Biosecurity scare for salmon farmer

Salmon covered in open wounds, unexplained fish deaths, and the discovery of bacteria never previously identified in New Zealand.

All three issues feature in a new report detailing a biosecurity scare in the Marlborough Sounds that put the country’s biggest salmon farmer on notice.

And despite concerns over the presence of two newly discovered bacteria, that company – New Zealand King Salmon – continued to take risks, the report says.

Berley made from salmon at risk of infection was sent to the North Island, despite the Ministry for Primary Industries (MPI) saying that its bait product could spread the bacteria.

But King Salmon chief executive Grant Rosewarne defended the move by saying there were no salmon farms in the north, so his company thought there was no risk involved.

Upon being notified by King Salmon, the ministry issued a notice in July 2016 demanding the firm stop the policy. That notice that was later revoked to allow the distribution of berley so long as it was treated first.

MPI scientists discovered the two newly identified bacteria after the ministry stepped in to investigate higher than usual rates of salmon deaths at King Salmon’s farms in the Marlborough Sounds.

During the worst incident, in March 2015 at Waihinau Bay, more than 320 fish per 10,000 were dying a day – resulting in an overall loss of almost 70 per cent of fish at the site.

But scientists were not convinced the bacteria was solely to blame, pointing to factors such as water temperature, stocking density and nutritional stress.

The report, released in May, said wider testing after the Marlborough Sounds investigation had found the bacteria was present in salmon farming zones outside the region.

‘‘As such, MPI believes that the recent mortality event has a range of causes, with the bacteria possibly being involved in the fish deaths in combination with other factors.’’

After the bacteria was discovered, the ministry implemented a range of controls under the Biosecurity Act, one of which required New Zealand King Salmon to apply ‘‘status red’’ measures in its biosecurity plan.

But a technical advisory group assembled to advise the ministry was scathing of that plan, labelling it ‘‘inadequate’’ and ‘‘vague’’.

The group also said the production cycle at King Salmon’s farms was ‘‘not consistent with international best practice’’ for disease prevention.