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Data on new findings of the Nikolsky loach Misgurnus nikolskyi in the south of Western Siberia are presented. The maximum distance from the place of the first detection is about 200 km downstream of the Ob River. It has been suggested that the main method of dispersal of the Misgurnus nikolskyi in this region is deliberate introduction. It has been shown that the mtDNA haplotypes of the cyt b locus of the Misgurnus nikolskyi from the Ob River basin are identical to those described from the Lower Amur River basin.

Biological diversity is the basis for, and an indicator of biosphere integrity. Together with climate change, its loss is one of the two most important planetary boundaries. A halt in biodiversity loss is one of the UN Sustainable Development Goals. Current changes in biodiversity in the vast landmass of Siberia are at an initial stage of inventory, even though the Siberian environment is experiencing rapid climate change, weather extremes and transformation of land use and management. Biodiversity changes affect traditional land use by Indigenous People and multiple ecosystem services with implications for local and national economies. Here we review and analyse a large number of scientific publications, which are little known outside Russia, and we provide insights into Siberian biodiversity issues for the wider international research community. Case studies are presented on biodiversity changes for insect pests, fish, amphibians and reptiles, birds, mammals and steppe vegetation, and we discuss their causes and consequences. SUPPLEMENTARY INFORMATION: The online version of this article (10.1007/s13280-021-01570-6) contains supplementary material, which is available to authorized users.

Rainbow trout Oncorhynchus mykiss (Walbaum, 1792) and brown trout Salmo trutta Linnaeus, 1758 are popular aquaculture species worldwide. At the same time, it is known that when these species enter natural water bodies, they are able to form self-reproducing populations and cause significant damage to native fauna due to food competition, hybridization with native species, and predation. In the basin of the Upper Ob in the second half of the twentieth century, there was not only a large aquaculture farm specializing in trout but also work was carried out to introduce trout into natural water bodies: lakes in the basins of Lake Teletskoye and the Katun river. It is known about the formation of a self-reproducing population of brook trout in Lake Lebedinoe (in the basin of the Pervaya Koksha River, a second-order tributary of the lower reaches of the Katun River), which still exists. Currently, rainbow trout is a popular object of aquaculture in southern Siberia; it is grown mainly for the purpose of organizing recreational fishing, often in water bodies that are not isolated from the river network. This determines the regular ingress of this species into rivers. Nevertheless, currently no evidence of natural reproduction of trouts in natural water in the Upper Ob basin, except in Lake Lebedinoe. However, given the high risks associated with the potential invasiveness of trouts, it is necessary to recommend a cautious attitude towards the distribution of these species and to provide for an environmental impact assessment of projects related to their cultivation in water bodies of Western Siberia.

Information about some features of the Prussian carp Carassius gibelio (Bloch, 1782) in three different floodplain lakes in the Middle Ob river basin are presented. Individuals of younger age groups predominate in populations. Fish over the age of 9+ are not noted. The ratio of females to males is different, from 4:1 to 8:1, always in favor of females, which is typical for Prussian carp populations in Western Siberia. There were specimens in the sample from 152 to 355 mm long and weighing from 115 to 1250 g. When comparing males and females of the same age, the latter are generally larger. The noted size characteristics — 335 mm and 1250 g — are the maximum of the published data for Prussian carp Carassius gibelio in the Middle Ob river basin. When comparing individuals of the same age, it was shown that Prussian carp Carassius gibelio is a larger size in the big not-frozen lake Monatka than in the small, frozen lakes Zmeevo and Taskino. The maturity of female Prussian carp Carassius gibelio in floodplain lakes of the Middle Ob river basin occurs at the age of 3+, but some 2+ were mature. At the age of 4+, all specimens in the samples were sexually mature. Sexual dimorphism Prussian carp from lake Monatka is weakly expressed: in males, the length of the head, the height of the dorsal and the length of the pectoral fins are statistically significantly greater. A higher dorsal fin can be considered a characteristic feature of the male Prussian carp in the south of Western Siberia in comparison with the females.

