Atlantic Halibut Aquaculture and Flatfish Welfare

Atlantic halibut are among the most difficult and expensive fish to farm, with welfare challenges related to their unique physiology and sensitivity to handling stress.

Key Facts

Atlantic halibut can reach 300 kg and live 50 years in the wild — farmed halibut are harvested at 3-5 kg after 3-4 years
Halibut are highly sensitive to handling stress — cortisol spikes of 10-fold normal are documented within minutes of net contact
Cataracts affect 50-80% of farmed Atlantic halibut, caused by dietary imbalances — particularly vitamin A and riboflavin deficiency
Halibut are cannibalistic and require precise size-grading to prevent smaller fish being eaten by larger tankmates
Their unique lateral orientation requires specially designed tanks with flat, darkened bottom surfaces to minimise stress responses
Mortality rates during first feeding — one of the most critical stages — commonly reach 50-90% in poorly managed hatcheries

Welfare Considerations

Halibut farming is technically demanding precisely because these fish are physiologically and behaviourally complex. Their extreme sensitivity to handling, tendency toward cannibalism and dietary-related health problems all require close management attention to achieve acceptable welfare outcomes. The cataracts affecting the majority of farmed halibut in some operations represent a preventable chronic welfare condition caused by dietary deficiency — a problem with a known, tractable solution. Developing robust welfare protocols for halibut, including validated stress indicators, handling minimisation procedures and dietary standards, is essential before this species is farmed at larger commercial scale.

What You Can Do

Choose halibut from operations certified under aquaculture welfare standards with documented handling and dietary protocols
Support research into halibut hatchery and grow-out welfare, particularly cataract prevention and handling stress reduction
Ask retailers about the welfare standards of their halibut suppliers before purchasing
Advocate for halibut to be included in developing fish welfare frameworks at national and EU level
Reduce consumption of farmed halibut from uncertified sources where welfare standards are unknown