Before transfer to sea cages, salmon spend 12-18 months in freshwater hatcheries. Welfare challenges in this phase significantly affect later sea cage performance and health.
Freshwater phase welfare is foundational to salmon wellbeing throughout the production cycle. Smoltification - the dramatic physiological transformation enabling salt water adaptation - is a period of significant vulnerability. Crowding stress during this phase elevates cortisol and impairs immune development. Disease challenges including bacterial kidney disease and infectious salmon anaemia affect crowded hatcheries. Vaccination handling causes acute stress to thousands of fish simultaneously. Water quality management including temperature, oxygen, and flow rates critically affects welfare. Investment in good freshwater welfare produces healthier smolts with better sea cage survival, creating economic alignment with welfare improvement.