NZ King Salmon CEO Grant Rosewarne says company vets believe the farm was the subject of some extraordinary natural event or combination of factors.
“There are no environmental problems at the farm and testing has ruled out the presence of any known disease-producing agents,” Mr Rosewarne says.
“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.
“From time to time nature throws curve balls at farmers everywhere – two years ago a massive snow storm killed almost a million lambs in Southland. Major events can occur in the marine environment and go undetected because they are underwater.”
The Ministry of Primary Industries confirms on its website that it is not always possible to determine a cause for a mortality event.
It says its Waihinau investigations “focused on ensuring that the event was not caused by infectious agents. The investigation has ruled out a number of exotic and endemic disease threats. No cause for the excess mortality has been identified”.
The MPI says because no infectious agents were found it “has not imposed movement controls or any other form of biosecurity restriction on the Waihinau Bay farm”.
NZ King salmon says 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 any tell-tale evidence of unknown diseases. Furthermore, electron microscopy (up to 100,000 times magnification) 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 bio-security measures, Mr Rosewarne says.
“We have extremely stringent bio-security procedures to protect our international market-leading position and the environment within which we operate. It was a regimental process of rolling out our policies to isolate the farm until we determined it was given the all-clear. That is now confirmed.”
As a result of the experience NZ King Salmon is 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.
“In these situations our research helps us to better understand the science. Aquaculture is advancing marine science all the time – and operations such as ours improve the learning for the entire industry.”
Mr Rosewarne says salmon farming – especially King salmon farming – is a complex business.
“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.”
The total cost to the company has been considerable in terms of sales revenue and lost stock. Mr Rosewarne says NZ King Salmon is grateful to the Ministry of Primary Industries for its comprehensive support and diligent work on the issue.
NZ King Salmon has spent around NZ$20,000 on testing in New Zealand, Canada and Norway.
