Unlocking a river: rare silver fish returns to its ancient spawning grounds – in pictures

When four navigational weirs were built on the Severn in the 1840s they blocked the route of shoals of twaite shad as they made their way upriver. Now, a newly built system of fish passes means they can come home to breed

• Words and photographs by Alexander Turner

The twaite shad was once a common sight in Britain's waterways. A member of the herring family, the small silvery fish with a single dorsal fin and a forked tail was once so bountiful it was sold as food locally and abroad. But in recent times, it has been harder to spot and today the River Severn contains one of just four breeding populations in the UK.

A model of the twaite shad, a fish that was once abundant in the UK's rivers but has become an increasingly rare sight