Monosex male tilapia production via hormonal masculinisation or selective breeding raises welfare questions about the ethics of hormonal manipulation of fish at larval stage.
The welfare implications of hormonal masculinisation are uncertain due to limited evidence on larval fish sentience. The procedure occurs at a developmental stage when nervous system complexity is low. Concerns centre on downstream welfare effects — monosex male populations show increased aggression at high stocking densities compared to mixed-sex groups. The principle of minimising unnecessary intervention argues for developing non-hormonal alternatives where feasible.