African catfish (Clarias gariepinus) are intensively farmed in recirculating aquaculture systems across Europe, with welfare challenges from extreme stocking densities and the species tolerance of poor water quality masking welfare costs.
African catfish welfare in intensive RAS faces a particular challenge: the species physiological tolerance of poor water conditions and high density has been used to justify intensive practices without adequate welfare assessment. Hardiness does not equal absence of suffering. Research demonstrates that high-density African catfish show elevated stress hormones, fin damage, and abnormal behaviour even if they survive. The precautionary principle of welfare assessment — rather than production tolerance as the welfare benchmark — should guide stocking density standards. Water quality optimisation, enrichment, and density reduction measurably improve welfare outcomes.