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

The movement of boats around the country between harbours increases the risk of marine pests spreading. Marine pests often ‘hitchhike’ on boats and equipment moving around the country, either from biofouling on boat hulls or from the discharge of ballast and bilge water.

The Bay of Plenty Regional Pest Management Plan 2020 – 2030 (RPMP) contains new rules to protect the region’s coast from unwanted marine pests.

Rule 1

The occupier in charge of a craft moving to, or within Bay of Plenty waters must ensure the hull is sufficiently cleaned and antifouled, so that the hull has no more than a slime layer and/or barnacles.

Rule 2

All aquaculture equipment (including ropes and floats) used within Bay of Plenty waters must not have been used outside Bay of Plenty waters or used within a known pest incursion zone in the Bay of Plenty.

Look out for the following pests

Asian paddle crab, Australian Droplet tunicate, Clubbed tunicate sea squirt and Mediterranean fanworm which are included in the Bay of Plenty Regional Pest Management Plan 2020 – 2030 (RPMP).

Mediterranean fanworm (Sabella spallanzanii)

A fast breeder with no known natural predators, they form dense colonies and compete with mussels and oysters for food. Can look like some native NZ fan worms but the Mediterranean fanworm is larger and has one single fan (instead of the usual two). Usually found on boat hulls, soft mud or anchored to solid surfaces like rocks, up to 30m deep.

Clubbed tunicate sea squirt (Styela clava)

This brown coloured, club shaped sea squirt can reach high densities and out competes native species for habitat and food. It can grow up to 16cm and has a stalk that it uses to attach itself to hard surfaces such as rocks, boat hulls or marine structures.

Asian paddle crab (Charybdis japonica)

An aggressive swimming crab that’s native to South East Asia. They live in estuaries where there’s firm or fine muddy sand. Adult shells grow up to 12cm wide and range in colour from pale green, olive green or chestnut brown. Most easily distinguished from the native paddle crab by their black tipped pincers.

Australian tunicate sea squirt (Eudistoma elongatum)

Grows rapidly in clusters, quickly smothering beaches, rocks and tie pools. Usually found just below the waterline in muddy tidal areas and on wharf piles and other structures. They grow between 5–30cm in length, are usually cream or white with light brown specks and will die back in winter but then rapidly re-grow in summer.

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.