Perccottus Research Articles

Geographically Isolated Wetlands as a Reserve for the Conservation of Amphibian Biodiversity at the Edge of Their Range

Wetlands are of great importance for biodiversity and nature conservation, especially geographically isolated wetlands (GIW). Yet literature about the ecological value of such GIW is missing, especially at the edge of the distribution of endangered species such as amphibians. In 2018 and 2022, we monitored amphibian communities in 15 isolated (GIW) and 12 non-isolated (nGIW) ponds by counting individuals using three methods: (1) capturing with hand nets, (2) visual counting, and (3) capturing with fyke traps. The three methods provided similar results, showing the great importance of GIW for amphibians, especially newts, whose abundance was 5–13 times greater in GIW compared to nGIW. The largest numbers of species and individuals (adults and larvae) were found in isolated wetlands (GIW). In non-isolated water bodies (nGIW) where more than 10 individuals of the Chinese sleeper Perccottus glenii, an alien invasive fish, were found, amphibians were not found at all. Importantly, between 2018 and 2022, the northern crested newt, T. cristatus, dramatically decreased in the nGIW. As a result of our work, it was revealed that the reconstruction of geographically isolated wetlands is very important for the conservation of amphibian biodiversity in a changing climate. One of the most effective measures aimed at protecting amphibians from negative factors—the spread of alien invasive fish species and diseases—is the reconstruction of wetlands in historically exploited landscapes with the creation of a wide range of water bodies yet broadly dominated by geographically isolated ponds.

Biota of floodplain lakes of the Ob river in the lower reaches of the Novosibirsk hydroelectric power station

An overview of typical lakes of the floodplain system of the river is presented. Ob in the lower reaches of the Novosibirsk hydroelectric power station, data on the species structure and biomass of fish, zoobenthos and zooplankton are presented. Most lakes of the Ob floodplain have an elongated channel-like shape and have a constant hydrological connection with the channels of the Ob River. The area of the lakes does not exceed 40 hectares. According to the research results, the zooplankton of the lakes is represented by 20 species, the total number of zooplankton varied from 50 620 copies/m3 (Kolkhoznoye lake) to 477 740 copies/m3 (Bolshoy Elbak lake). The biomass of zooplankton in the surveyed lakes was 2488–3443 mg/ m3. 24 species were found in the zoobenthos of floodplain lakes, the total number of zoobenthos varied from 887 copies/m2 (Kolkhoznoye lake) to 3468 copies/m2 (Bolshoy Elbak Lake). The biomass of zoobenthos varied from 3,100 to 38,152 g/m2. According to the indicators of zooplankton biomass, lakes are characterized as reservoirs of beta-mesotrophic type, i.e. of the middle productivity class, according to the classification of feeding capacity — as reservoirs above the average feeding capacity for planktophagous fish. On the development of zoobenthos lake. Vilannoe refers to high–fed, eutrophic type reservoirs, high productivity class, Kolkhoznoye lake — to medium-fed, mesotrophic type reservoirs, moderate productivity class, Bolshoy Elbak lake refers to high-fed reservoirs of mesotrophic type of medium productivity class. The main species of ichthyofauna of floodplain lakes are the firebrand rotan (Perccottus glenii) and silver carp (Carassius gibelio). The biomass of the ichthyofauna is 45.1–100.9 kg/ha. As a result of the study, it was revealed that commercial development of the ichthyofauna of these lakes is impractical, but their use for commercial fish farming is possible.

Multi-omics Investigation of Freeze Tolerance in the Amur Sleeper, an Aquatic Ectothermic Vertebrate.

