On the Lower Units of a Zoogeographical Regionalization

A lower-level zoogeographical regionalization of Northern Europe is proposed on the basis of the distribution of 50 species and subspecies of typical freshwater fishes and anadromous fishes native to the region. European species are found to give way gradually to Siberian species from west to east. A detailed zoogeographical regionalization for freshwater fishes has practical use because it meets the planning needs of inland fisheries, which are greatly dependent on the distributional patterns of the ichthyofauna. In general, lower-level zoogeographical regional units can be established only for organisms distinguished by a relatively low level of vagility, the capacity to move freely about. For highly vagile species, only more generalized regional units can be established.