Salmon Welfare: Sea Cage Thermal Stress in Warming Oceans

Rising sea temperatures are increasingly creating summer thermal stress for farmed Atlantic salmon in surface cages. Understanding thermal welfare requirements guides better cage depth management.

Key Facts

Atlantic salmon prefer water temperatures between 8-14 degrees Celsius and show stress above 18-20 degrees
Summer sea surface temperatures in some Norwegian fjords now regularly exceed 20 degrees Celsius
Deep water cooling involves submerging cages or providing snorkels to access deeper, cooler water
Salmon experiencing thermal stress show reduced appetite, increased disease susceptibility and mortality
Climate projections indicate increasing frequency of summer heatwaves affecting salmon thermal welfare

Welfare Considerations

Salmon thermal stress in warming seas represents an emerging welfare challenge that will intensify with climate change. Fish confined to sea surface cages cannot thermoregulate by moving to cooler depths as wild fish do. Summer temperatures exceeding 18 degrees Celsius cause appetite suppression, immune impairment and increased susceptibility to salmon rickettsial syndrome and other pathogens. Prolonged exposure above 20 degrees causes acute welfare problems including haemorrhage and mortality. Deep water snorkel systems that allow fish to access cooler water at 8-15 metres depth provide a practical welfare solution but require infrastructure investment and careful management of cage geometry and oxygen levels at depth.

What You Can Do

Support salmon welfare standards that require thermal monitoring and deep water access above temperature thresholds
Choose certified farmed salmon from producers with documented heat stress management protocols
Advocate for regulatory requirements for thermal welfare management in salmon farming
Support research into climate-resilient cage designs that protect salmon welfare in warming seas
Engage with salmon farming industry about thermal welfare as an increasing priority in farm planning