Freeze tolerance, the ability of an organism to survive internal ice formation, is a striking survival strategy employed by some ectotherms living in cold environments. However, the genetic bases of this remarkable adaptation are largely unknown. The Amur sleeper (Perccottus glenii), the only known freeze-tolerant fish species, can overwinter with its entire body frozen in ice. Here, we sequenced the chromosome-level genome of the Amur sleeper and performed comparative genomic, transcriptomic, and metabolomic analyses to investigate its strategies for surviving freezing. Evolutionary analysis suggested that the Amur sleeper diverged from its closest non-cold-hardy relative about 15.07 million years ago and has experienced a high rate of protein evolution. Transcriptomic and metabolomic data identified a coordinated and tissue-specific regulation of genes and metabolites involved in hypometabolism, cellular stress response, and cryoprotectant accumulation involved in freezing and thawing. Several genes show evidence of accelerated protein sequence evolution or family size expansion were found as adaptive responses to freezing-induced stresses. Specifically, genetic changes associated with cytoskeleton stability, cryoprotectant synthesis, transmembrane transport, and neuroprotective adaptations were identified as potentially key innovations that aid in freezing survival. Our work provides valuable resources and opportunities to unveil the molecular adaptations supporting freeze tolerance in ectothermic vertebrates.

Potential Threat of an Invasive Fish Species for Two Native Newts Inhabiting Wetlands of Europe Vulnerable to Climate Change

In the modern world, when the problems of the environment are most acutely associated with climate change, amphibians are considered to be the most vulnerable group of anamniotes as an indicator of the state of wetlands. Along with a decrease of numbers among amphibians in Europe, nowadays newts especially suffer from the impact of invasive species, in particular predators such as the Chinese sleeper, Perccottus glenii. This predatory fish species has recently spread to areas of primary relevance for newt reproduction. This fish consumes eggs, larvae, and even adult newt individuals. Using an ecological niche approach and climate based species distribution models (SDM), we applied the coefficient of determination (R2) for comparing the level of similarity of the built SDM for the newts Triturus cristatus and Lissotriton vulgaris, and the Chinese sleeper. We show that by 2050, the level of climatic niche similarity for these native and invasive species will increase from 12% to 22% throughout Europe, and from 44% to 66% in Eastern Europe. This study highlights the expansion of the Chinese sleeper as a real threat to European biodiversity of wetlands in the near future, especially in their most northeastern distribution range.

The Species Diversity Assessment of Azygia Looss, 1899 (Digenea: Azygiidae) from the Volga, Ob, and Artyomovka Rivers Basins (Russia), with Description of A. sibirica n. sp.

This study is devoted to the investigation of Azygia (Digenea: Azygiidae) species diversity using classical morphological, recent molecular tools (28S rRNA and cox1 mtDNA for genetic-based inference) and robust statistical techniques (Principal component analysis, PCA). The analysis revealed that the genus Azygia included four valid species: A. lucii, A. longa, A. hwangtsiyui, and A. sibirica n. sp. The distribution of the type species A. lucii was confirmed in the largest Russian rivers: the Volga and the Ob. The worms isolated from Perccottus glenii were determined as the Chinese species A. hwangtsiyui, according to the genetic data for the cox1 mtDNA gene, at 1.32–1.56%. The new species, Azygia sibirica n. sp, was described from Esox lucius in the Ob River and differentiated from the type species A. lucii by the smaller ovary, testes and prostatic sac, wider body, very narrow pharyngeal lumen and form of anterior margin of ovary. In addition, multivariate analysis and three methods for species delimitation (ABGD, GMYC, bPTP) showed the subdivision of A. lucii and A. sibirica n. sp. into two separate groups, one from the Volga River and another from the Ob River, respectively. To conclude, A. lucii infects Esox lucius in the western (European part of Russia, the Volga River basin), and northern (Western Siberia, the Ob River basin) parts of Russia; A. sibirica n. sp. has also been found to infect Esox lucius in the Ob River, while A. hwangtsiyui infects Perccottus glenii in the South of the Russian Far East (the Artymovka River basin).

ПИТАНИЕ РОТАНА PERCCOTTUS GLENII (PERCIFORMES: ODONTOBUTIDAE) В ПОЙМЕННЫХ ВОДОЕМАХ САРАТОВСКОГО ВОДОХРАНИЛИЩА

An alien species, Perccottusglenii, penetrated more than two decades ago into the reservoirs of the Volga River basin in the Samara region. Amur sleeper feeding in some floodplain reservoirs of the Saratov reservoir is shown. Field observations have shown that the basis of amur sleeper nutrition from the reservoirs of the Mordovian floodplain are insects and their own juvenile fish, and juveniles of other fish species.

