What the Undaria? A look at an intriguing marine pest species

Also known as wakame and Asian kelp, Undaria is a species of kelp native to the cold temperate coasts of the northwest Pacific Ocean, and considered to be one of the most invasive marine algae species in the world.

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It was first noticed in New Zealand in 1987 in Wellington, where it enjoyed the colder waters, and it is now found in more than 30 locations from the far North to Stewart Island and including two of our offshore islands. 

It moves around by hitchhiking with other biofouling species on boat hulls and on gear such as ropes on crayfish pots, and depending on the location it can thrive and change our underwater environments forever by competing with native species for nutrients and space. Or, where conditions aren’t so suitable for it, it can simply exist within the ecosystem. 

In Fiordland, Undaria is present in two locations (Breaksea and Dusky sounds). Extensive efforts by the joint-agencies (Environment Southland, the Department of Conservation, and Ministry for Primary Industries) have been ongoing since 2010 to manage Undaria in Fiordland. In 2024, Chalky Inlet was declared Undaria free again after a five-year joint-agency elimination programme.

Undaria can be commercially harvested and farmed under certain circumstances*. Near Dunedin, Ngāi Tahu is attempting to raise funds for Undaria management by harvesting and selling it as a food product, and also for stock food and fertiliser. The aquaculture industry is also harvesting it from the wild in Otago and the Coromandel. 

While it has been found in Northland as far as Houhora, it doesn’t fare so well in the warmer temperatures. However if you see it there, it should be reported to Northland Regional Council. 

Undaria is featured in our Marine Pest ID guide. Click here.

* MPI’s Commercial Use Policy contains further information.

Photos / Northland Regional Council