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American mink Neovison vison is one of the most harmful non-indigenous species in Iceland and has been proven to be a useful indirect bioindicator and biomonitor for numerous environmental pollutants. Therefore, the main objective of the study was to determine the total nickel concentration in the spleen of 35 females and 30 males obtained from Brokey archipelago and the south coast of Hvammsfjörður (Dalabyggð, Iceland) using graphite furnace atomic absorption spectroscopy. We also assessed the correlation between nickel concentration and selected anatomical and morphological parameters, hypothesising that invasive alien N. vison is a promising candidate species for biomonitoring the deposition of this trace element. The results indicated a substantial variation in nickel concentration in the spleen tissue of examined animals. For males, the maximum concentration exceeded the average level by more than 16 times, and for females by more than 7 times. The correlation coefficient between morphometric features and the level of nickel concentration in the spleen did not show a significant relationship in any of the tested combinations, for all tested animals or for each sex separately. In conclusion, American mink in Iceland can be considered a promising species for qualitative and quantitative assessment of ecosystems in terms of nickel pollution.

The increase in fish and seafood consumption observed in recent years is a consequence of the growing consumers' awareness of proper nutrition. One of the possibilities to provide fish-friendly, qualitatively attractive (both in terms of nutrition and sensory quality) raw fish materials is the production of hybrids, which would improve production rates without compromising their meat quality. This study compares the carcass and fillet yields of

Climate change will expose the food-producing sector to a range of challenges. Inland aquaculture farms are particularly vulnerable, due to the difficulty in changing their location, and therefore require specific tools to predict the influence of direct and indirect effects on production, environment and economic feasibility. The objective of our study was to apply a simple set of models to produce a set of growth, risk and suitability maps for stakeholders within the common carp sector in Poland, to assist decision-making under two different scenarios of climate change: a moderate situation (RCP 4.5) and an extreme situation (RCP 8.5). We used present (2000-2019) and future projections (2080-2099) for water surface temperature based on land surface temperature data from regionally downscaled climate models to draw maps to: (i) show optimal temperature conditions for carp growth, (ii) assess risk of disease outbreak caused by three important common carp pathogens: Cyprinid herpesvirus 3 (CyHV-3), carp oedema virus (CEV) and spring viremia of carp (SVCV) and (iii) predict potential suitability changes of carp farming in Poland. The study identified areas with the most and least favourable temperature conditions for carp growth, as well as those areas with the highest/lowest number of days with suitable temperatures for virus infection. These suitability maps showed the combined effect of direct and indirect effects of climate change projections under RCP 8.5 and RCP 4.5 scenarios. The approach applied herein will be of use worldwide for analysing the risks of temperature increase to land-based aquaculture, and the results presented are important for carp farmers in Poland and elsewhere, industry in general, and government stakeholders, to understand the direct and indirect effects of climate change on the triple bottom line of people, planet, and profit.

Introduction White sturgeon iridovirus (WSIV) disease is caused by a virus of the eponymous family and is mostly triggered by stressful environmental conditions, i.e. high rearing density, excessive handling, or temporary loss of water. The aim of this study was to develop the most effective diagnostic method for quick and efficient confirmation or exclusion of the presence of WSIV. Material and Methods A total of 42 samples (spleen, gills, intestine, skin, kidney, and brain) were collected from eight sturgeon (Acipenser gueldenstaedtii and A. oxyrinchus) aged ≤5+ farmed or caught between 2010 and 2014 in open waters (Dąbie Lake and Szczecin Lagoon). They were tested for WSIV presence using conventional PCR, qPCR, and in situ hybridisation (ISH). Results In gross examination, all fish appeared to be healthy. Neither species showed clinical signs typical of WSIV infection. In the majority of cases, fragments of iridoviral DNA were found using molecular methods in the kidneys, and also in the liver, gills, and skin. The detection rate using ISH was 47.37% and most commonly the brain and kidney tissues were positive. The most efficient of the methods used was real-time PCR, with 100% effectiveness in detection of WSIV DNA. Conclusion The study demonstrates the capabilities for WSIV diagnosis available to sturgeon farmers and water administrators, indicating useful methods of adequate sensitivity as well as organs to sample in order to achieve the highest probability of viral detection.

