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The salmon feed composition has changed the last decade with a replacement of traditionally use of fish oil and fishmeal diets with vegetable ingredients and the use decontaminated fish oils, causing reduced concentrations of dioxins and dioxin-like PCBs in farmed Norwegian Atlantic salmon. The development of novel salmon feeds has prompted the need for prediction on dioxins and dl-PCB concentrations in future farmed salmon. Prediction on fillet dioxins and dl-PCB concentrations from different feed composition scenarios are made using a simple one-compartmental transfer model based on earlier established dioxin and dl-PCB congener specific uptake and elimination kinetics rates. The model is validated with two independent feeding trials, with a significant linear correlation (r 2 = 0.96, y = 1.0x, p < 0.0001, n = 116) between observed and predicted values. Model fillet predictions are made for the following four scenarios; (1) general feed composition of 1999, (2) feed composition of 2013, (3) future feed composition with high fish oil and meal replacement, (4) future feed composition with high fish oil and meal replacement and decontaminated fish oil. Model predictions of fillet dioxin and dl-PCB concentrations from 1999 (1.05 ng WHO 2005 -TEQs kg −1 ww) and 2013 (0.57 ng WHO 2005 -TEQs kg −1 ww) are in line with the data observed in national surveillance programs of those years (1.1 and 0.52 ng WHO 2005 -TEQs kg −1 ww, respectively). Future use of high replacement and decontaminated oils feeds gave predicted fillet concentrations of 0.27 ng WHO 2005 -TEQs kg −1 ww, which is near the limit of quantification. [ABSTRACT FROM AUTHOR]

Abstract: The effects of feeding six diets spiked with increasing levels of DON for 45days to zebrafish (Danio rerio) on performance and liver gene biomarkers were investigated. In addition long term effects on fecundity, offspring larvae swimming activity and global DNA methylation in embryos were investigated. Zebrafish performance was not affected. Liver CYP1A mRNA levels were significantly higher in fish fed 2.0ppm DON compared to the control group, 0.1, 0.5 and 1.5ppm group. Gene transcripts of CuZn SOD and Cyclin G1 increased with increasing content of dietary DON. The percentage of 5-methylcytosine in embryos did not differ and was 7.0–7.1% across the groups. Fecundity showed a biphasic response pattern. Interestingly, fish fed 1.5ppm DON had 22% higher fecundity compared to control. A trend towards increased larvae swimming activity was seen in the high DON group. Our data suggest that DON is detoxified in the liver through the phase 1 system resulting in a disturbance in the oxidative balance. We do not know if effects observed on fecundity and larvae swimming activity are attributed to a direct interaction of DON with the reproductive organ or secondary to the maternal/paternal liver oxidative imbalance. [Copyright &y& Elsevier]

Genetically modified (GM) plants were first grown commercially more than 20 years ago, but their use is still controversial in some parts of the world. Many GM plant varieties are produced in large quantities globally and are approved for use in fish feeds both in Norway and the European Union. European consumers, however, are skeptical to fish produced by means of GM feed ingredients. Concerns have been raised regarding the safety of GM plants, including potential toxicity and (or) allergenicity of the novel protein, potential unintended effects, and risk of horizontal gene transfer to other species. This review will present the current state of knowledge regarding GM plants as fish feed ingredients, focusing on fish performance and health as well as the fate of the GM DNA fragments in the fish, identifying limitations of the current work and areas where further research is needed. Les plantes génétiquement modifiées (GM) ont commencé à être cultivées commercialement il y a plus de 20 ans, mais leur utilisation reste controversée dans certaines régions du globe. Plusieurs variétés de plantes GM sont produites en grande quantité à l'échelle mondiale et sont acceptées dans la préparation de la nourriture de poissons, tant en Norvège que dans l'Union européenne. Les consommateurs européens maintiennent cependant une certaine inquiétude concernant les poissons produits par l'usage d'ingrédients alimentaires GM. On a manifesté des préoccupations en ce qui a trait à l'innocuité des plantes GM, en particulier à la toxicité et (ou) l'allergénicité potentielles des protéines nouvelles, aux effets potentiels imprévus et au risque de transferts horizontaux des gènes aux autres espèces. Notre rétrospective résume l'état actuel des connaissances sur les plantes GM utilisées comme ingrédients dans l'alimentation des poissons, avec une emphase particulière sur la performance et la santé des poissons, ainsi que sur le sort des fragments d'ADN GM chez les poissons, tout en soulignant les limites des travaux actuels et en identifiant les domaines de recherche additionnelle nécessaire. [ABSTRACT FROM AUTHOR]