The data on the catch, age composition and growth of the roach Rutilus rutilus L. in commercial herd in the Middle Ob basin (in the Tomsk region) are presented. It is shown that the catches of the roach in the middle of the 20th century were 2098 tons per year. In the second half of the 1960s, they fell sharply by more than two times. It was caused by a decrease in the areas of effective spawning due to the reduction of runoff in the Ob during spring floods as a result of the regulation of the level regime by the dam of the Novosibirsk hydroelectric power station. After that, the catch of roach remained at about 1013 tons per year until the beginning of economic reforms in the country, when the catch of this species became unprofitable, as a result of which catches decreased to an average of 436 tons per year. Currently, the basis of commercial catches is made up of roach with a commercial length of 140 to 210 mm and a weight of 50 to 150 g at the age of 2+...5+. It is noted, compared with the 1970–1980s, there is a shift in the age series towards an increase in the value of older age groups, which may indicate underutilization of the stock of the roach. The statistically significant positive relationship between catches of roach and the average duration of flooding of the floodplain in the years of the occurrence of generations that form the basis of catches was revealed. Prolonged floods also provide better conditions for fish feeding (a statistically significant positive relationship between the mass of fish of the same age and the duration of flooding of the floodplain is shown). Thus, the hydrological regime in the spring has a decisive influence on the state of the stocks of roach in the Middle Ob.

The aboriginal form of the Prussian carp in lakes and rivers in the south of Western Siberia is currently being replaced by the Amur forms of the same species introduced into the water bodies of the region in the late 1970s. We analyze the genetic diversity of this species in Southern Siberia based on the polymorphism of a D-loop fragment of mitochondrial DNA (460 bp) and reveal the presence of two haplogroups, one of which (B) is extremely rare in South East Asia and is likely an indicator of the autochthonous forms of the Prussian carp, and the other (A) is similar to haplotypes typical of the Far Eastern populations.

The study of juvenile fish is a necessary component of fishery research, is of great theoretical interest and is widely used in the study of ontogeny, influence of various environmental factors on the final trophic link of aquatic ecosystems. Traditionally, fry samples are fixed with a 4–5 % formalin solution. However, formalin is a toxic compound, which entails special requirements for the organization of work in laboratory. In order to search for alternative means of fixing biological preparations, an experimental assessment of the possibility of using the drug “Aldofix” as a substitute for formalin in studies of juvenile fish. It was shown that the fixation of juvenile fish with the “Aldofix” preparation immediately after collection of samples is possible only for the subsequent analysis of the length and weight of the specimens. For species identification and for the study of the morphology of fish specimens, fixed with the preparation “Aldofix” immediately after capture unsuitable. However, the re-fixation of fish juvenile samples with “Aldofix”, initially fixed with formalin, seems reasonable, since the quality of the material does not decrease, but at the same time, due to the non-toxicity of the “Aldofix” preparation, there is no negative impact on the health of specialists and students who process these wet preparations.

Data are presented on fish community structure in ponds and floodplain and mainland lakes in the southern taiga subzone of Western Siberia (within Tomsk region), where a total of 14 fish species have been recorded. The ordering of data on the fish biomass using a factor classification program has allowed us to distinguish three population groups, with one of them including three subgroups. Winter hypoxia is the most important among external factors determining the structure of fish communities. Its absence determines the presence of perch in the fish communities; in turn, the abundance of perch affects the abundance of other fish species. Therefore, the primary organization of the communities is determined by the environment and their secondary organization by the relationships between the species.

The data on feeding of the Amur sleeper Perccottus glenii in a pond located in the southern taiga subzone in West Siberia obtained in May–October 2017 are presented. A total of 15 components have been identified in its guts. The diet of Amur sleeper is largely composed of larvae of amphibiotic insects and amphibians in spring and fish in summer and autumn periods; the diversity of food composition decreases by autumn.

Based on a critical analysis of scientific publications for the last 200 years and on the collected specimens, a complete annotated list of both typical freshwater ichthyofauna of Sakhalin Island, with the inclusion of marine species that can be found in brackish coastal waters, is reported for the first time. The annotated list includes 226 species classified in three classes, 26 orders, 68 families, 29 subfamilies, and 148 genera. For 160 species, information is provided on collection samples deposited in various museums around the world, 36 of which are type specimens. For each species, conservation status (according to IUCN Red List of Threatened Species and the Red Book of the Sakhalin region), zoogeographic characteristics (distribution within Sakhalin Island and globally), abundance and commercial value are given. For a number of species, more detailed information on synonymy and nomenclature is provided. The study area is located in the western North Pacific and includes the entire coast of Sakhalin Island in the Sea of Okhotsk and the northern Sea of Japan, as well as the adjacent Sea of Okhotsk coast of northern Hokkaido, Japan.

