Sea cages degrade marine and freshwater ecosystems in multiple ways. The sea lice that infest the cages feed off of, and sometimes kill, nearby wild Atlantic salmon, sea trout and other fish. The antibiotics and pesticides used in sea cages also are lethal to other forms of sea life. And untreated waste from the salmon farms pollutes surrounding waters.
Sourcing food for ocean-farmed Atlantic salmon not only contributes to the industry’s large carbon footprint but also takes protein off the plates of citizens in low-income countries. To feed farmed salmon, giant trawlers off the coast of Africa haul in tons of small fish that are ground into feed. Ninety percent of these wild fish could help feed Africans.
The conditions in sea cages are inhumane by any measure. The cages are extremely overcrowded, which leads to all kinds of health concerns. Each year, millions of salmon die prematurely from viruses and parasitic infections. The sea lice that swarm the fecal-infested cages literally eat the salmon alive, despite ongoing treatment with antibiotics and pesticides.
They are among only one percent of species that live in both freshwater and saltwater ecosystems, and they link environments up and down their annual migratory paths. They are a keystone species, relied on by 137 different species of mammals, birds, reptiles, fish and other animals. And as an indicator species, wild Atlantic salmon reflect the planet’s overall health.
Ocean-farmed salmon are intensively and selectively bred to grow fatter and mature faster than wild Atlantic salmon, which are not commercially fished. When ocean-farmed salmon escape through holes in sea cages, they interbreed with wild salmon to create a hybrid species. This pollutes the wild Atlantic salmon gene pool.
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