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Mediterranean freshwater systems are under threat owing to increased drought driven by climate change, intensive human land uses and non‐native species. This is causing increased fish hybridization in isolated watercourses.The genetic and morphological characteristics of hybrids of sympatric native and non‐native fish species were studied in four streams of the Mediterranean Guadalquivir basin (south‐west Spain). Fish morphology was analysed using geometric morphometrics, and molecular determination of parenthood was inferred through one mitochondrial gene (cytb) and one nuclear gene (Beta‐actin) for all hybrids and a subset of pure parental specimens.Molecular analyses confirmed hybrids between the native Squalius alburnoides and non‐native Alburnus alburnus in a stream with continuous flow. Haplotype analyses suggested that they originated from backcrossing of hybrid offspring. Intergeneric crosses between native species S. alburnoides and Pseudochondrostoma willkommii, and S. alburnoides and Iberochondrostoma lemmingii were detected in streams under reduced connectivity scenarios.Morphometrics revealed that hybrid phenotypes were similar to S. alburnoides. In some cases, molecular markers uncovered hybridization events that were neither detected in the field nor by morphometric analyses, potentially supporting a backcrossing/introgression scenario.Hybridization is likely to be increasing in Mediterranean rivers where S. alburnoides are present owing to increased fragmentation caused by summer drought exacerbated by climate change and human land uses and pressures. This can become a problem for these endemic vulnerable species if genetic diversity is lost, morphological homogenization occurs and hybrids cannot be easily detected in the field.The potential risks could be addressed by monitoring and eradication of non‐native species and segregation from natives. To avoid native–native crosses, habitat quality and desiccation risk could be tackled by improved water quality and riparian reforestation to provide shade and reduce evapotranspiration. This would need increased coordination and intervention between the institutions that share conservation responsibilities in the area. [ABSTRACT FROM AUTHOR]

Diplostomum is a taxonomically problematic genus of trematodes, with many members harmful at the metacercarial stage to fish in aquaculture. We found metacercariae in the eye vitreous humor of the rudd, Scardinius erythrophthalmus; the bleak, Alburnus alburnus; and the roach, Rutilus rutilus, in Karelia (Russia) and identified them as Diplostomum numericum based on a combination of morphological and ecological data. Previously, D. numericum was thought to be conspecific with Diplostomum gavium. However, our phylogenetic analysis based on the sequences of the cox1 mitochondrial DNA gene did not support this hypothesis. We demonstrated the conspecificity of D. numericum with the larval trematode Diplostomum sp. Lineage 3 of Blasco-Costa et al. (2014) from the eye vitreous humor of European salmonid and cyprinid fishes. Therefore, we resurrected the species D. numericum and identified Diplostomum sp. Lineage 3 of Blasco-Costa et al. (2014) as D. numericum. Finally, we hypothesized that D. numericum was, in fact, conspecific with Diplostomum colymbi and that the latter was distinct from D. gavium sensu stricto. [ABSTRACT FROM AUTHOR]

Environmental studies which aim to assess the ecological impact of chemical and other types of pollution should employ a complex weight-of-evidence approach with multiple lines of evidence (LoEs). This study focused on in situ genotoxicological methods such as the comet and micronucleus assays and randomly amplified polymorphic DNA analysis as one of the multiple LoEs (LoE3) on the fish species Alburnus alburnus (bleak) as a bioindicator. The study was carried out within the Joint Danube Survey 4 (JDS4) at nine sites in the Danube River Basin in the Republic of Serbia. Out of nine sampling sites, two were situated at the Tisa, Sava, and Velika Morava rivers, and three sites were at the Danube River. The three additionally employed LoEs were: SumTUwater calculated based on the monitoring data in the database of the Serbian Environmental Protection Agency (SEPA) (LoE1); in vitro analyses of JDS4 water extracts employing genotoxicological methods (LoE2); assessment of the ecological status/potential by SEPA and indication of the ecological status for the sites performed within the JDS4 (LoE4). The analyzed biomarker responses in the bleak were integrated into the unique integrated biomarker response index which was used to rank the sites. The highest pollution pressure was recorded at JDS4 39 and JDS4 36, while the lowest was at JDS4 35. The impact of pollution was confirmed at three sites, JDS4 33, 40, and 41, by all four LoEs. At other sampling sites, a difference was observed regarding the pollution depending on the employed LoEs. This indicates the importance of implementing a comprehensive weight-of-evidence approach to ensure the impact of pollution is not overlooked when using only one LoE as is often the case in environmental studies. [ABSTRACT FROM AUTHOR]

