Whirling disease hits salmon export trade

Press, 31 May 1985, Page 2

Whirling disease hits salmon export trade

All salmon exports from New Zealand have been suspended after the discovery of whirling disease at the Ministry of Agriculture and Fisheries Glenariffe salmon research station in the Rakaia River.

Whirling disease is potentially as disastrous for the fish farming industry as foot-and-mouth disease would be for conventional farmers.

The Glenariffe research station has been put under quarantine, and the Ministry is making intensive efforts to trace movements of fish stocks and check for the presence of the disease in other parts of New Zealand. In the meantime, all cer-

tification of salmon stocks has been stopped. Salmon exported from New Zealand must have a certificate from the Ministry stating, among other things, that the fish is free of whirling disease.

Although it involves only seven companies, the fledgling salmon farming industry in New Zealand is already big business. Hundreds of tonnes of the fish worth millions of dollars is exported each year, mainly to the United States.

Whirling disease is caused by a parasite that attacks the skulls of young fish, eventually making them become disoriented and swim in tight circles.

It was first identified in New Zealand in 1966, but has been found only in trout, never in salmon.

The Ministry's director of animal health, Dr Peter O’Hara, said that the Glenariffe quarantine was an interim measure while the significance of the discovery was assessed and ways of dealing with the infection considered.

"The most significant effect is interference with the certification of salmon exports to the United States,” he said.

Certification depends on the routine testing of fish stocks to ensure that sea

cages and river systems are free from infection. Dr O’Hara said that discussions would be held soon with the managers of affected salmon farms.

The secretary of the New Zealand Salmon Farmers’ Association, Mr P. J. Sheldon, of Christchurch, declined to comment on the effects of the outbreak until after members had met next Tuesday. Mr Peter Townsend, managing director of the New Zealand Salmon Company, Ltd, which has hatcheries on the Rakaia River, said that the export ban should not have any immediate effect on his company because it was not exporting fish at present, and would not start again until late this year. “The company is confident that this incidence of whirling disease will not adversely affect our operation or our export marketing,” said Mr Townsend. He emphasised that whirling disease had been found in various parts of New Zealand before, always in rainbow trout and never in salmon. The stocks of the New Zealand Salmon Company, Ltd, one of the biggest in New Zealand, had been certificated for the last two years, and there had never been any evidence of whirling disease.

The whirling disease-in-fected rainbow trout at Glenariffe were being held in cages at the outflow from the research station to monitor the presence or absence of the disease.

The main purpose of the station is to produce salmon for commercial and recreational use. It also supplies salmon eggs to fish farms. Fish in the wild are rarely affected by whirling disease, which is already known to be in the Waimakariri River system.

Rainbow trout are the most susceptible species. Quinnat salmon (those farmed in New Zealand) are less susceptible, and sockeye salmon are almost resistant to the disease. The salmon hatcheries of New Zealand Marine Farms, Ltd, on the Hurunui River in North Canterbury and the Kaniere River on the West Coast are free of whirling disease, according to the company’s chief executive. Dr Paul O'Connor.

All of the company’s seacage salmon in the Marlborough Sounds had also been declared disease-free by the Ministry. Dr O’Connor said he hoped that the consequences of the Rakaia outbreak could be resolved with minimal damage to the United States salmon export market.