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Higher than usual salmon deaths

In 2012, a king salmon farm in Waihinau Bay, Marlborough Sounds reported higher than usual fish deaths to MPI. Affected fish had been eating less, were lacking in energy and had lesions on their skin. In the following summers, fish deaths occurred again in the same area.

MPI's response

MPI has been looking at a number of factors that could be involved in the fish deaths, such as the environment, management at the farm and the presence of bacteria.

After the first reported deaths in 2012, MPI took samples and analysed records from the affected farm. Samples were tested at MPI's Animal Health Laboratory (AHL) for a range of pathogens (organisms that cause disease) that infect salmon. None were found, and we concluded that environmental factors probably caused the deaths.

The 2012 salmon investigation report [PDF, 155 KB]

Further testing

By 2015, the AHL had developed new diagnostic tests for fish pathogens. Further testing discovered 2 bacteria – that hadn't previously been found in New Zealand – in samples from salmon farms in Pelorus Sound and Queen Charlotte Sound. The 2 bacteria were:

  • a Rickettsia-like organism that lives inside fish cells
  • Tenacibaculum maritimum – a bacterium that causes ulcers in fish skin.

The Rickettsia-like organism is listed as an unwanted organism under the Biosecurity Act 1993.

These bacteria do not pose a known risk to human health. In addition, the management and quality control procedures required at salmon processing plants ensure no affected fish are distributed for human consumption.

MPI believes the bacteria could have contributed to the fish deaths, in combination with a range of other factors. A second investigation report was published in May 2017.

The 2017 salmon investigation report [PDF, 687 KB]

Controls to prevent spread

In April 2016, to prevent the bacteria from spreading, MPI put legal controls on the movement of salmon and equipment from affected areas. The controls are set out in a Controlled Area Notice.

Two areas have been identified as 'Contained Zones': the outer Pelorus Sound and Queen Charlotte Sound. It's illegal to move salmon farming equipment out of the Contained Zones. It's illegal to move farmed salmon out of the Contained Zones unless it's going straight to a processor or laboratory for testing. In December 2019, the Controlled Area Notice was updated to also allow the legal movement of dead salmon to a specific composting facility.

Map of Contained Zones: Outer Pelorus Sound and Queen Charlotte Sound 
Map of Contained Zones: Outer Pelorus Sound and Queen Charlotte Sound.

Find out more

Who to contact

If you have questions about the information on this page, email info@mpi.govt.nz

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