Vegetable protein sources like soybeans, canola and maize gluten are good alternatives to fish meal. However, a large proportion of such products available on the international market may possess genetically modified (GM) components. This report concerns a study to investigate the fate and survival of ingested GM soy DNA fragments (120 and 195 bp) and a 180-bp fragment of the lectin gene of soybean (Glycine max) during feeding trials with Atlantic salmon post-smolt. Specifically, the study focused on the fate of selected GM soy DNA fragments from feed to fish to investigate their survival through the fish gastrointestinal (GI) tract and whether the DNA could be traced in a variety of fish tissues. Fish were fed three experimental diets for 6 weeks, which were formulated from defined components and represented either GM or non-GM materials (17.2% of the fish meal was replaced with either GM or non-GM soy). A control diet composed of fish meal as the only protein source was used for comparison purposes. The transgenic sequences (120 and 195 bp) and the lectin gene (180 bp) could be detected in the GM soy feed. In the fish GI tract, however, only the smaller DNA fragment (120 bp) could be amplified from the content of the stomach, pyloric region, mid intestine and distal intestine. No transgenic or conventional soy DNA fragments could be detected in liver, muscle or brain tissues resected from sacrificed fish. The sensitivity limit of the method was evaluated to be 20 copies. These data indicate that GM soy transgenic sequences may survive passage through the GI tract but that they cannot be traced in fish tissues. [Copyright &y& Elsevier]

The present study aims to elucidate interactions between glucose and alanine and their influence on pentose phosphate pathway (PPP) activity, using primary cultures of Atlantic salmon hepatocytes. Hepatocytes were exposed to either glucose or alanine for 24 h in different concentrations and combinations. High glucose concentration (10 mM) resulted in significant increased 6-phosphogluconate dehydrogenase (6PGDH) (EC1.1.1.44) and decreased malic enzyme (ME) (EC1.1.1.40) activities compared to physiological glucose concentrations (5 mM). Physiological alanine concentrations (5 mM) resulted in significant increased glucose-6-phosphate dehydrogenase (G6PDH) (EC1.1.1.49) enzyme activity compared to low alanine concentrations (0 mM). These results indicate that both glucose and alanine are able to modulate the oxidative part of the PPP in Atlantic salmon hepatocytes, and to inhibit cytosolic ME activity. This modulating effect of glucose and alanine adds to earlier suggestions of PPP being of major importance for the turnover of glucose in Atlantic salmon, and suggests a central role of alanine in the same pathway. However, no interaction between glucose and alanine was found. [Copyright &y& Elsevier]

Demand for n-3 polyunsaturated fatty acids (n-3 PUFAs) exceeds supply. Large-scale studies on effects of season and geography of n-3 PUFAs in marine fish from the Northeast Atlantic Ocean (NEAO) may be used to optimize utilization and improve nutrition security. Using a sinusoid model, seasonal cycles of n-3 PUFAs were determined and found to be species-specific and clearly pronounced for the pelagic zooplankton feeding species. The Greenland halibut showed very little seasonal variation. The n-3 PUFA content in North Sea autumn-spawning (NSAS) herring peaked in summer, while Norwegian spring-spawning (NSS) herring and mackerel had their peak in autumn. A time shift of peaks in n-3 PUFAs between the two herring stocks was detected, likely due to different spawning strategies in addition to a delay of n-3 PUFAs flux in the northern regions of the NEAO. This study demonstrates that consideration of nutrient contents, such as n-3 PUFAs, when organizing and structuring fishery approaches may improve overall nutritional yield. Based on total annual Norwegian fish landings and seasonal variation in n-3 PUFA contents, n-3 PUFAs yield could theoretically be increased from 13.79 kilo ton per year from the current fishing tactics, to 15.54 if the pelagic species were only caught during the time of their seasonal n-3 PUFA peaks. Pelagic fish is a good source for dietary n-3 PUFAs, but harvest timing will also influence n-3 PUFAs intake by human consumers. One portion of fatty fish harvested during winter/spring may not meet the weekly intake reference nutritional guidelines for n-3 PUFAs. Marine n-3 PUFAs yields also varied geographically and decreased southwards, with the lowest values in Skagerrak. This study can serve as a model to understand patterns of reproductive cycles and geographical distribution of n-3 PUFAs in fatty fish from the NEAO and the novel approach may be useful to support sustainable, seasonal fishing programmes for optimization of n-3 PUFAs yields. [Display omitted] • Seasonal cycles of n-3 PUFAs were species-specific and pronounced for pelagic fish. • Catching pelagic fish at their n-3 PUFAs peaks may increase nutrient yields. • A weekly portion of fish caught in winter/spring may not provide sufficient n-3 PUFAs. • n-3 PUFAs in marine fish varied geographically and decreased southwards. [ABSTRACT FROM AUTHOR]

