Monitoring program for pharmaceuticals, illegal substances, and contaminants in farmed fish - Annual report for 2021

This report summarises the monitoring data collected in 2021 on the status of illegal substances, pharmaceuticals and contaminants in Norwegian farmed fish. In 2021, a total of 14135 fish were sampled. Samples examined for illegal compounds were collected at all stages of farming and are representative of farmed fish under production. The samples were analysed for substances with anabolic effects or unauthorized substances. Residues of the dye crystal violet were detected in two samples of salmon. A follow-up investigation conducted by the Norwegian Food Safety Authority (NSFA) concluded with the cause likely being a contamination of the samples during sample taking. No other residues of illegal compounds were found. Samples tested for approved veterinary drugs and contaminants were collected at processing plants and are representative of Norwegian farmed fish ready for human consumption. Residues of the anti-sealice agents cypermethrin, emamectin and lufenuron were found, with concentrations below the respective Maximum Residue Limits (MRLs). Other veterinary drugs, like antibiotics or drugs used against internal parasites were not found. No environmental contaminants were found above the EU maximum level (ML).Monitoring program for pharmaceuticals, illegal substances, and contaminants in farmed fish - Annual report for 2021publishedVersio

Bioaccumulation of mercury and transcriptional responses in tusk (Brosme brosme), a deep-water fish from a Norwegian fjord

High concentrations of mercury (Hg) have been documented in deep-water fish species from some Norwegian fjords. In this study, tusk (Brosme brosme) was sampled from four locations in the innermost parts of Sognefjorden in Western Norway. Total Hg and methylmercury (MeHg) levels were measured in liver tissue. To search for potential sublethal effects of Hg, we characterized the hepatic transcriptome in tusk with high and low levels of Hg bioaccumulation using global transcriptomics analysis (RNA-seq). The results showed that there was a significant correlation between fish weight and accumulated concentrations of MeHg but not total Hg. MeHg accounted for 30–40% of total Hg in liver of most of the fish, although at concentrations above 2–3 mg Hg/kg wet weight the percentage of MeHg dropped considerably. Transcriptome analysis resulted in hundreds of differentially expressed genes in the liver of tusk with high Hg levels. Functional enrichment analysis suggested that the top affected pathways are associated with protein folding, adipogenesis, notch signaling, and lipid metabolism (beta-oxidation and phospholipids). Based on transcriptional responses pointing to well-known effects of Hg compounds in fish, the study suggests that tusk in Sognefjorden could be negatively impacted by Hg bioaccumulation.publishedVersio

Mercury bioaccumulation pathways in tusk (Brosme brosme) from Sognefjord, Norway: Insights from C and N isotopes

Seafood is the main source of methylmercury (MeHg) exposure for humans and elevated total mercury (Hg) concentrations have been reported in marine fish from Norwegian fjords compared with offshore areas. Hg in tusk fillets (n = 201) and liver samples (n = 177) were measured in individuals from different habitats including offshore, coastal area, outer and inner Sognefjord. Specifically, the effects of habitat, energy sources and trophic complexity on Hg bioaccumulation pathways in tusk (Brosme brosme) were investigated using stable isotopes of carbon (δ13C) and nitrogen (δ15N). The concentrations of Hg in tusk increased from offshore towards inner Sognefjord. While Hg concentrations in sediment were at background levels, tusk fillet samples from 7 of 8 sites in Sognefjord had higher Hg levels than the maximum level set by European Union. Based on these findings, human consumption advice for tusk from Sognefjord was issued by the Norwegian Food Safety Authority. δ13C values in tusk successfully discriminated individuals from different habitats and were positively correlated to Hg concentrations in tusk across individuals, sites and habitats, outlining the potential importance of terrestrial carbon and most likely the atmospheric deposition of Hg from the catchment to the overall Hg bioaccumulation and exposure regime in tusk. Additionally, we postulate that the effects of terrestrial carbon sources increased towards inner Sognefjord and likely influenced Hg bioavailability throughout the food web. In contrast, δ15N values were patchy throughout the fjord system and although trophic position explained some of the Hg variation between individual fish, it was not correlated with Hg variation across sites and habitats. Our results suggest that tusk can accumulate high levels of Hg in fjord ecosystems and that catchment runoff is likely an important driver of Hg bioaccumulation in this species.publishedVersio

Congener-specific accumulation of persistent organic pollutants in marine fish from the Northeast Atlantic Ocean