Diplostomum is a taxonomically problematic genus of trematodes, with many members harmful at the metacercarial stage to fish in aquaculture. We found metacercariae in the eye vitreous humor of the rudd, Scardinius erythrophthalmus; the bleak, Alburnus alburnus; and the roach, Rutilus rutilus, in Karelia (Russia) and identified them as Diplostomum numericum based on a combination of morphological and ecological data. Previously, D. numericum was thought to be conspecific with Diplostomum gavium. However, our phylogenetic analysis based on the sequences of the cox1 mitochondrial DNA gene did not support this hypothesis. We demonstrated the conspecificity of D. numericum with the larval trematode Diplostomum sp. Lineage 3 of Blasco-Costa et al. (2014) from the eye vitreous humor of European salmonid and cyprinid fishes. Therefore, we resurrected the species D. numericum and identified Diplostomum sp. Lineage 3 of Blasco-Costa et al. (2014) as D. numericum. Finally, we hypothesized that D. numericum was, in fact, conspecific with Diplostomum colymbi and that the latter was distinct from D. gavium sensu stricto.

The present study presents the results from examinations of bleak’s endohelminth species and structure of helminth communities from the Bulgarian part of the Lower Danube River. In 2015 and 2016, on a seasonal manner, 91 specimens of Alburnus alburnus (Linnaeus, 1758) (bleak) were examined with standard techniques for parasites. Five species of parasites: Nicolla skrjabini (Ivanitzky, 1928), Ligula intestinalis (Linnaeus, 1758), Acanthocephalus lucii (Müller, 1776), Pomphorhynchus laevis (Müller, 1776) and Contracoecum microcephalum (Stossich, 1890), larvae were identified. The analysis of the dominant structure of the found parasite species is presented to the component and infracommunities levels. All parasite species were accidental for the parasitic communities of examined fish with the exception of P. laevis and N. skrjabini. P. laevis was a core parasite species and N. skrjabini was a component parasite species for the helminth communities of bleak. The parasite communities of A. alburnus were discussed and compared with previous research data on parasite communities of bleak from River Danube in Bulgaria. New data for helminths and helminth communities of A. alburnus from Danube River (biotope Vetren) and their seasonal occurrence are presented.

In 2020, 30 specimens of bleak (Alburnus alburnus Linnaeus, 1758), 3 samples of water and 3 samples of sediments were collected from the Danube River (Kudelin) in the northwestern part of the Republic of Bulgaria. Samples of water and sediments, of tissues/ organs (liver, skin and muscles) of bleak were investigated for the presence of cadmium (Cd). The concentrations of Cd in the studied tissues/ organs of Alburnus alburnus decreased as follows: liver (CCd = 1.38 ± 0.55 mg.kg-1 wet weight) > skin (CCd = 0.50 ± 0.18 mg.kg-1 wet weight) > muscles (CCd = 0.09 ± 0.05 mg.kg-1 wet weight). The reported concentrations of Cd in water samples are CCd = 0.008 ± 0.006 mg.l-1, and in sediments samples CCd = 1.55 ± 2.35 mg.kg-1 dry weight. [ABSTRACT FROM AUTHOR]

This study deals with bleak (Alburnus alburnus) sensitivity in detecting of the wastewater related pressure in large lowland rivers. The major objective was to investigate if the response measured in bleak should be linked to a certain stretch of the river and characterised as "stretch specific", or it should be linked to the sampling site and characterised as "site specific". The response was evaluated via condition index, metal pollution index, DNA damage and cell viability using integrated biomarker response approach. The study was conducted at 3 sub-sites characterized by different pollution levels in a relatively short stretch (2 km) of the Sava River (Serbia). Results indicated that the response of the biomarkers in bleak can be interpreted as "site specific". Among the studied biomarkers, DNA damage assessed by comet assay and micronucleus test has shown high sensitivity in differentiation of the sites. [ABSTRACT FROM AUTHOR]

