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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.

Акватични екосистеми су данас угрожени на глобалном нивоу, стога је у циљу одрживог управљања воденим ресурсима неопходно успоставити континуирани мониторинг њиховог квалитета. Положај риба на врху ланца исхране и употреба у исхрани људи чини их важним за процену контаминације акватичних екосистема токсичним супстанцама. У оквиру ове дисертације вршена је процена дистрибуције различитих полутаната на три локације на Дунаву: Батајница, Велико ратно острво и Гроцка, у периоду од новембра 2012. године до марта 2014. године. На основу анализе релативне заступљености (абунданције) и масеног удела присутних врста риба у укупном улову, као и биолошких и еколошких карактеристика самих врста, на испитиваним локалитетима најпре јеодређенокоје врсте би могле бити оптималне индикаторске врсте, тако да су у даљим истраживањима коришћени штука, деверика, крупатица,соми смуђ. На узорцима сома,применом масене спектрометрије са индуктивно спрегнутом плазмом (ICP-MS),испитана је дистрибуција 11 елемената у ткивима, као и њихове концентрацијеу различитим сегментима мишића, шкрга, јетре и цревакако би се утврдио потенцијал коришћења ових ткива у мониторингу популација риба. Потенцијална корелација између концентрације метала и елемената у траговима у мишићу са концентрацијама у крљуштима и аналном перају испитана је на јединкама штуке, деверике, крупатице, сома и смуђа, у циљу развоја неинвазивних метода мониторинга квалитета рибљег меса. Такође, испитано је и присуство акумулације органохлорних загађивача (полихлорованих бифенила и пестицида) код јединки деверике и смуђа применом гасне хроматографије са детектором електронског захвата(GC-ECD). Хистопатолошке промене праћене су на шкргама и јетри деверике и смуђа, како би се утврдио потенцијал коришћења хистолошких анализа у развоју метода мониторинга популација риба... Aquatic ecosystems are today globally endangered;thus, in order to ensure sustainable water resources management, it is necessary to establish continuous monitoring of their quality. Considering that fish are situated at the top of the food chain and used for human nutrition, it makes them important for the assessment of contamination of aquatic ecosystems with toxic substances. In scope of this dissertation,the estimation of the distribution of different pollutants was carried out at three localities on the Danube: Batajnica, Veliko Ratno Ostrvo, and Grocka, in the period from November 2012 to March 2014. Based on the analysis of abundance and mass fraction of individual species in the total catch, as well as their biological and ecological characteristics, the optimal indicator species for this study were determined, and accordingly the following species were used northern pike, freshwater bream, white bream, wels catfish, and pike-perch. The distribution of 11 elements wasassessed in the wels catfish tissue samples by inductively coupled plasma mass spectrometry(ICP-MS), as well as their concentrations in different segments of muscles, gills, liver, and intestine, in order to determine the potential for the use of these tissues in monitoring fish populations. The potential relationship of metal and trace element concentrations in the muscle and their concentrations in scales and anal fins was assessed in northern pike, freshwater bream, white bream, wels catfish and pike-perch in order to develop non-invasive methods for monitoring the quality of fish meat. Using the gas chromatography with electron capture detector(GC-ECD), concentrations of organochlorine pollutants (polychlorinated biphenyls and pesticides) in freshwater bream and pike-perch were determined. Histopathological changes were assessed in gills and liver of freshwater bream and pike-perch in order to determine the potential for using histological analyses in the development of methods for monitoring fish populations...

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.

