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The article focuses on the intensive anthropogenic impact on the aquatic ecosystems, which makes it necessary to monitor the populations of different fish species. The method of mor-phophysiological indicators was used to study the kidneys of silver bream in different water bodies of the Volga Delta. The morphometric characteristics of the kidneys of silver bream are presented. It is shown that the reactions of organs and body systems are caused by the environmental impact on the living organisms, which results, in particular, in the pathological changes in the fish body. Reactions in the body of fish are the result of a combined effect of environmental factors and natural physiological processes related to feeding, migrations, generative cycles, etc. The detected changes in the organ structure make it possible to assess the impact of the environment on fish. The seasonal and sexual variability of the indices of the mesonephros of silver bream from the Volga Delta is shown. Analysis of the kidneys of fish from two water bodies showed the variability of kidney mass due to the anthropogenic load on the water body, in particular, an increase in the kidney index in silver bream Blicca bjoerkna was registered in the ecosystem with an increased toxic load. It has been stated that the increase in the relative mass of mesonephros was caused by the changes in the organ. Changes were detected both in the intratubular tissue, and in the convoluted tubules and renal capsules. The study helped to find the differences in the relative weight and structure of the kidneys of silver bream, which lives in the water bodies with different anthropogenic load. A real increase of the kidney index was found in fish from the water body with a higher level of anthropogenic impact.

Purpose.To analyze the array of special literature and summarize the information obtained on the features of the white bream (Blicca bjoerkna (Linnaeus, 1758)) and its commercial catch from the Kуiv reservoir. Consider the basic principles of its forecasting, based on the current ecological state of this reservoir, which is of strategic importance for Ukraine. Findings. An overview of modern scientific publications devoted to the peculiarities of the commercial catch of white bream from the Kуiv reservoir, its forecasting and the prospects for using this species in fisheries is presented. The literature data on the specifics of industrial fishing in the Kуiv reservoir are summarized based on the ecological characteristics of this reservoir. The main factors influencing the adaptation of white bream populations to their commercial exploitation are described. The general directions of the impact of anthropogenic pressure on them and their consequences are considered. The prospects of using white bream as an economically valuable species are shown under the condition of rational industrial fishing in the Kуiv reservoir. Practical Value. The review can be useful for scientists, applicants, students, government authorities and private entrepreneurs involved in the process of research and commercial harvesting of living aquatic resources in reservoirs, namely in Kуiv reservoir. Keywords: white bream (Blicca bjoerkna Linnaeus, 1758), Kуiv reservoir, industrial fishing, ichthyofauna.

The in vitro effects of amorphous phenol and its liquid fractions formed 12 months after production were studied in seven freshwater bony fish species: the common carp Cyprinus carpio L., bream Abramis brama (L.), silver bream Blicca bjoerkna (L.), roach Rutilus rutilus (L.), perch Perca fluviatilis L., and sander Zander lucioperca (L.). The study revealed that the effects of amorphous phenol and its liquid fractions are species-specific and depend on the concentration of phenol and localization of peptidases (intestine mucosa or intestinal cavity in case of chyme). The specific features of the effect of amorphous phenol differ considerably from the effect of crystalline phenol.

The current state of size and weight parameters and age structure of silver bream in the upper part of the Volga stretch of the Kuibyshev water reservoir show persistence of a negative trend at the beginning of the current century: a decrease in the size and weight parameters of the silver bream and an increase in the number of younger fish. The current situation can be considered as an indicator of the general negative state of fish resources in the study area.

Background Host specificity is one of the outputs of the coevolution between parasites and their associated hosts. Several scenarios have been proposed to explain the pattern of parasite distribution in parental and hybrid genotypes ranging from hybrid resistance to hybrid susceptibility. We hypothesized that host-parasite co-adaptation limits the infection of host-specific parasites in hybrid genotypes even under the condition of the high frequency of hybrids. The experimental monogenean infection in pure breeds of Blicca bjoerkna and Abramis brama and cross-breeds (the F1 generation of hybrids) under the condition of similar frequencies of pure and hybrid genotypes was investigated. We also examined the potential effect of the maternal origin of hybrids (potential co-adaptation at the level of mitochondrial genes) on monogenean abundance. Methods Pure breeds of two cyprinids and two cross-breeds (one with B. bjoerkna, the next with A. brama in the maternal positions) were exposed to infection by monogeneans naturally occurring in B. bjoerkna and A. brama. The experiment was run under similar frequencies of the four breed lines. Results We showed similar levels of monogenean infection in B. bjoerkna and A. brama. However, each species harboured specific monogenean fauna. Hybrids harboured all monogenean species specifically infecting one or the other species. Monogenean infection levels, especially those of Dactylogyrus specific to A. brama, were lower in hybrids. For the majority of host-specific parasites, there was no effect of the maternal origin of hybrids on monogenean abundance. Asymmetry was found in the distribution of specific parasites in favour of specialists of B. bjoerkna in the monogenean communities of hybrids. Conclusions Our results indicate that the maternal mtDNA of hybrids is not an important predictor of host-specific monogenean infection, which may suggest that mitochondrial genes are not strongly involved in the coadaptation between monogeneans and their associated hosts. The asymmetry of species-specific parasites suggests similarity between the molecular components of the immune mechanisms in hybrids and B. bjoerkna. Our results revealed a difference between the degree of host-parasite coadaptation in specific parasites of A. brama and the degree of host-parasite coadaptation in specific parasites of B. bjoerkna and their associated hosts.

Bugune kadar Buyuk Akgol’den Blicca bjoerkna ’da bulunan parazitler hakkinda herhangi bir veri bildirilmemistir. Bu nedenle calismamiz, hiperoytrofik karakterdeki Buyuk Akgol’de yasayan bu cyprinid baligin parazit component ve infra-komunitesinin kompozisyon ve cesitliliginin arastirilmasini amaclamis ve Temmuz 2016 ile Haziran 2017 arasinda toplam 61 B. bjoerkna ile calisilmistir. Tum baliklar asagida belirtilen taksonlardan en az bir parazit turune konak olmustur: Trichodina sp., Epistylis sp. (Protozoa); Myxobolus sp. (Myxozoa); Dactylogyrus sphyrna, D. cornu, D. cornoides, D. distinguendus ve Paradiplozoon homoion (Monogenea); Caryophyllaeus laticeps ve Cestoda gen. sp . (Cestoidea); Diplostomum sp., Thylodelphys clavata ve Posthodiplostomum cuticola (Digenea); Piscicola geometra (Hirudinea); Glochidium sp. (Mollusca) ve Argulus foliaceus (Crustacea). Komponent komunitedeki baskin turler Diplostomum sp., D. cornoides ve D. cornu olarak belirlenmis ve toplam olarak 2063 adet cok hucreli parazit bireyi toplanmistir. B.bjoerkna ’nin parazit infra komunitesinin 1-10 tur tarafindan enfekte edildigi ve ortalama tur zenginliginin 5.3 oldugu belirlenmistir. Cok hucreli parazit ortalama cesitliligi (Shannon’s H index) 2.08 ve Shannon-Wiener Evenness (E) ortalama degeri 0.81 olarak bulunmustur. B.bjoerkna ’da teshis edilen parazit turleri Buyuk Akgol icin ilk kayitlardir.