The study aimed to present the results of investigations on the content of heavy metals/metalloids (Cu, Cd and As) in tissues and organs (liver, skin and muscles) of Alburnus alburnus (Linnaeus, 1758), and in waters and sediments of the Danube River (Kudelin, Vidin), Bulgaria. The highest Cd contents were found in liver samples (0.80 ± 0.56 mg.kg-1), followed by contents in skin samples (0.21 ± 0.15 mg.kg-1) and muscle (0.08 ± 0.07 mg.kg-1). The highest As contents were found in liver (28.14 ± 10.98 mg.kg-1) and skin (14.36 ± 11.45 mg.kg-1), and the lowest in muscle (2.14 ± 0.64 mg.kg-1). The highest content of Cu was established in liver samples (7.32 ± 2.39 mg.kg-1), followed by this in the skin (3.78 ± 2.24 mg.kg-1) and muscles (1.29 ± 1.03 mg.kg-1). The highest values for As contents (0.07 ± 0.05 mg.l-1) were determined in surface waters, and the highest values for Cu contents were determined in sediments (204.09 ± 121.05 mg.kg-1). The results of studies on the circulation of the studied elements in the water-sediment-tissue and organs of A. alburnus system were analysed. [ABSTRACT FROM AUTHOR]

In the spring, summer and autumn of 2019, ecoparasitological studies were conducted on 165 specimens of Alburnus alburnus (Linnaeus, 1758) from the Danube River (Koshava, Kudelin and Novo selo villages, Vidin region). The species diversity of parasites of the bleak was determined. Seven species of parasites were identified: 4 species of Trematoda (Nicolla skrjabini (Iwanitzky, 1928), Allocreadium isoporum (Looss, 1894), Posthodiplostomum cuticola (von Nordmann, 1832), Sphaerostomum bramae (Müller, 1776)), one species of Cestoda (Neogryporhynchus cheilancristrotus (Wedl, 1855), larvae), one species of Acanthocephala (Pomphorhynchus laevis (Müller, 1776)) and one species of Nematoda (Contracaecum sp., larvae). In the spring the dominant species was the trematode A. isoporum, detected in 9 specimens of A. alburnus from the Koshava biotope. The dominant parasite species in summer and autumn was the trematode P. cuticola. A. alburnus is a new host for S. bramae and N. cheilancristrotus, from the studied river ecosystem. The structure of the parasite communities of the bleak from the investigated section of the freshwater ecosystem of the Danube River was presented. [ABSTRACT FROM AUTHOR]

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 present study presents the results from examinations of bleak's endohelminth species and structure of helminth communities from the Bulgarian part of the Lower Danube River. In 2015 and 2016, on a seasonal manner, 91 specimens of Alburnus alburnus (Linnaeus, 1758) (bleak) were examined with standard techniques for parasites. Five species of parasites: Nicolla skrjabini (Ivanitzky, 1928), Ligula intestinalis (Linnaeus, 1758), Acanthocephalus lucii (Müller, 1776), Pomphorhynchus laevis (Müller, 1776) and Contracoecum microcephalum (Stossich, 1890), larvae were identified. The analysis of the dominant structure of the found parasite species is presented to the component and infracommunities levels. All parasite species were accidental for the parasitic communities of examined fish with the exception of P. laevis and N. skrjabini. P. laevis was a core parasite species and N. skrjabini was a component parasite species for the helminth communities of bleak. The parasite communities of A. alburnus were discussed and compared with previous research data on parasite communities of bleak from River Danube in Bulgaria. New data for helminths and helminth communities of A. alburnus from Danube River (biotope Vetren) and their seasonal occurrence are presented. [ABSTRACT FROM AUTHOR]

During summer 2018, 29 specimens of bleak (Alburnus alburnus (Linnaeus, 1758)) from Maritsa River were collected and examined with standard techniques for parasites. Helminth parasites were recorded in 24 bleak specimens (82.75%) from Maritsa River. Five species of parasites were identified: one trematode species (Allocreadium isoporum (Looss, 1984)), two cestode species (Caryophyllaeus brachycollis Janiszewska, 1951, Ligula intestinalis (Linnaeus, 1758)); one acantocephalan species (Pomphorhynchus laevis (Müller, 1776)) and one nematode species (Rhabdochona denudatа (Dujardin, 1845; Raillet, 1916). The analysis of the dominant structure of the found parasite species is presented to the component and infracommunities level. In the component community of Alburnus alburnus from Maritsa River C. brachycollis, P. laevis and, R. denudatа are corespecies. L. intestinalisis component parasite species and A. isoporum is accidental parasite species for the helminth communities of bleak. The infracommunities data was used to be fixed principal biotic indices. Bioindicator significance of established parasite species was discussed for ecological evaluation of the state of the studied freshwater ecosystem. New data for the helminths and helminth communities of bleak from Maritsa River are presented. [ABSTRACT FROM AUTHOR]

