The Koblenz-based IKSR said more than 1,900 adult salmon had been counted returning to the waterway and that the real figure was probably significantly higher.

Other measures, including so-called fish passes, have also encouraged sea trout and salmon back into the Rhine.

A fish pass is a structure, usually a series of small steps and pools, that fish can swim up or jump over and so head upriver.

The commission said that water quality in the Rhine had "greatly improved" as less untreated water was being pumped in, although there was still a small problem with nitrates seeping in from neighbouring farmlands.

There were now 63 fish species in the Rhine, the IKSR went on, noting also an increase in riverside creatures such as insects and snails.

The IKSR, which was created to look after the Rhine's bio-diversity, groups representatives of Germany, France, Luxembourg, the Netherlands, Switzerland and the European Union.

TERRA.WIRE