MPI and salmon farmers examine summer fish mortality issue

The Ministry for Primary Industries (MPI) is working closely with the country’s salmon farming industry to better understand an issue that has emerged over the past few summers in the Marlborough Sounds.

As reported previously, a salmon farm in Waihinau Bay experienced higher than normal fish mortality rates in early 2012 and this has continued in subsequent summers.

MPI officials met yesterday with industry representatives to outline the situation, share knowledge and discuss next steps.

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.

“In addition, new genetic tests developed by our Animal Health Laboratory have revealed the presence of two bacteria not previously detected in New Zealand.”

The bacteria – a Rickettsia-like organism (strain yet to be defined) and Tenacibaculum maritimum can cause disease in fish but do not affect people.

“There are no concerns about food safety associated with this situation,” Dr Rodwell says.

“Our focus now, is to determine, what if any, link these bacteria have with the higher summer mortality rates.

“MPI is actively managing the situation and is working with salmon farmers around the country to collect information and sample fish to determine if the bacteria exist outside of Marlborough.

“This information will help us decide how we continue to manage the situation,” Dr Rodwell says.

“We know the bacteria have been present in New Zealand for a number of years. Our new genetic tests enabled us to retest samples from the first mortality event in 2012 and these revealed the bacteria were present then. It is possible it may even naturally occur here.”

There have been no reported increased mortality events in wild fish or in farmed salmon outside of the Marlborough Sounds.

As a precautionary measure the Marlborough farms put biosecurity controls in place to prevent any spread of the bacteria and MPI is enforcing this.

The future welfare of fish is also top of mind for MPI which is the lead agency in animal welfare.

“We take animal welfare seriously and are working with the company to plan for the upcoming summer.”

ENDS

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