Divers searching for invasive seaweed Undaria in Te Puaitaha/Breaksea Sound
Image: Richard Kinsey | DOC

Asian seaweed (Undaria pinnatifida)

Introduction

The pest seaweed Undaria is a threat to Fiordland’s marine environment with its ability to quickly establish and outcompete native marine species.

Your help is needed to limit the spread of this invasive pest in Fiordland waters.

The threat of Undaria

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Undaria on mooring rope, Sunday Cove
Image: DOC

The Asian seaweed Undaria pinnatifida (Undaria) is an invasive seaweed which thrives in our marine environment.

It can grow and spread through areas very quickly and has established in many parts of New Zealand over the last 30 years. Often called 'the gorse of the sea', Undaria has the potential to significantly impact Fiordland’s unique marine environment and the fishing and tourism economies it supports.

Undaria grows from spores which are released into the water column by mature plants. These spores attach to vessel hulls and are easily transported to different areas via travelling vessels.

Controlling Undaria

Until 2010, Undaria had apparently not yet reached Fiordland waters. In April, 2010, a single mature Undaria plant was found in the remote Sunday Cove in Te Puaitaha/Breaksea Sound and subsequent investigation uncovered a small area of growth.

Since 2010, Environment Southland, MPI Biosecurity New Zealand and DOC have joined forces to try and eliminate Undaria from Te Puaitaha/Breaksea Sound. Monthly diving inspections are carried out to remove any plants in the area. Additional monitoring is carried out in Taiari/Chalky Inlet, where a mature plant was found in 2019.

Map of Sunday Cove (JPG, 237K)

This incursion of Undaria in Fiordland highlights the importance of the new Fiordland Marine Regional Pathway Management Plan which requires that all vessels entering the Fiordland Marine Area hold a ‘Fiordland Clean Vessel Pass’.

You can help

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An Undaria plant in Te Puaitaha/Breaksea Sound
Image: DOC

The Asian seaweed Undaria pinnatifida (Undaria) is an invasive seaweed which thrives in our marine environment.

Your help is needed to ensure Undaria doesn't spread to new locations in Fiordland and other pest species aren't introduced.

Pests like Undaria and other fouling species can hitchhike to new locations on dirty boat bottoms and marine equipment so you should:

  • make sure your antifouling paint is in good condition and have your hull checked for marine pests regularly
  • check, clean and dry mooring lines and buoys, fishing or dive gear, kayaks and other recreational equipment before travelling to Fiordland and after mooring in Breaksea Sound.

If you are visiting Te Puaitaha/Breaksea Sound:

  • clean mooring lines, buoys, fishing and dive gear with detergent before you move on.
  • mooring in more than 30 m of water will limit the likelihood of picking up Undaria.

Don’t be the next boatie to spread this pest species.

More information

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