Marine pests

Marine pests pose a serious risk to the coastal waters of Waitaha Canterbury. They spread rapidly, outcompete native species, alter marine habitats, and can harm mahinga kai, recreation, and marine industries such as aquaculture.

Everyone who uses our marine environment can help stop the spread of marine pests, and small actions can make a big difference.

How marine pests spread

Marine pests often spread by hitchhiking on boats and equipment. They can attach to hulls, anchors, chains, ropes, and other gear, and be moved to new locations when vessels relocate.

Marine pests to watch for in our waters:

Mediterranean fanworm (Sabella spallanzanii)

  • What it is: Mediterranean fanworm (Sabella spallanzanii) is a highly invasive species
  • Where it’s found: Randomly distributed around New Zealand from Auckland to a one-off sighting in Bluff (2025).
  • Why it matters: It forms dense colonies that can outcompete and smother native species, changing marine habitats. In high densities, it is likely to also impact commercially and culturally important kaimoana species.
  • How it spreads: Sabella is commonly found on vessel hulls, moorings, wharf piles and other submerged structures.
Check how to identify mediterranean fanworm and what to do next

Undaria (Japanese kelp) (Undaria pinnatifida)

  • What it is: Undaria is a large invasive seaweed with a crinkly appearance, ranging in colour from brown to green and yellow. It can grow 1–2 metres long.
  • Where it’s found: Widely established in coastal areas around New Zealand.
  • Why it matters: It forms dense underwater forests that compete with native seaweeds and can significantly alter marine ecosystems.
  • How it spreads: Often spread via boat hulls and contaminated marine equipment.
Check how to identify Undaria and what to do next

Clubbed tunicate (Styela clava)

  • What it is: Clubbed tunicate (a type of sea squirt) is a short, bottle-shaped organism with a narrow base. It has rough, rubbery skin, is brown to reddish in colour, and can appear fuzzy underwater.
  • Why it matters: Heavy infestations can impact biodiversity and increase maintenance costs for marine users.
  • Where it’s found: Present in several coastal areas of New Zealand (especially around ports and harbours).
  • How it spreads: Attaches to hard surfaces such as pontoons, wharves, ropes, and aquaculture gear.
Check how to identify clubbed tunicate and what to do next

What you can do to stop the spread

You can help protect Canterbury’s marine environment by taking a few simple steps every time you’re on the water:

  • Check your hull, propeller, anchor, chain, ropes and gear
  • Clean off any seaweed, slime or marine growth before moving locations
  • Maintain antifouling and keep up regular hull maintenance
  • Dispose of removed material safely at landfill— never put it back in the wate

Check out our handy guide to good boat maintenance practices.  

These actions support Protect Our Paradise, a national campaign led by Biosecurity New Zealand (MPI) to stop the spread of marine pests.

Seen something unusual? Report it

Early reporting is critical

If you see a marine organism that looks unusual or out of place:

  • Take clear photos
  • Note the exact location (including vessel name and mooring, or physical site)

Report it as soon as possible by:

What we’re doing to protect Canterbury’s waters

As the Regional Council we work with Biosecurity New Zealand, iwi, industry, and communities to prevent the spread of marine pests and respond quickly to new incursions.

We regularly monitor our coastal waters, including seabed mapping and marine surveillance, to detect pests early.

We also work with Earth Sciences New Zealand to help stop the spread of marine pests, using new technology to protect our harbours.

More about marine pests and responsibilities

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