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The European eel (Anguilla anguilla) is an economically important species in Poland, not only due to the quality and price of its meat, but also due to the eel stock management plan implemented since 2010. However, the imported juvenile eels for reintroduction are directly introduced into waters or reared in fish farms without necessary monitoring of the health status, especially for hazardous and pathogenic viruses. The study was conducted in the second half of 2014 using the European eels collected from Poland (Dąbie Lake, Szczecin Lagoon, hatcheries) and Denmark, mainly from importers and organizations producing material for reintroduction. A total of 256 samples were analysed including gills, liver, kidney, spleen, intestine and heart. Detection of the AngHV-1 was performed using pair primers designed to amplify the gene fragment encoding the viral DNA polymerase. Each PCR product was confirmed by bidirectional sequencing and sequence alignment with GenBank sequences. Obtained results indicate that the infection status of the eels imported to Poland is in the range of 0 to 100%, with the highest percentage of asymptomatic carriers among the fish imported from Denmark for the purpose of reintroduction and rearing. The eels collected in natural waters demonstrated an AngHV-1 infection rate of 30% (Dąbie Lake) and 40% (Trzebież). Bioinformatics analysis demonstrated that all these sequences were identical and represented the haplotype characterized for the first time in Poland by Kempter et al. (2014). The intensity of eel reintroduction in Poland is 1.2 million individuals per year, which permits a conclusion that the species is important for the fishing economy and should be monitored against AngHV-1. The demonstrated existing high risk posed by mass kills of the European eel in domestic waters after the introduction of the herpesvirus AngHV-1 from imported fish.

The Community Action Plan requests EU member states to implement measures that ensure the recovery of the severely depleted European eel stocks. One of the main threats is posed by Anguillid herpesvirus 1 (AngHV-1) leading to increased mortality in both wild and farmed eels. Following recommendations of the OIE to minimize the risk of obtaining false-negative results, the main aim of the study was to optimize diagnostic methods for AngHV-1 detection using conventional PCR, nested PCR and in situ hybridization assay. While 53.3% of the individual organ samples were tested positive for AngHV-1 by PCR, the additional virus analysis via nested PCR revealed that the actual prevalence was 93.3%. In the cell cultivation passages, a cytopathic effect was hardly found in the first two rounds. In the third passage onto cell cultures, a lytic CPE was detected. The identification and confirmation of the viruses obtained from cell cultures as well as directly from the organ tissues were proceeded by PCR, nested PCR and sequencing of the PCR products. While no positive signal was detectable in the first round by PCR using samples from the third cell culture passages, the nested PCR provided weak but visible positive signals.

Tench, Tinca tinca is a freshwater species which receives increasing attention as marine resources are overexploited and alternative feed components must be implemented to enable sustainable development of aquaculture. The aim of the study was to provide scientists and fish farmers with first high quality annotated tench transcriptome and open a new chapter in tench research, especially when practical diets are tested. Therefore, the second aim was to identify differentially expressed contigs (DECs) in tench gut after 86-day trial where adult tench females were fed with 0% and 100% replacement of fish meal (FM) with poultry by-product meal (PBM). De novo assembling using de novo RNA-Seq Assembly Pipeline (DRAP) produced 64070 contigs where these exceeding 1 kbp were mostly annotated. Microsatellite search identified 23668 SSRs and SNPs were distributed in 118002 transitions and 83577 transversions. High quality of the assembly and annotation completeness of the tench transcriptome was confirmed using BUSCO and by mapping contigs against common carp, Cyprinus carpio and zebrafish, Danio rerio data sets. Analysis of gene expression differences between gut samples tench fed with FM and PBM diets revealed 721 and 69 DECs using edgeR and DESeq2, respectively. Venn diagram for these results filtered out 57 DECs which were common for both analysis. Due to a low number of annotated DECs enrichment analysis provided a low number of useful contigs for pathway or functional analysis. Nevertheless, each contig in the set was analysed through BLASTn and BLASTx and eighteen DECs were characterised and identified as mainly involved in response to different immune stimuli and disease states (e.g. cluster of differentiation 48, F-type lectin), cell adhesion (e.g. paracingulin), digestion (e.g. serine proteases) and signal transduction (e.g. neurexophilin 3, complexin 2). Moreover, study has shown that most of the identified in our study DECs (70.2%) were down regulated in gut samples of tench fed with PBM comparing to these with FM-based feed. This observation might indicate on disorganization of inter-epithelial junctions in ongoing inflammation process. Our de novo tench gut transcriptome assembly (online NGS Pipeline) provide a guide for further diverse studies because, understanding feed-gut interactions and intestinal homeostasis in farmed tench is important to maximise performance of this species and to ensure that freshwater aquaculture continues to be a sustainable source of food for a growing world population.