Summary The study analyses for the first time the diet composition of grey seals inhabiting the Polish Baltic Sea coast. Samples of seal scat were collected in the Mewia Łacha Nature Reserve at the mouth of the Vistula River. Using genetic and osteological methods, the remains of organisms included in the grey seals diet were analysed for their taxonomy (families and species). Based on the analysis of 49 scat samples from grey seals, 761 hard parts that could be identified by taxon were isolated. The predominant species in the samples were perch, Perca fluviatilis (almost 78% of samples); pikeperch, Sander lucioperca (67%); lamprey, Lampetra fluviatilis (almost 35% of samples); Baltic cod, Gadus morhua callarias (almost 31% of samples) and sea trout, Salmo trutta trutta (26.5%). Genetic analysis confirmed the presence of Atlantic cod DNA in 69% and sea trout in 63% of samples. The genetic material of the Atlantic herring, Clupea harengus has not been identified in the analysed scat samples. Information on grey seals feeding on river lampreys seems to be valuable in the context of lack of knowledge on the occurrence of lampreys in the Vistula River. The methodology used showed that seals fed on species that were the most abundant in the area which is directly associated with the migration cycle of fish. The results of our study allowed the conclusion that the grey seal is an opportunistic predator and its diet reflects and exploits the variations in its habitat.

Overwintering impacts common carp performance, yet the nature of changes is not known. The aim of the study was to compare the zootechnical and key performance indicators (KPI) of Cyprinus carpio wintering in a pond with no supplementary feeding (MCF), in a Recirculating Aquaculture System (RAS) fed typical (30% of protein and 8% of fat) carp diet (AFC), and in a RAS fed high protein (42%) and fat (12%) diet (ABF). The analysis showed that ABF fish had the highest final body weight and the Fulton’s condition factor, as well as the lowest food conversion rate compared with AFC and MCF fish. Histomorphological assessment revealed that MCF fish had thinner skin layers, a depleted population of mucous cells in skin, an excessive interlamellar mass in the gills, and no supranuclear vacuoles in the intestine compared to fish from RAS. At the molecular level, higher transcript levels of il-1β and il-6 transcripts were found in the gills of MCF than in fish from RAS. The transcript level of the intestinal muc5b was the highest in ABF fish. Relative expression of il-1β and il-6 in gills were presumably the highest due to lamellar fusions in MCF fish. Described KPIs may assist carp production to ensure sustainability and food security in the European Union.

Fish biofortification with natural ingredients like iodine-rich macroalgae and selenized-yeast is an excellent strategy to enhance the nutritional quality of farmed fish. This study aimed to assess the effect of frozen storage during 12-months on physicochemical quality of biofortified seabream (Sparus aurata) and carp (Cyprinus carpio). Frozen storage reduced iodine content in biofortified seabream fillets (17%), as well as selenium content in biofortified carp fillets (24%). Yet, biofortified fillets still presented enhanced iodine and selenium contents at the end of the storage period. Increased lipid oxidation (3.45 mg MDA kg-1 for seabream and 2.41 mg MDA kg-1 for carp) and decreased water holding capacity (23-29% for seabream and 14-23% for carp) was observed during storage, whereas major changes in colour and texture occurred after 45 days (seabream) and 225 days (carp) of storage. In general, biofortified fish fillets maintained their nutritional value and quality after 360 days of frozen storage. Highlights: In general, the quality parameters of fish fillets during frozen storage were not relevantly affected by the biofortification strategies; Frozen storage led to increased lipid oxidation of gilthead seabream and common carp fish fillets; Decreased I and Br contents were observed in biofortified seabream fillets during frozen storage; Decreased Se and As contents were observed in biofortified carp fillets during frozen storage; Overall, biofortified fillets maintained acceptable conditions for consumption after 360 days of frozen storage. The research leading to these results has received funding from the European Union’s Horizon 2020 research and innovation programme under Grant Agreement No 773400 (SEAFOODTOMORROW). This output reflects the views only of the author(s) and the European Union cannot be held responsible for any use which may be made of the in- formation contained therein. The authors also thank to i) Gelpeixe, S.A. for providing the installations and resources, allowing the study devel- opment; ii) the Portuguese Foundation for Science and Technology (FCT) supported the contract of PA in the framework of CEECIND/ 01739/2017; iii) the Marine and Environmental Sciences Centre (MARE) through the strategic project UIDB/04292/2020 granted to MARE and under the project LA/P/0069/2020 granted to the Associate Laboratory ARNET; iv) the Portuguese national funds (DIVERSIAQUA MAR 2020 – 16-02-01-FEAM-66; DIVERSIAQUA II MAR 2020 - 02.01.01-FEAMP-0175); v) the project CALIBRA/EYIE (MIS 5002799), which is implemented under the Action “Reinforcement of the Research and Innovation Infrastructures,” funded by the Operational Programme “Competitiveness, Entrepreneurship and Innovation” (NSRF 2014–2020) and co-financed by Greece and the European Union (Eu- ropean Regional Development Fund), and vi) the technical support of the master student Analdeth Marvão. info:eu-repo/semantics/publishedVersion

