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Marine pests

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Unwanted marine pests have been recorded in New Zealand waters. See a map of marine pests in NZ.

They’re easily spread through ballast water and hull fouling, threatening our fabulous underwater environments, seafood stocks and aquaculture industry. They can also cause costly and unsightly damage to boat equipment, wharves and other marine structures.

Stop the spread - keep your boat hull clean

Keep your favourite fishing and diving spots pest-free.

  • Keep your boat bottom and any niche areas clean (no more than light slime, all the time)
  • Keep your anti-fouling paint fresh - manufacturers usually recommend replacement every 1-2 years 
  • Check your hull before you travel to a new area, every time
  • If your boat is heavily fouled, haul it out. Cleaning underwater will only spread any pests that were hiding on there.

We'll be doing spot checks on boat hulls in Bay of Plenty this summer. If pests are found on your boat you may be asked to haul it out for cleaning.

Visiting a marina in the Bay of Plenty?

To prevent the spread of marine pests, Bay of Plenty marinas require visiting vessels to have been recently cleaned. That means:

  • Antifouled in the last six months
  • Lifted and washed in the last month

PROVE IT! Haul out and paint receipts - check with the marina what proof is required. Some high-risk vessels may be subject to additional marina requirements.

Tauranga marinas have their own hull hygiene rules for visiting vessels. Plan ahead - contact Tauranga Bridge Marina on 07 575 8264 or Tauranga Marina on 07 578 8747 for details.

See the Boaties Guide to Marine Pests to check the rules for Auckland, Northland and Coromandel regions.

See hull cleaning advice from our Harbourmaster or view the MPI Clean Marine video for helpful tips on hull hygiene.

Keep watch, call it in

If you think you’ve seen the marine pests below (or any others) in the Bay of Plenty, call us on 0800 STOP PESTS (0800 786 773) or MPI on 0800 80 99 66. Note the location and grab a sample if you can.

Download our marine pests poster,  the MPI Marine Pest Identification Guide (pdf, 1.59MB), visit the MPI website or contact a Regional Council Biosecurity Officer to find out more about identifying and managing marine pests.

Mediterranean FanwormMediterranean fanworm (Sabella spallanzanii)

This pest can look like some native New Zealand fanworms, but it’s larger and has just one single fan (instead of the usual two fans). The fan is white and banded with orange/brown, in a parchment-like tube up to 40 cm tall. It’s already become established in Lyttelton and Auckland and is being controlled in Northland. Elimination programmes are underway in Coromandel, Tauranga and Nelson harbours where it’s been found recently. Read more

Watch One News video about Mediterranean fanworm. 

Styela clava, clubbed tunicate sea squirt. Credit Northland Regional CouncilClubbed tunicate sea squirt (Styela clava)

This brown coloured, club shaped sea squirt often appears fuzzy underwater. It has a stalk that it uses to attach itself to hard surfaces such as rocks, boat hulls or marine structures. It’s become widespread throughout Auckland’s Hauraki Gulf and has been found in Coromandel Harbour, parts of Lyttleton Harbour, Nelson Harbour and Northland. It’s being controlled in Picton and Waikawa Bay.

Read more


Asian paddle crabAsian paddle crab (Charybdis japonica)

A swimming crab that’s native to South East Asia and now present in Auckland and Northland.

They live in estuaries where there’s firm or fine muddy sand. They’re more aggressive than our native paddle crab. Adult shells grow up to 12cm wide.

Read more 

 Australian tunicate sea squirtAustralian tunicate sea squirt (Eudistoma elongatum)

This sea squirt grows in clusters of white tubes, usually found in muddy bottomed tidal areas and on wharf piles and other structures.

It’s known to be present in some Northland sites where it lives just below the waterline and can often be seen in high densities at low tide during summer. It dies back in winter. 

Read more 


These marine pests have become established in Tauranga Harbour. Make sure you clean your boat before travelling somewhere new to avoid spreading to other places:

Didemnum sea squirt. Credit A.Coutts Cawthron InstituteDidemnum sea squirt (Didemnum vexillum)

Spongy looking and light mustard colour, this is also known as the Whangamata sea squirt. 

It can look like a yellowish wax dripping over ropes or mussel lines. It readily occupies hard surfaces including boat hulls, rocks and wharf pilings. 

This pest has become established in the Marlborough Sounds, Tauranga Harbour and at Whangamata.

Read more



Undaria, Asian kelp. Credit K.Blakemore Department of ConservationAsian kelp (Undaria pinnatifida)

Mature plants have brown, green and yellow colouring, growing 1-2m tall. It has a distinctive midrib that you don’t see on native Ecklonia kelp.  It’s present in most major New Zealand ports, including Tauranga Harbour. 

The West Coast of the South Island and large areas of the North Island's West Coast are still thought to be Undaria free. 

It was recently detected in Fiordland and is being controlled there.

Read more 


Mediterranean fanworm, clubbed tunicate sea squirt, and Asian kelp are classified as Unwanted Organisms under the Biosecurity Act.  You could be fined or prosecuted for knowingly moving or transferring these pests, so keep your boat hull clean!

Find out more about Tauranga Harbour and Regional Council's work to protect it.

Regional Council's work on marine pests

Our work to stop the spread of marine pests involves more than just hull checks. Regional Council has declared two marine pest Small Scale Management Programmes (SSMPs). This is a Biosecurity Act process that enables Council to respond more quickly and effectively when marine pests are detected in the Bay of Plenty.

Where voluntary co-operation can’t be achieved, the SSMPs empower Regional Council staff to take action such as inspecting or seizing boats or other equipment, or directing owners to remove or clean their boats or marine structures, to prevent the spread of specific marine pests.