Background. Oxidative stress poses a serious threat to farmed fish, exemplified by depressed growth, decreased disease resistance, and reduced flesh quality. Therefore, the aim of this study was to examine differences in activity of antioxidant enzymes and concentration of selected biochemical parameters between blood plasma of both sexes of three species important for sustainable development of aquaculture: tench, Tinca tinca (Linnaeus, 1758); wels catfish, Silurus glanis Linnaeus, 1758; and sterlet, Acipenser ruthenus Linnaeus, 1758. Materials and methods. Experimental fishes were fed ad libitum for 60 days with a formulated diet (45% proteins, 20% fat, 16% carbohydrates, 8% ash and 2% fibre). At the end of the study venous blood samples were collected and 11 biochemical parameters were assessed: superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione-S-transferase (GST), total antioxidant capacity (FRAP), alanine transaminase (ALT), aspartate transaminase (AST), lactate dehydrogenase (LDH), bilirubin, albumin, and uric acid. Results. Comparison between species revealed that the most significant differences were observed for tench and sterlet (in FRAP, GPx, CAT, GST LDH, ALT, bilirubin, and uric acid), less significant—for sterlet and wels (in FRAP, GST, LDH, AST, bilirubin, uric acid), followed by tench and wels catfish (in FRAP, GPx, GST, AST, and uric acid). Moreover, significant variations in the level of biochemical markers were also detected between sexes within each species, where the highest number was observed for tench (in FRAP, GPx, albumin, and uric acid), next wells catfish (in SOD, albumin, and bilirubin), and the lowest in sterlet (in ALA). Additionally, numerous differences in antioxidant potential (FRAP), antioxidant defence indices, as well as in markers of liver function, heart dysfunction, and markers of nutritional status were observed as species-specific and sex-specific. Conclusion. Results obtained in this study for the first time demonstrated species- and sex-related differences in plasma activity of antioxidant enzymes and concentration of selected biochemical parameters between tench, wels catfish, and sterlet reared in cage culture. The presented findings provide significant contribution not only to the existing knowledge of fish physiology but will also help to design optimal feeding practices to achieve sustainable cage aquaculture.

Summary The activity of antioxidant enzymes [superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT) and glutathione-S-transferase (GST)] in the liver and gills of tench (Tinca tinca L.) from distinct habitats were studied. Fish were collected in the same season from three different water bodies: a cage culture supplied with cooling water from a power plant; traditional aquaculture in fishponds; and from the Odra River estuary. In all water bodies, the activity of antioxidant enzymes was significantly higher in the liver than in the gills. The highest activities of GST in the liver and GPx in the gills were detected in tench from the Odra River estuary, which may suggest abiotic stress connected with water quality in the estuary.

BackgroundConservation of noble crayfish (Astacus astacus) populations is becoming particularly important since the number of individuals is rapidly declining across the distribution range of the species in Europe. Five crayfish populations in northwestern Poland have been constantly monitored for two decades. However, the genetic structure of these populations has not been analysed, although this information is important to devise effective conservation strategies.MethodsNoble crayfish were collected in the autumn of 2014 by scuba diving in Lakes Graniczne, Babinki, Biwakowe, Sęki and Kwisno, all of which are situated in the Bytów Lakeland of northwestern Poland. Genetic diversity of the five populations was assessed based on allele variability in nine SSR regions and six AFLP primer combinations.ResultsMicrosatellite results analysed with AMOVA showed that the diversity between populations corresponds to 18% of total variability, which was confirmed by similar results obtained using AFLP. Additionally, significant genetic diversity was revealed by high average FSTvalues. All of the studied crayfish populations significantly deviated from the expected Hardy–Weinberg genetic equilibrium and were characterised by negative values of inbreeding coefficient (FIS).DiscussionThe invariably negative inbreeding coefficients (FIS) suggest a low number of mating individuals, a possible consequence of the phenomenon known as genetic bottleneck. However, additional comprehensive analyses are needed to assess the genetic structure, origin and vulnerability of the remaining populations of noble crayfish in the Bytów Lakeland of northwestern Poland, which have high conservation value and are particularly important as a live genetic bank for breeding and restitution purposes.