Length-weight relationships (LWRs) and length-length relationships (LLRs) were determined for six fish species: Alburnus alburnus, Blicca bjoerkna, Gymnocephalus cernua, Perca fluviatilis, Rutilus rutilus and Sander lucioperca caught using a Nordic multi-mesh gill net in Lake Kirkkojärvi in Southwestern Finland in August 2015. The measurements were done using a photographic method and the dataset is available on the Comprehensive R Archive Network (CRAN). The dataset was done with a scientific catch, which showed lower limits on specimen size than the ones from fisheries. The LWRs were calculated for the total length (TL) and found to be consistent with models from Finland. The length measurements were taken to the nearest 0.01 cm, which also allowed for juveniles to be represented in the model. The goodness of fit of the models is high, with the coefficients of determination above 95%. This study is the first one to estimate LWRs of fish species for this hypereutrophic lake, and is useful for fishery managers and biologists.

Metacercariae of species of the genus Apophallus Luhe, 1909, infecting the fins and skin of freshwater fishes, frequently cause black spot disease. Two species, Apophallus muehlingi (Jagerskiold, 1899) and A. donicus (Skrjabin & Lindtrop, 1919), are known to occur in Hungarian fishes. It has generally been thought that metacercariae of A. muehlingi infect cyprinid fishes, whereas those of A. donicus develop in percids. As part of a morphological, experimental and molecular study, metacercariae were collected from 99 infected specimens of five cyprinid hosts (Abramis brama, Blicca bjoerkna, Chondrostoma nasus, Squalius cephalus, Scardinius erythrophthalmus) and 18 infected specimens of two percid hosts (Gymnocephalus cernua, Perca fluviatilis) in Hungarian natural waters (Lake Balaton, River Danube). Moreover, 1024 common carp (Cyprinus carpio) specimens collected from Hungarian fish ponds were investigated for Apophallus infection, but without positive results. For reliable species identification, experimental infections of chicks were carried in order to produce adult specimens from metacercariae collected from the fins and skin of the cyprinid and percid hosts. Within 8 days, adult specimens of both A. muehlingi and A. donicus developed in chicks infected with metacercariae from the cyprinid common bream (Abramis brama) and the white bream (Blicca bjoerkna) and the ruffe (Gymnocephalus cernua), a percid, respectively. The morphology of the collected metacercariae and adult individuals developed in the feeding experiments was characterised. A molecular analysis was extended to cercarial samples from the snail Lithoglyphus naticoides and to a single adult specimen of Apophallus from a fox. Sequences of 28 specimens were analysed using molecular methods (sequencing the internal transcribed spacer region and the cytochrome oxidase I subunit). Phylogenetic analysis was executed, and the Apophallus samples clustered into three distinct branches using both genes, A. muehlingi from cyprinids, A. donicus from percids and, a third, previously unknown, Apophallus clade, also from cyprinids.

It has been revealed that, as a rule, Roundup herbicide inhibits activities of peptidases in the intestine mucosa and chyme in various fish species, both benthivorous (common carp Cyprinus carpio, silver bream Blicca bjoerkna, roach Rutilus rutilus, and crucian carp Carassius carassius) and piscivorous (perch Perca fluviatilis, pike Esox lucius, and sander Sander lucioperca). The tolerance of peptidases to the herbicide is species-specific. The magnitude and vector of the effects of Roundup depend on its concentration and localization of an enzyme. In the mucosa, the enzymes of common carp and pike are most tolerant, while the enzymes of common carp, silver bream, and pike are most tolerant in the chyme.

To inform aquatic conservation policy and management decisions, translocated freshwater fish species, i.e. those native to part but not all of Great Britain (GB), were assessed with the Aquatic Species Invasiveness Screening Kit (AS-ISK) at two spatial levels (River Basin District [RBD] and GB overall), the outcome scores calibrated and analysed to determine the relevance of geographical scale (GB, RBD and freshwater ecoregion) on AS-ISK outcome score rankings. The 16 species assessed received scores that showed limited among-RBD variation, with all but only one species (silver bream Blicca bjoerkna) receiving the same risk ranking across all RBDs for which they were assessed. A trend of increasing AS-ISK score with decreasing RBD latitudinal location was observed, with two species (bleak Alburnus alburnus and tench Tinca tinca) found to have significantly higher AS-ISK scores in west-coast RBDs than in RBDs to the north and east, and one species (bleak Alburnus alburnus) to have significantly higher AS-ISK scores in southern RBDs than in northern RBDs. The Water Framework Directive classification of Scotland was found to be inconsistent with the latitudinal gradients in that country's environmental conditions, which are better reflected in the distinction of northern and southern freshwater ecoregions. The ramifications of these legislative classifications for aquatic conservation are discussed.

Purpose. The determination and analysis of main biological characteristics of silver bream from the point of view of the formation and exploitation of its commercial stock in the Kyiv reservoir. Methodology. The work is based the results of monitoring field studies carried out on the Kyiv reservoir during 2012–2014. Ichthyological materials were collected from standard commercial gill nets with mesh sizes of 30–80 mm, which were set in different habitats and depths of the reservoir. Collection and processing of samples was carried out using conventional ichthyological methods adapted for the Dnieper reservoirs. Findings. According to the data of monitoring gill nets, silver bream population in 2014 was composed of 10 age groups. The majority of their population (70.8%) in catches was composed of age-5 to age-7 fish, i.e. the number of modal classes increased due to the right wing of the older age groups. The frequency distribution of silver bream had a shape of a curve with wide, however broken (due to the reduction in age-5 fish) peak and gradual decrease. Age-length properties, fatness parameters and condition factor of silver bream in the Kiev reservoir during last years remained on the stable high level indicating on favorable fattening conditions and forming the ichthyomass of this species. At the present time, silver bream of the Kyiv reservoir formed a commercial stock with such qualitative and quantitative characteristics, which allow exploiting it in the mode of traditional commercial harvest and specialized harvest of silver bream concentrations with the use of gill nets with mesh sizes of 50, 60 mm. Originality. We obtained and analyzed the new data on the current state of silver bream (Blіcca bjoerkna) in Kyiv reservoir as an important element of commercial fish production. Practical Value. The results of the work allows increasing qualitative and quantitative characteristics of silver bream catches and will be used for the preparation of commercial fishery regime for the Kyiv reservoir.

