General considerations regarding the decline of species

Abstract

Man-made alterations of aquatic environment, changes in land use and management of fish stocks lead to general decline of species diversity, and often to dissappearance of several species. Slight improvement of water quality in several large rivers, as at present, does not provide a guarantee for reestablishing the original fish communities; it enhances the "universalists" in the majority of cases. In the effort to reintroduce the vanished taxa, their geographic origin and taxonomic status should be strictly observed. The Red Data Books helped to draw attention to the endangered status of the fish fauna considerably, and it is expected that new editions should record the status of species according to respective watersheds instead of administrative and/or political boundaries