by the Coastal Plan rules of the relevant regional council/unitary authority, following the completion of MPI biosecurity inspections in accordance with CRMS.

International vessels arriving in New Zealand waters have additional obligations under the Craft Risk Management Standard: Biofouling on Vessels Arriving to New Zealand (May 2014).

Found something unusual?

If you see anything out of the ordinary in a harbour, estuary or beach - such as unusual marine plants and animals, or unusual numbers of dead fish or aquatic life - please contact Alice McNatty, the Regional Council’s marine biosecurity advisor.

06 833 8083 or 0800 108 838

Send an email

It helps too if you can take a photo or sample, and record the location.

 Stay updated

Visit Marine Pests NZ's website for the latest updates. 

marinepest poster A2 fin nocrop



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