РЕТРОСПЕКТИВНЫЙ АНАЛИЗ ИХТИОФАУНЫ РЕКИ ТОМЬ В ПРЕДДВЕРИИ СТРОИТЕЛЬСТВА КРАПИВИНСКОГО ВОДОХРАНИЛИЩА

The resumption of design and survey work for the construction of the Krapivinsky Hydroelectric Power Plant on the Tom River has necessitated the assessment of the current state of its fish resources and called for making the prediction of their transformation in the event of the hydroelectric complex being put into operation. In the early 20th century, the Tom River was classified as a salmonid habitat. At that time, such valuable commercial species as the Siberian taimen Hucho taimen, blunt-snouted lenok Brachymystax tumensis , tugun Coregonus tugun, humpback whitefish Coregonus pidschian, Nickolsky’s grayling Thymallus nikolskyi , nelma Stenodus leucichthys nelma, muksun Coregonus muksun, and peled Coregonus peled were permanent residents. Sturgeons, such as the Siberian sturgeon Acipenser baerii and sterlet Acipenser ruthenus, were also abundant. Currently, out of these species, grayling, occasionally taimen and lenok are caught in the Tom River; the common roach Rutilus rutilus , European perch Perca fluviatilis, Siberian dace Leuciscus baicalensis and Eurasian ruffe Gymnocephalus cernuus comprise 95 % of all fish caught. If construction of the Krapivinsky Reservoir on the Tom River is completed and it is put into operation, a deep-water, slow-flowing “lake-type” water body will be created. The river bed will be blocked, so semi-anadromous fish species, many of which are listed in the Red Data Book-such as Siberian sturgeon, sterlet and nelma,-will disappear. A decrease in the abundance of grayling, taimen and lenok, already low in number, should also be expected. These fish species winter in the pits, some of them migrate to the Ob River, so, after passing the spillway, they will not be able to return upstream to the spawning grounds. The abundance of lake and lake-river species is expected to increase, among them the common roach, dace Leuciscus leuciscus , European perch, Prussian carp Carassius gibelio (introduced locally, subsequently self-dispersed), as well as common bleak Alburnus alburnus and sunbleak Leucaspius delineates (accidental invaders). In the future, it is possible to make an attempt to introduce peled to the upper basin of the Krapivinsky Reservoir. There is a prospective threat of the Chinese sleeper Perccottus glenii spreading in the upcoming reservoir, which can severely undermine its fish stocks.

New record of Tylodelphys metacercariae (Diplostomidae) from Perccottus glenii (Odontobutidae) and their phylogenetic assessment.

Metacercariae of Tylodelphys sp. were found in the abdominal cavity of the Chinese sleeper (Perccottus glenii) collected in Liaoning Province and Inner Mongolia Autonomous Region of China. The sequences of the mitochondrial cox1 gene and ribosomal ITS1-5.8S rDNA-ITS2 region were obtained and used for molecular identification and phylogenetic assessment of this parasite species. Results of phylogenetic analyses based on ITS and cox1 markers showed that the metacercariae of Tylodelphys sp.ex P. glenii from China were conspecific with specimens of Tylodelphys sp. collected by Sokolov etal. (2013) from the same fish-host species captured earlier in West Siberia, Russia. The examined Tylodelphys sp. ex. P. glenii is the only member of the genus whose metacercariae parasitise the abdominal cavity of fish in northern Eurasia. Tylodelphys sp. ex P. glenii clustered with T. darbyi, T. immer, T.podicipina, and Tylodelphys sp. of Soldánová etal., 2017 based on mitochondrial DNA markers, and with T. darbyi, T. immer, T. kuerepus, and T. schreuringi using nuclear DNA markers.