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. 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 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 dužinskomasene odnose ribljih vrsta za ovo hipereutrofno jezero i korisno je za ribarsku proizvodnju i biologe. [ABSTRACT FROM AUTHOR]

The Velika Morava River is the greatest national Serbian river and the significant tributary of the Danube River. The major problems in the Velika Morava River Basin (VMRB) represent untreated industrial and municipal wastewaters. In this study, the level of genotoxic potential at the sites along the VMRB was evaluated by parallel in vitro and in situ approach. Within in vitro testing, genotoxicity of native water samples collected from the sites in VMRB was evaluated by SOS/ umuC test on Salmonella typhimurium TA1535/pSK1002 and by the comet assay on HepG2 cells. DNA damage in situ was assessed in bleak ( Alburnus alburnus ) erythrocytes by the comet (alkaline and Fpg-modified comet) and micronucleus assays. Additionally, the concentration of heavy metals in fish tissue was measured and this data, compiled with the data of the physico-chemical parameters measured in water, was used as a measure of the pollution pressure at the sites. Results showed that applied in vitro tests with native water samples are less sensitive in comparison with in situ tests and should be taken with precaution when making predictions on the status of the ecosystem. Within applied battery of in situ assays differential sensitivity of assays was observed where alkaline comet assay showed the highest potential in differentiation of the sites based on genotoxic potential. Integrated biomarker response showed that usage of the battery of bioassays provides better insight in a genotoxic effects in animals, and consequently, that the holistic approach is more suitable for this type of study. [ABSTRACT FROM AUTHOR]

During the ecological study of 28 specimens bleak (Alburnus alburnus (Linnaeus, 1758)) by applying standard techniques for parasites was found infestation with the acantocephalan Pomphorhynchus laevis (Müller, 1776). Aim of the present study is to establish the content of nickel in water, sediments, tissues and organs of A. alburnus and its parasite Pomphorhynchus laevis, and the possibilities of accumulation and circulation in the freshwater ecosystem of Danube River. From the tissues and organs of the studied specimens Alburnus alburnus, the content of nickel in samples of liver are higher than in the skin and muscles (in both infected and uninfected specimens). Differences were observed not only in nickel content, but also in the amendment of nickel content of infected (Ni Liver> Ni Muscles > Ni Skin) and uninfected (Ni Liver> Ni Skin> Ni Muscles) specimens of bleak. The obtained values for nickel content in liver, muscles and skin of A. alburnus infected with P.laevis were found to be lower than the obtained values for nickel content in liver, muscles and skin of uninfected specimens of bleak. The acanthocephalan Pomphorhynchus laevis showed significantly higher content of nickel than its host tissues and organs. Significant correlation (p<0.05) was fixed for relationships between CP. laevis Ni- CSkin Ni. [ABSTRACT FROM AUTHOR]

The aim of the study was to determine the degree of overlap in the feeding niches of early developmental stages of roach, Rutilus rutilus (L.), perch, Perca fluviatilis L., bleak, Alburnus alburnus (L.) and sunbleak, Leucaspius delineatus (Heckel). The hypotheses were that (i) larvae of different fish species of similar body sizes feed on similar food, and that (ii) smaller fish compete with larger ones for similar prey. The results of the analysis was to answer the question of whether the diet overlap of juvenile fish stages decreases with ontogenetic development. The study was conducted for two years (2001-2002) in two shallow, polymictic, eutrophic lakes. The diets of early developmental stages of fish species of similar body sizes differed. The few instances of diet overlap resulted from the abundance of food resources in the environment. However, fish of smaller body sizes exploited the same food resources as did individuals of the same species that belonged to different cohorts.