Unlike the sporocyst stages, adult leucochloridiid digeneans are difficult to differentiate. Sporocyst broodsacs can be identified on the basis of their colour and banding pattern, but in the absence of broodsacs and when experimental infection cannot be performed, tentative morphological identification needs to be verified, and molecular techniques offer a tool to do this. In this study, adult leucochloridiid digeneans were collected from the great tit (Parus major) found dead at three localities at or near the Baltic Sea coast (Hel, Bukowo-Kopań and Szczecin) in northern Poland. On the basis of differences in their morphological characters, Hel specimens were tentatively assigned to Leucochloridium perturbatum, Bukowo-Kopań and Szczecin specimens being identified tentatively as L. paradoxum. Subsequent ribosomal DNA sequence analysis confirmed the identification of these leucochloridiid flukes. Nucleotide sequences discriminating between the two species were identical to those used by earlier authors as characteristic of two distinctly different sporocyst broodsacs representing L. perturbatum and L. paradoxum.

Background. The study is a contribution to Project CELFISH which involves genetic identification of populations of fish species presenting a particular economic importance or having a potential to be used in the so-called commercial substitutions. The EU fish trade has been showing a distinct trend of more and more fish species previously unknown to consumers being placed on the market. Molecular assays have become the only way with which to verify the reliability of exporters. This paper is aimed at pinpointing genetic markers with which to label and differentiate between two populations of splendid alfonsino, Beryx splendens Lowe, 1834, a species highly attractive to consumers in Asia and Oceania due to the meat taste and low fat content. Materials and methods. DNA was isolated from fragments of fins collected at local markets in Japan (MJ) (n = 10) and New Zealand (MNZ) (n = 18). The rhodopsin gene (RH1) fragment and 16 microsatellite DNA fragments (SSR) were analysed in all the individuals. The sequences obtained were processed using the BioEdit and BLAST software, whereas SSR data were processed with the GeAlEX analysis package. Results. The BioEdit software-aided comparison of MJ and MNZ nucleotide sequences of the rhodopsin gene fragments were identical and showed 100% agreement with the alfonsino sequence deposited under access number DQ197832. The preliminary analysis of SSR markers showed all the loci analysed in both populations to be polymorphic, and when randomly selected specimens were assigned to the original populations. The affinity test correctly identified the provenance of all those specimens. Conclusion. The results obtained constitute a tool for molecular differentiation between alfonsino populations collected in the FAO 81 (New Zealand) and FAO 71 (Japan) areas for the purpose of catch quota control and for checking the agreement between the label declaration and the actual product.

The genetic variability between individuals from five crayfish (Astacus astacus L.) populations was determined. The analysis was based on sequences variations of mitochondrial DNA (cytochrome oxidase subunit I (COI) and 16S ribosomal DNA. Mitochondrial DNA sequences are widely used to detect genetic variation within and between populations. Data analysis revealed the existence of two COI haplotypes – most common haplotype Hap01 and one new haplotype, differed only in one substitution. Analysis of the 16S rDNA sequences obtained showed no differences in nucleotide composition. The results of the analysis are important part of project “Active protection of noble crayfish in lakes of Pomeranian Complex Landscape Parks” financed by Financial Mechanism of the European Economic Area 2014–2016.

The analysis of the tench growth hormone gene structure revealed a comparable organization of coding and non-coding regions than other from cyprinid species. Based on the performed mRNA and amino acid sequence alignments, gh tench is related to Asian than to European representatives of Cyprinidae family. Second aim of the work was to characterize and predict protein structure of the tench growth hormone. Tinca tinca GH share many common features with human GH molecule. The Tench GH protein binds to the growth hormone receptor (GHR) using two regions I and II that are situated at opposite sites of molecule. Binding site I is placed in the central part of T. tinca GH and H 189 amino acid in the middle region of the IV helix is crucial for GH–GHR interactions.

