Salmon and trout stocks have fallen due to pollution

Part of a �740,000 scheme, farmers are being advised about how to keep the Afon Cain pollutant-free.

Running through Llanfyllin and Llanfechain to Llansantffraid, near Welshpool, it once had a healthy population of fish.

However, in recent years numbers have dwindled, according to the Environment Agency Wales.

The agency said anglers have also noticed an increase in a breed called Brook Lamprey, a fish which prefers silty water.

Monitoring and regular analysis of the water quality showed that the likely cause for decline in salmon and trout was "diffuse pollution".

The project has been running about a month and we've already visited 11 farms Ioan Williams, FWAG

This is often minor discharges of pollutants from industries such as farming, forestry, mining and construction.

In a joint initiative funded by the European Union's structural funds programme , the agency and Farming and Wildlife Advisory Group Cymru (FWAG) will work with farmers.

The cash will be used to put up fences and build bridges to stop farm stock walking through the river.

Ioan Williams, of FWAG, said: "The project has been running about a month and we've already visited 11 farms and we intend to eventually visit 50.

"The funding will be used to advise farmers about how to avoid inadvertently polluting the river.

"Money will be spent to provide them with such things as fencing and even bridges so stock don't have walk through the river.

"Healthy stocks of salmon and trout have a knock-on effect for tourism and the local economy because people stay in hotels and use local amenities."

Salmon stocks have improved in the River Wye

An Environment Agency Wales spokesman explained what caused pollution in the Afon Cain.

"Soil washed into a watercourse is one example of diffuse pollution which affects fish populations," he said.

"To help the hatching of their eggs, salmon and trout rely on a good flow of oxygenated water through the riverbed gravels.

"Heavy rain can wash soil off land into the river, smothering the gravels and suffocating the eggs and newly-hatched young fish.

"Livestock trampling areas near the riverbank can make it easier for soil to enter a river through erosion."

The Afon Cain project is part of a larger scheme to address water quality in both the Upper River Severn and River Vyrnwy catchments.

In recent years, stocks of salmon in the River Wye have improved dramatically after a sustained project to improve numbers.

It was once among the best known salmon rivers in the world, but pollution brought that to an end.