Two cyprinid fish species, bleak (Alburnus alburnus (Linnaeus, 1758)) and vimba bream (Vimba vimba (Linnaeus, 1758)) from the Bulgarian part of the Danube River (Lower Danube) were examined for cadmium content in their tissues and organs. The aim of the present study is to establish the content of cadmium in the water, sediments, skin, muscles, and liver of Alburnus alburnus and Vimba vimba. In the tissues and organs of the studied fish species - A. alburnus and V. vimba, the content of cadmium in samples of the liver was higher than in the muscle and skin samples, and ranged as follows: CCd/Liver>CCd/Skin>CCd/Muscles (for both fish species). The cadmium content in the analyzed samples of muscles of V. vimba was above the maximum acceptable concentrations. The obtained values for the content of cadmium in the muscle samples of A. alburnus were found to be more than 4 times lower than the obtained values for the content of cadmium in the muscle samples of V. vimba. In general, the content of cadmium in the tissues and organs of A. alburnus was lower than the content of cadmium in the tissues and organs of Vimba vimba. Significant correlations (p<0.05) were fixed for Vimba vimba for the relationships between С Cd/Liver - С Cd/Water and С Cd/Liver - С Cd/Sediments. [ABSTRACT FROM AUTHOR]

During the ecological study of 45 specimens of bleak (Alburnus alburnus (Linnaeus, 1758)) by applying standard techniques for parasites in ten specimens of fish an infestation was found with the acantocephalan Pomphorhynchus laevis. Aim of the present study is to establish the content of arsenic in water, sediments, tissues and organs of A. alburnus and its parasite Pomphorhynchus laevis, and the impact that the acanthocephalan has on the content of arsenic in his host tissues and organs. From the tissues and organs of the studied specimens of Alburnus alburnus, the content of arsenic in samples of liver were higher than in the samples of muscles and skin, and ranged as followed: CAs/Liver>CAs/Muscles>CAs/Skin (in both infected and uninfected specimens). The obtained values for the content of arsenic in skin of uninfected specimens of A. alburnus were found to be more than 3 times higher than the obtained values for content of arsenic in skin of A. alburnus infected with P. laevis. In general the content of arsenic in tissues and organs of uninfected A. alburnus was higher than the content of arsenic in tissues and organs of infected with P. laevis specimens of bleak. The acanthocephalan Pomphorhynchus laevis showed 115-3042 times higher content of arsenic than its host tissues and organs. Significant negative correlation (p<0.05) was fixed for the relationship between С As/P. laevis- С As/Sediments. [ABSTRACT FROM AUTHOR]

During 2016, 45 specimens of barbel (Barbus barbus (Linnaeus, 1758)) and 45 specimens of bleak (Alburnus alburnus (Linnaeus, 1758)) are collected and examined from the Danube River. The aim of the study is to analyse the lead content in sediments, tissues and organs of two fishes that inhabit different water levels and in their common parasite - P. tereticollis from the Bulgarian section of River Danube. New data for the lead contents in sediments, parasites, tissues and organs of barbel and bleak from the Danube River are presented. From the tissues and organs of the studied fish specimen B. barbus, the lowest concentrations of lead were found in skin, while in A. alburnus the lowest concentrations of lead were found in muscles. The acanthocephalan Pomphorhynchus tereticollis showed significantly higher content of lead than its hosts tissues and organs. Bioconcentration factor for lead (Pb) in the tissues and organs of barbel and bleak and their common parasite Pomphorhynchus tereticollis were presented and discussed with respect to their content in sediments. Highly significant correlation (p<0.01) was fixed for relationship between P. tereticollis Pb-Skin Pb for Barbus barbus. Highly significant correlation (p<0.01) was also fixed for relationship between P. tereticollis Pb-Sediments Pb for Alburnus alburnus. [ABSTRACT FROM AUTHOR]

The chromosomal spread and karyotype of Bleak (Alburnus alburnus) from Anzali lagoon were identified using tissue squashing techniques with injection of 0.5ml/100g body weight of 0.01% Colchicines solution in fish fingerlings. Kidney and gill tissues were then extracted and chopped in KCl 0.045M for 20 min and fixed in Carnoy solution in 3 stages. The chromosomal spreads were stained in 20% Gimsa for 30 min. From 347 chromosomal spread counts, the results showed diploid chromosome number of this species 2n=50. Karyotype composed of 7 metacentric, 13 submetacentric and 5 acrocentric or subtelocentric choromosome pairs, and the number of chromosome arms (NF) was determined as NF=90.