Data on feeding of the bream Abramis brama, roach Rutilus rutilus, and white bream Blicca bjoerkna in Chogray Reservoir in 2010 and 2012 are presented. The main diet of bream consists of Chironomidae, and the diet of roach and white bream consists of the bivalve mollusk Dreissena polymorpha.

In recent years, the silver bream of the upper part of the Volga stretch of the Kuibyshev reservoir maintained a tendency to reduce the average size and weight indicators. Given the good availability of food and the fact that in the area under consideration, commercial fishing of this species has not been carried out in recent years, it can be assumed that changes in biological indicators are caused by a significant impact of anthropogenic impact in the form of individual and poaching fishing. It is necessary to strengthen control measures for such types of fishing.

The aim of this study was to determine the exploitation of 7 freshwater species, Freshwater bream ( Abramis brama Linnaeus, 1758), Vimba bream ( Vimba vimba Linnaeus, 1758), Wels catfish ( Silurus glanis Linnaeus, 1758), Roach ( Rutilus rutilus Linnaeus, 1758), European perch ( Perca fluviatilis Linnaeus, 1758), Prussian carp ( Carassius gibelio Bloch, 1782) and White bream ( Blicca bjoerkna Linnaeus, 1758), from Lower Sakarya River, Turkey. Samplings were conducted from June 2017 to May 2018. Length-based estimations were evaluated in FiSAT II software. Total (Z), natural (M), fishing (F curr ) mortality, exploitation rate (E curr ) and CPUEs of all 7 species were determined. Results showed that almost all reference points stayed below the natural and fisheries mortality values. Besides overfishing, pollutants (chemical, physical and biological) and changes in the river morphology may affect the fish populations. Study results could be used for further fisheries management applications.

The inferior pharyngeal bones are a characteristic feature of the Cyprinidae. Morphology of inferior pharyngeal bones is important in the diagnosis of carnivorous food, or determining the diet of fishes. Due to the lack of literature data, the aim of the study was to examine the morphology of the inferior pharyngeal bone in detail. 102 Blicca bjoerkna specimens caught in the River Warta (Poland) were analysed. 204 inferior pharyngeal bones were collected. The parameters of the inferior pharyngeal bones correlated with the measured head features and the total fish length. The arches of inferior pharyngeal bones did not have directional asymmetry for the two main parameters (height and width of inferior pharyngeal bone). However, there was a left-sided directional asymmetry of the ventral part of inferior pharyngeal bone. In the case of the B. bjoerkna from River Warta, large differences in terms of individual parameters of inferior pharyngeal bones were observed. Fluctuation asymmetry was low. Shape of inferior pharyngeal bones was very round. In total, 12 teeth formulas were described. The 35.29% of the fish had formula different than described in the literature 2.5-5.2 and more teeth in the right arches. Following identification, measurements of the structures enable estimation of the lengths and weights of prey to be determined from biometric relationships. Analysis of body morphological features in combination with pharyngeal bone morphology could show a hybrid in the Warta river's population.

This paper describes spawning events of the white bream Blicca bjoerkna (Linnaeus, 1758 )in astronomical and biological time depending on seasonal patterns of climatic conditions. The research was conducted in the "Dnipro-Orilskiy" Nature Reserve (Ukraine) during the years 1997–2015 in four habitat types. The timing of the spawning event (start, end) was evaluated using astronomical time (number of days from January 1 each year), with correction for the lunar and the semilunar cycle, and using biological time (number of days from the end of spawning in the previous year to the beginning and end of spawning in the current year). The spawning phenology of the white bream was found to be dependent on the dynamics of weather conditions over time. Patterns of varying climatic regimes which are expressed by means of multivariate principal component are the most informative predictors of the spawning events. Evaluation of occurrence of spawning events in astronomic or biological time gives somewhat different models of the impact of climate regimes. The impact of the principal components indicating variability of rainfall during the year in which spawning occurs is statistically significant for almost all regression models. Models using the solar calendar are also more sensitive to the course of air temperatures within the year when spawning occurred. Correction of time based on the lunar cycle allows us to assess events which are sensitive also to the temperature and rainfall variation during the second half of the previous year. Biological time was shown to be sensitive to environmental influences over time from the end of spawning in the previous year to spawning in any given year.

According to the reducible-channel model of filter-feeding (Hoogenboezem et al., '91), small food particles are retained in the channels between the medial gill rakers, while the mesh size can be reduced by lowering the lateral gill rakers into these channels. This movement requires that all lateral gill rakers have a m. abductor branchiospinalis (MAB). MAB runs from the radii branchiales to the raker feet. It is present on the lateral side of all four gill arches of the cyprinids Abramis brama and Cyprinus carpio but only on the first arch of Blicca bjoerkna, Rutilus rutilus, Ctenopharyngodon idella, Aspius aspius, and Scardinius erythrophthalmus. Therefore, the latter species do not fulfill the structural requirement for the reducible-channel model, whereas A. brama and C. carpio do. Laboratory and field data confirm that A. brama and C. carpio can reduce their mesh size according to this model and are the better filter-feeders. The seven cyprinid species studied show the same principal microanatomy of their branchial sieve. M. abductor filamenti is a sheet of muscle fibers between the lateral radii branchiales and the ceratobranchial bone. M. branchialis superficialis is a specialized region of the subepithelial muscle fiber network, with origins along both sides of the ceratobranchial bone. The lateral gill rakers of the first gill arch differ conspicuously from all other rakers. They are longer and flattened, and they are tilted anteriorly. They probably form a sieve across the wide slit between the first gill arch and the operculum. The most revealing anatomical feature is the presence of MABs on gill arches 1–4. It might be a suitable bio-assay for identifying the better facultative filter-feeders among cyprinids. © 1994 Wiley-Liss, Inc.

