The controversial New Zealand King Salmon farm at Waihinau Bay in Pelorus Sound has been given the all-clear after comprehensive testing, the company has announced.

NZ King Salmon chief executive Grant Rosewarne said no known pathogens or evidence of unknown diseases showed up, there were no environmental problems, and company vets believed the farm was the subject of some extraordinary natural event or a combination of factors.

“Our experts believe the farm may have suffered from an extraordinary event that directly killed the fish by interfering with them physiologically. Whatever it was, it also put other fish off their feed."

The deaths of a much higher percentage than usual of fish at the Waihinau farm has been the focus of attention from groups opposing the company's application to expand in the Sounds.

The Ministry of Primary Industries has confirmed on its website that its Waihinau investigations had ruled out a number of exotic and endemic disease threats, and found no cause for the increased salmon deaths at the farm.

Because no infectious agents were found it had not imposed movement controls or any other form of biosecurity restriction on the farm, the ministry said.

Mr Rosewarne said more than a dozen specific pathogens were tested for and ruled out. Microscopic examination of thin tissue samples was also used to try to detect unknown diseases. Electron microscopy was used to look for the presence of any viral particles but both techniques turned up nothing.

NZ King Salmon staff at the Pelorus Sound farm first noticed an unusual feed pattern in mid-February and quickly implemented biosecurity measures, he said.

With the all-clear confirmed, NZKS was implementing several new procedures. “We are boosting our preventative research programme including closer examination of the physiological changes young fish go through. We are also increasing the frequency of our water sampling programme so we can more quickly react to the natural elements."

Salmon farming was complex, Mr Rosewarne said.

“I can understand how people can be concerned about fish mortalities. But sometimes commentators who have no comprehension of the intricacies of our business can colour opinion out of proportion to the issues.

“We are completely transparent about our operations and anyone with any concerns at any time is invited to contact us to discuss their worries.”

NZ King Salmon spent around $20,000 on testing in New Zealand, Canada and Norway, and faced a considerable loss in terms of revenue and stock, Mr Rosewarne said.

Sustain our Sounds chairman Danny Boulton said the group still had concerns about sustainable management of the farm.

"We are also very sceptical as fish do not die from nothing and it is not a natural occurrence for fish to have lesions," Mr Boulton said.

"The question remains, are the Marlborough Sounds the right environment for concentrated fish feeding farms?"

An Environmental Protection Authority board of inquiry will begin hearing the company's application in Blenheim on August 27, and has drawn up a tentative 10-week timetable.

The company has five salmon farms in the Sounds and is seeking approval for nine more.

Although only a small fraction of the world salmon industry, it is the biggest farmer of the premium king salmon variety with 55 per cent of the global market, and earns around NZ$60 million a year in foreign exchange.

- © Fairfax NZ News

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