Moss covered rocks surround a crystal clear stream in Scotland

Salmon Farming in Scotland

Moss covered rocks surround a crystal clear stream in Scotland

Salmon Farming in Scotland

  • Salmon is one of Scotland's biggest food exports, second only to whiskey. Unfortunately, this booming industry comes with a cost. The salmon we buy across Britain typically comes not from wild fish but farms, many of them located off the coast of Scotland. So, while wild salmon numbers reached a record low in 2018, in supermarkets, salmon was plentiful. In this article, we'd like to outline some of the issues surrounding salmon farming and its impacts on wild fish populations and the wider ocean ecosystems.

1. A Difficult Journey

2. Farming Salmon

3. The Threats

4. Making A Difference

  • Salmon is one of Scotland's biggest food exports, second only to whiskey. Unfortunately, this booming industry comes with a cost. The salmon we buy across Britain typically comes not from wild fish but farms, many of them located off the coast of Scotland. So, while wild salmon numbers reached a record low in 2018, in supermarkets, salmon was plentiful. In this article, we'd like to outline some of the issues surrounding salmon farming and its impacts on wild fish populations and the wider ocean ecosystems.
  •  

1. A Difficult Journey

2. Farming Salmon

3. The Threats

4. Making A Difference

A Difficult Journey

  • Every year in Autumn, Scotland's crystal clear salmon rivers and streams are transformed into a frenzy of fish leaping and swimming their way upstream to spawn in freshwater gravel beds, before returning to sea. Today, the number of salmon making this arduous journey is a fraction of what it once was. As a result, anglers are now engaged in a voluntary scheme to release any salmon caught in Scotland's glens, but many sources argue that the problem is out at sea. Though dams and weirs are known to obstruct migratory routes of salmon, at sea, they’re facing a combination of severe threats. Climate breakdown, a diminishing food supply and commercial salmon farming are all threatening the survival of Scotland’s iconic salmon.

A salmon leaps out of the water up stream

A Difficult Journey

  • Every year in Autumn, Scotland's crystal clear salmon rivers and streams are transformed into a frenzy of fish leaping and swimming their way upstream to spawn in freshwater gravel beds, before returning to sea. Today, the number of salmon making this arduous journey is a fraction of what it once was. As a result, anglers are now engaged in a voluntary scheme to release any salmon caught in Scotland's glens, but many sources argue that the problem is out at sea. Though dams and weirs are known to obstruct migratory routes of salmon, at sea, they’re facing a combination of severe threats. Climate breakdown, a diminishing food supply and commercial salmon farming are all threatening the survival of Scotland’s iconic salmon.
  •  
A salmon leaps out of the water up stream

The Farms

Hundreds of salmon farms populate the oceans off the west coast and Western and Northern Isles of Scotland. With the longest coastline on the British Isles, Scotland's ocean habitats are precious. Now, some of the most important areas for wild salmon and sea trout in Scotland are shared with thousands of farmed salmon. They’re kept in open-net pens that allow fresh water to flow in and faeces, diseases, uneaten food, chemical treatments, medicines, and sometimes even fish themselves, to flow out into the wider ecosystem.  

Salmon pens spread across the sea accompanied by a fishing boat
Salmon pens spread across the sea accompanied by a fishing boat

The Farms

Hundreds of salmon farms populate the oceans off the West Coast and Western and Northern Isles of Scotland. With the longest coastline on the British Isles, Scotland's ocean habitats are precious. Now, some of the most important areas for wild salmon and sea trout in Scotland are shared with thousands of farmed salmon. They’re kept in open-net pens that allow fresh water to flow in and faeces, diseases, uneaten food, chemical treatments, medicines, and sometimes even fish themselves, to flow out into the wider ecosystem.  

The Threats

Sea Lice

With thousands of fish in each pen, salmon farms can act as a breeding ground for diseases and pests, in particular, sea lice. Almost half of the salmon farms in Scotland are infested with the common salmon louse (Lepeophtheirus salmonis). The louse causes skin lesions and heavy infestations can result in death. This is a particular problem for wild salmon and trout as farms are often located in areas inhabited by these species.

Pollution

Antibiotics and pesticides are often used to manage sea lice and other diseases. These chemicals can flow out of the pens and into the surrounding waters, threatening the health of Scotland’s coastal ecosystems and the wildlife that lives there. According to some sources, the levels of chemicals used to kill sea lice have breached environmental safety limits more than 100 times in the last 10 years.

Wild Harvests

Farmed salmon are also often fed with small fish, such as anchovies, herring and sardines, harvested from the wild. Wild wrasse is also harvested for use as cleaner fish to control sea lice numbers. Though it's argued that farmed fish are more sustainable because they’re not harvested from wild populations, it's likely that they're still contributing to the depletion of other wild fish populations.

Genetic Mixing

Occasionally, fish can escape from farms and enter the ocean ecosystems. These fish can spread disease, compete for food and habitat, and cross-breed with wild salmon. In doing so, they dilute the gene pool of wild salmon, which are adapted to local conditions, and reduce the fitness of wild populations.