Background. One of the largest European populations of white bream, Blicca bjoerkna  (Linnaeus, 1758), can be found in the estuary of the Oder River. This fish is not only very abundant in this area but also attains sizes that have no match in other areas of central Europe. In search for the clues behind such reproductive success we decided to study the annual development cycle of gonads of white bream from three sites in the lower Oder River, north-western Poland, differing in temperature regimes (depending on their position and the distance from the discharge outlet of the Dolna Odra Power Plant). Materials and methods. White bream individuals were obtained from the three sites as bycatch of commercial fishing in 2009 and 2010. Three sites were sampled: (1) the Oder River above the power plant, (2) the warm-water canal with post-cooling water discharged from the power plant, and (3) Lake Dąbie, 20 km below the warm-water canal. The fish age was determined as 2+ through 9+. In total, 506 females and 190 males were designated for histological analyses. The analysis of the annual cycle of gonad development was performed in both sexes using histological methods. A standard paraffin technique and Heidenhain’s iron hematoxylin staining were used. Results. In the Oder River, spawning of white bream lasted from early May to late June. In Lake Dąbie, it extended until the beginning of July. The spawn was laid in 2 or 3 portions. In the warm-water canal spawning began one month earlier, in April. The bream males from the thermally unaffected Oder River were ready for reproduction approximately one month earlier than the females and maintained their reproductive potential similarly to the females. Males from the warm-water canal became sexually mature two months earlier (February) than those from the river above the power plant. Conclusion. In waters with elevated temperature, gametogenesis of white bream occurs without problems and the fish exhibit a typical pace of growth depending on the temperature. In the perspective of climate warming, white bream will be able to maintain its status of a common species in the natural waters of the region.

Aims: To determine the prevalence and density of the larval digenean trematode Paracoenogonimus ovatus in fish muscle tissue. To determine larval survival under selected thermal conditions. Place and Duration of Study: Division of Hydrobiology, Ichthyology and Biotechnology of Breeding, West Pomeranian University of Technology, Szczecin, October 2009 and 2014. Methodology: Twelve fish species from Lake Dąbie (Poland) that are exploited by both commercial and recreational fisheries were selected. Samples of muscle tissue were weighed and then viewed under a trichinoscope where encysted P. ovatus larvae (metacercariae) could be counted. Then, they were subjected to artificial digestive juice (0.1% activated pepsin and 5% citric acid) to facilitate isolating the cysts from the muscle tissues. The parasites that were isolated were removed from their shells, and the species was identified. Further, ten freshwater bream fillets with encysted larvae were placed under refrigeration (4oC) and frozen (-18oC); larval viability was checked after 24, 48, and 78 h. Results: The prevalence of P. ovatus larvae increases (76.5% in 2009 and 80.5% in 2014). The highest density was noted in roach (Rutilus rutilus), freshwater bream (Abramis brama), and white bream (Blicca bjoerkna). It was confirmed that metacercariae are resistant to decreases in temperature to 4oC, but that further reducing the temperature to -18oC results in larval death in 24 h. Conclusion: Many species of freshwater fishes are infected by P. ovatus metacercariae. Eating Original Research Article Linowska and Sobecka; EJNFS, 5(4): 275-280, 2015; Article no.EJNFS.2015.025 276 improperly prepared fish and fisheries products may provide serious health problems. Further studies are needed to neutralize the living metacercariae in raw materials and food products.

The econometric model can be a precise instrument for the analysis of the impact of the natural environmental degradation on the fishing economy. This paper aims at analysing the influence of the water quality changes in Charzykowskie Lake on the fishing economy. The economic-ecological models have been constructed, explaining the changes of economic effects of the lake fishery in the conditions of an increasing water pollution in the hypolimnion on the example of the catch of Rutilus rutilus , Blicca bjoerkna , Coregonus lavaretus , Anguilla anguilla and Esox lucius in Charzykowskie Lake. Performed empirical research focuses on the influence of the environmental factors on the size of fish catch. Calculations and analysis show clearly that even though the habitat factors have an influence on the catch size of each studied fish species, they do it with different intensity and in various combinations. Both, lake water quality and climate factors changes, cause measurable effects on fishing industry of Charzykowskie Lake. Among the examined Rutilus rutilus and Blicca bjoerkna, Blicca bjoerkna has the highest high environmental requirements regarding the water quality. Empirical calculations showed as well that Coregonus lavaretus has considerably higher water cleanness requirements than Rutilus rutilus and Blicca bjoerkna . While considering Rutilus rutilus and Blicca bjoerkna , most water characteristics still rather stimulate a development of these species, but when it comes to Coregonus lavaretus , in general they suppress its development. The model has also proved quite high habitat requirements for Anquilla anquilla and correctness of the thesis that Esox lucius avoids polluted water. Climatic factors influence is significant for the endogenous variables. The above prejudges the itineration of Rutilus rutilus , Blicca bjoerkna , Coregonus lavaretus , Anquilla anquilla and Esox lucius catch in Charzykowskie Lake. The results of the modelling can be used in managing the fishing economy of the lake. DOI: https://doi.org/10.3846/enviro.2017.042

Fish avoidance behaviour in the trawl mouth at night was investigated in the extremely shallow and turbid Lake Neusiedl in Austria. To evaluate fish reactions, a fixed frame benthic trawl with three electricity modes (without electricity, with continuous electricity and with interrupted electricity) was used and the captured fish abundances, biomasses and size structures were compared between modes. Simultaneously, the dual-frequency identification sonar (DIDSON) monitored fish abundance and size in front of and beside the trawl mouth during all tows. White bream ( Blicca bjoerkna ), bleak ( Alburnus alburnus ) and razor fish ( Pelecus cultratus ) were dominant fish species in the trawl catches. We did not find differences in fish abundance or biomass when the tows with different electricity modes were compared. The length frequency distribution of fish was not significantly different between modes, but trawls with the two electrified modes contained a higher proportion of fish larger than 130 mm than trawls with the non-electrified mode. Additionally, the DIDSON recordings did not display any significant differences in abundance, length frequency distribution and from length–weight relationships calculated biomass between the electrical modes. Not even the two avoidance behaviour categories used as indicators of trawling error displayed significant differences between avoidance and biomass. Our results indicate that based on trawling abundance and biomass comparisons, and supported by observations by DIDSON, all electrical modes were similarly effective for all size groups of fish. The study found minimal avoidance reactions by the dominant fish species in the trawl mouth opening when a relatively small fixed frame trawl was used to sample fish in a shallow and turbid lake at night.

This study investigated the post-spawning dispersal of seven species occurring in a tributary of the Řimov Reservoir during the years 2000–2004. Fish were captured during spawning migration to the tributary, marked and released. The subsequent distribution of marked fish was followed in the reservoir and tributary during three successive periods 1) early summer, 2) late summer and 3) the next spawning season. Species were divided into two groups — obligatory tributary spawners (white bream Blicca bjoerkna, chub Squalius cephalus, bleak Alburnus alburnus and asp Aspius aspius) that did so predominantly in the tributary of the reservoir and generalists (bream Abramis brama, perch Perca fluviatilis and roach Rutilus rutilus) that usually spawned in the tributary as well as at different sites within the reservoir main body. We hypothesized that obligatory tributary spawners would distribute across the reservoir after spawning according to their species-specific preferences for certain feeding ground...

