Restoring degraded freshwater and marine habitats reduces chronic stress in wild fish populations by improving water quality, reducing crowding and re-establishing food availability and refuge from predators.
While discussions of fish welfare often focus on aquaculture and angling, the chronic welfare impacts of degraded habitats on wild fish populations deserve equal attention. Fish living in warming, hypoxic or polluted water experience sustained physiological stress equivalent to chronic pain or illness in mammals. Crowding at remaining cold-water refugia during heat waves causes injury through competition and increased pathogen transmission. Habitat restoration — through dam removal, riparian planting, pollution reduction and cold-water refugia preservation — directly improves the welfare of billions of individual fish by allowing them to express natural thermoregulatory, migratory and foraging behaviors.