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Cyprinid herpesvirus 2 (CyHV-2) is the agent of herpesviral haematopoietic necrosis (HVHN), a serious disease affecting two fish species of the Carassius genus, i.e. goldfish (C. auratus) and Prussian Carp (C. gibelio). In Poland, no asymptomatic vectors of CyHV-2 and no farms in which the virus would cause mortalities have been identified. In 2016 and 2017, mass mortalities of ornamental varieties of C. auratus were observed in a cage culture submerged in a channel receiving post-cooling water from the Dolna Odra power plant (north-western Poland). End-point PCRs and sequencing of the mA marker confirmed the presence of CyHV-2 DNA in the gills and pool (kidney, liver, gut and spleen) samples collected from four ornamental types of goldfish, i.e. Veiltail, Wakin, Red Cap Oranda and Ranchu imported from Thailand and UK. Further analysis revealed that the obtained sequences represent a new type of a 295-bp mA sequence (RSD-PL, GenBank accession no. KX852452.1), which had the greatest similarity to the AMS-8 and FR types of CyHV-2 identified in diseased fish imported from Israel and Asia, respectively. Additionally, our study identified common carp (Cyprinus carpio) individuals reared in neighbouring cages as asymptomatic carriers of CyHV-2. The virus was not detected in fish, i.e. ide (Leuciscus idus), perch (Perca fluviatilis), pumpkinseed (Lepomis gibbosus) and common bleak (Alburnus alburnus), collected from the environment of the power plant discharge channel. Identification of CyHV-2 is the first case reported in Poland and the only one in which blood, gills and pool samples of common carp were CyHV-2-positive. Our study identified the cause of mortalities of ornamental goldfish in cage culture, but also shed a new light on issues concerning the species-specificity of CyHV-2.

Giant mottled eel (Anguilla marmorata) farming in Vietnam is a multistage process starting from wild harvest of glass eels through the so-called "hatcheries" and distribution centres from which individuals are transferred to rearing farms and subsequently sold by one eel farm to another every 3-5 months. The information on viral agents spread and persistence in the Vietnamese eel aquaculture is scarce. Therefore, the mortality of A. marmorata at the Van Xuan Farm was the prerequisite to identify the possible aetiologic agent and additionally to formulate first recommendations for viral disease screening in the Vietnamese eel aquaculture. Juvenile giant mottled eels with haemorrhagic lesions in the skin and liver, and hyperaemia of the gut were tested with qPCR and end-point PCR for AngHV-1 presence. Here, we report the first detection of AngHV-1 associated with mortality in giant mottled eel in winter and spring seasons. On the basis of the obtained results, we recommend to test eel seeds in "hatcheries," since tropical eel farms operate in interconnected scheme and monitoring of AngHV-1 prevalence requires well-implemented measures. Disease screening in the rearing centres and on-growing facilities should be based on everyday health checks, including by-catch fish used as a base of the feeding programmes at eel farms in Vietnam.

Sustainable freshwater aquaculture has been recently gaining attention owing to the potential of nourishing the world. The study aimed to evaluate the influence of finishing diets on the activity of 21 genes involved in hepatic lipid metabolism and intestinal homeostasis, liver and intestine histology, and the level of eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids in common carp fillets. We compared two experimental diets: control diet mimicking a commercial feed (CTRL) and a test diet (CB) fortified with EPA and DHA retrieved from salmon by-products. An additional control (eCTRL) from extensively cultured carps was investigated. The study revealed that the expression of seven hepatic genes, e.g.,lipoprotein lipaseandfatty acid synthase, and six intestinal genes e. g.,claudin-3candγ-glutamyl transpeptidase, was influenced specifically by the experimental diets and farming type. Fish from the eCTRL group had the smallest hepatocytes and the largest nuclei compared with CTRL and CB. No pathological signs were found in intestine samples. Additionally, the levels of EPA and DHA in fillets were significantly higher in fish receiving CB compared with CTRL and eCTRL. The use of fortified diets is a promising solution to produce freshwater species with enhanced nutritional value without compromising the safety of fillets.