The egg-release, mating, courting and aggressive acts for the spawning behaviour as well as the survival rates after spawning at stages of eyed embryos, viable hatchlings, and larvae to dry food consumption for the mating success were studied in cultured silver bream Blicca bjoerkna × rudd Scardinius erythrophthalmus hybrids at their first sexual maturity. Experiments were conducted in experimental environments simulating natural reproductive conditions of the parental species. Spawning behaviour was analysed over 1 day from 8.00 to 18.00 hours using a remote-controlled video. Mating success was assessed from eggs and hatched embryos collected on the spawning ground. The results showed that these hybrids exhibited all the reproductive behaviours of the parental species with significantly more courtship than mating. Each egg-release act was accompanied by mating behaviour, involving all the experimental males. A surprising aggressive behaviour was observed in one male which attacked all other experimental fish. Successful mating resulted in the presence of fertilized eggs, the production of hatched embryos in experiments, and the survival of larvae at the dry food consumption stage. However, the low viable hatchling rate observed could indicate a very low chance of survival for these hybrids in rivers in which the occurrence of post-F1 individuals may be more possible by backcrossing.

The content of elements in fish tissues and organs from Swarzedzkie Lake was investigated in order to evaluate the possible risk associated with their consumption by animals as well as humans. Samples of muscle, liver and fish bone of three fish species; roach (Rutilus rutilus), silver bream (Blicca bjoerkna) and crucian carp (Carassius carassius) were collected from seine catches undertaken as part of the biomanipulation of Swarzedzkie Lake. Element concentration (Al, As, Cd, Co, Cr, Cu, Hg, Ni, Pb, Zn) was determined by inductively coupled plasma mass spectrometry (ICP-MS), with the exception of Hg where the flow injection analysis system cold vapour atomic absorption spectrometry (FIAS-CVAAS) was applied. The study indicated a large variation in the occurrence of the investigated elements in different parts of the fish body. The highest content of Al and Zn was stated in all fish organs for each fish species. The majority of the applied statistical and chemometric methods (e.g., PCA, CA) refer to roach since we had a large number of data for this species. The obtained results were assessed in terms of their accuracy and precision using certified reference material of Fish Muscle ERM BB422.

The gonadosomatic index at spawning, absolute fecundity, and egg size for the female sexual products as well as the density and consistency of semen for the male sexual products were examined in cultured Abramis brama × Blicca bjoerkna F1 hybrids and compared with the parental species at their first sexual maturity. Females ovulated under environmental conditions, and their eggs were weighed, counted and measured. Semen of males was macroscopically examined and spermatozoa counted using a hemocytometer. Results revealed that hybridization affected the quality of female and male gametes but with an overlap between hybrids and parents. The gonadosomatic index and fecundity were significantly lower than those of parental species. Egg sizes in hybrids showed a parental effect but to the benefit of hybrids. Semen of hybrids was more diluted which was classified into two groups: the white semen overlapping slightly with parents and the aqueous without any overlap with parents. Overlapped areas between hybrids and parents in term of quality of sexual products could translate that females and males of these hybrids have the biological capacity to produce high quality gametes and thus, a greater chance to produce F2 and backcross generations in rivers.

Three new fish species were found in southeastern Armenia. The presence of Kura gudgeon Romanogobio macropterus is reconfirmed after 80 years of absence. Kura roach Rutilus caspicus, Transcaucasian white bream Blicca bjoerkna transcaucasica, and European pikeperch Sander lucioperca were found for the first time. All three species were registered in Aras River. Kura gudgeon was caught in 2008 just before flooding of the Aras Reservoir. The other two species were found during the period of flooding in 2010. Attempts to find Kura gudgeon failed in the Aras River and its nearest tributaries in 2010 after damming and change of the hydrological regime. Probably, penetration of the species from the lower reach of the Aras River to the middle and upper reach became possible owing to subsequent appearance of a broad limnetic zone after damming. Range expansion of widely distributed cyprinid species upstream may lead to the replacement and even disappearance of local endemic forms, the Armenian roach Rutilus schelkovnikovi and the Armenian white bream Blicca bjoerkna derjavini, which inhabit the Mezamor River and its tributaries.

WOS: 000303101500007 In this research, age, sex compositions, mortality, age-length, age-weight, length-weight relations, condition factors of white bream, Blicca bjoerkna (L., 1758), were determined from 183 specimens between April 2002 and March 2003 caught in Uluabat lake, in the northwest of Turkey. The age compositions of specimens were between 1-7 years and sex percentages were found as 50.27% for females and 49.73% for males. The mean forked length varied between 8.35 and 17.85 cm while mean weight ranged from 9.56 to 122.68 g. Growth of population was the most rapid at the first years of life afterwards growth ratio was slower. The weight of white bream increased allometrically for all sexes as seen b = 2.58. It was determined that the average condition factor of ages was between 1.62 and 2.51. The population has shown better growth performance than other habitats because the lake is low in latitude. We have given some of the population parameters and characters from Uluabat lake in northwestern part of Anatolia.

SUMMARYSampling of the fish community was carried out for 20 years in the Mirgenbach reservoir, in North-Eastern France. The prevalence and the mean intensity of Ligula intestinalis (Cestoda) were analysed in roach (Rutilus rutilus) and silver bream (Blicca bjoerkna) populations, the main two infected species. The aim of this study was to investigate the host switch from roach to silver bream and the consequences of L. intestinalis infestation in silver bream, which is an unusual host for this parasite as Ligula parasitism in silver bream appears to be rare. We analysed in detail the relationships between parasitism index (PI), gonadosomatic index (GSI), perivisceral fat abundance (PFA) and condition index (CI) in the silver bream population. In 1998, prevalence of L. intestinalis highlighted a clear host switch from roach to silver bream. In the silver bream population, young fish were the most severely infected and the impact of plerocercoids appeared to be different depending on the host sex. In male silver bream, plerocercoids drew energy from fat reserves even if GSI was also slightly impacted. On the contrary, in females energy was diverted from gonad maturation rather than from perivisceral fat reserves. No significant difference was observed in terms of CI in either sex.

Although Myxobolus spp. from cyprinid fishes are generally characterised by a strict host-specificity, this study has found that the breams Abramis brama (L.), Blicca bjoerkna (L.) and Vimba vimba (L.) may be infected by the same Myxobolus spp. It is demonstrated that M. macrocapsularis Reuss, 1906, a parasite of the gill filaments of B. bjoerkna, can also infect A. brama. In the same way, M. bliccae Donec & Tozyyakova, 1984, also a parasite of B. bjoerkna, can also occur in V. vimba. The molecular sequences of M. macrocapsularis spores from B. bjoerkna and A. brama were 100% identical. Two of the 18S rDNA sequences of three replicate samples of M. bliccae from B. bjoerkna were 100% identical, whereas the third sequence exhibited a 99.7% similarity with sequences from V. vimba. M. bliccae sequences of spores collected from V. vimba showed a 99.8% similarity to the first two isolates and 99.6% to the third. Data obtained by morphological, histological and molecular biological methods all suggest that Myxobolus spp., known for their strict host-specificity, may sometimes infect several closely related cyprinids.

