Marine pests are plants or animals that originate from overseas and have aggressive growth or feeding habits that pose a threat to our underwater environments, seafood stocks or aquaculture potential.

Large clusters of unwanted marine pests such as fanworms or sea squirts can also cause costly and unsightly damage to boat equipment, wharves and other marine structures.

Most marine traffic entering the Bay of Plenty originates from Auckland or Northland and pose a risk to our region as both of those areas host populations of marine pests (such as Mediterranean fanworm and clubbed tunicate sea squirt) that are not yet established in the Bay of Plenty.

If pest-infested boats moor in the Bay and the pests are knocked off or allowed to spawn here, they could spread quickly and become difficult to control or eradicate.

Look out for the following pests

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!

Mediterranean fanworm (Sabella spallanzanii)

This pest can look like some native NZ fan worms, 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 established in Lyttelton and Auckland. Elimination programmes are underway in Coromandel, Tauranga and Nelson harbours.

Clubbed 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. 

Asian 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.

Australian 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.

Didemnum 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.

Asian 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. 

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.

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.

Here's how you can help:

  • 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.

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.