Polyploid species represent a challenge for both cytogenetic and genomic studies due to their high chromosome numbers and the morphological similarity between their paralogous chromosomes. This paper describes the use of low-coverage high-throughput sequencing to identify the 14 most abundant tandemly arranged repetitive elements in the paleotetraploid genome of the crucian carp (Carassius carassius, 2n = 100). These repetitive elements were then used for molecular cytogenetic studies of a closely related functionally triploid form of the Prussian carp (Carassius gibelio, 3n = 150 + Bs) and a relatively distant diploid species, the tench (Tinca tinca, 2n = 48). According to their distribution on the chromosomes of the 3 aforementioned species, the repetitive elements here identified can be divided into 5 groups: (1) those specific to a single genomic locus in both Carassius species, despite the recent carp-specific genome duplication; (2) those located in a single genomic locus of T. tinca, but amplified in one or both Carassius species; (3) those massively amplified in the B chromosomes of C. gibelio; (4) those located in a single locus in C. gibelio, but amplified in many blocks in C. carassius; and (5) those located in multiple pericentromeric loci in both Carassius species. Our data indicate that some of the repetitive elements are highly conserved in cyprinoid species and may serve as good cytogenetic and genomic markers for discriminating paralogous chromosomes, while others are evolutionarily recent, and their amplification may be related to the last whole-genome duplication event.

Polyploid genomes present a challenge for cytogenetic and genomic studies, due to the high number of similar size chromosomes and the simultaneous presence of hardly distinguishable paralogous elements. The karyotype of the Siberian sturgeon (Acipenser baerii) contains around 250 chromosomes and is remarkable for the presence of paralogs from two rounds of whole-genome duplications (WGD). In this study, we applied the sterlet-derived acipenserid satDNA-based whole chromosome-specific probes to analyze the Siberian sturgeon karyotype. We demonstrate that the last genome duplication event in the Siberian sturgeon was accompanied by the simultaneous expansion of several repetitive DNA families. Some of the repetitive probes serve as good cytogenetic markers distinguishing paralogous chromosomes and detecting ancestral syntenic regions, which underwent fusions and fissions. The tendency of minisatellite specificity for chromosome size groups previously observed in the sterlet genome is also visible in the Siberian sturgeon. We provide an initial physical chromosome map of the Siberian sturgeon genome supported by molecular markers. The application of these data will facilitate genomic studies in other recent polyploid sturgeon species.

To inform regional managers of potentially invasive non-native (NN) freshwater fishes in the principal hydrosystem that drains the West Siberian Plain, the River Ob basin, 31 extant and potential future NN fish species were screened using the Aquatic Species Invasiveness Screening Kit (AS-ISK) with respect to current and projected future climate conditions. Calibration of the AS-ISK scores, using receiver operating characteristic curve analysis, identified ‘basic risk assessment’ and ‘climate change assessment’ threshold scores of 27.5 and 34.75, respectively, with which to distinguish species that pose a high risk of being invasive in the Ob basin and those that pose a low-to-medium risk. Of the species screened, 12 ranked as high risk (black bullhead Ameiurus melas, brown bullhead Ameiurus nebulosus, grass carp Ctenopharyngodon idella, common carp Cyprinus carpio, eastern mosquitofish Gambusia holbrooki, silver carp Hypophthalmichthys molitrix, oriental weatherfish Misgurnus anguillicaudatus, rainbow trout Oncorhynchus mykiss, Chinese (Amur) sleeper Perccottus glenii, topmouth gudgeon Pseudorasbora parva, brown trout Salmo trutta, pikeperch Sander lucioperca and rudd Scardinius erythrophthalmus). The remaining species ranked as medium or low risk. Although the risk scores increased in 68% of species under climate change conditions, this affected the risk rankings of only two species: Salmo trutta decreased in rank from high to medium and Sander lucioperca increased in rank from medium to high. The outcomes of the present study, which identified 12 species for which full risk assessments are recommended, serves to inform the development of NN species policy and management in Russia.

Sexual reproduction is a ubiquitous basic feature of life and genetic sex determination is thus widespread, at least among eukaryotes. Understanding the remarkable diversity of sex determination mechanisms, however, is limited by the paucity of empirical studies. Here, we traced back the evolution of sex determination in an entire clade of vertebrates and uncovered that the northern pike (Esox lucius) master sex-determining gene initiated from a 65 to 90 million-year-old gene duplication and remained sex-linked on undifferentiated sex chromosomes for at least 56 million years. Contrasting with its ancient origin, we identified several independent species- or population-specific transitions of sex determination mechanisms in this lineage, including an unexpected complete and recent Y-chromosome loss in some North American northern pike populations. These findings highlight the diversity of the evolutionary fates of master sex-determining genes and raise the importance of careful considerations of population demographic history in sex determination studies. Our study also puts forward the hypothesis that occasional sex reversals and genetic bottlenecks provide a non-adaptive explanation for sex determination transitions.