The state of the reproductive system in four species of Cyprinidae from the Teterev River and Kiev Reservoir (Ukraine)—descendants of F3–F6 generations of individuals subjected to the radiation impact because of accident at the Chernobyl Nuclear Power Plant—has been studied. It was shown that 20 years after the accident, there is a wide range of morphofunctional anomalies of this system in fish. The most significant of them are asymmetry and abnormal morphology of gonads; proliferation of connective tissue-sterilization; and mass destruction of sexual cells of different stages of development. Disturbances of reproductive gonads among the studied species are expressed most strongly in bream Abramis brama and rudd Scardinius erythrophthalmus. In the series of studied generations, maximum frequency of occurrence of gonad anomalies in bream and silver bream Blicca bjoerkna was recorded in F3–F4 and that in roach Rutilus rutilus and rudd was recorded in F4–F5, which is determined by the phenomenon of prolonged mutagenesis.

This study describes the reproductive behaviour of silver bream, Blicca bjoerkna, in an aquarium environment with hormonal injection, constant temperature and natural photoperiod conditions. The results revealed that the reproductive behaviour of silver bream was polyandrous with courting tactics including a high level of tactile stimulation and following behaviour developed by the males, but without territorial or aggressive acts. The individual participation of males in mating acts showed a significant positive correlation with the individual participation of males in following a female. A successful spawning act included trembling movements and violent splashing while eggs and sperm were released on plants. The female mated with one to five males without an active inter- and intra-sexual selection.

Karyotypes of six species of Cypriniformes from the water bodies of Armenia—blackbrow Acanthalburnus microlepis, white bream Blicca bjoerkna transcaucasica, chub Leuciscus cephalus orientalis, stone moroco Pseudorasbora parva, mursa Barbus mursa, and Angora stone loach Barbatula angorae were studied. The karyotype of A. microlepis is represented by 50 chromosomes (2n = 50), 10M + 28SM + 12STA, NF = 88; of B. bjoerkna transcaucasica, by 2n = 50, 12M + 24SM + 14STA, NF = 86; of L. cephalus orientalis, by 2n = 50, 12M + 18SM + 20STA, NF = 80; of P. parva, by 2n = 50, 8M + 16SM + 26STA, NF = 74; of B. mursa, by 2n = 100, 6M + 36SM + 58STA, NF = 142; and of B. angorae, by 2n = 50, 8M + 24SM + 18STA, NF = 86. The intraspecific and interspecific chromosome polymorphism of species of the genera Blicca, Leuciscus and Pseudorasbora is described.

Investigations on the ovarian cycle of fish species that inhabit Hungarian rivers are necessitated by both environmental and economic reasons. The objective of our research was to explore new fundamental knowledge concerning the ovarian cycle of the white bream (Blicca bjoerkna, Linnaeus, 1758), barbel (Barbus barbus, Linnaeus, 1758), orfe (Leuciscus idus, Linnaeus, 1758) and nase (Chondrostoma nasus, Linnaeus, 1758). Histological investigation of ovaries and determination of proportions of oocytes in different stages of development is an appropriate method for the description of spawning characteristics of these species. Our results show that the GSI value for all four investigated species starts to increase at the end of summer and reaches its maximum before spawning. In the barbel and white bream, the presence of oocytes in the stage of cortical alveoli and the heterogeneous size of oocytes in the stage of vitellogenesis in the pre-spawning period indicate that barbel and white bream are multiple spawners. In contrast, in the orfe and nase, the absence of oocytes in the stage of cortical alveoli and the homogeneous size of cells in the stage of vitellogenesis indicate that orfe and nase are single spawners.

This study used passive telemetry (passive integrated transponders) to evaluate winter migration in three species of cyprinids (roach (Rutilus rutilus (L.)), white bream (Blicca bjoerkna (L.)) and rudd (Scardinius erythrophthalmus (L.))) and their potential predators (pike (Esox lucius (L.)) and perch (Perca fluviatilis (L.))) between a shallow lake and its streams. Migration patterns were investigated from October to June, and a substantial part of the roach (40%) and white bream (55%) populations tagged in the lake during autumn migrated during winter into the streams, whereas only very few piscivores (

Success of embryonic development of reciprocal hybrids of bream Abramis brama and white bream Blicca bjoerkna was tested under laboratory conditions. Fertilization and embryonic development success of hybrids until hatching was high and comparable to that of pure species.

Members of the family Coronaviridae are evolutionarily related and play an important role in human and veterinary medicine. Taxonomic classification is based on the ultrastructure and morphogenesis of viral particles and on biochemical and molecular features. The family Coronaviridae belongs to the order Nidovirales , and is divided into two subfamilies: Coronavirinae and Torovirinae . The number of coronaviruses isolated from aquatic organisms is negligible; indeed, coronaviruses have only been identified in aquatic mammals, including harbor seal (genus Alphacoronavirus ), bottlenose dolphin and beluga whale (genus Gammacoronavirus ). White bream virus, isolated from the teleost Blicca bjoerkna (L.), is the type species of the genus Bafinivirus within the subfamily, Torovirinae .

Summary Changes in the behaviour of cyprinids belonging to different ecology groups were observed below a weir that was restricting their upstream migrations during the spawning period May–July. Positions of chub Leuciscus cephalus (L.), Prussian carp Carrasius auratus gibelio (Bloch 1783), bream Abramis brama (L.) and white bream Blicca bjoerkna (L.) were recorded every 12 min over a 24-h period using an automatic data logger (ALS) in the upper Elbe River, Czech Republic. For all observed species, two activity peaks occurred; however, the interspecies timing of these peaks differed. Peak times for chub, bream and white bream occurred at night and during daylight, whereas Prussian carp was active mostly at night. Specimens belonging to the rheophilous group suggested more efficient behavioural tactics in passing the weir, staying below the obstacle one month longer than did eurytopic species.

Hybridization success at early developmental stages and larval resistance to osmotic, thermal and fasting tests in roach Rutilus rutilus, silver bream Blicca bjoerkna, common bream Abramis brama and their F1 hybrids were investigated. Results revealed that hybrid survival rates were similar to parents. At the eyed embryo stage, however, a maternal effect was observed as a general trend during hatchling and larval stages. After these stages, hybrids displayed a higher survival rate than their parents. Under stress tests, no survival was observed after 40 min for osmotic and thermal shocks and after 24 days for the prolonged fasting test in these species and their F1 hybrids. The median survivals of hybrids were intermediate between the two parents. For total mortality, hybrids were also affected by a maternal effect but to the advantage of the hybrids.

