River Barriers and Migratory Fish Welfare

Weirs, dams, and other river barriers block migratory fish from completing journeys essential for their survival and welfare.

Key Facts

The UK has an estimated 30,000 barriers to fish migration on rivers
Atlantic salmon must reach their natal rivers to spawn; barriers cause migration failure and death
Fish passes and eel passes improve migration success but are absent from most barriers
Removing obsolete weirs is more effective than passes and improves overall river ecology
Coho salmon in dammed rivers show chronic physiological stress markers throughout their lives

Welfare Considerations

Migratory fish blocked by barriers experience acute and chronic welfare consequences. The motivation to migrate upstream is extremely strong — salmon will attempt barrier passage repeatedly until exhausted, with physiological indicators of extreme exertion. Migration failure leads to fish dying below barriers without completing their life cycle. Removing obsolete barriers — disused mill weirs, redundant hydro structures — is the single most welfare-effective intervention for migratory fish, and its ecological benefits are extensive.

What You Can Do

Support the River Restoration Centre and Rivers Trust barrier removal programs
Advocate for barrier removal requirements as part of all water body management plans
Report unauthorised barriers to the Environment Agency or equivalent authority
Support eel pass installation programs for barriers that must remain
Learn about migratory fish barriers in your local river catchment