Flatfish like Atlantic halibut and Japanese flounder are increasingly farmed commercially. Their unique biology — including metamorphosis from bilateral to flatfish form — creates distinctive welfare challenges.
Flounder welfare in aquaculture is complicated by their specialized biology. As benthic fish, flounders require bottom substrate for resting — without it, they stack on top of each other in high-density tanks, causing abrasion injuries and competition for space. Metamorphosis failure — where juveniles do not complete the eye migration process — is a welfare concern in intensive hatcheries. Albinism in hatchery flounder, caused by artificial lighting that disrupts pigmentation development, impairs camouflage and may affect predator avoidance. Slaughter practices for flatfish typically involve asphyxiation or ice slurry — neither is humane given evidence of fish pain processing. CO2 stunning followed by spiking (ikejime) is more humane but requires significant handling infrastructure.