Bioaccumulation of persistent organic pollutants (POPs) in marine fish may pose a health risk to human consumers. Using data from ∼8400 individuals of 15 fish species collected in the North-East Atlantic Ocean (NEAO), we assessed concentrations of individual POP congeners, including dioxins, polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs). POPs analyses were performed with accredited methods using high-resolution gas chromatography/high-resolution mass spectrometry, gas chromatography/tandem mass spectrometry (GC-MS/MS) and GC/MS. The results showed that POPs congener composition profiles were more influenced by fish species than by geography. However, due to long range transport from emissions at lower latitudes, lighter congeners made a larger contribution to the total POPs concentrations in the northernmost areas compared to southern regions. A model was developed to elucidate the relative effects of several factors on POPs concentrations and showed that variation among and within fish species was associated with fat content, fish size, trophic position, and latitude. For the first time, POPs concentrations were shown to increase nonlinearly with fat content, reaching an asymptotic plateau when fat content was > 10%. This study explored detailed POP congener profiles and the factors associated with POPs accumulation in commercially relevant fish harvested from the NEAO.publishedVersio

Metabolic effects of diet containing blue mussel (Mytilus edulis) and blue mussel-fed salmon in a mouse model of obesity

Alternative feed ingredients for farmed salmon are warranted due to increasing pressure on wild fish stocks. As locally farmed blue mussels may represent an environmentally sustainable substitute with a lower carbon footprint, we aimed to test the potential and safety of substituting fish meal with blue mussel meal in feed for Atlantic salmon. Salmon were fed diets in which fish meal was partially replaced with blue mussel meal in increments, accounting for up to 13.1 % of the ingredients. Fillets from the salmon were subsequently used to prepare obesity-promoting western diets for a 13-weeks mouse feeding trial. In a second mouse trial, we tested the effects of inclusion of up to 8% blue mussel meal directly in a meat-based western diet. Partial replacement of fish meal with blue mussel meal in fish feed preserved the n-3 polyunsaturated fatty acid (PUFA) content in salmon fillets. The observed blue mussel-induced changes in the fatty acid profiles in salmon fillets did not translate into similar changes in the livers of mice that consumed the salmon, and no clear dose-dependent responses were found. The relative levels of the marine n-3 fatty acids, EPA, and DHA were not reduced, and the n-3/n-6 PUFA ratios in livers from all salmon-fed mice were unchanged. The inclusion of blue mussel meal in a meat-based western diet led to a small, but dose-dependent increase in the n-3/n-6 PUFA ratios in mice livers. Diet-induced obesity, glucose intolerance, and hepatic steatosis were unaffected in both mice trials and no blue mussel-induced adverse effects were observed. In conclusion, our results suggest that replacing fish meal with blue mussel meal in salmon feed will not cause adverse effects in those who consume the salmon fillets.Metabolic effects of diet containing blue mussel (Mytilus edulis) and blue mussel-fed salmon in a mouse model of obesitypublishedVersio

Differences in nutrient and undesirable substance concentrations in Maurolicus muelleri across the Bay of Biscay, Norwegian fjords, and the North Sea

IntroductionWe are having pressing issues of global food insecurity and malnutrition. Mesopelagic communities in the North Atlantic have been estimated to have high biomasses of organisms. Some of these low-trophic organisms are known to be nutrient-dense and may thus contribute to food security and nutrition. Here, we aim to understand the variation in nutrient and undesirable substance concentrations in a common mesopelagic species, Maurolicus muelleri in the North Atlantic Ocean.MethodsWe sampled the M. muelleri from the Bay of Biscay (BB), Norwegian fjords (NF), and the North Sea (NS). The concentrations of micro- and macronutrients, undesirable metals, and persistent organic pollutants (POPs) were measured in composite whole fish samples.ResultsWe found no difference across the sampling areas in the selected micronutrients except that the NF and NS samples had higher vitamin A1 concentrations than the BB samples. The NF samples had higher concentrations of fat, fatty acids, and POPs but lower concentrations of cadmium than the BB and NS samples; the differences in fat and fatty acids were only marginal in the NF-BB pair. The BB samples had lower arsenic concentrations than the NS samples, and lower concentrations of erucic acid and mercury than the NF and NS samples. Comparing the measured values against existing EU regulation values for nutrients and undesirable substances for human consumption, we found that the samples from NS and BB may cause food safety concerns due to their high cadmium concentrations, while the M. muelleri from all the sampling areas are qualified as good sources of iron, selenium, vitamin A1, and ω-3 fatty acids.DiscussionThis study confirms that M. muelleri from the North Atlantic Ocean may play an important role in food security and nutrition. However, potential variations in nutrient and undesirable substance concentrations related to seasonality, fish body size, and maturity level shall be taken into consideration prior to exploiting such a marine resource. Further understanding of trophic ecology, life cycles, and productivity of M. muelleri is essential to investigate the drivers behind the observed variation in nutrient and undesirable substance concentrations

