There has been an 'unacceptable' rise in agricultural pollution incidents in Wales, according to the chairwoman of Natural Resources Wales.
Diana McCrea said there were 679 cases of slurry pollution coming from dairy farms since 2010.
Salmon and Trout Conservation Cymru (S&TC Cymru) also spoke out in May following a number of high-profile incidents in Carmarthenshire and Ceredigion.
Ms McCrea wrote a letter to Welsh environment secretary Lesley Griffiths saying that she has become 'increasingly concerned' about the rise.
Richard Garner Williams, national officer for S&TC Cymru said slurry spraying on fields in wet conditions are two main factors contributing to the pollution of Welsh rivers.
"Threats to the very survival of the wild fish of Wales, including salmon, sea trout and brown trout, can no longer be ignored," said Mr Williams.
"The pollution of Welsh rivers by intensive agriculture has reached epidemic proportions and it is vital that the Welsh Government takes a more active stance to protect our precious waterways."
'Devastating impact'
Nick Thomas, also Natural Resources Wales, said of a recent slurry polluting incident: "Slurry can have a devastating impact on our rivers and the wildlife that depend on it, as we’ve seen here.
"We continue to work with farmers, and the farming unions, to reduce the chances of incidents like this happening.
"Farmers concerned about their slurry stores should contact us for advice and guidance about how to reduce the risk of pollution."
Ms McCrea, who is expected to meet the environment secretary at the Royal Welsh Show, set out her thoughts on inspecting slurry and silage stores while they are being built and regulating anaerobic digestion plants on farms.
Ms Griffiths is also being asked to look at allowing the use of civil sanctions to help tackle agricultural pollution, to bring Wales in line with England, but it needs the Welsh Government to pass the legislation.
'Farmers' responsibility'
A Welsh government spokesperson said tackling agricultural pollution is 'crucial' if water quality is to be improved.
"Pollution incidents from farms, of which we have had a spate recently, are having a significant and detrimental impact.
"This is an issue where we, as a government, have a role to play but farmers must also recognise the important responsibility they have in addressing this problem. We are determined to work with them and other respective parties to find a solution.
"Where there is evidence of any breach of regulations we expect Natural Resources Wales to take appropriate action."