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.

This paper reports the occurrence of three new fish species, extremely rare in the Baltic Sea, and provides new data on their parasite fauna. The fish collected were Barbus barbus (Linnaeus, 1758), Salvelinus fontinalis (Mitchill, 1814), and Scophthalmus rhombus (Linnaeus, 1758). Their taxonomic identity was confirmed through genetic analyses using DNA extracted from fin clips. The stomach contents were examined, and age was determined by otolith or scale readings. Parasitological examinations focused on the skin, vitreous humour, eye lenses, mouth and nasal cavities, gills, gonads, viscera, and muscles. Furthermore, the changes of fish species composition over 20 years in Pomeranian Bay were analysed. The sequence comparisons against GenBank records revealed that sequences obtained for B. barbus and S. rhombus from Pomeranian Bay represent new rhodopsin barcodes. Record of the juvenile B. barbus in this study is the first in the Baltic Sea. Scophthalmus rhombus is a new host for the ciliate Trichodina jadranica, while Neogobius melanostomus (Pallas, 1814) is a new food item in the diet of S. rhombus in the Baltic Sea. Acanthocephalan Pomphorhynchus laevis found in the adult specimen of B. barbus and myxozoan Myxobolus musculi, noted in the juvenile specimen, have not been recorded previously in this fish species in Polish waters. Species collected as bycatch can potentially be used for monitoring potential changes in the overall fish community structure and biodiversity.

Atlantic and Pacific salmon are frequently consumed species with very different economic values: farmed Atlantic salmon is cheaper than wild-caught Pacific salmons. Species replacements occur with the high valued Pacific species (Oncorhynchus keta, O. gorbuscha, O. kisutch, O. nerka and O. tshawytscha) substituted by cheaper farmed Atlantic salmon (Salmo salar) and Atlantic salmon by rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo trutta). Here we use High-Resolution Melting Analysis (HRMA) to identify eight salmonid species. We designed primers to generate short amplicons of 72 and 116 bp from the fish barcode genes CO1 and CYTB. The time of analysis was under 70 min, after DNA extraction. Food processing of Atlantic salmon (fresh, “Bellevue”, “gravadlax”, frozen and smoked) did not impact the HRMA profiles allowing reliable identification. A blind test was conducted by three different institutes, showing correct species identifications irrespective of the laboratory conducting the analysis. Finally, a total of 82 retail samples from three European countries were analyzed and a low substitution rate of 1.2% was found. The developed tool provides a quick way to investigate salmon fraud and contributes to safeguard consumers.