Mating patterns among first-generation hybrids of the roach, Rutilus rutilus, and the silver bream, Blicca bjoerkna, between hybrids or with parent-species males, have been investigated under experimental reproduction conditions. The results reveal that the level of sexual activity of these hybrids is high. Hybrid females mated simultaneously and successively with all types of male, resulting in fertilised eggs. Individual participation of roach males in mating was never observed, however.

In our study, we sampled 82 fish specimens as follows: 62 rudd ( Scardinius erythrophthalmus ), 8 roach (Rutilus rutilus) and 12 silver bream (Blicca bjoerkna). The sampling was done in A¢aga Mare Lake, Cluj County. The investigations took into account the incidence and infestation levels of fish with Posthodiplostomum cuticola metacercaria. The study results show an incidence of parasitosis of 80.60% for rudd, 75.00% for roach and 25.05% for silver bream. Regarding the intensity of infestation (low, medium and high), low levels of infestation are predominant (rudd - 72%; roach 83.30%; silver bream - 66.60%). The preferred body area for metacercaria (in descending order) are as follows: for rudd - 90.00% on the body, 86.00 on the fins and caudal peduncle, and 28.80% on the head; for roach - 50.00% on the body, 66.00% on the fins and caudal peduncle, and 33.00% on the head; for silver bream - 100.00% on the body, 33.00% on the fins and caudal peduncle, and 33.00% on the head.Histopathological sections were taken from musculocutaneous tissue extracted from the dorsal area of fish which was parasitized with cystic metacercariae. The central points of metacercaria is surrounded by a connective structure in the form of a capsule, in which melanocyte-like cells are predominant. Intracytoplasmically, they show a brown-blackish granular pigment which masks the cell nucleus. Perifocally, the inflammatory cell infiltrate is discreet with few mononuclear heterophile cells. Â

In this study we tried to develop a uniform method of sperm cryopreservation for four cyprinid fish species indigenous to Hungarian waters: the roach (Rutilus rutilus L.), the bream (Abramis brama L.), the silver bream (Blicca bjoerkna L.) and the barbel (Barbus barbus L.). The sperm was frozen in liquid nitrogen vapor in the presence of five extenders (350 mM fructose, 30 mM Tris, pH 8.0; 350 mM glucose, 30 mM Tris, pH 8.0; 300 mM sucrose, 30 mM Tris, pH 8.0; 200 mM KCl, 30 mM Tris, pH 8.0 and modified Kurokura’s extender) and two cryoprotectants: 10% methanol (MeOH) and 10% dimethyl-sulfoxide. The highest post-thaw motility (roach: 77 ± 6%, bream: 77 ± 6%, silver bream: 67 ± 5%, barbel: 75 ± 6%), fertilization (roach: 84 ± 4%, bream: 83 ± 2%, silver bream: 63 ± 2%, barbel: 70 ± 4%) and hatching (roach: 74 ± 2%, bream: 67 ± 6%, silver bream: 54 ± 2%, barbel: 61 ± 4%) rates were found when either fructose or glucose extenders were used in combination with MeOH as cryoprotectant for all four investigated species. Strong correlations were found between post-thaw motility of the sperm and fertilization or hatching rates, which indicates that motility can be used to predict fertilization success in these species.

Mar‰alek P., Z. Svobodova, T. Randak, J.·vehla: Mercury and Methylmercury Contamination of Fish from the Skalka Reservoir: A Case Study. Acta Vet. Brno 2005, 74: 427-434. The aim of this case study was to investigate the total mercury and methylmercury contamination of fish from the Skalka reservoir, Czech Republic. The reservoir had been polluted with mercurycontaining sewage water for several decades. In total, 30 fish was sampled in August 2003. The fish caught included 5 roach (Rutilus rutilus), 8 bream (Abramis brama), 2 silver bream (Blicca bjoerkna), 7 big head carp (Aristichthys nobilis), 4 asp (Aspius aspius), 3 eel (Anguilla anguilla) and 1 wels catfish (Silurus glanis). Muscle tissue, the liver and the gonads were used for mercury determination. Total mercury in muscle tissue of the asp (as the representative of predatory species) and the bream (as the representative of non-predatory species) averaged 3.11 ± 0.20 mg·kg-1 and 0.96 ± 0.22 mg·kg -1 , respectively. All total mercury in muscle tissue of the asp and the bream was in methylmercury form. The content of total mercury and methylmercury was significantly (p < 0.05) higher in muscle tissue and the liver than in the gonads. The methylmercury-to-total mercury ratio in muscle tissue, the liver and the gonads averaged 1.012, 0.545 and 0.907, respectively. The results showed that mercury contamination of the Skalka reservoir continues to be very high, that consumption of predatory fish in particular poses a major health risk and that methylmercury was the predominant contaminant in fish tissues. Total mercury, methylmercury, MeHg/THg ratio, bream, big head carp, roach, asp, muscle, liver, gonads, freshwater fish

During the day, juveniles and typical inshore species in the lower Oder River, Germany, inhabited the littoral (0·05–1·50 m deep) while potamal species inhabited the mid-channel (40–100 m from the banks). During the night, two behavioural groups were distinguished: 1) potamal species and large individuals of other species, moved from offshore to the littoral, and 2) nocturnal foraging species, became active and increased in inshore and offshore habitats. Inshore, the most significant differences at night was the increasing density of silver bream Blicca bjoerkna increasing both total biomass and total length of fishes caught. Offshore, the increasing density of whitefin gudgeon Gobio albipinnatus at night was most significant. Additional night electrofishing improved the assessment of the abundance, age and size structure of typical potamal fish species. It should be incorporated in large river fish monitoring programmes.

The objectives of this study were to compare the seasonal hepatic activity and to evaluate whether this activity was related to the dynamics of oocyte recruitment in three cyprinids from the River Meuse (Belgium): the roach Rutilus rutilus as a single spawner, and the bleak Alburnus alburnus and the white bream Blicca bjoerkna as multiple spawners. In roach, hepatosomatic index (HSI) was low during exogenous vitellogenesis. However, the strong development of the rough endoplasmic reticulum (RER), the presence of large mitonchondria with many inner folds, and the depletion of glycogen, lipid droplets and phospholipids indicated intense hepatic activity during that period. Prior to spawning, hepatic activity decreased as indicated by a decrease of the HSI and in the hepatocytes a regression of the RER and the disappearance of the lipid droplets and glycogen. In bleak, the oocyte recruitment occurred continuously throughout the spawning season and the vitellogenic activity of the liver remained intense throughout that period as suggested by high HSI and the ultrastructure of the hepatocytes. In contrast in white bream the vitellogenic activity of the liver decreased during the spawning season as the completion of the vitellogenesis took place prior to spawnings. We concluded that the vitellogenic activity of the liver is strongly related to oogenesis.

