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

Undaria on mooring rope in Sunday Cove.
Undaria on mooring rope, Sunday Cove

The Asian seaweed Undaria pinnatifida (Undaria) has established in many parts of New Zealand over the last 20 years. Often called 'the gorse of the sea', Undaria is a threat to Fiordland’s unique marine environment and the fishing and tourism economies it supports.

Controlling Undaria

Until April 2010, Fiordland had been apparently free of this pest weed. At that time a single mature plant was found in the remote Sunday Cove in Breaksea Sound and subsequent investigation uncovered a small area of growth.

Environment Southland, MPI Biosecurity New Zealand and DOC joined forces to try and eliminate Undaria from Sunday Cove. Regular diving inspections were carried out and any new plants were removed before they had a chance to reproduce. This joint-agency response continued succesfully for seven years with no mature plants discovered since the original find.

Map of Sunday Cove (JPG, 237K)

In April 2017 a compliance patrol found six mature Undaria plants on a mooring line in Beach Harbour about 2 km from Sunday Cove in Breaksea Sound. Further investigation revealed more of the invasive weed throughout Beach Harbour and the John Islands. Experts believe it has come in from a vessel rather than being spread from Sunday Cove.

This incursion highlights the importance of the new Fiordland Marine Regional Pathway Management Plan. The plan incorporates rules for clean vessels, gear and residual seawater, and requires all vessels entering the area to hold a 'Fiordland Clean Vessel Pass'.

Current monitoring of these sites in Breaksea Sound will determine the course of action.

You can help

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.

  • 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 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.

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