More than 8 million farmed salmon in Norway killed by algae bloom

[Norway] About eight million farmed salmon have suffocated in northern Norway over the past week as a result of persistent algae bloom, an industry body estimated on Thursday, a blight that some experts suggest has been aggravated by climate change.

Norway is a dominant producer of farmed salmon, and the economic impact of the bloom is significant.

A statement from the Norwegian Directorate of Fisheries estimated the amount of salmon lost at 11,600 metric tons, worth about 720 million kroner, or more than $82 million. An industry group, the Norwegian Seafood Council, suggested the total could be much higher.

“Preliminary numbers point to eight million dead fish — corresponding to 40,000 metric tons of salmon that won’t reach markets,” Dag Sorli, a spokesman for the council, said in an email on Thursday. He put the value of the losses at 2.2 billion kroner.

That would still amount to less than 1 percent of the industry’s output last year, when Norway produced approximately 1.3 million metric tons of salmon, according to Mr. Sorli.

Nine salmon companies have been affected so far, in the regions of Troms and Nordland.

Aleksander Balteskard, a spokesman for Northern Lights Salmon and Sorrollnesfisk, two privately owned family companies that operate together in northern Norway, said in an email on Thursday that they had lost “about 80 to 90 percent of the salmon that we had this generation” — most of this year’s production and part of next year’s.

Salmon leaping from the water at a fish farm in Norway. CreditSergey Ponomarev for The New York Times

Marine algae, microscopic plant-like organisms that are a form of phytoplankton, are usually not noticeable in normal concentrations. But under certain circumstances — when currents slow and water warms, for example — the population of algae can explode. Some algae blooms are visible from space.

Though the algae bloom is a natural event, Mr. Balteskard said, it is rare for it to be as concentrated and as lethal as it is this year.

Peter Jones, a reader in environmental governance at University College London, said, “The blooms are being exacerbated.” He noted that an algae bloom had hit salmon farming in Scotland last month.

“It looks like the mortalities in Norway in the last few days have been almost as great as the mortalities in an entire year in Scotland,” he said, though he noted that Norway’s salmon farm industry is far larger than Scotland’s.

Salmon farms are at special risk from blooms.

“Plankton blooms like these happen naturally and the fish would swim away from them, but obviously farm salmon don’t have that option,” Mr. Jones said.

The phytoplankton stop the fish’s breathing, Lars-Johan Naustvoll, a biologist at Norway’s Institute of Marine Research, said by phone.

“The algae comes in contact with the gills — it has a chemical composition that affects the membranes of the cells in the gills and they are effectively destroyed — so the fish actually dies due to lack of oxygen,” he said.

Mr. Naustvoll was hesitant to blame climate change for the bloom, pointing out that Norway experienced a growth of similar magnitude in 1991. But he said warm temperatures were not helpful.

“The increase in temperature and higher stability of the water increases the production season of the phytoplankton,” he said, to the extent that it can now grow from February to December.

 

Photo: A fish farm in Norway. The country is a dominant producer of farmed salmon.CreditCreditSergey Ponomarev for The New York Times

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