The composition of Atlantic salmon feed has changed considerably over the last two decades from being marine-based (fishmeal and fish oil) to mainly containing plant ingredients. Consequently, concern related to traditional persistent contaminants typically associated with fish-based feed has been replaced by other potential contaminants not previously associated with salmon farming. This is the case for many pesticides, which are used worldwide to increase food production, and may be present in plant ingredients. Earlier studies have identified two organophosphorus pesticides, chlorpyrifos-methyl and pirimiphos-methyl, in plant ingredients used for aquafeed production. In the present study, we developed a reliable and sensitive analytical method, based on liquid chromatography coupled to tandem mass spectrometry, for the determination of these pesticides and their main metabolites in warm water (zebrafish) and cold water (Atlantic salmon) species, where possible differences in metabolites could be expected. The method was tested in whole zebrafish and in different salmon tissues, such as muscle, bile, kidney, fat, and liver. The final objective of this work was to assess kinetics of chlorpyrifos-methyl and pirimiphos-methyl and their main metabolites in fish tissue, in order to fill the knowledge gaps on these metabolites in fish tissues when fed over prolonged time. [ABSTRACT FROM AUTHOR]

Abstract Brominated flame-retardants (BFRs) such as polybrominated diphenyl ethers (PBDE) and hexabromocyclododecane (HBCD) are considered hazardous to human health. Due to their persistence, they are still present in the environment and in biota and seafood is major contributor of BFRs to human exposure. Here, we used data from >9700 samples of wild and farmed fish, fish feed and fish feed ingredients collected from the North Atlantic between 2006 and 2016 aiming to investigate factors influencing the risk assessments of BFRs. Due to most representative number of analyses, PBDEs were the main focus of investigation. Mean ∑PBDE in fillet samples ranged from below quantification in Atlantic cod fillet to 2.0 μg kg−1 in Atlantic halibut. The main congener contributing to the ∑PBDE in all species was BDE 47. Factors affecting the level of BFR in seafood were multifaceted, and the levels were within species mainly determined by fish age, geographical origin and time of sampling. BDE 47, 99, 153 and HBCD were selected for margin of exposure (MOE) evaluation. When other sources of BFR than seafood were excluded, our risk assessment showed low risk at the current dietary intake of seafood. However, the dietary intake of BDE 99 may be of concern for toddlers when all sources are considered. The choice of fish species, dietary studies, choice of statistics, as well as exposure from other sources than seafood, were all factors that influenced the final MOE of BFRs. We propose the use of regression on order statistics as a tool for risk assessment, to illustrate means and spreads in large surveillance datasets to avoid the issue of measurements below the limit of quantification. A harmonized, updated evaluation of the risk associated with exposure to BFRs from diet, air and dust is warranted, where the fish species most commonly consumed also is taken into consideration. Highlights • Risk assessment of BDE 47, 99, 153 and HBCD in North East Atlantic seafood indicates low risk at current intake. • BDE 99 could pose a risk at current dietary intake when all exposure sources of brominated flame-retardants are considered. • The large variation in Levels of brominated flame retardants in different Seafood affects the outcome of risk assessments. • Statistical interpretation of surveillance data affect the outcome of risk assessments. [ABSTRACT FROM AUTHOR]

