Freshwater fish in UK rivers face welfare threats from pollution, abstraction, barriers to movement, and invasive species, with river restoration providing multi-species welfare benefits.
Freshwater fish welfare in UK rivers has improved significantly since the water quality legislation of the 1970s-80s enabled recovery of species including salmon and sea trout from rivers like the Thames. Yet significant welfare challenges remain across the freshwater fish community. Flow reduction through water abstraction is a persistent welfare concern: reduced river levels increase water temperature (stressful for cold-water species like salmonids), reduce oxygen availability, concentrate pollutants, and expose invertebrate food sources that fish depend on. Passage barriers including weirs, culverts, and dams fragment populations and prevent the migratory movements that many species require for welfare and reproduction. The growing recognition that fish are sentient animals capable of experiencing pain - evidenced by nociceptor presence, pain avoidance behaviour, and opioid-mediated pain relief responses - has elevated the welfare significance of these habitat threats. River restoration projects that restore natural flow regimes, remove barriers, and improve water quality benefit freshwater fish welfare directly and have positive cascade effects on the invertebrate communities on which they depend.