The aim of this study was to characterize whitefish and peled populations in Miedwie Lake by means of the genetic analysis of ND-1 (NADH dehydrogenase 1) gene and the ITS-1 (internal transcribed spacer 1) region in order to distinguish native forms from whitefish/peled hybrids. In the analysis, archival specimens of Coregonus lavaretus maraena from the Berlin Museum fur Naturkunde were used. Genetic analysis performed with the aid of MEGA 4.0 software explicitly indicated that samples from Miedwie Lake belonged entirely to a native (rapidly growing) form of whitefish. Furthermore, the conducted research has also provided crucial information for a C. lavaretus management program for Miedwie Lake.

Among members of the Cyprinidae family, hybridisation is more widespread than in any other group of freshwater fish. Therefore, the aim of this work has been to use two different approaches, biometric and genetic, to assess differences between common carp (Cyprinus carpio) × goldfish (Carassius auratus) hybrids and their parents. Twenty-three length measurements of 10 fish from each group have been performed. Statistical analyses of results were conducted using Levene’s, ANOVA, NIR and Kruskal–Wallis tests. Genetic analysis has been conducted by means of amplified fragment length polymorphism (AFLP) technique. The AFLP allowed us to distinguish groups of fish and showed that hybrids had more in common with C. auratus than with C. carpio.

A total of 124 specimens of the tufted duck, Aythya fuligula, and 63 greater scaup, A. marila, were examined for digenean parasites. Both duck species, which overwinter in a coastal lake connected with the southern Baltic (north-west Poland) were found to support Amblosoma exile, Cyathocotyle prussica,Paracoenogonimus ovatus, Australapatemon minor, Cotylurus cornutus, Echinoparyphium recurvatum, Echinostoma revolutum and Notocotylus attenuatus. In addition, the tufted duck hosted Hypoderaeum conoideum, Bilharziella polonica, Neoeucotyle zakharovi, Renicola mediovitellata, Psilochasmus oxyurus, Psilostomum brevicolle and Cryptocotyle concava; Echinostoma nordiana occurred in the greater scaup only. The two duck species differed significantly in the intensity and abundance of their digenean infection. Aythya marila harboured higher intensity levels and a wider assemblage of digeneans than A. fuligula, and this was likely to be due to differences in the pre-wintering exposure of the duck species to infective stages of these freshwater digeneans. Digenean communities in both duck species, strongly dominated by E. recurvatum, were relatively similar in their structure. No significant sex-dependent differences in digenean infections were revealed, except for the infection with N. attenuatus in A. fuligula. Similarly, there were no significant age-dependent differences (adult versus immature birds) in digenean infections, except for that with N. attenuatus in A. fuligula. The structural similarity between digenean communities in the two duck species is most likely an effect of overlapping diets based on freshwater molluscs, components of the digenean transmission pathway to definitive hosts.

Aphanomyces astaci is a fungus-like oomycete agent responsible for an illness called crayfish plague, reaching 100% mortality in infected animals. Therefore, the aim of the work was to detect and estimate the rate of infection of spiny-cheek crayfish (Orconectes limosus) by A. astaci in selected water reservoirs of north-western Poland, as this crayfish is described as a main cause of crayfish plague. The material for the study were 54 spinycheek crayfish individuals from 3 sites in Poland: Trzebiocha River, Lake Sominko and Lake Dąbie. A total of 162 samples (muscle samples were taken from abdomen, legs and carapace) were taken and used for DNA extraction followed by PCR and bidirectional sequencing of 5.8S ribosomal RNA gene. The electrophoretic separation of the PCR products confirmed the presence of A. astaci in 17 samples (Trzebiocha River and Lake Dąbie). Lake Sominko proved to be a zone free of the investigated pathogen. The collected information on the presence or absence of A. astaci in the investigated reservoirs might be used for restocking purposes..

