How selective breeding programs in rainbow trout aquaculture affect welfare, and the opportunities and challenges of breeding for welfare-relevant traits alongside production efficiency.
Selective breeding represents a powerful but underutilized tool for improving trout welfare at the production system level. Breeding programs that have focused exclusively on growth and feed efficiency have created fish with welfare trade-offs — skeletal deformities, potentially higher baseline stress reactivity — that affect every individual of those strains across the industry. The alternative — explicitly including welfare-relevant traits in breeding objectives — is technically feasible and would improve welfare for billions of fish across multiple production generations from a single breeding program improvement. The welfare case for welfare-inclusive breeding programs is strong and represents one of the highest-leverage welfare interventions available in trout aquaculture.