Dismay at mussel harvesting threat in Far North

INVASION: An infestation of Pyura stolonifera, in the process of smothering a mussel bed at Twilight Beach.PHOTO/SUPPLIED

A Far North conservationist fears the days of recreationally harvesting mussels in the region may soon be over thanks to an invasion of the Australian sea squirt Pyura stolonifera.

Worse, Laurie Austen has grave fears for the future of the country's $400 million mussel industry, which to a great extent relies upon wild spat collected on the west coast. Eighty per cent of the industry was seeded from spat collected on Ninety Mile Beach.

Mr Austen, who serves Ahipara Komiti Takutaimoana as a research observer, said he had no doubt Far North mussel beds were in real peril - the sea squirt was now well established from Twilight Beach to Ahipara and down the coast, perhaps as far as Mitimiti - and could be past saving, due to a lack of action by the Ministry for Primary Industries.

"The ministry has given the sea squirt a four-year head start," he said.

"There has got to be a better way of responding to biosecurity threats than this Neville Chamberlain approach."

The invasive sea squirt had first been reported, at Twilight Beach, by a member of the public in 2009 . It was investigated and surveyed by the Ministry for Primary Industries, and small-scale removal and destruction trials had been carried out over the past four years.

Unsurprisingly, Mr Austen said, the species had continued to spread, the ministry now concluding it was so widespread that limitation control on a small scale was the only realistic course of action.

"The end result of this will be the same as taking no action at all. Pyura is here to stay," he added.

"It shows a clear preference for the intertidal locations and habitats of the green-lipped mussel, and you don't need a degree in marine science to understand that it is smothering mussels, or that once established on the rocks it will occupy the habitat of the mussels."

The ministry was insisting that Pyura was not a threat to the mussel industry, despite the fact little was known about the origins of wild spat.

He found it difficult to imagine how a foreign species that was occupying the mussel habitat could fail to affect spat production.

"Only a serious, dedicated team could have any impact on it now, given that it has a four-year head start on any attempt to eradicate it," Mr Austen said, but the ministry's response had been to allocate $45,000 over three years to conduct limited control.

"We could have stopped this if something had been done in 2009. As it is there was really no point in even reporting it in the first place. It's the same scenario we saw with the tropical grass web worm at Pukenui and the sea squirt at Whangamata.

"The idea, apparently, is to do nothing. It's unbelievable."

The ministry failed to respond to questions on Mr Austen's concerns.