This study aimed to devise innovative, tailor-made, appealing, tasty and semi-industrialized dishes, using sustainable and under-utilized seafood species (bib, common dab, common carp, blue mussel and blue whiting), that can meet the specific nutritional and functional needs of children (8-10-years), pregnant women (20-40-years) and seniors (≥60-years). Hence, contests were organised among cooking schools from 6 European countries and the best recipes/dishes were reformulated, semi-industrially produced and chemically and microbiologically evaluated. The dishes intended for: (i) children and pregnant women had EPA + DHA and I levels that reached the target quantities, supporting the claim as "high in I"; and (ii) seniors were "high in protein" (24.8%-Soup_S and 34.0%-Balls_S of the energy was provided by proteins), "high in vitamin B12", and had Na contents (≤0.4%) below the defined limit. All dishes reached the vitamin D target value. Sausages_C, Roulade_P, Fillet_P and Balls_S had a well-balanced protein/fat ratio. Roulade_P presented the highest n-3 PUFA/n-6 PUFA ratio (3.3), while Sausages_C the lowest SFA/UNS ratio (0.2). Dishes were considered safe based on different parameters (e.g. Hg-T, PBDEs, Escherichia coli). All represent dietary sources contributing to meet the reference intakes of target nutrients (33->100%), providing valuable options to overcome nutritional and functional imbalances of the three groups., This project has received funding from the European Union's Horizon 2020 research and innovation programme under Grant Agreement no. 773400 (SEAFOODTOMORROW). This work was also supported by the Spanish Ministry of Science and Innovation (Project CEX 2018-000794-S), the Generalitat de Catalunya (Consolidated Research Group Water and Soil Quality Unit 2017 SGR 1404) and Fundação para a Ciência e a Tecnologia (FCT)/Ministério da Ciência, Tecnologia e Ensino Superior (MCTES) through national funds (UID/QUI/50006/2019, UIDB/50006/2020, UIDP/50006/2020, UIDB/04423/2020 and UIDP/04423/2020). The authors also thank FCT and the European Union's H2020 Research and Innovation Programme for funding through the project Systemic - An integrated approach to the challenge of sustainable food systems: adaptive and mitigatory strategies to address climate change and malnutrition. Sara Cunha also acknowledges FCT for the IF/01616/2015 contract. Biotage is acknowledged for providing SPE cartridges and Bekolut for the QuEChERS kits. This output reflects the views only of the author(s), and the European Union cannot be held responsible for any use that may be made of the information contained therein.

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.

Background Recurring escapes or deliberate releases and subsequent infiltration or establishment of feral populations by individuals from fur farms have been commonly noted since the beginning of fur industry expansion. Once animals have invaded ecosystems adjacent to source farms escapees can change the demography of the feral populations through hybridization, outbreeding depression, competition and spreading of various pathogens which can decimate wild populations. In our study, we aimed to assess spread of Aleutian mink disease virus (AMDV) in the feral population of American mink (Neovison vison) in Iceland. The additional objective was to elucidate whether basic morpho-anatomical parameters (i.e., Fulton’s condition factor or spleen to body weight ratio) might be used as a preliminary indicator of AMDV infection. Methods American mink (n = 164) were captured by professional hunters in 8 regions of Iceland. The detection of AMDV in the spleen of male and female individuals was based on PCR amplification of an NS1 gene fragment. Results We confirmed AMDV presence in 23.8% (n = 39) of collected samples with no significant difference in infection rate between males and females. Additionally, we revealed that the prevalence of virus in the feral population was higher closer to fur farms. However, the countrywide prevalence and direction of AMDV distribution needs to be further investigated. Comparison of condition indices in non-infected and infected animals showed significant deterioration of body and spleen parameters in the latter group. Therefore, the application of basic measurements of the American mink may be used to evaluate the health status of individuals in terms of pathogen infection. Conclusions The study shed a new light on prevalence and distribution of AMDV in the feral population of American mink in Iceland and the results might be successfully applied to develop models to infer dynamics of various pathogens, even those latently transmitted by disease-free animals.

