Thousands of baby eels have been released into a West Yorkshire river in an effort to boost the population.
Thousands of elvers are being released in the River Aire
Experts from the Environment Agency's fisheries team released 63,000 elvers into the River Aire at Rodley on the outskirts of Leeds on Monday.
European eel stocks have been in major decline since the 1970s. The number of young eels reaching the UK's shores are thought to have fallen by 95%.
Weirs, locks and pumping stations have all caused eels numbers to dwindle.
Elvers, which are about 7cm (2.8in) in length, spend at least a year drifting across the Atlantic in the Gulf Stream.
Predators and prey
They then swim up rivers to find a suitable place to live and grow, and when they mature, they return to sea and swim across the Atlantic to spawn south-west of Bermuda.
"Stocking eels into waters that they can no longer reach by themselves will increase the number of eels returning to their spawning grounds.
"Stocking is very important for local biodiversity and eels form an important link in the food chain as both predators and prey."
The elvers have been supplied to the Environment Agency after being caught in the Severn Estuary.
The large tides of the River Severn act as a funnel, sweeping in larger numbers of elvers than the river can cope with, so despite the general decline in eel numbers, elvers can still be taken from the Severn without harming the ecology, the agency said.