YOUNGSTERS have been up to something fishy in a remote corner of the North York Moors – for the very best of reasons.

They released 70 young Atlantic salmon into the River Esk at Beck Hole after raising them from eggs in a hatchery tank at their school in nearby Goathland.

And as well as boosting the fish population they were also helping the rare freshwater pearl mussel – which depends on salmon and trout as a host for its larvae.

The Salmon in the Classroom project was organised by the North York Moors National Park Authority in partnership with the Yorkshire Esk Rivers Trust.

The river is the only one in Yorkshire with a freshwater pearl mussel population but numbers are in drastic decline.

But with the help of landowners, the National Park is carrying out restoration work to benefit the mussels and a host of other species.

It is also involved in a captive breeding programme in the hope that juvenile pearl mussels can be re-introduced to the Esk to bolster the existing ageing population.

School head Susan Chadwick said: “This has been a wonderful experience for the children who have delighted in watching the fish develop from eggs to small fry.

“They have all been very diligent in feeding the fish and monitoring the temperature in the tank to make sure they don’t get too warm, and have proudly shown them off to parents and visitors to the school.”

The park’s project officer Simon Hirst added: “The fish released this week will remain in the River Esk for around two years as they grow and develop until they are big enough to migrate out to sea.

“Hopefully they’ll then return to the river Esk in about three years to spawn and produce young of their own.”