Since 1990 and within the “Rhine” and “Rhine 2020” Action Programmes of the International Commission for the Protection of the Rhine (ICPR), biological inventories of the fish fauna of the Rhine are regularly being carried through along the entire course of the river. 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 years cycle.
Some species are equally analysed with respect to their contamination with pollutants.
The last inventory of fish in the Rhine in 2012/2013 showed that 67 fish species are again present in the Rhine. Many fish species, such as salmon, sea trout, sea and river lamprey have returned. The reintroduction of the houting has been successful. In 2013, the first allis shad was observed in the new fish passage on the Moselle at Koblenz. Its population had vanished as a result of excessive fishing and increasing water pollution. The only fish species formerly typical for the Rhine which is still lacking is the sturgeon.
During the past years, 4 goby species from the Black Sea region have settled as new, non-indigenous fish species. The ICPR report no. 208 "Goby Species immigrated into the Rhine System" gives an overview over the goby species presently occurring in the Rhine system and the possible consequences for the ecosystem. Another newcomer in the list of species is the European sea bass which from time to time migrates from the North Sea into river estuaries. After the inventories of 2000, the species great sturgeon, lake trout and silver carp have no longer been detected. Comparatively undemanding species (roach, bream, chub, perch, bleak, ruff) are dominant. The predatory asp has distinctly increased and spread to further areas.
Most fish species are found in the Upper Rhine and the Delta Rhine including Lake IJssel, where some marine species as well as brackish water species are detected. The least number of species is in found in the Alpine Rhine. The reasons for this are partly natural. However, neither the course of the river, nor developments since the middle of the 1990s give evidence of a distinct development tendency of the number of species. On the whole, frequency and biomass are comparably low. Today, Rhine water quality is not a limiting factor for the fish fauna.
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)