NORWAY
Solving the issues of sea lice and salmon escapes is a question of time
Improvements now need to be consolidated Sea lice and escaping ďŹ sh are two of the salmon farming industry’s biggest concerns. The goal in Norway is to eliminate the one and prevent the other so that the government’s vision of a ďŹ ve-fold increase in salmon production by 2050 can be realised. The problem of lice is one that continues to confound the global salmon industry. Sea lice are naturally occurring marine parasitic crustaceans that attach themselves to the salmon and feed on its mucus, skin and blood. An attack by lice causes wounds on the fish leaving it weakened with reduced appetite and vulnerable to secondary infections. The degree of damage is influenced by the number of lice and the size of the host.
SpeciďŹ c to salmonids The sea louse (Lepeophtheirus salmonis) is a parasite on
all salmonid species including salmon, trout and char. Infestation of other species is temporary until the louse finds a salmonid host. Sea lice develop faster in warmer temperatures, and in the early growth stages cannot survive low salinities. An adult female can produce some 1,700 eggs over the course of her existence. The life cycle of sea lice is divided into eight stages, three free-swimming, two stationary, and three mobile, starting with the egg that hatches into a free floating nauplius. After moulting, the nauplius enters the infective copepodit stage which attaches to the host fish. The louse moults
several times attached to the fish before becoming a mobile preadult at which point it can move on the surface of the fish and can swim. While sea lice have always been present in nature they have become more of a problem with the spread of salmon farming as the presence of large numbers of salmon living in close proximity to each other is thought to provide conditions conducive to the proliferation of the parasite. Higher temperature seas as a result of global warming are also likely to cause sea lice to multiply. There are several issues associated
with sea lice: they have a negative impact on salmon production both directly, by damaging or, in extreme cases, killing the fish, and indirectly by making the fish more susceptible to disease; the spread of sea lice may also be affecting wild salmonids adding to the impacts of commercial fishing, climate change, and habitat destruction on these fish; finally combating the problem with drugs or chemicals often has a wider environmental impact. Ways to treat sea lice infestations include the use of drugs in the feed, bathing the fish in chemicals, and the use of cleaner fish, which live in the cage with the salmon and feed off the lice. But, according to a report prepared for the Scottish Parliament reviewing the environmental impacts of salmon farming in Scotland, nearly all these methods are expensive, not effective, and must be repeated. In addition, sea lice are demonstrating resistance to many of the drugs being used to treat the fish.
Fighting sea lice is a costly affair
Sea lice are marine parasitic crustaceans and a signiďŹ cant nuisance for the salmon industry.
For the salmon industry sea lice are a source of additional costs caused by direct losses, as well as by the cost of chemicals/ medicines, increased manpower requirements to treat the fish and to deal with weight loss, stress Eurofish Magazine 3 / 2018
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