Fish fortification with iodine-richmacroalgae(Laminariadigitata) and Selenium-rich yeast is expected to promote nutritional added value of this crucial food item, contributing to a healthy and balanced diet for consumers. However, it is not known if steaming can affect these nutrient levels in fortified fish. The present study evaluates the effect of steaming on nutrients contents in fortified farmed giltheadseabream(Sparus aurata) and common carp (Cyprinus carpio). Fortified seabream presented enhanced I, Se and Fe contents, whereas fortified carp presented enhanced I, Se and Zn contents. Steaming resulted in increased I and Se contents in fortified seabream, and increased Fe and Zn levels in fortified carp, with higher elements true retention values (TRVs >90%). The consumption of 150g of steamed fortified seabream contributes to a significant daily intake (DI) of I (up to 12%) and Se (up to >100%). On the other hand, steamed fortified carp contributes to 19–23% of I DI and 30%–71% of Se DI. These results demonstrate that steaming is a healthy cooking method, maintaining the enhanced nutritional quality of fortified fish. Moreover, the present fortification strategy is a promising solution to develop high-quality farmed fish products to overcomenutritional deficiencies.

Polar and subpolar regions are known for their particular vulnerability and sensitivity to the detrimental effects of non-indigenous species, which is well exemplified by the Nootka lupin (Lupinus nootkatensis) spread in Iceland. Since understanding the population and ecological genetics of invasive alien species offers hope for counteracting harmful biological invasions, the objective of the present study was to investigate interspecific variation in L. nootkatensis in Iceland in relation to a native population in Alaska. Moreover, we aimed to assess whether internal transcribed spacer 2 (ITS2) has sufficient phylogenetic applicability for a large-scale screening of the genetic diversity of a non-indigenous population of this species. This study, which is the first attempt to investigate the genetic diversity of the Nootka lupin in Iceland, included plant samples from eight locations in Iceland and one in Alaska. The analyses included genotyping by sequencing of the 417-nucleotide fragment of the 5.8S ribosomal RNA, ITS2 and part of the large subunit ribosomal RNA (GenBank MT026578-MT026580, MT077004). The main findings showed the presence of five previously unexplained single-nucleotide polymorphisms (SNPs); however, their discriminatory power for Icelandic populations was relatively low, since polymorphism information content (PIC) values ranged from 0.0182 to 0.0526, with average heterozygosity 0.0296. Concomitantly, analysis of multilocus genotypes (MLG) revealed sufficient differences in MLGs variants and their frequency to form genotypic patterns unique for Alaskan and Icelandic populations, revealing an internal genetic structure of the studied group. The proposed SNP panel needs to be supplemented with other nuclear and organellar markers.

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.

Simple Summary Freshwater crayfish species are critical for both local communities and the modern food industry. The study characterised the meat of invasive spiny-cheek crayfish, analysing the yield, basic chemical composition, nutritional value, as well as culinary value. Crayfish meat has high nutritional parameters due to favourable fatty acid and amino acid profiles, as well as balanced mineral content. Crayfish meat is an alternative to livestock meat in the human diet and draws attention of the food industry to the processing of underutilised resources of high-quality aquatic species. Abstract 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–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.

Real-time quantitative reverse transcription PCR (RT-qPCR) is a sensitive and broadly used technique of assessing gene activity. To obtain a reliable result, stably expressed reference genes are essential for normalization of transcripts in various samples. To our knowledge, this is the first systematic analysis of reference genes for normalization of RT-qPCR data in spiny-cheek crayfish (Faxonius limosus). In this study, expression of five candidate reference genes (actb, &beta, actin, gapdh, glyceraldehyde-3-phosphate dehydrogenase, eif, eukaryotic translation initiation factor 5a, ef-1&alpha, elongation factor-1&alpha, and tub, &alpha, tubulin) in muscle samples from male and female F. limosus in spring and autumn was analyzed. Additionally, the most stable reference genes were used for accurate normalization of five target genes, i.e., tnnc, troponin c, ak, arginine kinase, fr, ferritin, ccbp-23, crustacean calcium-binding protein 23, and actinsk8, skeletal muscle actin 8. Results obtained using the geNorm and NormFinder algorithms showed high consistency, and differences in the activity of the selected actb with eif genes were successfully identified. The spring and autumn activities of the target genes (except ak) in the muscle tissue of males and females differed significantly, showing that both sexes are immensely involved in an array of breeding behaviors in spring, and females intensively recover in the autumn season. Characterization of first reference genes in spiny-cheek crayfish will facilitate more accurate and reliable expression studies in this key species.