The effect of halide salts on the uptake, deposition and depuration rate of radioiodine in zebrafish (Danio rerio)

Master i ErnæringMAMN-NUNU39

Mercury in fish from the North East Atlantic: sources, bioaccumulation dynamics and co-occurrence with selenium

Mercury (Hg) is a global neurotoxin distributed at trace levels in the earth’s crust. Although Hg input from anthropogenic sources has been reduced in North America and Europe, in some other parts of the world the emission is still high. Considering the longrange transport and long atmospheric half-life, Hg and particularly its most toxic form monomethylmercury (MeHg), remains an environmental concern at the global level causing threat to both wildlife and human health. In general, seafood is the main source of MeHg exposure to humans and Hg is the main reason for seafood consumption advisories. Therefore, measuring the Hg levels in seafood species and understanding the processes governing the variation of Hg levels are very important for seafood safety and security. Synthesis, bioaccumulation and biomagnification of MeHg are very critical processes controlling the MeHg levels in the environment and the biota. The main goals of this study were to investigate how Hg levels vary between different fish species as well as between different communities in offshore, fjord and coastal areas of the North East Atlantic Ocean (NEAO). The contribution from different Hg sources and parameters influencing these variations were also investigated. Large variation in Hg levels between fish species form NEAO was found (Paper I). The pelagic species including Atlantic mackerel (Scomber scombrus) and blue whiting (Micromesistius poutassou) with mean value of 0.04 mg kg-1 ww had the lowest Hg concentrations. Blue ling (Molva dypterygia) had the highest Hg levels with a mean of 0.72 mg kg-1 ww. Selenium (Se) varied in a smaller range compared to Hg, with mean concentrations from 0.27 mg kg−1 ww in Atlantic cod (Gadus morhua) to 0.56 mg kg−1 ww in redfish (Sebastes spp.). The Hg level in fish increased from north towards south in most species and this process was independent of Hg pollution in the environment (sediment). It was hypothesized that a gradual increase in water temperature and primary production duration from the north towards the south are the main parameters governing the intraspecific geographical variation. Fish species collected from fjords and coastal areas contained higher Hg levels compared to the same species sampled offshore. High levels of organic matter and atmospherically deposited Hg washed from the catchment inducing high MeHg production and high Hg bioavailability in fjords and coastal areas were suggested as the main drivers. The Hg variation between species was mostly driven by Hg trophodynamics and δ15N as a proxy for trophic position explained the Hg variation between fish species from different areas in NEAO. The results indicated that the fjord and coastal areas and the Barents Sea had lower Hg levels at the base of the food web while demonstrating higher trophic magnification rates compared to the other areas (PhD thesis). In order to investigate the effect of an industrial point source on environmental Hg levels in a fjord, levels of Hg and MeHg were measured in seawater, sediment and seafood species (fish and crustaceans) close to industrial point source of Hg pollution in Hardangerfjord ecosystem (Paper II). Elevated levels of Hg and MeHg were found in all compartments with increasing levels towards the point source in Sørfjord. However, in predatory species, tusk (Brosme brosme), Hg was accumulated at the same level in the sidearm of Eidfjord, where Hg contamination in sediment is low. Thus, organic matter and atmospheric Hg from the catchment area were suggested as other important drivers of Hg variation in biota in fjord ecosystems. In a continuation of this study, a similar investigation was conducted in Sognefjord with no major pollution source. There, Hg in tusk increased from offshore North Sea to the coast and further into outer and inner Sognefjord, while Hg levels measured in sediment samples were at the background level. Measurements of δ13C, as a proxy for energy/carbon source, showed that the contribution of allochthonous carbon to the food web increases towards the inner fjord and explained the majority of the Hg variation in tusk (Paper III). It is suggested that surplus Se may provide protection against Hg toxicity for consumers. In most fish species from NEAO, Hg and Se were correlated and particularly in species with high Hg levels, this correlation was stronger (Paper I). All species from NEAO on average had higher molar concentrations of Se than Hg, and Se health benefit values (HBVSe) were above 2. In predatory species including tusk and blue ling from the inner part of Hardangerfjord, mean Hg levels were above the European maximum level (EUML) and the HBVSe were negative, indicating higher molar concentration of Hg than Se with a relatively high risk for consumers. Although tusk from Sognefjord also had mean Hg levels exceeding the EUML, while HBVSe values were above 3 in the fillet. Overall in the NEAO, only blue ling had an average Hg level above EUML, and the Hg exposure assessment showed that consumers having two servings of blue ling, tusk and/or Atlantic halibut per week will exceed the tolerable weekly intake (TWI) of MeHg. Consumption of all species from NEAO except Haddock (Melanogrammus aeglefinus), common ling (Molva molva), tusk and blue ling, on average provide more benefit from essential fatty acids than risk from MeHg. In the Hardangerfjord and Sognefjord studies both total mercury (THg) and MeHg were measured in tusk fillet and liver. The MeHg to THg ratio (%MeHg) decreased when THg levels increased in tusk fillet and liver in both fjords, indicating MeHg demethylation as a response to MeHg accumulation (Paper II and III). Our results suggest that inorganic Hg (iHg) produced from MeHg demethylation can bind Se and be stored in fish liver. Discovering the details of demethylation process in marine fish may help better understand the Hg fate and cycling in the food web with implication for food safety and security

