Invasive Asian seaweed threatens Hauraki Gulf

It may be too late to protect the Hauraki Gulf from an invasive kelp dubbed "the gorse of the sea" after the discovery of an infestation on Auckland's waterfront.

Undaria, also known as Asian kelp and listed as one of the world's 100 worst invasive species, was discovered at Westhaven Marina late last year. A survey found colonies from the marina to Marsden Wharf and in the Viaduct Basin near the Team New Zealand base.

The worry now is that the kelp, which can grow to around 1.8m and rapidly colonises the seabed, will spread into harbours at Great Barrier Island or into marine reserves further north such as the one at Goat Island, Leigh.

It is thought the kelp arrived here on the hull of a contaminated barge or similar vessel. Undaria spreads by clinging to the hull of boats or to wharf and marina piles and releases reproductive spores. It was first found in New Zealand in Wellington Harbour in 1987 and since then has been found at every major port except Tauranga.

It has spread to Stewart Island, Kaikoura, Golden Bay and the Coromandel Peninsula but so far none has been found in Fiordland. Biosecurity New Zealand, the government agency dealing with land and marine pests, kicked for touch on the problem three years ago by decreeing the seaweed a "regional" problem, handing the control costs to regional councils.

It has been controlled at Stewart Island and was eradicated from the Chatham Islands but all government funding for control or eradication has now stopped.

Yesterday Auckland Regional Councillors lashed out at Biosecurity New Zealand.

"Fair and square it's the Government's responsibility," said David Hay.

ARC parks and heritage chairwoman Sandra Coney said because undaria was thought to like colder water, it was thought it would not get this far north.

"It's not behaving as predicted. We don't even know if it's spread to the outer islands of the gulf but a do-nothing approach is not an option," she said.

The ARC estimates containing it in the Waitemata could cost $300,000 in the first year and around $150,000 each year after that. Ms Coney said the council would raise the issue with Biosecurity Minister Jim Sutton and Conservation Minister Chris Carter.

Spreading weed

* Undaria is native to Japan and known as one of the world's 100 worst invasive species

* It was found in New Zealand in 1987 and has spread from Bluff to Auckland

* It is feared it could spread to Hauraki Gulf harbours such as Port Fitzroy at Great Barrier Island and to marine reserves such as Goat Island