Phenotypic Plasticity of the Amur Sleeper (Perccottus glenii) Invasive Populations during the Colonization of Water Bodies

Phenotypic Plasticity of the Amur Sleeper (Perccottus glenii) Invasive Populations during the Colonization of Water Bodies

РАЗНООБРАЗИЕ И ДИНАМИКА РЫБНЫХ СООБЩЕСТВ В БАССЕЙНАХ ГОРНЫХ ПРИТОКОВ АМУРА

Between 1975 and 2021 the diversity of fish communities of mountain rivers was studied in seven areas of the river Amur drainage: “Onon”, “Upper Zeya”, “Upper Bureya”, “Upper Amgun”, “Lower Amgun”, “Khingan”, “Lower Amur and Ussuri”. In these areas, various reaches of typical mountain watercourses were surveyed: 1) upper reaches (24), 2) “middle” (17) and 3) “lower” (10); 9 small mountain tributaries of lowland rivers – Amur and Ussuri, 5 mountain lakes and 6 floodplain reservoirs. According to the results of the research, 6 main types of communities were identified, including river ones: 1) upper reaches, 2) “middle” parts, 3) “lower” parts, 4) small mountain tributaries of large lowland rivers. Lake communities are represented by two main types of communities: 5) mountain lakes and 6) floodplain water bodies. In river communities, 30 fish species and one lamprey species were found; river communities are dominated by Barbatula toni, Cottus szanaga, Brachymystax tumensis, species of the genus Thymallus, as well as Rhynchocypris lagowskii and Phoxinus phoxinus. Upper reaches communities include from 4 to 12–13 species. Barbatula toni, Cottus szanaga, Brachymystax tumensis, and species of the Thymallus dominate here. In the communities of the middle parts of the rivers, there are from 7 to 17 species. Up to 23 species and one lamprey species are found in the lower parts. In the upper reaches and middle sections of the rivers, the composition of the community changes during the year as a result of seasonal migrations. In communities of mountain lakes 6 species of fish were found; three species are most common: Barbatula toni, Cottus szanaga, Brachymystax tumensis. 8 species inhabit floodplain water bodies, dominated by Rhynchocypris percnurus, Perccottus glenii, Misgurnus mohoity. The specificity of the region's coenotic diversity is determined by its position in the Amur basin, the presence or absence of mountain and floodplain lakes, as well as geomorphological and paleogeographic features.

PHENOTYPIC PLASTICITY OF THE AMUR SLEEPER (<i>PERCCOTTUS GLENII</i>) INVASIVE POPULATIONS DURING THE COLONISATION OF WATER BODIES

The variability of the body shape in invasive fish species - Amur sleeper (Perccottus glenii) - from natural and anthropogenic water bodies of the Middle Urals with different completeness of the species composition was studied by the use of geometric morphometrics methods. We compared samples of the Amur sleeper from neighboring adjacent water bodies - Lake Shitovskoye and two peat quarries filled with water. Samples of different seasons and years of collection were taken in the lake, which allowed us to correlate the influence of climate and season on the morphogenesis of the Amur sleeper. According to the control catches, the fish community of the lake is represented by 10 species, i.e. it has a poly-species composition: 6 native species (roach, river perch, ruff, tench, crucian carp, and pike) and 4 alien species (bream, belica, Amur sleeper, carp). The share of the Amur sleeper in the control catches in the lake was no more than 3-5%. In the water bodies of peat quarries, oligoid communities of 2 species were formed (Amur sleeper and crucian carp). Discriminant analysis of the body shape of fish from the lake and peat pits allowed us to reveal the origin of 93-98% of individuals. Comparing the samples of the younger (2+-3+ years) and older (4+-7+ years) age groups of fish divided by sex and biotope, different directions of changes in the shape of the Amur sleeper body in ontogenesis were revealed between the biotopic groups. The range of age variability was almost 5 times lesser than the intergroup biotopic differences of fish from ecologically contrasting water bodies. Seasonal and inter-annual intra-population variability of body shape in the Amur sleeper in the lake is significantly lesser pronounced than the intergroup differences between samples from the lake and peat quarries. Sex differences accounted for only 6% of the intergroup variance (3 times lower than the level of age differences), and in the poly-species lake community, sex differences decrease with age, and in the water bodies of quarries, on the contrary, they increase. Within-group morphological disparity ( MNND ) is significantly higher in samples from peat quarries. The data obtained are of a key character, since they characterize a high degree of phenotypic plasticity of the Amur sleeper and a rapid adaptive restructuring of its morphogenesis to different conditions of natural and anthropogenic water bodies of the Middle Urals.