The Iberian Peninsula has been subjected to numerous fish introductions and the colonization of new areas by non-native species is constantly reported. However, there is a lack of knowledge about many aspects of the bio-ecology of these species and their invasive success within the environmental context of Mediterranean temporary rivers. This study aimed to address the following questions: (i) what are the main regional and local environmental drivers influencing fish assemblages and differentiating native from non-native species, particularly A. alburnus?; (ii) what are the environmental and anthropogenic disturbance factors responsible for the occurrence and abundance of A. alburnus?; (iii) is there a pattern in the spatiotemporal distribution of A. alburnus size classes, along the tributaries of reservoirs where the species occurs? Data on fish species, environmental variables, and anthropogenic disturbance were collected in 77 sites of the Guadiana and Sado river basins in the south of Portugal. Additionally, a seasonal sampling was performed along an upstream-downstream gradient of several tributaries from three reservoirs in these river basins. A multivariate analysis and a multi-model approach were used in data analyses. Native and non-native fish assemblages showed different environmental drivers and responses to anthropogenic disturbance levels, though A. alburnus has revealed similarities with native species. The occurrence of A. alburnus was mainly determined by hydrological and morphological disturbances driven by anthropogenic activities. Furthermore, this species apparently performed seasonal movements along the tributaries of several reservoirs, profiting from these lentic habitats as a stepping-stone for further invasions. This study highlighted the wide ecological plasticity of A. alburnus, as it benefits from the anthropogenic hydrological disturbance (induced by reservoirs), and is also able to cope with the natural hydrological disturbance (resulting from the intermittency of these streams), to guarantee and enhance its invasive success in Mediterranean intermittent streams. It also gives a sound contribution to understand the spread of A. alburnus in these vulnerable freshwater ecosystems, and to delineate management measures, namely by identifying critical points in the river network along with prioritizing river restoration measures that benefit native species.

Environmental studies which aim to assess the ecological impact of chemical and other types of pollution should employ a complex weight-of-evidence approach with multiple lines of evidence (LoEs). This study focused on in situ genotoxicological methods such as the comet and micronucleus assays and randomly amplified polymorphic DNA analysis as one of the multiple LoEs (LoE3) on the fish species Alburnus alburnus (bleak) as a bioindicator. The study was carried out within the Joint Danube Survey 4 (JDS4) at nine sites in the Danube River Basin in the Republic of Serbia. Out of nine sampling sites, two were situated at the Tisa, Sava, and Velika Morava rivers, and three sites were at the Danube River. The three additionally employed LoEs were: SumTUwater calculated based on the monitoring data in the database of the Serbian Environmental Protection Agency (SEPA) (LoE1); in vitro analyses of JDS4 water extracts employing genotoxicological methods (LoE2); assessment of the ecological status/potential by SEPA and indication of the ecological status for the sites performed within the JDS4 (LoE4). The analyzed biomarker responses in the bleak were integrated into the unique integrated biomarker response index which was used to rank the sites. The highest pollution pressure was recorded at JDS4 39 and JDS4 36, while the lowest was at JDS4 35. The impact of pollution was confirmed at three sites, JDS4 33, 40, and 41, by all four LoEs. At other sampling sites, a difference was observed regarding the pollution depending on the employed LoEs. This indicates the importance of implementing a comprehensive weight-of-evidence approach to ensure the impact of pollution is not overlooked when using only one LoE as is often the case in environmental studies., (© The Author(s) 2022. Published by Oxford University Press on behalf of the UK Environmental Mutagen Society. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

The purpose of the present study is to analyze the sex and size structure of roach (Rutilus rutilus) and bleak (Alburnus alburnus) populations from carp family (Cyprinidae) in Zhrebchevo Dam. The survey was conducted in February 2013. The main task of the Dam visit was to collect representatives of all fish species active in the season and caught by the fishermen. In order to obtain a representative samples of fish, was taken specimen of each species, fishermen had caught. Were got 26 sexually mature roach (7♂ and 19♀) and 27 sexually mature bleak (12♂ and 15♀). A specific feature of roach sex structure is the bigger number of females (73.08%) than males (26.92%) in the population. In the bleak (Alburnus alburnus) population the number of males and females is almost equal with a small predominance of the females (55.55%) over the males (44.45%). The analysis of the size structure of roach and bleak populations inhabiting Zhrebchevo Dam indicates that males are relatively smaller than females and these differences apply with accuracy of (P≤0.001) for the total body length and with accuracy of (P≤0.01) for the live weight of the examined fish species. The trend is the same within the bleak population where the differences apply with accuracy of (P≤0.01) for the total body length and with accuracy of (P≤0.001) for the live weight. Bleak’s yield is 88% which is higher than the one of the roach - 16%. [ABSTRACT FROM AUTHOR]