Fish farmers seek new weapons to fight thriving parasites

Horizon –

Salmon farmers battling large numbers of parasites that flourish on fish farms are seeking – and finding – new ways to cut their losses and protect marine wildlife.

About 20% of farmed salmon in Norway die as a result of parasites, according to Seafarm Development, a company developing technologies for fish farms, and researchers say new strategies are vital to prevent further damage to the sector and to safeguard local wild fish.

They warn that the number of parasites is rising with global warming, and as fish farms become more common.

In Norway, ‘sea lice are a major problem’, costing salmon farmers about 5bn NOK (€500m) a year, says Stein Åge Davidsen, head of Seafarm Development, which has developed a way to curb sea lice infestations.

Norway’s fish-farming industry – almost all of it salmon – was worth €7bn in 2017, more than the entire EU’s fish farming industry combined.

Sea lice feed off salmon skin, mucous and muscle, and they can grow up to 18mm long. They thrive in densely populated farm cages where they can easily jump from fish to fish.

And their peak reproductive season – when a female lays up to 2,000 eggs a month – has lengthened because of rises in sea temperatures in the last five to ten years, says Davidsen.

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