Salmonid Welfare and Temperature: Thermal Stress Management

Temperature is a primary welfare determinant for salmonid species in aquaculture, with thermal stress causing immune suppression, disease, and behavioural changes.

Key Facts

Rainbow trout show welfare impairment above 18 degrees Celsius with significant distress above 21C
Atlantic salmon prefer cooler water and show stress above 16 degrees Celsius
Freshwater heatwaves cause mass mortality events in inland trout farms
Deep intakes and shading reduce summer temperatures in flow-through systems
Welfare-based temperature monitoring is increasingly required by certification schemes

Welfare Considerations

Salmonids experiencing thermal stress show surface crowding, reduced feeding, increased gill ventilation rate, and eventually lethal hyperthermia. Chronic suboptimal temperatures above welfare thresholds cause immune suppression increasing disease susceptibility. Climate change is increasing the frequency and severity of summer thermal stress events at vulnerable sites. Welfare-focused thermal management includes investing in cold water sources, shade provision, deep water intakes, and emergency protocols for predicted heat events. Sites that cannot maintain welfare-appropriate temperatures may need to reconsider whether they can produce salmonids ethically.

What You Can Do

Support salmonid welfare standards specifying temperature monitoring and thresholds
Advocate for emergency thermal management protocols at salmonid farms
Back research into climate adaptation strategies for freshwater salmonid aquaculture
Choose salmonids from farms with documented temperature management welfare protocols
Encourage certification bodies to include thermal welfare as a key indicator