Monitoring program for pharmaceuticals, illegal substances, and contaminants in farmed fish - Annual report for 2021

This report summarises the monitoring data collected in 2021 on the status of illegal substances, pharmaceuticals and contaminants in Norwegian farmed fish. In 2021, a total of 14135 fish were sampled. Samples examined for illegal compounds were collected at all stages of farming and are representative of farmed fish under production. The samples were analysed for substances with anabolic effects or unauthorized substances. Residues of the dye crystal violet were detected in two samples of salmon. A follow-up investigation conducted by the Norwegian Food Safety Authority (NSFA) concluded with the cause likely being a contamination of the samples during sample taking. No other residues of illegal compounds were found. Samples tested for approved veterinary drugs and contaminants were collected at processing plants and are representative of Norwegian farmed fish ready for human consumption. Residues of the anti-sealice agents cypermethrin, emamectin and lufenuron were found, with concentrations below the respective Maximum Residue Limits (MRLs). Other veterinary drugs, like antibiotics or drugs used against internal parasites were not found. No environmental contaminants were found above the EU maximum level (ML)

Effects of geography and species variation on selenium and mercury molar ratios in Northeast Atlantic marine fish communities

Methylmercury (MeHg) is a potent neurotoxin that bioaccumulates in seafood. Co-occurrence of selenium (Se) may affect the bioavailability and toxicity of MeHg in organisms. Here we report the concentrations of total mercury (Hg) and Se in 17 teleost fish species (n = 8459) sampled during 2006–2015 from the North East Atlantic Ocean (NEAO) and evaluate species variation and effects of geography. Mean Hg concentration ranged from 0.04 mg kg−1 ww in Atlantic mackerel (Scomber scombrus) and blue whiting (Micromesistius poutassou) to 0.72 mg kg−1 ww in blue ling (Molva dypterygia). Se concentrations were less variable and ranged from 0.27 mg kg−1 ww in Atlantic cod (Gadus morhua) to 0.56 mg kg−1 ww in redfish (Sebastes spp.). The mean Se:Hg molar ratio ranged from 1.9 in blue ling to 43.3 in mackerel. Pelagic species had the lowest Hg concentrations and the highest Se:Hg ratios, whereas demersal species had the highest Hg concentrations and the lowest Se:Hg ratios. Se and Hg concentrations were positively correlated in 13 of the 17 species. Hg concentrations increased from the North to South in contrast to the Se:Hg molar ratio which exhibited the opposite trend. Fish from fjord and coastal areas had higher concentrations of Hg and lower Se:Hg molar ratios compared to fish sampled offshore. All species had average Se:Hg molar ratios >1 and Hg concentrations were largely below the EU maximum level of 0.5 mg kg−1 ww with few exceptions including the deep water species tusk (Brosme brosme) and blue ling sampled from fjord and coastal habitats. Our results show that two fillet servings of tusk, blue ling or Atlantic halibut (Hippoglossus hippoglossus) exceeded the tolerable weekly intake of MeHg although the surplus Se may possibly ameliorate the toxic effects of MeHg. However, some individuals with selenium deficiencies may exhibit greater sensitivity to MeHg