More than 2,000 baby eels have been released into the River Severn in Shropshire.
Severn Rivers Trust said eel populations in the river have crashed in recent years.
The elvers were captured at Gloucester and the Sustainable Eels Group transported them to Attingham Park, at Atcham, for release into a tributary.
Night patrols along the river in Gloucestershire last year helped protect against their illegal netting.
In October, 20,000 eels were released in Ludlow in a bid to boost numbers.