The mystery of dead salmon in a Marlborough Sounds fish farm is being worked on by a government agency and the farm's owner NZ King Salmon.
Officials from the Ministry for Primary Industries and industry representatives met yesterday to mull the causes of high fish mortalities at NZ King Salmon's Waihinau farm in Pelorus Sound during summer months. The trend was first noticed in 2012.
Response manager Chris Rodwell says MPI believes there are a range of factors at play including high water temperatures, water flow, diet and even sea anemone stings.
Two bacteria not previously detected in New Zealand have also been found.
There are no concerns about food safety associated with this situation, Dr Rodwell says.
NZ King Salmon chief financial officer Andrew Clark says the losses occurred during record high water temperatures.
"We believe this is a significant contributor along with diet and sea anemones. Our research focuses on these areas and we are collaborating with the MPI and sharing the information," he said.
There's no proven causal link between the two organisms identified by the MPI and fish mortality, he says.
The company is co-operating with MPI to ascertain if a link exists.
MPI is also working with salmon farmers around the country to collect information and sample fish to determine if the bacteria exist outside of Marlborough.
There have been no reported increased mortality events in wild fish or in farmed salmon outside of the Marlborough Sounds.
As a precautionary measure Marlborough farms put biosecurity controls in place to prevent any spread of the bacteria and MPI is enforcing this.