Background. Sturgeons have long been extinct in Polish inland waters. A substantial effort has recently been put into their restitution, covering the drainage areas of two major Polish rivers, the Oder and the Vistula. The stocked fishes are clinically healthy, but very little is known about their potential to transmit viral diseases including koi herpes virus (KHV) to healthy fishes of other species, which may pose a threat to the disease-free zones. This study was intended to determine if sturgeons could be asymptomatic carriers of KHV. Materials and methods. A total of 29 sturgeons (two species; length 8–37 cm) originating from fish farms in northern Poland with a known KHV history in common carp or koi in the area were examined: 15 Russian sturgeons, Acipenser gueldenstaedtii, with clinical signs of a disease and 14 asymptomatic Atlantic sturgeons, A. oxyrinchus. The former were sent to the laboratory alive while the latter were sent fixed in ethanol. As it is required for detection of a latent KHV infection in acipenserids, two independent procedures were applied. The preliminary results were obtained using PCR. Those findings were subsequently confirmation by nested PCR. The latter procedure consists of sequence analysis of PCR products and direct detection of KHV infected cells in tissue materials by in-situ hybridization on nucleic acid level or indirect immunofluorescence on KHV protein level. Results. KHV genome parts were found in nine Russian sturgeons and four Atlantic sturgeons. Comparison of PCR results obtained from three primer pairs used for KHV diagnostic in sturgeon showed that those designed by Bercovier et al. were most sensitive and robust for this purpose. In order to confirm the presence of viral particles the most useful method was in-situ hybridization (ISH), allowing the detection of KHV in gill samples obtained from live sturgeons. Conclusion. This preliminary study shows that sturgeons can be carriers of KHV. Therefore a viral diagnostics is highly recommended not only for sturgeons obtained from the environment but also for fertilized eggs, fry, and fish intended for re-stocking measurements of inland waters.

Nine species-specific microsatellites were used to characterize 792 tench, Tinca tinca (L.), from 21 wild and cultured populations. Seven loci were polymorphic expressing four to 22 alleles. A Spanish cultured strain was homozygous at all loci for all individuals studied. Low variability was also observed in a wild population from Sapanca Lake, Turkey and a Chinese cultured strain. In contrast, the highest variabilities were found in wild tench from lake Felchowsee (average number of alleles), and the cultured strain from Konigswartha (average heterozygosity), both from Germany. Genetic differentiation between populations was moderate to high. The smallest genetic distances were found between the geographically most distant populations. A Neighbor-Joining tree showed only two major clades consisting of 4 and 17 populations, respectively. Within the smaller clade the Turkish wild and Spanish and Chinese cultured tench formed a sub-cluster with 100% bootstrap support. Possible reasons for the latter unexpected grouping are discussed.

Background. Monitoring the genetic diversity of fish populations can provide information necessary to determine fishing quotas for the commercially caught species. One of the species subjected to intensive exploitation is the yellowstripe scad, Selaroides leptolepis (Cuvier, 1833), commonly occurring in the coastal waters of Vietnam, Cambodia, Malaysia, and Indonesia. This paper is the third part of a larger project: ”Development of a genetic-based system for identification of food products from fisheries and aquaculture introduced to the European Union customs area”. Materials and methods. Fin fragments of the yellowstripe scad, Selaroides leptolepis, were obtained in 2012 and 2013 from local markets in Vietnam (SVN), Cambodia (SKH), Malaysia (MMY), and Indonesia (MID). The analyses focused on the amplification and sequencing of a fragment of the nuclear rhodopsin gene which utilized as identification label. Subsequently, in the obtained SVN, SKH, MMY, and MID samples, 11 microsatellite regions (SRR) were analysed. Sequence analyses were performed using the BioEdit and BLAST software, while the analysis of the obtained SRR data was conducted using the GenAlEx software. Results. The analysis of the obtained loci variants divided the investigated populations into two genetically homogeneous groups: the Vietnamese–Indonesian group and the Malaysian–Cambodian group. The analysis of genetic diversity revealed statistically significant deviations from the Hardy–Weinberg equilibrium in the investigated populations and indicated the Vietnamese population as the most stable, while the Malaysian population as the least stable. Conclusion. The study provides information on the genetic diversity of the investigated populations and allows assignment of the captured fish to the geographical regions specified. Moreover, indicate that among analysed populations the safest populations were those caught in the local fisheries (continental shelf) of Vietnam and Cambodia due to their high mean genetic diversity.