A dead fish floats on the surface surrounded by murky waterA dead fish floats on the surface as the water remains still around it
A fishing boat is followed by hundres of seabirds hoping to make the most of the catch

The Threats

Sea Lice

With thousands of fish in each pen, salmon farms can act as a breeding ground for diseases and pests, in particular, sea lice. Almost half of the salmon farms in Scotland are infested with the common salmon louse (Lepeophtheirus salmonis). The louse causes skin lesions and heavy infestations can result in death. This is a particular problem for wild salmon and trout as farms are often located in areas inhabited by these species.

Pollution

Antibiotics and pesticides are often used to manage sea lice and other diseases. These chemicals can flow out of the pens and into the surrounding waters, threatening the health of Scotland’s coastal ecosystems and the wildlife that lives there. According to some sources, the levels of chemicals used to kill sea lice have breached environmental safety limits more than 100 times in the last 10 years.

A dead fish floats on the surface surrounded by murky waterA dead fish floats on the surface as the water remains still around it
Salmon try to make their way up a waterfall surrounded by moss covered rocks and lush trees

Making A Difference

Many of the threats impacting wild salmon populations, like climate breakdown, will take time to rectify. Unsustainable farming, on the other hand, is comparatively easy to solve. Salmon farms must address the issues outlined above and adapt quickly to safeguard the survival of salmon in Scotland. As consumers, we also have an opportunity to make a big difference, by consuming more consciously and sustainably. Along with many other species of fish, salmon are facing considerable threats, but there is a lot we can do to change things for the better.

Wild Harvests

Farmed salmon are also often fed with small fish, such as anchovies, herring and sardines, harvested from the wild. Wild wrasse is also harvested for use as cleaner fish to control sea lice numbers. Though it's argued that farmed fish are more sustainable because they’re not harvested from wild populations, it's likely that they're still contributing to the depletion of other wild fish populations.

Genetic Mixing

Occasionally, fish can escape from farms and enter the ocean ecosystems. These fish can spread disease, compete for food and habitat, and cross-breed with wild salmon. In doing so, they dilute the gene pool of wild salmon, which are adapted to local conditions, and reduce the fitness of wild populations.

A fishing boat is followed by hundres of seabirds hoping to make the most of the catch

Making A Difference

Many of the threats impacting wild salmon populations, like climate breakdown, will take time to rectify. Unsustainable farming, on the other hand, is comparatively easy to solve. Salmon farms must address the issues outlined above and adapt quickly to safeguard the survival of salmon in Scotland. As consumers, we also have an opportunity to make a big difference, by consuming more consciously and sustainably. Along with many other species of fish, salmon are facing considerable threats, but there is a lot we can do to change things for the better.

Salmon try to make their way up a waterfall surrounded by moss covered rocks and lush trees

Sources & further reading

  1. ✅ for peer reviewed research
  2.  
  3. 1. “A Global Assessment of Salmon Aquaculture Impacts on Wild Salmonids” – Ford JS, Myers RA. 2008 - PLoS Biol – Vol 6, Issue 2 – Journals Plos Biol
  4.  
  5. 2. “Wild salmonids and sea louse infestations on the west coast of Scotland: sources of infection and implications for the management of marine salmon farms” - Butler JRA. 2002 – Pest Management Science – Vol 58, Issue 6 – Wiley Online Library
  6.  
  7. 3.Assessing and Managing the Impacts of Marine Salmon Farms on Wild Atlantic Salmon in Western Scotland: Identifying Priority Rivers for Conservation” – Butler JRA, Watt, J. 2003 – Salmon at the Edge - Wiley Online Library
  8.  
  9. 4. “Aquaculture and environmental drivers of salmon lice infestation and body condition in sea trout” – Shephard S, MacIntyre C and Gargan P. 2016 - Aquacult Environ Interact – Vol 8 - int-res.com
  10.  
  11. 5. “Salmon near crisis point” – BBC news 2020 – bbc.com
  12.  
  13. 6. Scotland's salmon crisis: 'Anglers only want one. But it's just not happening’” – The Guardian 2019 – theguardian.com
  1. ✅ for peer reviewed research
  2.  
  3. 1. “A Global Assessment of Salmon Aquaculture Impacts on Wild Salmonids” – Ford JS, Myers RA. 2008 - PLoS Biol – Vol 6, Issue 2 – Journals Plos Biol
  4.  
  5. 2. “Wild salmonids and sea louse infestations on the west coast of Scotland: sources of infection and implications for the management of marine salmon farms” - Butler JRA. 2002 – Pest Management Science – Vol 58, Issue 6 – Wiley Online Library
  6.  
  7. 3.Assessing and Managing the Impacts of Marine Salmon Farms on Wild Atlantic Salmon in Western Scotland: Identifying Priority Rivers for Conservation” – Butler JRA, Watt, J. 2003 – Salmon at the Edge - Wiley Online Library
  8.  
  9. 4. “Aquaculture and environmental drivers of salmon lice infestation and body condition in sea trout” – Shephard S, MacIntyre C and Gargan P. 2016 - Aquacult Environ Interact – Vol 8 - int-res.com
  10.  
  11. 5. “Salmon near crisis point” – BBC news 2020 – bbc.com
  12.  
  13. 6. Scotland's salmon crisis: 'Anglers only want one. But it's just not happening’” – The Guardian 2019 – theguardian.com