The aim of this work was to compare the concentration of lead in the meat of common bream (Abramis brama L.), white bream (Blicca bjoerkna L.) and common bleak (Alburnus alburnus L.). The experimental fish were obtained in natural condition from Vistula River, located within Toru., near wastewater treatment plant. The study involved 60 individuals of freshwater fish caught in autumn. Analyses were carried out on 10 individuals of common bream, 20 white bream and 30 individuals of common bleak. The muscles samples for analyses were taken from the large side muscle of fish body above the lateral line. There were chosen for analyses individuals with similar biometric measurements. Due to a relatively low amounts of meat obtained from white bream and common bleak, the material from individuals of similar body length was combined (about 2-3 pieces). Pb concentrations were determined by atomic absorption spectrophotometer Solaar 939 QZ, ATI Unicam. Analyses of variance (test post hoc -Tukey test) indicated that the mean value of lead was the highest in the meat of common bream (0.086 ƒĘgEg-1 wet weight) and the lowest in the meat of white bream (0.075 ƒĘgEg-1 wet weight). There were no statistical significant differences in the lead content between the analyzed fish species (at p< 0.05). Analysis of correlation indicated a negative and statistical significant correlation between the fish body length and Pb concentration.

This study examines the responses of antioxidant parameters in the white muscle of four freshwater fish species: Rutilus rutilus (roach), Blicca bjoerkna (white bream), Carassius gibelio (Prussian carp) and Perca fluviatilis (European perch) after exposure to a bloom of Aphanizomenon flos-aquae (Cyanobacteria) in the Gruza Reservoir in Serbia. The set of analyzed biomarkers included the activities of antioxidant enzymes: superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR) and biotransformation phase II enzyme glutathione-S-transferase (GST), and the concentrations of total glutathione (GSH) and sulfhydryl (-SH) groups that were measured before and during the bloom. Our results show that SOD activity in C. gibelio and P. fluviatilis, GSH-Px and GST activities in all four fish, GR activity in R. rutilus and C. gibelio and the -SH group concentration in P. fluviatilis markedly decreased during the bloom. The activity of CAT in all four fish and the concentration of GSH in B. bjoerkna and P. fluviatilis significantly increased. The observed changes in nonspecific antioxidant biomarkers in fish muscle (especially CAT, GSH-Px and GST activities) suggest that these parameters could be useful tools in environmental monitoring programs of the freshwater ecosystems where cyanobacterial blooms occur. Ministry of Education, Science and Technological Development of the Republic of Serbia {[}173041]

Topmouth gudgeon, Pseudorasbora parva is the most common invasive fish in Europe, which can compete with the juveniles of valuable commercial fishes. The goal of this work is to study the diet of topmouth gudgeon and trophic relationships with some native fishes inhabiting the littoral zone of the Dniprodzerzhynsk reservoir. The obtained relatively low values of diet overlaps between topmouth gudgeon and other co-occurring cyprinids such as juvenile roach, Rutilus rutilus; silver bream, Blicca bjoerkna; rudd, Scardinius erythrophthalmus; Prussian carp, Carassius gibelio and bleak, Abramis brama, indicate that it is not a serious food competitor for them, especially commercially valuable ones. On the contrary, high diet overlaps were observed among some native cyprinids such as juvenile roach, silver bream, rudd, and bleak. The major prey items of topmouth gudgeon were Chydorus sphaericus and chironomids, whereas other cyprinids selected Bosmina spp. This peculiarity may be due to different vertical distributions of these fish in the littoral zone of the reservoir, where topmouth gudgeon inhabit near-bottom water layers, where they preyed on near-bottom and benthic zooplankters and chironomids, while juvenile roach, silver bream, rudd, and juvenile and adult bleak live in higher water layers, where they preyed on pelagic zooplankton.

Daily rations of five cyprinid species, bream Abramis brama, silver bream Blicca bjoerkna, roach Rutilus rutilus, gibel Carassius auratus gibelio and carp Cyprinus carpio, in Lake Balaton, a large shallow lake, estimated by the Eggers model differed from that of the Elliott-Persson model by only - 4.3 to +7.3% (the differences were insignificant). Daily rations varied within the range of 0.23-0.69 in bream, 0.55-3.61 in silver bream, 0.69-4.65 in roach, 0.38-3.16 in gibel and 0.50-9.74 g dry 100 g wet fish mass -1 day -1 in carp at temperatures ranging from 8.7-25.8° C. Daily ration was related exponentially with temperature in silver bream, roach, gibel and carp. For bream, a significant relationship was obtained only when a daily ration value was excluded from the analysis. Annual rations were assessed using the relationships between the daily ration estimates from the Elliott -Persson model and water temperature, and the long-term averages of the monthly water temperature data. From these estimates the bream population consumed 104%, silver bream 424%, roach 487%, gibel 363% and carp 913% dry mass of food of its wet biomass annually.

Gut evacuation and its dependence on the temperature in bream Abramis brama, silver bream Blicca bjoerkna, roach Rutilus rutilus, gibel Carassius aurtaus gibelio and carp Cyprinus carpio, held in mesh cages in Lake Balaton, was best fitted by an exponential model in 18 of 36 trials, while in 14 and four trials, a linear and a square-root model, respectively, gave a better fit. Adjusted r 2 values, however, often did not differ markedly between the three models. The shape parameter, B, was 0.36 for carp and ranged from 0.81 to 1.24 for the other four cyprinids, according to the general evacuation model expanded with the temperature variable, and fitted to whole data sets. Relationships between the food evacuation rates obtained from the exponential models and the temperature were described by exponential functions for bream, silver bream, roach and gibel.

During a fish health inspection in the Viennese waterway 'Old Danube', a virus was isolated exclusively from white bream Blicca bjoerkna (L.) (formerly Abramis bjoerkna L.), one of the most abundant cyprinids present and not known as a host species for this virus. The virus pref- erentially replicated in cultures of the epithelioma papulosum cyprini cell line where focal plaques of infection developed slowly. Examination of infected cell cultures by electron microscopy revealed non-enveloped 60 to 70 nm icosahedral virions that had characteristic multiple segre- gated protrusions of their outer capsid. A partial RNA-dependent RNA polymerase gene sequence was obtained and a BLAST search indicated 76% identity to golden shiner reovirus and grass carp reovirus. These results suggested that the virus belonged to the genus Aquareovirus (Family Reoviridae). Phylogenetic analysis placed the isolated virus within a clade of the species Aqua - reovirus C species. Accordingly, the virus was tentatively designated as white bream reovirus (WBRV) strain A-127/06 within the species Aquareovirus C.