Invasive Alien Species of Benthic Macroinvertebrates and Fish in the Bulgarian Sector of the Danube River—Results of the Joint Danube Survey 4 (JDS4)

The aim of this study was to assess the status of aquatic invasive alien species (IAS) in the shoreline zone of the Bulgarian sector of the Danube River, Danube tributaries, and adjacent standing water bodies in the frame of the Joint Danube Survey 4 (JDS4). Seven benthic macroinvertebrates and seven fish IAS were identified. The crayfish Faxonius limosus was frequently found and abundant in the tributaries. The mussels Corbicula fluminea, Dreissena rostriformis bugensis, and Sinanodonta woodiana dominated in the Danube River and the middle and lower reaches of the tributaries, while the fish Carassius gibelio, Perccottus glenii, and Lepomis gibbosus were most abundant in the standing water bodies. The integrated biocontamination estimated by taxonomic groups (crayfish, molluscs, and fish), sampling methods, and type of water bodies ranged from moderate in the shoreline zone of the Danube River, through moderate to high in the canals and lakes, to severe in the Danube tributaries and the reservoirs. The results demonstrate the importance of IAS in the assessment of the ecological status/potential of the water bodies in the DRB. The comprehensive evaluation of the aquatic IAS pressure will provide valuable information and support for the implementation of the national and EU IAS and water policies in the DRB.

Genetic Variability of the Amur Sleeper (Perccottus glenii) and their Parasite, Cestode (Nippotaenia mogurndae), outside the Natural Area of Distribution

Based on the polymorphism of multilocus DNA markers (inter simple sequence repeat (ISSR)), we assessed the level of genetic variability and differentiation of populations of two invasive species, the Amur sleeper (Percottus glenii) and its specific parasite, Nippotaenia mogurndae, from five reservoirs in the acquired part of the range, the Irtysh River basin, Western Siberia. We revealed a high genetic polymorphism of neutral DNA markers in P. glenii. In general, the proportion of polymorphic loci was 92%, the average heterozygosity was 0.32. These parameters were lower in particular populations of P. glenii and varied within 53–74% and 0.20–0.23, respectively. The interpopulation component accounted for approximately 35% of the variability (GST = 0.35). In N. mogurndae, polymorphism was 73.7%, heterozygosity was 0.18, varying within 18–45% and 0.06–0.15, depending on the population. The level of genetic differentiation of N. mogurndae (GST = 0.38) was similar to that of P. glenii, which indicates that the processes of genetic differentiation of the parasite and the host are synchronous. Polymorphism and genetic distances of the parasite were lower than those of the host. The population genetic structure of P. glenii was partially consistent with the structure of the hydrographic network, in contrast to N. mogurndae. The data obtained indicate that during dispersal, no significant reduction in genetic polymorphism occurred in the Amur sleeper, and over several decades a population-genetic structure characteristic of this species in the native range was formed in the acquired part of the range.