Long-chain omega-3 rich oils from crops genetically modified with algal genes are a promising new source of the omega-3 fatty acid DHA (docosahexaenoic acid; 22:6n-3) in Atlantic salmon diets. In this study, the fish oil and fish meal content were held constant across diets, and conventional canola oil was replaced with DHA canola (DHA-CA) oil in a step-wise manner at 0%, 25%, 50%, and 100% replacement, respectively. Growth of salmon, reared in seawater, from approximately 465 g to 1.5 kg was equal across all dietary treatments. Survival was >98% in all cases, with no difference between the dietary groups. Digestibility of lipids was high, approximately 93% in all dietary groups. Fatty acid retention in whole body was also high, with greater retention of α-linolenic acid (ALA, 18:3n-3) and eicosapentaenoic acid (EPA; 20:5n-3) in groups containing higher proportions of DHA-CA oil. Fillet, liver, and intestinal fatty acid compositions were influenced by the different fatty acid contents of the diets, with progressively higher inclusion of ALA, EPA, and DHA and a higher n-3:n-6 ratio in fish fed the 25%, 50%, and 100% DHA-CA diets. Increased dietary inclusion levels of DHA reduced the conversion to 1-14C labelled ALA to 1-14C EPA in liver cells, but some conversion of ALA to 1-14C EPA was maintained even at high dietary DHA levels. There was also a significant increase in anti-inflammatory pro-resolving lipid mediators, resolvins , with increased dietary DHA-CA. The visual colour impression of both muscle and skin was improved at higher DHA-CA inclusion levels in diets. Overall, our findings demonstrates that DHA-CA oil is an effective ingredient in Atlantic salmon diets in seawater, and that fatty acids (FA) from this oil are incorporated into the fish tissues in a manner equivalent to FA from conventional sources, with positive effects on fillet quality. • Omega-3 rich canola oil is an effective ingredient in Atlantic salmon diets in seawater. • Dietary Omega-3 rich canola oil improved filet quality in Atlantic salmon. • Dietary Omega-3 rich canola oil decreased n-6 fatty acids and increased ALA, EPA and DHA levels in tissues. • Some innate production of EPA is maintained even at high dietary DHA levels. [ABSTRACT FROM AUTHOR]

This study aimed to investigate whether dioxin (TCDD) and methylmercury (MeHg) pose a threat to offspring of fish exposed to elevated concentrations of these chemicals via epigenetic-based mechanisms. Adult female zebrafish were fed diets added either 20µg/kg 2,3,7,8 TCDD or 10mg/kg MeHg for 47days, or 10mg/kg 5-aza-2'-deoxycytidine (5-AZA), a hypomethylating agent, for 32days, and bred with unexposed males in clean water to produce F1 and F2 offspring. Global DNA methylation, promoter CpG island methylation and target gene transcription in liver of adult females and in 3days post fertilization (dpf) F1 and F2 embryos were determined with HPLC, a novel CpG island tiling array containing 54,933 different probes and RT-qPCR, respectively. The results showed that chemical treatment had no significant effect on global DNA methylation levels in F1 (MeHg and TCDD) and F2 (MeHg) embryos and only a limited number of genes were identified with altered methylation levels at their promoter regions. CYP1A1 transcription, an established marker of TCDD exposure, was elevated 27-fold in F1 embryos compared to the controls, matching the high levels of CYP1A1 expression observed in F0 TCDD-treated females. This suggests that maternal transfer of TCDD is a significant route of exposure for the F1 offspring. In conclusion, the selected doses of TCDD and MeHg, two chemicals often found in high concentrations in fish, appear to have only modest effects on DNA methylation in F1 (MeHg and TCDD) and F2 (MeHg) embryos of treated F0 females. [ABSTRACT FROM AUTHOR]

• Co-occurrence of contaminants in marine fish from the North East Atlantic Ocean was assessed. • Concentrations of mercury (Hg), dioxins, PCBs, and PBDEs increased from North to South. • Fish Hg and POPs were positively correlated with sea temperature and sediment contamination. • Pelagic species had high fillet concentrations of dioxins and dioxin-like PCBs. • Benthopelagic and demersal species had high fillet concentrations of Hg. Marine fish from the North East Atlantic Ocean (NEAO) are nutrient rich and considered a valuable economic resource. However, marine fish are also a major dietary source of several contaminants, including persistent organic pollutants (POPs) and heavy metals. Using one of the world's largest seafood datasets (n > 25,000 individuals), comprising 12 commercially important fish species collected during 2006–2019 in the NEAO, we assessed the co-occurrence of elements and POPs, and evaluated potential risks to human consumers. Several positive correlations between concentrations of mercury (Hg), dioxins, polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) were observed. Concentrations of Hg, dioxins, PCBs and PBDEs increased from North to South and associations between marine sediment contamination, sea temperature, and fish Hg and POPs concentrations were identified using multi-linear regression (MLR) models. In general, Hg concentrations in fillet and liver of fish were positively associated with increases in both sediment contamination and sea temperature. POPs concentrations in both fillet and liver were positively associated with increases in sediment contamination, and only POPs concentrations in the liver of benthopelagic and demersal species were found to be positively correlated with sea temperature. Using a probabilistic approach to estimate human contaminant exposure from seafood, we showed that intake of pelagic species posed the highest risk of dioxins and dioxin-like PCBs (DL-PCBs) exposure, while intake of benthopelagic and demersal species posed the highest risk of Hg exposure. This study can serve as a model to further understand the distribution, co-occurrence, and trends of contaminants in seafood harvested from the NEAO and their potential risks to human consumers. [ABSTRACT FROM AUTHOR]