Akvatični ekosistemi su danas ugroženi na globalnom nivou, stoga je u cilju održivog upravljanja vodenim resursima neophodno uspostaviti kontinuirani monitoring njihovog kvaliteta. Položaj riba na vrhu lanca ishrane i upotreba u ishrani ljudi čini ih važnim za procenu kontaminacije akvatičnih ekosistema toksičnim supstancama. U okviru ove disertacije vršena je procena distribucije različitih polutanata na tri lokacije na Dunavu: Batajnica, Veliko ratno ostrvo i Grocka, u periodu od novembra 2012. godine do marta 2014. godine. Na osnovu analize relativne zastupljenosti (abundancije) i masenog udela prisutnih vrsta riba u ukupnom ulovu, kao i bioloških i ekoloških karakteristika samih vrsta, na ispitivanim lokalitetima najpre jeodređenokoje vrste bi mogle biti optimalne indikatorske vrste, tako da su u daljim istraživanjima korišćeni štuka, deverika, krupatica,somi smuđ. Na uzorcima soma,primenom masene spektrometrije sa induktivno spregnutom plazmom (ICP-MS),ispitana je distribucija 11 elemenata u tkivima, kao i njihove koncentracijeu različitim segmentima mišića, škrga, jetre i crevakako bi se utvrdio potencijal korišćenja ovih tkiva u monitoringu populacija riba. Potencijalna korelacija između koncentracije metala i elemenata u tragovima u mišiću sa koncentracijama u krljuštima i analnom peraju ispitana je na jedinkama štuke, deverike, krupatice, soma i smuđa, u cilju razvoja neinvazivnih metoda monitoringa kvaliteta ribljeg mesa. Takođe, ispitano je i prisustvo akumulacije organohlornih zagađivača (polihlorovanih bifenila i pesticida) kod jedinki deverike i smuđa primenom gasne hromatografije sa detektorom elektronskog zahvata(GC-ECD). Histopatološke promene praćene su na škrgama i jetri deverike i smuđa, kako bi se utvrdio potencijal korišćenja histoloških analiza u razvoju metoda monitoringa populacija riba. Rezultati su ukazali na visok nivo diferencijalne akumulacije elemenata među analiziranim tkivima u somu. Najviši sveukupni nivo akumulacije uočen je u kičmenom pršljenu, bubrezima i jetri, dok su minimalne vrednosti uočene u žučnoj kesi, mišiću, mozgu i ribljem mehuru. Akumulacija elemenata u mišiću i koži,kao i u škržnim filamentima i luku, značajno se razlikovala za većinu elemenata, dok između dva ispitivana dela jetre, proksimalnog i distalnog, nije bilo razlika u koncentracijama analiziranih elemenata. U proksimalnom i medijalnom segmentu creva uočen je isti akumulacioni nivo, dok su u oba segmenta zabeležene značajno više koncentracije Co i Zn i niže koncentracije Mn u odnosu na distalni segment. Nije uočena značajna korelacija koncentracija elemenata između mišića i krljušti kod ispitivanih vrsta, pa se može zaključiti da metoda korišćenja krljušti za procenu kontaminacije mišića datim elementimanije zadovoljavajuća, mada se može koristiti kao metoda ranog upozorenja na kontaminaciju tkiva. Koncentracije organohlornih zagađivača bile su ispod propisanih maksimalno dovozvoljenih vrednosti. Na akumulaciju organohlornih jedinjenja utiču kako položaj ribe u lancu ishrane tako i sadržaj lipida, međutim u ovom istraživanju nisu uočene značajne razlike u koncentracijama PCB i pesticida između deverike i smuđa. Histopatološkom analizom utvrđene su više prosečne vrednosti nivoa histopatoloških promena u škrgama deverike, što je i očekivano imajući u vidu da su škrge riba u stalnom kontaktu sa supstancama koje se nalaze u vodi koja ih okružuje, pa predstavljaju relevantne indikatore izloženosti riba zagađivačima u vodi. Ukupni histopatološki indeks jetre nije se značajno razlikovao među vrstama. Aquatic ecosystems are today globally endangered;thus, in order to ensure sustainable water resources management, it is necessary to establish continuous monitoring of their quality. Considering that fish are situated at the top of the food chain and used for human nutrition, it makes them important for the assessment of contamination of aquatic ecosystems with toxic substances. In scope of this dissertation,the estimation of the distribution of different pollutants was carried out at three localities on the Danube: Batajnica, Veliko Ratno Ostrvo, and Grocka, in the period from November 2012 to March 2014. Based on the analysis of abundance and mass fraction of individual species in the total catch, as well as their biological and ecological characteristics, the optimal indicator species for this study were determined, and accordingly the following species were used northern pike, freshwater bream, white bream, wels catfish, and pike-perch. The distribution of 11 elements wasassessed in the wels catfish tissue samples by inductively coupled plasma mass spectrometry(ICP-MS), as well as their concentrations in different segments of muscles, gills, liver, and intestine, in order to determine the potential for the use of these tissues in monitoring fish populations. The potential relationship of metal and trace element concentrations in the muscle and their concentrations in scales and anal fins was assessed in northern pike, freshwater bream, white bream, wels catfish and pike-perch in order to develop non-invasive methods for monitoring the quality of fish meat. Using the gas chromatography with electron capture detector(GC-ECD), concentrations of organochlorine pollutants (polychlorinated biphenyls and pesticides) in freshwater bream and pike-perch were determined. Histopathological changes were assessed in gills and liver of freshwater bream and pike-perch in order to determine the potential for using histological analyses in the development of methods for monitoring fish populations. The results indicated a high level of differential accumulation of elements among the analyzed tissues in wels catfish. The highest overall accumulation level was observed in vertebra, kidneys, and liver, while minimal values were observed in gallbladder, muscle, brain, and swim bladder. The accumulation of elements in the muscle and skin, as well as in the gill filaments and gill arch, differed significantly among most elements, while between the two examined parts of the liver, proximal and distal, there were no differences in concentrations of the analyzed elements. The same accumulation level was observed in the proximal and medial segments of the intestine, while both segments had significantly higher concentrations of Co and Zn and lower Mn concentration in comparison with the distal segment. There were no significant correlations between muscle and scales in element concentrations in all investigated species, which indicates that the method of using scales is inadequate for assessing muscle contamination with these elements, but that it can be used as an early warning method for assessing overall tissue contamination. Concentrations of organochlorine contaminants were below the prescribed maximum allowed levels. While the accumulation of organochlorine compounds is affected by both the position of the fish in the food chain and the lipid content, no differences in concentrations of polychlorinated biphenyls and pesticides between the freshwater bream and pike-perch were observed in this study. Histopathological analysis revealed higher average histological scores in the gills of freshwater bream, which was expected, given that the gills are in constant contact with the substances found in the surrounding water, which makes them good indicators of fish exposure to pollutants in water. The total histopathological index of the liver did not differ significantly between species.

