Five additional species are often reported as being present in Mongolia but are only presumed to exist and should be deleted from the Mongolian faunal lists. Four other species introduced species that have not been sighted for years and presumably did not become established and a further two introduced species which have become found. Nine species are known from immediately adjacent waters in China and Russia. They might be present, either as permanent inhabitants or vagrant individuals. The systematic status and nomenclature of all species have been reevaluated. Compared to the last synthesis of the fishes known from the same area (Baasanjav & Tsendayush, 2001), 11 (15 per cent) of the 72 formerly recognized species are invalid, and the names of 28 (39 per cent) of the then-known species were incorrect (either because of misidentifications, or for various nomenclatural reasons). Therefore, in total, more than half (39 out of 72) of the species in this synthesis were incorrectly listed, to which a further 15 species not previously recognised should be added. This demonstrates that present knowledge of fish diversity in Mongolia is far from adequate, that the number of species is underestimated, and that more species probably still await discovery. Survey work is needed in addition to an approach of taxonomy incorporating modern standards, concepts, and procedures. The fish fauna of the Chinese provinces of Xinjiang and Nei Mongol and the Russian Tuva and Buryatia Republics have been compared with the Mongolian fish fauna, where relevant, in an attempt to make the vocabularies used in the three countries compatible and agreement with the International Code of Zoological Nomenclature. Some of the systematic findings and nomenclatural changes are summarised in the section containing species lists. This exercise has revealed a large number of nomenclatural inconsistencies across boundaries, and many species in Mongolia, China, and Russia which are not yet adequately named. There are indications (and in many cases, firm evidence) that several widely distributed “species” in fact are artificial assemblages of species restricted to a small geographic area. These immediate implications for resource management and conservation because species endemic to a small area, or a single lake or stream, have more excellent biodiversity value and thus require closer attention. Also, the transplantation across drainage boundaries of fish stocks believed to be different populations of a single species may be the introduction of a species into the range of another species, carrying all the risks associated with presentations, including the risk of replacement of the original species with a hybrid complex. Source: Marice Kottelat (2006): Fishes of Mongolia.