The aim of the study was to present a comprehensive characterisation of crayfish meat, which is crucial to assess its potential usefulness in the food industry. To this end, we assessed the yield, basic chemical composition (protein, fat, minerals), nutritional value (amino acid and fatty acid profiles, essential amino acid index (EAAI), chemical score of essential amino acids (CS), hypocholesterolaemic/hypercholesterolaemic ratio (h/H), atherogenicity (AI) and thrombogenicity (TI) indices), as well as culinary value (lab colour, texture, sensory characteristics, structure) of the meat of spiny-cheek crayfish (Faxonius limosus) (n = 226) from Lake Sominko (Poland) harvested in May&ndash, September 2017. Crayfish meat, especially that from the abdomen, was shown to have high nutritional parameters. It is lean (0.26% of fat), with a favourable fatty acid profile and a very high quality of fat (PUFA (sum of polyunsaturated fatty acids):SFA (sum of saturated fatty acids), n-6/n-3, h/H, AI, TI) and protein (high CS and EAAI). It is also a better source of Ca, K, Mg, Na, P, and Cu than meat from slaughter animals. Hence, crayfish meat can be an alternative to livestock meat in the human diet. Owing to its culinary value (delicateness, weak game flavour, and odour), it meets the requirements of the most demanding consumers, i.e., children and older people.

Demand for omega-3 long chain polyunsaturated fatty acids has become global challenge for aquaculture and different components have been used to increase nutritional value of fillets. The aim of this study was to evaluate influences of feeds on zootechnical parameters, biochemical plasma parameters, expression of lipid-dependent genes, hepatocyte histomorphologies, and fatty acid profiles in common carp fillets. We compared a control diet (CTRL), mimicking a commercial feed formulation for common carp, with three diets containing blends of vegetable oils and a DHA-rich alga (Schizochytrium sp.) included at 3.125% (CB1) or 1.563% (CB2), and 2.1% salmon oil (CB3). The study revealed no differences in final body weight of fish fed CB1-3 diets in comparison with significantly lower CTRL. Concentrations of all biochemical parameters in plasma increased gradually in fish fed CB1-3 diets when compared to CTRL diet, with exception of triacylglycerol levels. Expression of hepatic fas, elovl-5a and pparα genes increased significantly in fish fed CB1 and CB2. Additionally, eicosapentaenoic (EPA) and docosahexaenoic acid (DHA) accumulation in muscle tissue was directly proportional to the amounts supplied in the diets. Our study revealed that carp fillet profiles can be manipulated for DHA and EPA-contents using enriched diets, depending on the source of fat.

Homogeneous background (age, sex, genetic lineage, culture conditions) was created to clearly demonstrate the impact of the tested dietary treatments. No feeds optimized for the rearing of the tench (Tinca tinca L. 1758) are available. Feeds are formulated to increase the growth rate or eliminate skeletal deformations. With the increasing prices of the basic components, fish meal (FM) and fish oil, poultry by-product meal (PBM) can be used. The aim of the study was to evaluate the effects of substitution of FM with PBM on the tench blood parameters, body composition and structure of skeletal muscles. Cage-reared female tenches (325 ± 18 g) were fed for 86 days with five types of feeds with 0% (control), 25.7%, 48.6%, 71.4% and 100% substitution of FM with PBM. No significant differences between the formulations were reported for weight, total length, fillet weight, visceral, liver, gonado-somatic, proximate composition and biochemical blood parameters. However, significant differences were found in the fillet profiles of fatty acids—an increase in the PBM content correlated with an increase in saturated and monounsaturated fatty acids and a decrease in n-3 PUFA and, generally, n-6 PUFA. Significant differences were also observed in, for example, the content of intramuscular fatty tissue and the level of organ lipidosis between the control variant (0% PBM) and that with 100% substitution. A sensory assessment indicated a higher gustatory value of the fillets in the case of feeds with 48.6% and 71.4% substitution.

