Since 1990, comprehensive biological surveys of the Rhine fish fauna have been carried out at regular intervals along the entire length of the Rhine according to comparable criteria within the framework of the ICPR Rhine Measuring Programme Biology. With the inventory in 2006/2007, the programme has for the first time been adapted to the requirements of Annex V of the EU Water Framework Directive (WFD) and been extended to a 6 year cycle. Some species are equally analysed with respect to their pollutant contamination.
The Rhine fish fauna has undergone a major change over the last 25 years. Due to the improvement in water quality, some species have spread again, so that the species numbers have increased. All in all, today there are 71 fish species (including cyclostomata such as river and sea lamprey) in the Rhine, which corresponds to a considerable diversity. Apart from the European sturgeon, all historically proven species are again detected. Many migratory fish such as such as salmon, sea trout, sea and river lamprey have returned. In many places, results of electro fishing are however dominated by invasive goby species, above all the round goby which above all prefers the riprap of the riverbanks. Furthermore, mostly ecologically euryoecious species such as roach, bream, chub, perch and bleak are found.
Ein Rheinsalm schwamm den Rhein bis in die Schweiz hinein.
Und sprang den Oberlauf von Fall zu Fall hinauf.
Er war schon weißgottwo, doch eines Tages – oh! –
da kam er an ein Wehr: das maß zwölf Fuß und mehr!
Zehn Fuß – die sprang er gut! Doch hier zerbrach sein Mut.
Drei Wochen stand der Salm am Fuß der Wasseralm.
Und kehrte schließlich stumm Nach Deutsch- und Holland um.
Christian Morgenstern (1910)