The data on infestation of muscles of alien fish species with metacercariae of trematode Opisthorchis felineus Rivolta, 1884 in the Middle Ob River basin are presented. It is shown that bleak and bream are susceptible to infestation with the larvae of cat liver fluke Opisthorchis felineus, but the rates of infestation are low even in the hotbed of opisthorchiasis.

A biogeographical division of northern Eurasia (within the USSR borders as of 1991) based on cluster analysis of the cyclostome and fish fauna composition at 597 sites listed in the Biodat database has been performed. The classification based on the Jaccard similarity coefficients included two regions, 12 subregions, eight provinces, and 11 districts. The division performed explained 67% of the variance of the similarity coefficients, this being 21% higher than the respective value for an earlier scheme (Berg, 1962) that covered a significantly greater territory. Correlation with the climatic regimes and environmental factors identified could explain 82% of fish fauna heterogeneity (the multiple coefficient of correlation was 0.91). The nonorthogonal relations with the temperature regime (67% of the variance of similarity coefficients), landscape and climatic zoning (58%), location within a specific river basin (57%), and provinciality (30%) were the most important factors.

The threat posed by invasive non-native species worldwide requires a global approach to identify which introduced species are likely to pose an elevated risk of impact to native species and ecosystems. To inform policy, stakeholders and management decisions on global threats to aquatic ecosystems, 195 assessors representing 120 risk assessment areas across all six inhabited continents screened 819 non-native species from 15 groups of aquatic organisms (freshwater, brackish, marine plants and animals) using the Aquatic Species Invasiveness Screening Kit. This multi-lingual decision-support tool for the risk screening of aquatic organisms provides assessors with risk scores for a species under current and future climate change conditions that, following a statistically based calibration, permits the accurate classification of species into high-, medium-and low-risk categories under current and predicted climate conditions. The 1730 screenings undertaken encompassed wide geographical areas (regions, political entities, parts thereof, water bodies, river basins, lake drainage basins, and marine regions), which permitted thresholds to be identified for almost all aquatic organismal groups screened as well as for tropical, temperate and continental climate classes, and for tropical and temperate marine ecoregions. In total, 33 species were identified as posing a 'very high risk' of being or becoming invasive, and the scores of several of these species under current climate increased under future climate conditions, primarily due to their wide thermal tolerances. The risk thresholds determined for taxonomic groups and climate zones provide a basis against which area-specific or climate-based calibrated thresholds may be interpreted. In turn, the risk rankings help decision-makers identify which species require an immediate 'rapid' management action (e.g. eradication, control) to avoid or mitigate adverse impacts, which require a full risk assessment, and which are to be restricted or banned with regard to importation and/or sale as ornamental or aquarium/fishery enhancement. (c) 2021 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/)., Cefas Science Excellence fund; [TKP2020-NKA-16], This study is dedicated to our co-author, the late Prof. Olaf Weyl, whose sudden passing during field work in November 2020 was received by us with great sadness. This study represents a contribution to the term of reference 'd' (Advance knowledge base to further develop indicators to evaluate the status and impact of non-indigenous species in marine environments) of the ICES working group on Introductions and Transfers of Marine Organisms. The participation of GHC was supported by the Cefas Science Excellence fund. AW and AF were supported by TKP2020-NKA-16 project.

The paper contains a complete annotated list of freshwater ichthyofauna of the Middle Ob River basin. The list is based on an analysis of publications and on the results of the authors’ research, and it includes 43 species in two classes, 9 orders, 12 families, and 30 genera. Ten of all listed species are introduced and only seven are naturalized. For each species, taxonomic comments are provided where necessary and conservation status, distribution within the Middle Ob River basin, abundance and commercial value are indicated. Latin and English names are given.

The sterlet (Acipenser ruthenus Linnaeus, 1758) is a relatively small sturgeon widely distributed in Eurasian rivers from the Danube to the Yenisei. During the twentieth century, all wild sterlet populations have declined due to anthropogenic factors including: overfishing, poaching, construction of dams, and pollution. Despite the necessity of characterization both wild and captive stocks, few studies of population genetics have been performed thus far. Here we studied the genetic diversity and geographic structure of sterlet populations across the eastern range – Ob-Irtysh and Yenisei basins – by sequencing a 628-bp fragment of mitochondrial DNA control region. We identified 98 new haplotypes, delineated 12 haplogroups and estimated the time of basal haplogroup divergence within the species as over 8 million years ago. Our data suggest that Ob-Irtysh and Yenisei populations are isolated from each other and much lower genetic diversity is present in the Yenisei population than in the Ob-Irtysh population. Our data imply that sterlet populations in Siberian rivers underwent bottleneck or fragmentation, followed by subsequent population expansion. The data obtained here are important for sterlet population monitoring and restocking management.