Seafood is an important component of the human diet. With depleting fish stocks and increasing prices, seafood is prone to fraudulent substitution. DNA barcoding has illustrated fraudulent substitution of fishes in retail and restaurants. Whether substitution also occurs in other steps of the supply chain remains largely unknown. DNA barcoding relies on public reference databases for species identification, but these can contain incorrect identifications. The creation of a high quality genetic reference database for 42 European commercially important fishes was initiated containing 145 Cytochrome c oxidase subunit I (COI) and 152 Cytochrome b (cytB) sequences. This database was used to identify substitution rates of Atlantic cod (Gadus morhua) and common sole (Solea solea) along the fish supply chain in Belgium using DNA barcoding. Three out of 132 cod samples were substituted, in catering (6%), import (5%) and fishmongers (3%). Seven out of the 41 processed sole samples were substituted, in wholesale (100%), food services (50%), retailers (20%) and catering (8%). Results show that substitution of G. morhua and S. solea is not restricted to restaurants, but occurs in other parts of the supply chain, warranting for more stringent controls along the supply chain to increase transparency and trust among consumers. ispartof: FOOD AND CHEMICAL TOXICOLOGY vol:141 ispartof: location:England status: published

Developing tailor-made fortified farmed fish is a promising solution to overcome nutritional deficiencies and increase consumer confidence in these products. This study evaluated the supplementation of three fortified diets with I-rich seaweed and selenised-yeast on essential and toxic elements levels in gilthead seabream (Sparus aurata) and common carp (Cyprinus carpio). Fortified diets resulted in increased I, Se and Fe in fish muscle. Biofortified seabream and carp revealed lower Cu and Br. The reduction of fishmeal and fish oil in fortified diets resulted in lower Hg and Cd in seabream muscle. Contrarily, fortified diets increased As and Hg in carp fillets. The consumption of 150 g of fortified seabream enabled a significantly higher contribution to the daily recommended intake (DRI) of I (10%) and Se (76%) than non-fortified fish, whereas fortified carp fulfilled 23% of I DRI and 91% of Se DRI. Moreover, the exposure to Pb decreased with the consumption of biofortified seabream (23–82% BMDL01) and carp (26–92% BMDL01). These results support the strategy of developing eco-innovative biofortified farmed fish using sustainable, natural, safe and high-quality ingredients in feeds, to enable consumers to overcome nutritional deficiencies without significantly increased feed costs. Highlights: Farmed fish biofortification was successfully achieved through I and Se enriched diets from natural and sustainable sources; Biofortified fish fillets yielded a lower exposure to toxic elements, including Hg, Cd and Pb; Iodine fortification was more efficient in common carp, while Se biofortification was more efficient in gilthead seabream; Consumption of biofortified fish provides higher contribution to the DRI of I and Se, without compromising consumer safety. The research leading to these results has received funding from the European Union's Horizon 2020 research and innovation programme under Grant Agreement no. 773400 (SEAFOODTOMORROW) and Portuguese national funds (DIVERSIAQUA MAR 2020–16-02-01-FEAM- 66). The Portuguese Foundation for Science and Technology (FCT) supported the contracts of AM in the framework of the IF2014 program (IF/00253/2014), as well as the contract of PA in the framework of CEECIND/01739/2017 and the research contract of ALM in the framework of the project FISHBUDGET (PTDC/BIA-BMA/28630/2017). info:eu-repo/semantics/publishedVersion

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.