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.

Biomonitoring predstavlja neophodnu komponentu tradicionalnih tehnika monitoringa, sa ciljem da se uspostavi veza izmeŤu spoljašnjih koncentracija zagaŤivaţa, koncentracija zagaŤivaţa u tkivima bioindikatora i ranih štetnih efekata po ispitivane organizme. Ribe su korisni bioindikatori i ţesto se primenjuju u ekogenotoksikološkim ispitivanjima. U ovoj studiji, procena stanja kvaliteta površinske vode vršena je na reci Savi na lokalitetu Duboko i na reci Dunav na lokalitetu Višnjica tokom 2014. godine, kako bi se procenio uticaj razliţitih sezona na variranje parametara kvaliteta i odgovor biomarkera deverike, krupatice i crnooke deverike. Procena kvaliteta vode vršena je merenjem fiziţko-hemijskih i mikrobioloških parametara fekalnog i organskog zagaŤenja. Procena genotoksiţnog potencijala vršena je primenom alkalnog komet testa za kvantifikaciju DNK oštešenja u šelijama krvi, jetre i škrga riba, kao biomarkera izlaganja. Histopatološke promene u jetri i škrgama prašene su kao biomarker efekta. Paralelno, prašene su koncentracije metala i metaloida u jetri, škrgama, gonadama i mišišu, primenom metode ICP-OES. Na lokalitetu Višnjica zabeleţen je viši nivo fekalnog i organskog zagaŤenja. Na lokalitetu Duboko zabeleţene su više koncentracije ispitivanih elemenata u sva ţetiri tkiva, u poreŤenju sa lokalitetom Višnjica. Na oba lokaliteta škrge su akumulirale najviše koncentracije metala i metaloida, a mišiš najniţe. Na oba lokaliteta, krv je bila tkivo sa najvišim nivoom DNK oštešenja, dok je jetra tokom vešine meseci imala najniţe DNK oštešenje. Na lokalitetu Višnjica zabeleţene su više vrednosti DNK oštešenja krvi, na lokalitetu Duboko više vrednosti DNK oštešenja škrga, dok je nivo DNK oštešenja u šelijama jetre na oba lokaliteta bio pribliţno jednak. Na lokalitetu Duboko pri najvešim vrednostima histopatološkog indeksa škrga zabeleţeno je blago do umereno oštešenje, a na lokalitetu Višnjica umereno do teško oštešenje škrga. Na oba lokaliteta, jetra je bila organ sa vešim obimom histopatoloških promena u odnosu na škrge. Sveukupno, škrge kao prvi organ u direktnom kontaktu sa zagaŤivaţima iz vode pokazale su vešu akumulaciju ispitivanih elemenata i viši nivo DNK oštešenja, dok je jetra kao glavni organ za procesuiranje zagaŤivaţa iz vode i hrane pokazala viši nivo histopatoloških promena. Odabrane vrste pokazale su se kao pogodni bioindikatori za in situ ispitivanja efekata zagaŤenja. Biomonitoring represents an essential part of traditional monitoring techniques with the aim to establish relationship between external concentrations of pollutants, concentrations of pollutants in the tissues of bioindicators and early adverse effects in examined organisms. Fish are useful bioindicators often used in ecogenotoxicological studies. In this study, assessment of the surface water quality was performed on the Sava River locality Duboko and on the Danube River locality Višnjica during 2014 in order to examine the impact of different seasons on the variation of the quality parameters and biomarker response in common bream, white bream and white-eye bream. Assessment of the water quality was performed based on the physico-chemical parameters and microbiological parameters of fecal and organic pollution. Genotoxic potential was assessed by using the alkaline comet assay in order to quantify DNA damage level, in blood, liver and gill cells, as a biomarker of exposure. Histopathological analyses of liver and gill tissue were monitored as a biomarker of effect. Additionally, concentrations of metals and metalloids in liver, gills, gonads and muscle were performed by the ICP-OES method. The higher level of fecal and organic pollution was present on the locality Višnjica. The higher concentrations of examined elements in all four tissues were present in fish from the locality Duboko, in comparison to the locality Višnjica. At both sites gills accumulated the highest concentrations of metals and metalloids, while muscle accumulated the lowest concentrations. Blood was the tissue with the highest level of DNA damage, while liver had the lowest level of DNA damage during most of the months at both sites. Higher DNA damage level in blood cells was observed at the locality Višnjica, in gill cells at the locality Duboko, while the level of DNA damage in liver was approximately the same at both localities. Based on the highest level of histopathological index of gills at the locality Duboko gills were slightly to moderately damaged, while at the locality Višnjica gills were moderately to heavily damaged. At both localities liver had higher level of histopathological alterations in comparison to gills. Overall, gills as the first organ in direct contact with contaminants form water showed higher level of examined elements and DNA damage, while the liver as the main organ for processing contaminants from water and food showed higher level of histopathological alterations. Examined fish species proved to be useful bioindicators for in situ assessment of the pollution effects.