Background. Tench, Tinca tinca (Linnaeus, 1758), has been cultivated in Polish fish farms since centuries, due to its good quality meat. However, the most critical problem in tench culture is the slow growth, which makes farming of this species unprofitable. Growth rates of fish are influenced by numerous internal and external factors such as water temperature, food availability and quality, as well as photoperiod. In order to analyse and improve tench growth rate, the most important factors (GH, IGF-I) of the somatotropic axis should be analysed against selected culture factors. Key elements of the axis play a pivotal role in the coordination of protein and energy metabolism during postnatal growth. Therefore, the aim of this study was to assess effect of water temperature on the activity of somatotropic axis of tench. Obtained results can be useful in tench farming in order to deal with mass gain. Materials and methods. Forty tench, approximately 3+ years of age, were placed in eight 240 L tanks, five fish in each tank. There were four temperature regimes (10°C, 15°C, 20°C, and 25°C) studied separately for males and females during a period of one week. At the end of the experiment, 2 mL of blood, the whole pituitary gland, 2 liver samples, and one muscle sample were collected from selected fish specimens. Real-time PCR was used to assess the effect of water temperatures on the level of tench mRNA gh transcripts in pituitary-, liver-, and muscle samples. Also, the concentration of growth hormone (GH) protein was measured in relation to individual temperature treatments in blood plasma and liver samples using ELISA assay. Results. The highest cycle threshold (Ct) values of mRNA gh were detected in the pituitary samples. ELISA assays confirmed that water temperature affected GH and IGF-I concentrations in the blood and the liver samples. Additionally, results from ELISA assays confirmed sex size dimorphism (SSD) phenomenon in tench. Conclusion. Presented results shed new light on mechanisms of functioning of tench somatotropic axis and constitute benchmark information for future experiments on nutritional factors.

Background. Genetic traceability of seafood as well as population identification using molecular methods provide useful information about the fish origin and are important for protection of overfished populations, as well as for monitoring illegal, unreported, and unregulated (IUU) fisheries. The presently reported study focused on Indian mackerel, Rastrelliger kanagurta (Cuvier, 1816)—a pelagic species with a wide range of distribution—especially important for many tropical countries, such as India, Philippines, and Thailand. This paper is the first part of a larger project: ”Development of a genetic-based system for identification of food products from fisheries and aquaculture introduced to the European Union customs area”. Materials and methods. Samples consisting of fin fragments of Indian mackerel were obtained from local markets in Thailand (MTH), Vietnam (SVN), Cambodia (SKH), and Madagascar (SMG) within 2012–2013. Two genes were analysed: nuclear rhodopsin gene (RH1) and mitochondrial D-loop (D-loop) region through RFLP analysis simulation and sequencing. Additionally, the samples from Cambodia and Madagascar were analysed with eight microsatellite loci (SSR). The data processing was aided by GenAlEx 6.5 and GeneClass2 software. Results. A comparison of the RH1 gene section revealed a total homology among the studied samples. A comparative analysis of D-loop sequences in the studied groups revealed intrapopulational diversity for MTH-, SKH-, SMG-, and SVN samples, at the level of 1, 1, 0.5, and 0.6 percentage points, respectively. Furthermore, the D-loop sequences identified a characteristic restriction site for SMG population. Based on the allele frequencies, we randomly assigned selected individuals to their original populations. GeneClass2 software correctly assigned only 16 out of 21 individuals to either the Cambodian or the Madagascar population, which jointly constituted 76% of all samples. We demonstrated, using AMOVA and GenAlEx 6.5, that the highest level of variability occurred among individuals within the respective populations, while the lowest interpopulation diversity was between the SMG and SKH populations. Conclusion. Our results may help the relevant authorities in the countries of the European Union to identify Indian mackerel and especially its products and trace them to the respective locality. Our findings may also be used for species-specific conservation measures hopefully undertaken by fisheries authorities of the countries where we took our samples. Results on other fish species, prepared in the frames of the same project, will be presented in other papers that will follow soon.