Reconnaissance of Lake Simaki in North-Kazakhstan region for organizing lake commercial fish farm

Fishery is a traditional industry for North-Kazakhstan region and, therefore, restoration and organization of lake aquaculture enterprises will provide a significant rise in the economy of the region and creation of new jobs. Scale of the lake commercial fish farm development as a component of commercial fish farming, improvement of its contribution into delivery of food supplies to population depend first of all on the degree of its massive involvement. Status of Lake Peschanoye (Simaki) allows utilizing it for fish commercial cultivation. Application of science-based systems in organiz-ing the lake commercial fish farm will raise efficiency of using natural biopotential of this reservoir and correspondingly enlarge the volumes of production and quality of fish products. In 2021, the researches were conducted on Lake Peschanoye (Simaki). During the researches the hydrological regime of the lake was studied; the samples were taken and processed for hydrochemical and hydrobiological analysis; the material was collected to estimate the condition of ichtyofauna. Generally, the hydrological regime of Lake Peschanoye (Simaki) is found favorable for fish habitat. According to the research results of the year 2021, Lake Peschanoye (Simaki) is a freshwater reservoir with a total mineralization of 875.5 mg/dm3 which allows using it for obtaining commercial fish roe that will provide a greater economic effect from the lake’s utilization. According to the average value of the zoobenthos biomass, Lake Peschanoye (Simaki) belongs to a β-mesotrophic water reservoir which corresponds to the medium level of trophicity. According to the development of food reserves, the recommended volumes of stocking with commercial species are the following: northern whitefish (planktophage) – 4 500 larvae per ha (average value for the Northern Kazakhstan) and carp (benthophage) - 350 yearlings per ha. Pike stocking is recommended as an additional rearing target that will also act as a bio-ameliorator in the fight against the Amur sleeper.

Інвазивні види риб у річках басейну Західного Бугу в межах України

Purpose. To determine the occurrence of invasive fish species in ichthyofauna of rivers of the Western Bug basin in Ukraine. Methodology. Ichthiological studies were carried out during 2019-2021 in the Western Bug River and on its tributaries - Rata, Bushkov, Poltva and Mlynivka. Fish species identification was carried out in situ and was performed according to the identification keys of Yu.V. Movchan and A.F. Koblytska, incomplete biological analysis of invasive species was performed in the laboratory according to the methods of I.F. Pravdin, G.V. Nikolsky and I.I. Chugunova. Findings. The obtained data showed that invasive species in the composition of ichthyofauna in the studied rivers of the Western Bug basin were represented by five species: Prussian carp Carassius gibelio (Bloch, 1782), Stone moroko Pseudorasbora parva (Temminck & Schlegel, 1846), Pumkinseed Lepomis gibbosus (Linnaeus, 1758), Chinese sleeper Perccottus glenii Dybowski, 1877, Monkey goby Neogobius fluviatilis (Pallas, 1814). These species entered the ecosystem due to human activities through deliberate or accidental introduction into rivers of the Western Bug basin, where conditions are quite favorable for their vital activity and growth, due to a fairly warm climate and changes in hydrological regime of many rivers as a result of human impact. Originality. The article presents for the first time a list of invasive fish species of rivers of the Western Bug basin in Ukraine and provides a description of their habitats. Practical value. The obtained results can be used to regulate recreation fishery, for planning of conservation measures for rare fish species and for planning prevention of negative consequences from the spread of invasive fish species. Key words: ichthyofauna, the Western Bug River, invasive alien species, Prussian carp, Stone moroco, Pumkinseed, Chinese sleeper, Monkey goby.

Ecological status of fish fauna from Razim Lake and the adjacent area, the Danube Delta Biosphere Reserve, Romania

