“This shows that the quality of the Ruhr water has recovered so that is up to the high standards salmon require for their spawning waters,” said Harro Bode, the chairman of the Ruhrverband, a water quality management company.
In the summer of 2008, two young salmon were caught under an embankment near Essen. It sparked a new study and on June 23 of this year, in which researchers confirmed that the fish had returned to what was once the centre of Germany's industrial region. More than 20 specimens were found that day.
In addition to the salmon, scientists have also found more than 100,000 indicators that the river's quality is improving, they said in the first report. Near the sampling point at Essen-Rellinghausen, scientists found that levels of phosphorus and heavy metals were also at historically low concentrations.
The Ruhr River runs right through the heaviest-populated area in Germany and was first developed during the Industrial Revolution in the early 19th century. During that time, nearly 300 coal mines were in operation, fuelling the region's iron and steel factories. The river, a tributary of the Rhine River, served as the main transportation corridor for the industries in what is now North Rhine-Westphalia.