Gill health is fundamental to fish welfare as gills perform oxygen exchange and osmoregulation, with gill damage causing chronic respiratory distress.
Gill health represents a fundamental welfare determinant for fish that is often invisible to farmers until severe disease has developed. Gills damaged by parasites, disease, or poor water quality cause chronic respiratory distress analogous to breathing difficulty in mammals. Routine gill health monitoring and management is therefore a core welfare practice in responsible aquaculture.