Atlantic halibut is one of the most challenging species to farm due to its complex early life requirements. Welfare during the juvenile rearing phase is critical to production success and animal wellbeing.
Halibut juvenile welfare is challenged by the mismatch between the species' ecological requirements and intensive hatchery conditions. Halibut are benthic flatfish adapted to resting on the seabed, and larvae and juveniles that cannot access substrate show elevated stress and stereotypic swimming behaviour. High densities in weaning tanks increase competition for food and space, with subordinate individuals receiving inadequate nutrition. The very high early-life mortality in halibut farming reflects both the biological challenge of rearing a species with complex nutritional requirements and the welfare cost of conditions that do not meet the species' needs. Substrate provision and lower stocking densities during the juvenile phase improve welfare outcomes and often production performance.