Norway Salmon Farmers on Full algae Alert

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OSLO, May 7 (Reuters) - Salmon farmers in Norway, the top world producer of the fish, were watching on Thursday for a poisonous algae that has killed thousands of salmon on the country's southern tip.

The Directorate of Fisheries said it was monitoring waters in the Bokna fjord and near the port of Stavanger for signs that the Chattonella verruculosa algae was spreading up the west coast where most farms are located.

The yellowish-brown algae, never before monitored in northern European seas but which has been registered in Japan, has killed 350 tonnes of farmed Norwegian salmon so far.

"We cannot stop the algae but we can monitor the water at different depths and warn the farmers when concentrations become very high," Olav Lekve, spokesman for the fisheries directorate, told Reuters.

"It appears that if the fish stop feeding they have a better chance of surviving."

The outbreak began on Monday in the Flekka fjord on the southern tip of Norway where most of the dead fish were found. The algae attacks the gills of the fish, which die by asphyxiation.

No dead fish have been monitored in Bokna fjord yet but authorities were concerned that the bloom might continue its drift northwards, Lakve said.

"The problem is that we do not know if it is Chattonella verruculosa killing the fish. It is the dominant form in this outbreak but it is also traveling with a type known as Heterosigma, which is known to be toxic," he said.

There are 750 farms along Norway's vast coastline, which farm more than 300,000 tonnes of salmon a year.

The last major outbreak of algae in Norway was in 1989 off the west coast when 850 tonnes of salmon were lost to the algae Prymnesium Parvum.