Fish possess sophisticated chemical sensory systems that inform foraging, predator avoidance, and social behaviour, with welfare implications for how farmed and laboratory fish are managed.
The chemosensory richness of fish has direct welfare implications. In aquaculture, chemical cues from crowding stress and injuries are released into the water, potentially transmitting distress signals across entire tanks and triggering chronic alarm responses in healthy fish. Water quality parameters that damage olfactory epithelium, including chloramines and certain disinfectants, impair chemosensory function and compromise the fish's ability to detect food and dangers. Anaesthetic agents used in fish handling interfere with chemosensation. For laboratory fish, chemosensory enrichment through introduction of species-appropriate chemical signals from plants or conspecifics has been shown to improve activity levels and reduce abnormal behaviours. Recognising fish chemosensory sophistication is part of the broader scientific consensus on fish sentience.