The aim of this study was to determine the ecological status of fish fauna of Razim Lake under the conditions of the water salinity changing from brackish, almost 70 years ago, into freshwater nowadays. The natural processes of siltation and organic deposits, characteristic of Danube Delta lake complexes, intensified in the last decades and included also Razim Lake. The presently reported study of Razim Lake and the adjacent area was undertaken in 2020 with intention to cover fish fauna collected with three different sampling methods (electrofishing, gillnetting, and seining). For each sampling method, Catch per Unit Effort (CPUE), relative abundance, and biomass were determined, as well as selected ecological parameters to determine ecological status of richness species in the area. Published data included 55 fish species, mainly marine and euryhaline, but in 2020 only 43 species were reported. Also, the species composition shifted from marine ones to freshwater or euryhaline ones. Of those 43 species captured in 2020 from Razim Lake and neighboring areas, 39 were native and four were non-native, including a newcomer, the Chinese sleeper, Perccottus glenii Dybowski, 1877. Few species were migratory, reophilous, or reophilous-stagnophilous which rarely enter Razim Lake, but the majority were limnophilous or stagnophilous-reophilous species. Four species were dominant in terms of the abundance; Blicca bjoerkna (Linnaeus, 1758); Rutilus rutilus (Linnaeus, 1758); Alburnus alburnus (Linnaeus, 1758); and Carassius gibelio (Bloch, 1782). In terms of the biomass the dominants were: Cyprinus carpio Linnaeus, 1758; Carassius gibelio; Sander lucioperca (Linnaeus, 1758); Pelecus cultratus (Linnaeus, 1758); and Blicca bjoerkna. Some differences between sampling methods used were observed. Eudominant, euconstant, and main species were Blicca bjoerkna and the majority of fish species were accessories, with differences amongst sampling methods used. Fish diversity parameters indicate a stable ichthyocoenosis, more stable along the lake shoreline. Ecological indicators of fish fauna from Razim Lake in 2020 grade the water lake quality as a moderate ecological class according to the Water Framework Directive of the European Union.

Parasites of the invasive Chinese sleeper Percсottus glenii (Actinopterygii: Odontobutidae) in the region of the first introduction of the Carpathian population

Parasites of the invasive Chinese sleeper (Perccottus glenii) were studied in five different localities at the site of the first introduction of the Carpathian population of this fish. We recorded eight taxa of parasites in Lviv water bodies. The monogenean Gyrodactylus perccotti and the cestode Nippoteania perccotti were recorded in all five lakes studied. These parasites represent Far East species introduced together with their host. Also the copepod Neoergasilus japonicus is a Far East parasite introduced to Europe with its aquaculture vector. Differences between the surveyed bodies of water were mainly related to their local seasonal conditions and watershed characteristics. The current data confirm the presence of co-introduced populations of G. perccotti and N. perccotti, which probably affects the future invasiveness of their host. Due to low acquisition of local parasites, we cannot confirm any significant effect of invasive fish on local parasite assemblages in this region. However, the presence of the non-indigenous copepod, N. japonicus, requires additional attention in the future.

Post-invasion spread of Chinese sleeper (Perccottus glenii) in the Lower Danube drainage (Budjak region of Ukraine)

Post-invasion spread of Chinese sleeper (Perccottus glenii) in the Lower Danube drainage (Budjak region of Ukraine)

Variations in mercury concentrations in the muscles of fish in biotopes within the water body and in different water bodies of Russia

Abstract. In recent decades, researchers from Papanin Institute for Biology of Inland Waters Russian Academy of Sciences have been studying mercury concentrations in the muscles of fish from water bodies situated in different natural and climatic zones. Overall, more than 5000 fish samples from 102 lakes and 35 rivers in Russia were analysed. In the absence of local sources of mercury entering the water body, its concentrations in the fish muscles varied in wide ranges, exceeding two orders of magnitude. Minimum concentration (<0.03 mg/kg wet weight) was recorded in the muscles of omul, rotan (Chinese sleeper), minnow, and bleak (Lake Baikal, Transbaikalia and European Russia). Maximum mercury concentration (2-3 mg/kg wet weight) was recorded in the muscles of perches from lakes in the northwest of Russia (Vologda and Novgorod regions, Karelia). Most of the measurement results ranged from 0.05 to 0.30 mg/kg wet weight. Differences in mercury concentrations in the muscles of fish of the same species, similar in size and from one water body, as a rule, did not exceed ranges of one order of magnitude. In the absence of local mercury sources, mercury concentrations in fish muscles from closely spaced water bodies could have more than tenfold differences.

First report of the Chinese sleeper Perccottus glenii Dybowski, 1877 in the Drava River, Croatia

First report of the Chinese sleeper Perccottus glenii Dybowski, 1877 in the Drava River, Croatia