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.

The white bream, Blicca bjoerkna (L., 1758) specimens (n=434) were collected from Lake Ladik between November 2009 and October 2010 in order to determine the age, growth, and reproductive season. Fork lengths and weights of these samples varied between 11.5-24.3 cm and 22.80-259.00 g, respectively. Age estimates obtained from scales and vertebrae were compared to determine the most reliable bony structure for ageing. The precision analyses indicated that scales were the most appropriate hard structures for determining the age of white bream. Ages of all the specimens ranged from I to VI years and age group III was dominant. The parameters of the von Bertalanffy growth equations were calculated as L∞ = 32.85 cm, W∞ = 707.76 g, k = 0.11 year-1 and t0 = -2.64 year, and the growth performance index (Φ') value was computed as 2.074 for combined sexes. Fork length-weight relationship was found to be W = 0.0066 FL3.317. The mean condition factor was the highest in August and the lowest in October. The gonadosomatic index values showed that the reproduction occurred between May and June., Tahta Balığı, Blicca bjoerkna (L., 1758) örnekleri (n=434) yaş, büyüme ve üreme dönemini belirlemek amacıyla Kasım 2009-Ekim 2010 tarihleri arasında Ladik Gölü’nden yakalanmıştır. Çatal boy ve ağırlık dağılımları sırasıyla 11,5-24,3 cm ve 22,80-259,00 g arasında değişmiştir. Pul ve omurdan elde edilen yaşlar en güvenilir kemiksi yapının tespit edilmesi amacıyla karşılaştırılmıştır. Uyum analizleri Tahta Balığı’nın yaşının belirlenmesi için en uygun yapının pul olduğunu göstermiştir. Örneklerin yaşları I-VI arasında dağılım göstermiş ve III yaş grubu baskın yıl sınıfını oluşturmuştur. Populasyon genelinde von Bertalanffy büyüme denklemi parametreleri L∞ = 32,85 cm, W∞ = 707,76 g, k = 0,11 yıl-1 ve t0 = -2,64 yıl ve büyüme performans indeks değeri (Φ') 2,074 olarak hesaplanmıştır. Çatal boy-ağırlık ilişkisi W = 0,0066 ÇB3,317 şeklinde elde edilmiştir. En yüksek ve en düşük ortalama kondisyon faktörü değerleri sırasıyla Ağustos ve Ekim aylarında elde edilmiştir. Gonadosomatik indeks değerleri üreme faaliyetinin Mayıs-Haziran aylarında gerçekleştiğini göstermiştir.