The use of plant-based feeds has introduced undesirables, such as pesticides, that have previously not been associated with seawater farming of fish species such as Atlantic salmon. Earlier wide-scope chemical screening showed that the organophosphate (OP) pirimiphos-methyl (PM-m) is one of the most prevalent pesticides present in commercially produced Atlantic salmon feed. Information on the safe upper limit of background levels of PM-m in Atlantic salmon feeds with regards to possible adverse effect on fish health is lacking. Therefore, Atlantic salmon (132 ± 25 g) were fed graded levels of PM-m spiked feeds (0, 0.35, 1.5, 5, and 22 mg kg−1) in triplicate for 3 months. Adverse effects were assessed on OP target toxic exposure such as plasma choline esterase (ChE), and secondary toxic responses such as lipid metabolism and oxidative stress, as well as general adverse effect parameters (plasma biochemistry, haematology, and growth). Safe limits were set by model-fitting the effect data in a dose-response (lower bound) bench mark dose (BMDL) regression analysis. Fish fed 1.5 mg kg−1 and higher had a significant (p < 0.05) dose-dependent growth reduction, oxidative stress as seen from reduced glutathione ratio, liver damage as seen from plasma alkaline phosphatase, and reduced sum neutral and TAG liver lipids. Inhibition of ChE was observed in fish fed 5 mg kg−1 and above. Disturbance in phospholipid (PL) fatty acid composition and reduced level of liver phosphatidyl choline (PC) occurred at a lower exposure level (0.35 and 1.5 mg kg−1), however this was not dose-dependent as at higher exposure levels (5 and 22 mg kg−1), no significant differences were observed. A safe feed limit (as BMDL) for dietary PM-m was set at 0.14–0.46 mg kg−1 ww feed (daily dose 0.49–1.62 ng kg BW−1 day−1), based on inhibited growth, ChE, glutathione ratio, and sum neutral and TAG liver lipids. When including an estimated uncertainty factor (UF) of five for inter-species variability and extrapolation to chronic exposure, the safe limits are 0.028–0.092 mg kg−1, which is lower than the highest PM-m levels observed in commercially produced salmon feeds (0.038 mg kg−1). Thus indicating a potential risk for disturbance in lipid metabolism when fish are fed plant-based feeds. For the most sensitive lipid response, disturbance in PL metabolism, no certain BMDL could be assessed due to lack of a clear dose-response relationship. • Feed pesticide, pirimiphos-methyl, causes disturbed Atlantic salmon liver phospholipids. • Disturbed liver lipid metabolism occurs before other toxic responses. • Plant ingredients used in commercial salmon feeds are the source for pesticides. • Pesticide levels in commercial feeds are a potential risk. [ABSTRACT FROM AUTHOR]

Plastic pollution has become a major environmental concern due to its omnipresence and degradation to smaller particles. The potential toxicological effects of micro- and nanoplastic on biota have been investigated in a growing number of exposure studies. We have performed a comprehensive review of the main determining factors for plastic particle toxicity in the relevant exposure systems, from publications until including the year 2018. For a focused scope, effects of additives or other pollutants accumulated by the plastic particles are not included. In summary, current literature suggests that plastic particle toxicity depends on concentration, particle size, exposure time, particle condition, shape and polymer type. Furthermore, contaminant background, food availability, species, developmental stage and sex have major influence on the outcome of plastic particles exposures. Frequently reported effects were on body and population growth, energy metabolism, feeding, movement activity, physiological stress, oxidative stress, inflammation, the immune system, hormonal regulation, aberrant development, cell death, general toxicity and altered lipid metabolism. Several times reported were increased growth and food consumption, neuro-, liver- or kidney pathology and intestinal damage. Photosynthesis disruption was reported in studies investigating effects on phytoplankton. For the currently unquantified plastic particles below 10 μm, more toxic effects were reported in all aquatic life, as compared to plastic particles of larger size. Main plastic particle toxicity (PPT) determining factors, as published until including 2018. These nine factors were the most mentioned determining factors for PPT in the combined publications included in this review. Unlabelled Image • Plastic particle toxicity (PPT) factors: concentration, particle size, exposure time • PPT co-factors: Contaminants, food availability, species, developmental stage • PPT: Reduced growth, energy, movement. Stress, inflammation, aberrant development • More PPT reported below particle size 10 μm, as compared to above 10 μm • Amount of plastic <10 μm unquantified in all environmental niches [ABSTRACT FROM AUTHOR]