Staff at the Environment Agency are using 2,500 tonnes of gravel to increase the number of salmon in Teesdale's rivers by making it easier for them to breed.
The rivers Lune and Balder are important tributaries of the Tees but do not contain sufficient amounts, or the right type of gravel for salmon to breed. This is due to the chain of reservoirs west of Barnard Castle which disrupt the natural flow of gravel from the headwaters.
Fisheries staff at the Environment Agency say the habitat in the Balder is good and would support more salmon if their numbers could be increased.
Salmon need clean gravel in which to lay their eggs. The female digs a nest in the gravel known as a Redd, then lays her eggs which are fertilised by the male. The female then covers the eggs, where they incubate slowly in the gravel throughout the winter and hatch in early spring.
As part of the Environment Agency's Salmon Action Plan, 1,000 tonnes of gravel have already been put into the River Balder and is being released in phases down the river.
The project is being supported by Northumbrian Water which is releasing water from the Hury Reservoir to help the gravel move slowly downstream.
A further 1,500 tonnes will be introduced later this year, however tens of thousands of tonnes of gravel would have flowed down the rivers every year at one time.
Environment Agency fisheries officer for the River Tees, David Bamford said: â€œIn the past, the Balder Valley was one of the best salmon spawning areas in the River Tees catchment but this changed when Hury reservoir was built in the 1890s. Subsequently more reservoirs were added up the valley.
â€œWe need a healthy stock of salmon in the river if the Tees is to recover to the same extent as the River Tyne which is now one of the best salmon fisheries in England and Wales. By working closely with Northumbrian Water we are using the gravel to improve the chances of the salmon breeding successfully and hope that the numbers will increase as a result.â€
Salmon have been observed spawning on this new gravel and regular surveys are planned to monitor the effects on the number of salmon in the river.