The genetic variability of whitefish, Coregonus lavaretus (L.), was studied based on 114 individuals from nine populations inhabiting Polish lakes, including the Szczecin Lagoon, and from one population each from lakes in Austria and Switzerland. Differences within and among populations were assessed with mitochondrial ND-1 gene sequences that were PCR amplified and digested with ten restriction enzymes. The ten composite haplotypes obtained were sequenced and analyzed with MEGA4 software. The highest intrapopulation variability was noted in the whitefish populations inhabiting lakes Insko, Miedwie, Marianowo, Wisola, Œremskie, Morzycko, the Szczecin Lagoon, and Lake Lucerne, which possessed from two to five composite haplotypes. In contrast, populations inhabiting lakes Woœwin, Czarne, and Traunsee were fixed for the most common haplotype H2.

Background. The presently reported finding of leopard pleco, Pterygoplichthys gibbiceps (Kner, 1854) (Loricariidae), in open waters of the Brda River in the centre of Bydgoszcz, constitutes the first record of a south-American loricariid fish species in Poland. The specimen found is described and illustrated. The finding is discussed in association with other alien species sightings in Poland. The described leopard pleco is possibly the next example of an emerging alien fish species in inland Polish waters.

Global consumption steadily increases due to development of aquaculture but also more efficient fisheries sector. Therefore, fish processing plants and ultimately consumers face products from new fish species which significantly differ in case of their nutritional values, technological or culinary properties. The aim of the study was to randomly collect specimens of bigeye sea perch, Helicolenus barathri; New Zealand sole, Peltorhamphus novaezeelandiae; white bass, Morone chrysops; thicklip grey mullet, Chelon labrosus and ridge scaled rattail, Macrourus carinatus and provide multidimensional characteristics i.e. species authentication, proximate assessment, structure and texture analysis as well sensory evaluation. Study confirmed authenticity of all fish samples and new DNA barcodes were introduced into database of fish profiles. Chemical composition of fillets differed significantly among species, and the unfavourable nutritional values had ridge scaled rattail, bigeye sea perch and New Zealand sole which had unfavorable fatty acid profile, high atherogenic (AI) and thrombogenic (TI) indexes, and low hypocholesterolemic to hypercholesterolemic acids ratio. On the other hand, fillets of freshwater white bass had the best PUFA:SFA ratio, and favourable TI and AI indexes from the consumer’s health point of view. Moreover, fillet of the white bass was selected by panellists as the most desirable. Structural analysis also revealed different degree of undesirable changes in fillets observed as breakdown of myofibrils and connective tissue. Multidimensional analysis characterized randomly selected sample and provided a set of useful information both for customers and fish processing sector.

Characterization of asymptomatic KHV carriers may help understand virus transmission and storage. Such information allows farmers to minimize KHV on farms where this virus is present, also in common carp (Cyprinus carpio) monocultures. As asymptomatic KHV carriers, freshwater mollusks from the Unionidae family (swan mussels, Anodonta cygnea) and crustaceans from the Gammaridae family (scud, Gammarus pulex) were studied because of their unique method of feeding by accumulating bacterial and viral particles. The KHV genome was detected by nested PCR and confirmed by PCR recognizing the KHV glycoprotein gene in ORF 56 (KHV-U). Both PCR and nested PCR, which recognize the KHV thymidine kinase gene, always produced negative results in the swan mussels and scud samples.

The effect of carp feeding with n-3 PUFA-enriched feed (Schizochytrium sp. meal or salmon oil) on nutritional quality indicators (proximal composition, fatty acid profile of fat) and culinary quality (color parameters, texture, sensory properties) was evaluated. Highly significant effects of carp nutrition on chemical composition and fat characteristics, L* and a* color parameters, muscle fiber size, endomysium thickness, moisture and taste of fillets were determined. Fillets obtained from carps fed with the experimental feed contained less protein and more crude fat and had larger muscle fibers, but scored more highly in the sensory evaluation of moisture and fishy taste. In the fat of carp fed the enriched feed, a greater share of total PUFA, n-3 PUFA, total EPA and DHA, n-3/n-6 ratio, and a smaller share of total MUFA were observed compared with control fish. However, no effect of nutrition on the texture of carp fillets, assessed either instrumentally or using sensory methods, was found. The use of Schizochytrium sp. meal as a source of EPA and DHA gave much better results than salmon oil, as it allowed a higher content of these valuable fatty acids to be achieved, without compromising quality.