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

Blicca bjoerkna (Linnaeus, 1758), White Bream. Cyprinus bjoerkna Linnaeus 1758: 326. Blicca bjoerkna — Kottelat and Freyhof 2007: 180. Material examined. Table 1. Presence of 19–23 branched anal-fin rays and subinferior mouth, which cannot be extended as a tube. The white bream has been observed in all types of water bodies, except in the smaller rivers (up to 25 km from the source) and the karst and suffusion lakes. The species reached the maximum occurrence 101–500 km from the source. In general, this species most frequently occurs in flow-through lakes and least frequently in ponds., Published as part of Artaev, Oleg & Ruchin, Alexander B., 2017, The ichthyofauna of the Moksha River, a tributary of the Volga river basin, Russia, pp. 185-202 in Check List 13 (4) on page 195, DOI: 10.15560/13.4.185, {"references":["Linnaeus C (1758) Systema naturae per regna tria naturae: secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis, ed. 10. Laurentii Salvii, Holmiae, 824 pp. https: // doi. org / 10.5962 / bhl. title. 542","Kottelat M, Freyhof J (2007) Handbook of European Freshwater Fishes. The authors, Cornol / Berlin, 646 pp."]}

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...

This study aimed to identify of helminth parasites in some native and economic fish of Anzali wetland was performed . 314 fish specimens, including:Alburnus hohenackeri (60 Specimen), Blicca bjoerkna (75 Specimen), Hemiculter leucisculus (75 Specimen), Pseudorasbora parva (52 pcs) Rhodeus amarus (52 Specimen), from Cyprinidae (Cyprinidae), during 1 year (2012-2013) and seasonally, from three different stations (Shijan, Pirbazar and Pasikhan) via gill net (50-70 mm) and fyke net were sampled. Samples were transported to the Inlandwater Aquaculture Institute in Bandar Anzali. In the laboratory,After biometry and determine the age and sex of fish, different body parts for searching of parasites were checked and parasites by using identification keys were identified. As a result of this study, 9 species of helminth parasites of fishes were identified include: Gyrodactylus sp., Dactylogyrus sphyrna , Dactylogyrus sp., Ligula intestinalis, Diplostomum paraspathaceum, Diplostomum spathaceum, Diplostomum sp., Posthodiplostomum cuticola and Rhabdochona denudate.The highest frequency of parasites in trematodes (in 5 fish species studied) and the minimum frequency in cestodes (each at 1 fish species studied) were seen. According to statistical analysis using Chi-Square test and KruskalWallis, the pollution of the sex, weight, length and sampling stations, there is no statistically significant difference (P> 0.05). Iranian Fisheries Science Research Institute Published

Dužinsko-maseni odnosi i dužinsko-dužinski odnosi određeni su za šest vrsta riba: ukliju (Alburnus alburnus), krupaticu (Blicca bjoerkna), balavca (Gymnocephalus cernua), grgeča (Perca fluviatilis), bodorku (Rutilus rutilus) i smuđa (Sander lucioperca) ulovljenih pomoću nordijske mreže s više manjih mreža u jezeru Kirkkojärvi u jugozapadnoj Finskoj u kolovozu 2015. godine. Mjerenja su provedena pomoću fotografske metode i skup podataka je dostupan na Comprehensive R Archive Network (CRAN). Podaci su dobiveni znanstvenim ulovom koji je pokazao niže granice veličine uzoraka od onih iz ribarstva. Dužinsko-maseni odnosi su izračunati za totalnu dužinu te je utvrđeno da su u skladu s podacima iz Finske. Mjerenje dužine odvijalo se na najbližu dužinu od 0,01 cm, što je omogućilo da i mlađ bude zastupljena u modelu. Sposobnost prilagodbe modelu je visoka, s koeficijentom determinacije većim od 95%. Ovo istraživanje je prvo koje procjenjuje dužinsko-masene odnose ribljih vrsta za ovo hipereutrofno jezero i korisno je za ribarsku proizvodnju i biologe., 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.

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.