Environmental Impacts of Salmon Farming

Salmon farming might look like a sustainable solution, but beneath the surface, the reality is that industrial salmon farming can cause severe environmental damage.

  • Smothering the Seabed

    Salmon faeces and excess feed that falls through the cage netting accumulates on the seabed underneath fish farms, smothering and killing the wildlife living below. Particles in the water can block out the sun, killing sea plants. Physical buildup can suffocate plants and animals. Precious habitats like maerl beds are especially sensitive to damage from this as they can become clogged with the anoxic sulphurous silt.

  • Sea Lice

    Many sea lice attached to a salmon in Fiunary.Image from video by Abolish Salmon Farming

    Sea lice are small crustaceans that latch onto and eat the skin off salmon. They feed off the skin, mucus and blood of salmonids. In cramped conditions like fish farm cages, these parasites can quickly multiply and spread like wildfire. This can cause serious damage and suffering to the fish in the cages. Any wild salmon that happens to live or swim nearby is also likely to gain a few of these flesh eating hitchhikers.

  • Wild Fish used as Feed

    Salmon are carnivores, so to grow them, you have to feed them other fish. This means catching huge amounts of wild fish to grind up into feed for the farmed fish. Scottish Sea Farms website says it takes 1.2-1.5kg of feed to produce 1kg of salmon. However the site fails to mention that this feed is a heavily processed product refined down from much greater amounts of raw materials including fish meal and fish oil made from huge amounts of wild-caught fish.

  • Animal Welfare

    The farming of salmon is detrimental to the animals’ welfare. Indeed, keeping large numbers of fish cooped up in cages is the marine equivalent of the battery farming of chickens. The salmon are prevented from exhibiting natural behaviours. In the wild, salmon migrate for thousands of miles. In a fish farm cage, they can’t even travel for 30 metres. This is cruel and should not be allowed.

  • Salmon Escapes

    Over the last century, the wild fish stocks of numerous species have declined dramatically worldwide. To cope with the ever increasing impact of climate change and the pollution of marine environments, maintaining this genetic diversity is imperative. To ensure the continuing health of these wild stocks, their genetic diversity must be maintained.

    Farmed fish have very little genetic diversity. The interbreeding of escaped fish farm fish has a detrimental effect on the genetic diversity of wild stocks . The winds and waves around Orkney are some of the strongest on the planet. This obviously makes maintaining the integrity of fish farm enclosures very difficult. Increasing the size of the fish farm in Veantrow Bay would increase the risk of farmed fish escaping and interbreeding with wild fish. This is would not be good for the genetic diversity of the wild fish.

  • Local Crustacean Populations

    A SEPA Fish Farm Report, reported in Orkney News 7th November 2018 , mentions that ‘Scottish salmon farm medicine is significantly impacting local marine environments which increases the now substantial weight of scientific evidence that the existing approaches do not adequately protect marine life.’ It says that ‘The biggest negative effect’ was ‘on the crustacean abundance and richness’ and that ‘That is the conclusion of one of Scotland’s largest and most comprehensive marine research projects into aquaculture, undertaken by the Scottish Environmental Protection Agency.’

    Medicines, such as those used to treat sea lice infestations in farmed salmon, badly damage local crustacean populations and thereby have negative effects on marine ecosystems. Claims made in the past, that these chemicals soon dissipate and cause little concern, have been disproved.

  • Nutrient Pollution

    Fish waste and excess feed from fish farms pollute the local marine environment. This can result in a huge build up of nutrients in the water which can lead to harmful algal blooms and a depletion of oxygen levels in the water causing damage to marine ecosystems.

  • Chemical Treatments

    Chemical treatments (including antibiotics, anti-foulants and pesticides) can have unintended consequences for marine organisms, and the kind of biodiversity loss that is hard to reverse.