Background. Automated processing of the fish caught on board a ship can potentially lead to a quality control breach. Specimens visibly infected with parasites are processed, frozen, and directed to the market. On the other hand, the removal of the body elements of taxonomic importance (e.g., fins, head, skin) opens gates to variously motivated seafood frauds. We had been alerted by local veterinary authorities about a fish consignment from the Falklands with a substantial volume of muscles with black contents. Materials and methods. The material for the presently reported study were decapitated, finless, and gutted fish delivered to our lab by the County Veterinarian of Szczecin (Purchased by a local importer from a Spanish fish wholesaler). The fish were labeled as “Pseudophycis bachus (Forster, 1801)”, and allegedly came from the Falklands. After thawing, the fish muscles were dissected, focusing on the distinctly black areas, examined following methods commonly used in parasitology, and observed under a dissecting and a compound microscope. Samples were collected also for molecular studies aiming to disclose the fish taxonomic identity. DNA barcoding gene (cytochrome c oxidase subunit I, COX1) was used to perform the genetic characterization for the collected fish specimens. The degree of similarity between the new records (MT318699 and MT318700) and the other records of Moridae species in the GenBank was assessed by building COX1 gene phylogeny. Results. The muscles contained large galls filled with black fluid. The fluid stained the adjacent muscles. Inside each gall, we found a single female of Sarcotaces sp., several “dwarf” males, eggs, and newly hatched nauplius stages. Using the molecular methods, the fish were identified as Mora moro (Risso, 1810). Conclusion. A preliminary veterinary inspection of the catch on board of fishing vessels may help to avoid huge financial losses when a parasitized fish consignment is rejected by veterinary authorities on land. It is evident that the European regulation regarding fish parasites requires an urgent revision. Mora moro does not occur off the Falklands as declared by the wholesaler. This seafood fraud was probably motivated by the urge to conceal a catch from European waters and thus avoid exceeding national fishing quotas. Species of the genus Sarcotaces require a revision backed by molecular methods.

Summary: Etmopterus spinax is a deep-sea shark species that inhabits the northeast Atlantic and the western Mediterranean Sea. Skagerrak and Kattegat are reported to be part of the distribution of the species, but it has never been noted in the southern Baltic. Lacking any commercial value and commonly discarded in trawl and longline fisheries, E. spinax has been poorly studied. We reported on the first record of one specimen of E. spinax caught in the Pomeranian Bay on October 13, 2016 at a depth of 10 m. It was a female measuring 42.7 cm in total length. The morphological examination of the specimen was supported with COI barcode analysis, whereas species assignment to the population of origin was conducted based on a control region (CR) sequence of mtDNA. COI and CR sequence searches against GeneBank confirmed its identity as E. spinax and revealed that the specimen shared identical haplotypes with fish from populations in the Azores, Rockall Trough, and west of Ireland in the northeast Atlantic. The stomach contents, parasitic fauna, and hepatosomatic index of the individual were also examined. Only one L3 larval Anisakis simplex nematode specimen was collected from the stomach lumen of the shark. The specimen could have arrived in the Pomeranian Bay along with an inflow from the North Sea. In December 2014, a strong Major Baltic Inflow brought large amounts of water into the Baltic Sea, followed by some inflows of moderate intensity. Keywords: Etmopterus spinax, Anisakis simplex, Pomeranian Bay, Southern Baltic Sea, Inflow from the North Sea

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.

The tench ( Tinca tinca L., 1758) is a promising freshwater species in which numerous studies have been conducted recently to develop a dedicated feed for optimized growth rate. The aim of this study was to assess the stability of seven candidate reference genes, including 18S ribosomal RNA (18S rRNA), β-actin ( actb ), α-tubulin ( tuba ), ribosomal protein l8 ( rpl8 ), 40S ribosomal protein s11 ( rps11 ), glyceraldehyde-3-phosphate dehydrogenase ( gapdh ) and elongation factor 1 alpha ( ef1a ), to select the best calibrator for nutrigenomic studies that would improve our understanding and illustrate the molecular basis of nutrient-related gene expression in response to feed mixes in the tench. An additional aim was to verify the hypothesis that the functioning of the somatotropic axis in the tench (growth hormone receptor, ghr , and growth hormone, gh ) depends on dietary treatment. The analysis was based on five tissue samples (liver, spleen, gut, heart and muscle) collected from adult tench females fed with 0% and 100% replacement of fish meal (FM) with poultry by-product meal (PBM). The study demonstrated that the most stable genes in most tissues were rpl8 and rps11 , with gapdh showing the greatest stability, along with rpl8 , in the liver. Moreover, a comparison of relative transcript abundance between the tissues revealed that ghr demonstrated the highest expression in the liver, while gh demonstrated the highest expression in the spleen. Based on the selected reference genes, it was determined that the feed did not affect the level of expression of ghr and gh in most tissues except the spleen ( ghr ). The study also involved a phylogenetic analysis based on the amino acid sequences of Rpl8 , Rps11 and Ghr , and it was confirmed that the tench is the most closely related with Asian cyprinids (i.e. Megalobrama amblycephala ). The study identified suitable reference genes for RT-qPCR in the tench, and the effect of two feed variants on the somatotropic axis was determined. The study opens the way for further nutrigenomic studies aimed to develop a feed best matched for the needs of the tench and optimizing its growth. Statement of relevance The effect of feed intake on gene expression in fish species is of particular interest of aquaculture sector which seeks for alternative protein sources, but also new species to adapt for intensive culture. The study demonstrated that the most stable genes in most tissues were rpl8 and rps11 , with gapdh showing the greatest stability, along with rpl8 , in the liver. Comparison of relative transcript abundance between tissues revealed that ghr demonstrated the highest expression in the liver, while gh demonstrated the highest expression in the spleen. Presented work characterizes genes with stable expression across various tench tissue types and identifies suitable reference genes for RTq-PCR for nutrient-related gene expression studies. Presented study was performed for tench for the first time and provides information on influence of poultry by-product meal on the tench organism. Information on tench genetic studies, especially combined with dietary treatments are sparse, therefore presented results address this gap and will bring attention of Aquaculture readers.

