In recent years, the protection and rational utilization of natural resources, including animal resources, have acquired exceptional importance. Consequently, there is a need for more comprehensive information on the fish inhabiting various water bodies. The study of fish faunas in aquatic systems, the assessment of fish resources, and the development of measures for the conservation and rational exploitation of commercially valuable fish stocks constitute urgent tasks for the ichthyologists of Kazakhstan. The forthcoming fundamental five-volume compendium, Fishes of Kazakhstan, which contains all available information on fish morphology, distribution, biology, and behavior, is of great importance for advancing these studies. The absence of such a reference work has significantly hindered the formulation of numerous practical recommendations and scientific conclusions. For example, during the preparation of the Red Data Book of the Kazakh Soviet Socialist Republic, it became apparent that information on many rare fish species inhabiting the republic's waters was completely lacking. Owing to insufficient data, several rare species were not included in the first edition of that publication. The species composition of fish faunas in various drainage basins, particularly those of the Aral Sea and Lake Balkhash, has undergone such profound changes that information on some native fish species can now be obtained only from the literature, and even these sources provide far from adequate coverage. During the past several decades, non-commercial fish species, the so-called low-value and rough fish, have received little attention from researchers. As a result, reasonably complete information exists in the literature for only a few of these species, while the majority of native rough-fish species remain poorly studied. At present, the validity of a number of taxonomic units, including species, subspecies, and ecotypes, is being questioned. Only after careful taxonomic revision of individual species and genera will it be possible to determine whether they should continue to be recognized at these taxonomic ranks. The fundamental changes planned for Kazakhstan's hydrographic network, together with the ongoing acclimatization and introduction programs, require answers to many questions concerning the study of fish faunas in the country's waters. All of this makes the preparation and publication of the most comprehensive possible compendium on the fishes of Kazakhstan an even more urgent task. When undertaking this work, the authors were fully aware that the descriptions of many species would necessarily be compilatory in nature and that, in numerous cases, entries would be limited to the notation "no data available." Nevertheless, this compendium will reveal the degree to which individual species have been studied and will serve as a specific milestone and starting point for new investigations of the republic's ichthyofauna. The synthesis of accumulated information will facilitate the planning of future research and help avoid repeating earlier mistakes in both scientific organization and fisheries management. For this reason, a special section devoted to acclimatization and introduction activities has been included. The time has finally come to assess comprehensively what results have been achieved through the enormous investments made in efforts to transform fish faunas. In the literature, Kazakhstan's water bodies are often cited as one of the most convincing examples demonstrating the success of the acclimatization concept. Yet a simple comparison of fish catches before and after these programs, considering both quantity and species composition, yields results that are far from encouraging. The ichthyofauna of Kazakhstan developed under the harsh conditions of unstable and isolated water bodies, adapting historically to these circumstances and acquiring a high degree of endemism and uniqueness. Today this uniqueness has been almost completely lost and is virtually impossible to restore in full. Consequently, the establishment of aquatic nature reserves has become a necessity, not only, or even primarily, for the protection of valuable commercial fish, but also for the preservation of endemic species. Despite being fully aware of the complexity of the task, the authors believe that taxonomic revisions of certain genera are both feasible and necessary. They generally favor the concept of species polymorphism, which in many cases appears to provide the only acceptable explanation for morphological, ecological, and biological variation among closely related nominal species. The structure of the compendium is as follows. In addition to two general introductory chapters, Volume I describes native and introduced representatives of the lampreys, sturgeons, herrings, salmonids, and pikes occurring within the republic. Volumes II and III are devoted exclusively to native cyprinid fishes. Volume IV will describe representatives of the remaining families. Volume V will analyze acclimatization efforts and describe fish species that have become established in Kazakhstan. Species occurring exclusively in the Caspian Sea and not entering inland waters are not included. In Volume I, the Preface, Chapter I, and the introduction to Chapter III were written by G. M. Dukhravets and V. P. Mitrofanov; Chapter II was written by V. P. Mitrofanov. The Cyclostomata were described by A. N. Podtoreshina. The sturgeons (except shovelnose sturgeons and the Siberian sturgeon) were described by N. E. Pesheridi. The Syr Darya shovelnose sturgeon, the herrings, the Aral and Caspian salmon, the whitefish, and the pike were described by G. M. Dukhravets. The Siberian sturgeon and the spotted pike were described by V. I. Yelesenko. The taimen, lenok, and grayling were described by V. P. Mitrofanov, who also prepared the identification keys. A number of individual reviews were prepared with the participation of collaborators. The account of the beluga sturgeon was prepared with contributions from S. S. Zakharov; the account of the starry sturgeon with contributions from V. A. Melnikov (Aral Sea and Lake Balkhash populations); and the account of the pike with contributions from R. N. Soloninova (Irtysh River basin, chiefly the Bukhtarma Reservoir). I. V. Orlova participated in revising materials on the Siberian sturgeon and spotted pike and in preparing the corresponding species reviews. G. M. Dukhravets contributed to the account of the spotted pike and edited the sections on cyclostomes and sturgeons. A. I. Goryunova provided numerous comments and additions to Chapter I, mainly concerning fish culture and aquatic parasitology. The scientific editing of the volume was carried out by Professor V. P. Mitrofanov. The illustrations of fish and the diagram of the lamprey oral funnel were based primarily on figures published in the compilations of L. S. Berg (1948), G. V. Nikolsky (1971), and T. Z. Zakhidov and co-authors (1971). The illustrations of sturgeons (except the Siberian sturgeon and shovelnose sturgeons), the microphotographs of their gonads, and the sections of sterlet fin rays were prepared by N. E. Pesheridi. Photographs of the Siberian lamprey (Figs. 3-5) were taken by A. N. Podtoreshina. Charts and diagrams were prepared by the authors of the respective species accounts. All remaining illustrations, including the original drawing of the lenok from Lake Markakol, were produced by I. V. Mitrofanov. The authors hope that this book will prove useful not only to fisheries specialists and scientific researchers, including ichthyologists, fish-culture experts, and zoologists, but also to teachers, university students, and the broad community of nature enthusiasts.