Many fish species are highly social and benefit from appropriate group housing — while others are solitary and suffer from enforced group living in aquaculture settings.
Fish social behaviour is more complex than widely recognised. Many species have evolved in social groups where relationships, hierarchies, and cooperative behaviour are important components of daily life. Disrupting this social context — through isolation, inappropriate group composition, or chronic social disruption at stocking events — causes welfare harm. Conversely, housing naturally solitary species in forced groups creates chronic aggression and stress. Understanding the social needs of each farmed species and providing appropriate group structures is an important welfare intervention that is feasible within commercial operations.