Summary The presence of exotic fish species in the Baltic Sea and its tributaries poses a serious threat for native ichthyofauna, mainly due to the spread of new pathogens. As the accurate identification of species is essential for an effective assessment of changes related to the appearance of non-native species in an aquatic environment, in this paper we tested the usefulness of biometrics and molecular markers in identifying a specimen from the Mugilidae family found in the Odra estuary. The results demonstrated that unambiguous identification of the specimen using biometric features was impossible due to high morphological similarities shared by grey mullets. Unambiguous identification was possible only due to molecular markers, e.g. rhodopsin gene, which helped to identify the collected fish specimen as Liza ramada (Risso, 1827), the first specimen of this species found in the Odra River estuary. The presence of an L. ramada specimen in the Odra River – which could signal the expansion of non-native species into wider ranges – may be linked to climate change or human activity.

Spiny-cheek crayfish (Faxonius limosus, Rafinesque, 1817) females and males were examined as an alternative source of highly valuable material currently sought by the food industry. The aim of the study was to assess the profiles of 14 macro- and microelements (Al, Ca, Cd, Cu, Fe, K, Mg, Na, Ni, P, Pb, Se, Si, Zn) in the meat, exoskeleton and eggs (females) of crayfish collected in the spring and autumn seasons in the Lake Sominko (Poland). The content of heavy metals was analysed, and the degree of their accumulation in crayfish tissues was determined. The profile of the investigated elements in the tested samples was variable depending on the body part, sex of individuals and season of sample collection. A portion of crayfish abdomen meat or eggs (100 g) is particularly rich in P (41.5–73.9 %) of daily requirement), Zn (14.1–38.5 %), Mg (7.9–21.5 %), K (3.3–13.1 %) and Na (4.6–7.7 %) and small quantities of Ca (0.8–2.5 %) and Al (0.9–4.7 %). The study confirmed that consumption of crayfish meat is toxicologically safe and nutritionally complete.

Background Conservation 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. Methods Noble 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. Results Microsatellite 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 FST values. 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). Discussion The 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.

Biometric character analyses were conducted on Atlantic sturgeon Acipenser oxyrinchus, a species included in a re-establishment programme in the Baltic Sea basin. The study sought to identify measurable and countable characters most useful for distinguishing A. oxyrinchus from three alien species found in open waters of Poland: Acipenser baerii, Acipenser gueldenstaedtii, and Acipenser stellatus. Measurable characters that contributed most to discrimination included preorbital distance, eye diameter, ventral fin base to anal fin base, and postorbital distance. Among countable characters, the number of lateral scutes made the greatest contribution. The data from the present study may be used to supplement existing systematic keys and lay the foundations for creating a catalogue or atlas of popular species and interspecific hybrids of sturgeon, including their complete systematic determination.