MIDDLE-AGED mussels were given a helping hand as thousands of fish were freed into a Northumberland river.

Environment Agency officers released 11,000 sea trout at the top of the River Rede. The fish were carrying microscopic freshwater pearl mussel larvae, each of which is around a tenth of a millimetre in size.

It was the fruition of the agency’s matchmaking efforts in assembling Tyne mussels in an artificial stream at the Kielder hatchery in north Northumberland.

The North Tyne and the River Rede are two of the last few strongholds in England for the beleaguered species but their increasingly-empty beds are making it difficult for them to reproduce in the wild.

Baby mussels largely stopped appearing in the 1960s.

That has meant a population of increasingly senior mussel citizens, with the bulk of the 12,000 shellfish in Northumberland in the 40 to 80 years old bracket. They can live for up to 120 years.

As the population thins out because there are so few youngsters, the remaining adult shellfish are becoming more widely spaced.

And as the mussel has only one foot, mainly used for anchoring itself to the river bed but limiting movement, the creatures find it increasingly difficult to get it together.

The agency’s captive breeding programme mirrors what should happen in the wild, using trout as host fish for the mussels.

The larvae eventually drop from the fish and grow in the gravel beds of rivers. The sea trout were also bred at the Kielder Hatchery, where they were deliberately implanted with pearl mussel larvae from captive breeding population.

The fish were released in part of the River Rede where pearl mussels haven’t been seen for 50 years.

Environment Agency ecologist Anne Lewis said: “We’ve been working hard to get the right breeding conditions in the hatchery. It’s a really exciting time .

“Mussels are not breeding in the wild and will become extinct in Northumberland if we cannot find ways to support the species. In the past, pollution, dredging and poaching have all taken their toll on the population nationally but our rivers are now the healthiest they have been for 20 years.”

Kielder hatchery assistant David Kirkland said: “Stocking our first batch of host fish was a proud moment and a big step forward in our efforts to keep pearl mussels in the Tyne.

“We are learning all the time and hope to achieve a higher rate year on year.”