Environmental changes due to non-native species introductions and translocations are a global concern. Whilst understanding the causes of bioinvasions is important, there is need for decision-support tools that facilitate effective communication of the potential risks of invasive non-native species to stakeholders. Decision-support tools have been developed mostly in English language only, which increases linguistic uncertainty associated with risk assessments undertaken by assessors not of English mother tongue and who need to communicate outcomes to local stakeholders. To reduce language-based uncertainty, the ‘ecology-of-language’ paradigm was applied when developing the Aquatic Species Invasiveness Screening Kit (AS-ISK), a decision-support tool that offers 32 languages in which to carry out screenings and communicate outcomes to stakeholders. Topics discussed include uncertainty related to language-specific issues encountered during the AS-ISK translation and the potential benefits of a multilingual decision-support tool for reducing linguistic uncertainty and enhancing communication between scientists, environmental managers, and policy and decision makers.

To date, 22 alien fish species are known in the Ob River basin. Of them, nine species—Pike-perch Sander lucioperca, Freshwater bream Abramis brama, common carp Cyprinus carpio, belica Leucaspius delineatus, bleak Alburnus alburnus, Stone moroko Pseudorasbora parva, Amur sleeper Perccottus glenii, Nikolsky’s loach Misgurnus nikolskyi, and southern ninespine stickleback Pungitius platygaster—formed self-reproducing populations and started self-spreading in natural waterbodies. This paper summarizes the data on invasion of alien fish species in the Ob River basin. The data on history, rate of spread, modern distribution, and relative abundance are given. It is shown that water temperature is the main environmental factor which limits the expansion of introduced species in the Ob basin.

The genus Rutilus is a widely distributed lineage of cyprinids and ranges from West Europe to East Siberia. Although matrilineal phylogeny and phylogeography of western species were already studied, roaches from remaining part of the range were not examined. Phylogenetic analysis based on cytochrome b sequences detected the following three major phylogenetic clades: (i) R. frisii, (ii) R. rutilus s. str., and (iii) group of six Ponto–Caspian taxa: R. caspicus, R. heckelii, R. rutilus aralensis, R. rutilus lacustris, R. schelkovnikovi, and R. stoumboudae. Our results suggest that these “species” within Ponto–Caspian clade could be a single species (R. lacustris by priority of description). The Ponto–Caspian clade is most widely distributed among others and covers the freshwaters from the Aegean Sea basin to Laptev Sea tributaries. Both R. rutilus s. str. and Ponto–Caspian clades sympatrically occur in Black Sea and Caspian Sea basins, Azov Sea itself, and even in drainage of White Sea. The vastest zone of contact (approximately 1700 km) was detected in the Volga basin. The spatial pattern of haplotype diversity and the shape of haplotype network argued for multiple refugia in Ponto–Caspian region as well as a rapid post-glacial colonization of Volga River and Siberia.

The data show quantitative and qualitative composition of macrozoobenthos of the 12 left-bank confluences of the Middle Ob. The research has documented the presence of various groups, such as Oligohaeta, Diptera, Odonata, Hirudinea, Tabanidae, Trichoptera and Mollusca. The chironomids, molluscs and leeches play a significant role in the generation of biomass in the surveyed streams, and the abundance mostly depends on chironomids, oligochaetes and leeches. In general, zoobenthos abundance ranges from 8.8 (the Shudelka river) to 1839.9 (the Kochebilovka river) ind./m2, biomass is from 0.08 (Tatosh river) to 8.37 (Lozunga river) g/m2. The amount and benthos biomass of the Middle Ob’s second-order tributaries is higher than in the first-order tributaries.

Data on the species composition of the fish population inhabiting the tributaries of the Novosibirsk reservoir are given in the article. The structure of fish communities and possible environmental factors determining it have been revealed. The relation between the heterogeneity of fish communities and the river depth and length, relief, current velocity, floodplain, and estuarial areas, presence of sand-pebble shallow waters and channel order, has been studied.

We analyze Distribution and habitats of the belica (Leucaspius delineatus), a species accidentally introduced to waterbodies of southwest Siberia. The northern limits of the range of this species in the region are determined. Data are given on the sex ratios, size and age structure, growth, feeding, fecundity, and time and conditions of spawning of the belica in waterbodies of different types. It is shown that males of the earlier age groups are prevalent in belica populations.