Catch and consumption of torpedo scad (Megalaspis cordyla) over the western Indian Ocean, but also the western Pacific from Japan to Australia is constantly increasing. Taking into account the degree of exploitation and missing information on the population structure of torpedo scad stocks it is crucial to provide population data. The analysis included individuals obtained in 2012 and 2013 from local markets in Madagascar, Tanzania, Vietnam and Cambodia and after successful DNA extraction fragment of the nuclear rhodopsin gene (RH1) and 9 microsatellite regions (SSRs) were amplified and analysed. Based on the obtained results it was found that there was no 100% overlap between the compared RH1 sequences and those from GenBank. In the case of the studied SSRs, the results allowed the initial characterisation and assessment of the genetic diversity of populations. Moreover, population assignment test distinguished the studied populations into two geographically distant subpopulations.

Background. White sturgeon iridovirus (WSIV) is one of the most serious threats for sturgeon aquaculture as the mortality in juvenile individuals can reach 95%. At the turn of the century WSIV was reported among hatchery-raised white sturgeon, Acipenser transmontanus Richardson, 1836, in North America, Russian sturgeon , Acipenser gueldenstaedtii Brandt et Ratzeburg, 1833, in northern Europe but also pallid sturgeon, Scaphirhynchus albus (Forbes et Richardson, 1905) and shovelnose sturgeon, Scaphirhynchus platorynchus (Rafinesque, 1820) in North and South Dakota. The clinical signs of infection include cessation of feeding and edematous and pale gills. Those pathological changes lead to respiratory problems of the juveniles and deterioration of their overall condition. Rapid detection of pathogen particles under aquaculture conditions is crucial, therefore the principal aim of this study was to establish a molecular method for rapid and effective detection of the WSIV. This is the first study thoroughly comparing WSIV detection methods in sturgeons cultured in Poland, Germany, and Italy. Materials and methods. A total of 244 samples were collected from 82 sturgeons representing six species: beluga, Huso huso (Linnaeus, 1758); sterlet, Acipenser ruthenus Linnaeus, 1758; Siberian sturgeon, Acipenser baerii Brandt, 1869; Russian sturgeon, A. gueldenstaedtii; Atlantic sturgeon, Acipenser oxyrinchus Mitchill, 1815; and European sea sturgeon, Acipenser sturio Linnaeus, 1758, as well as five sturgeon hybrids: Siberian × Russian, Adriatic (Acipenser naccarii Bonaparte, 1836) × Siberian, Adriatic × beluga, Siberian × sterlet, and beluga × sterlet. The samples were screened for the WSIV using conventional PCR, real-time PCR, and in situ hybridization (ISH) methods. Results. In total, positive results were obtained in 231 (94.67%) out of 244 analysed samples, except for H. huso where DNA of WSIV was not identified. DNA of WSIV was most frequently detected in the kidney (97.92%), intestine (97.50%), skin (94.97%), and gills (93.29%). The most effective method for detecting DNA of WSIV in sturgeons was real-time PCR (92.62% of), PCR (90.98%), and ISH (49.24%). Conclusion. The host range of the WSIV seems to be wider than expected, however, further studies are necessary since no clinical symptoms were observed in sturgeons and their hybrids.

Declines across global fishery stocks forced aquaculture feed manufacturers to search for new and sustainable components. Therefore, the aim of study was assessing nutritional value and sensory properties of meat of common carp (Cyprinus carpioL.) fed for 116 days with two blends. The control feed contained 5% of fishmeal and vegetable oils (rapeseed and soybean) as sole fat sources. While in the experimental diet half of the fishmeal was replaced with a blend of microalgae (Spirulinasp.,Chlorellasp.), macroalgae (Laminaria digitata) and vegetable oil was replaced with salmon oil. Proximate composition, energy value, fatty acid profile of meat, nutritional characteristics of fat and protein as well as culinary properties of fillets were assessed. Fillets of carp fed experimental diet had a higher level of protein, lower level of fat and energy value. Intramuscular fat of fish fed with the experimental diet had a better parameters of quality. Protein in the meat of fish from both groups was characterized by a high quality comparing to the protein standard. Our study showed that meat of carp fed with experimental feed enriched with sustainable and natural feed ingredients can be a sensorily attractive source of nutritious ingredients in the human diet.

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.

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.

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.

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.

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.