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Norwegian Salmon Affected By Lice

December 24, 2009

Norwegian salmon is a popular holiday treat for many, but the fish is threatened by a small parasite that is spreading quickly among wild and farmed salmon.

According to an AFP report, fish farmers have recently noticed an increase in Lepeophtheirus salmonis, a tiny sea louse that feeds on salmon’s skin and mucous membranes. The alarming rate of parasitic infestation has risen threefold since last year.

The louse, which is naturally present in the sea, poses no threat to human consumption. The lice usually falls off during transport or processing, and fish that have been damaged by the parasite are usually cut up into fillets rather than be sold whole. Still, the louse’s rapid increase in fish farms along the Norwegian fjords are causing much concern.

Ole Fjetland of the Norwegian Food Safety Authority tolf AFP, “Today, the louse is the main threat to sustainable fish farming in Norway, both because of its effects on the farmed fish and its impact on wild salmon.”

Ketil Rykhus of the Norwegian Seafood Federation insists that the salmon can handle the lice without much problem, but it is likely that a louse infection could lead to other types of illnesses. A lot of the worrying comes from strong currents and fish that escape the farms and infect wild salmon, in particular the young that are on their migration routes to the sea that are more vulnerable than older salmon. In some areas, nearly 20% of the young succumb to the parasite.

Wild Atlantic salmon populations are already extremely fragile, having been reduced by almost 50% since 1970. The causes for this are not entirely known, but many factors are suspected: pollution, acidity levels in the water on the rise, hydroelectric dams, and breeding with escaped farmed fish that weakens the wild salmon gene pool. Add louse infestation to the mix and stocks could suffer even more.

Dedicated to the protection of a 3.5 billion dollar industry (last year), fish farmers spent nearly 80 million dollars this year on anti-lice measures. And they could spend twice that next year. The Norwegian government is waiting to see what happens before deciding to increase salmon production by five percent in 2010.

The industry has often used chemicals to delouse the salmon, or at times used wrasse, a small fish that sucks out the lice. However, the louse has become resistant to the chemicals, and, in winter the wrasse become lethargic. A new anti-lice campaign is planned for launch next year before the migration of the young to the sea in the spring.

The WWF has called for a slaughter for the most-infected farmed stocks in order to ease the tensions on wild salmon populations. The Norwegian Seafood Federation is not ready to let this happen right away, however.

Image Caption: Gravid female Lepeophtheiris salmonis on Atlantic salmon, Salmo salar. Courtesy Wikipedia

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