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Assessment of risk and risk-reducing measures related to the introduction and dispersal of the invasive alien carpet tunicate Didemnum vexillum in Norway
Get PDFDidemnum vexillum is colonial sea squirt, a marine species which originates from the northwest Pacific; it was first recorded in Norway in November 2020. Didemnum vexillum is an alien species, meaning that it is a species that has been transferred from its original region to other regions of the world through human activity, and it had not previously been recorded in Norwegian waters. The species is regarded as having great invasive potential and having strong negative ecological effects on biodiversity. It is also considered to pose a risk to marine industries such as shipping and aquaculture, with possible major negative economic impacts.Assessment of risk and risk-reducing measures related to the introduction and dispersal of the invasive alien carpet tunicate Didemnum vexillum in NorwaypublishedVersio
How to obtain clear images from in-trawl cameras near the seabed? A case study from the Barents Sea demersal fishing grounds
Get PDFUnderwater camera systems are commonly used for monitoring fish and fishing gear behaviours. More recently, camera systems have been applied to scientific trawl surveys for improved spatial resolution and less invasive sampling and to commercial fisheries for better catch control and reduced by-catch. A challenge when using cameras in demersal trawls is poor image clarity due to the door and ground gear generated sediment plume. In this study we have measured the height of the sediment plume produced by a large commercial trawl in the Barents Sea using acoustic methods and investigated its effect on in-trawl camera image clarity. The trawl extension was lengthened, and additional buoyancy added to lift the camera system in the aft end of the trawl. The camera system was tested at increasing heights above seabed until no sediment plume was visible in the images. Based on the acoustic data the sediment plume was measured to be on average 4–5 m (SD 1.7 m) above sea floor. Image clarity improved significantly as the camera system clearance from seabed increased from 4 to 11 m. No effect of sediment type on image clarity was identified. The trawl modifications did not affect the trawl’s opening geometry or bottom contact. However, the increased length and angle of the under panel aft in the trawl and in the extension appears to have resulted in reduced water flow and may influence the passage and retention of fish. The feasibility of using camera systems in demersal trawls and this and other solutions for obtaining clear images are discussed.How to obtain clear images from in-trawl cameras near the seabed? A case study from the Barents Sea demersal fishing groundspublishedVersio
Ecological network analysis of traits reveals variable response capacity to stress
Get PDFResponse diversity increases the potential ‘options’ for ecological communities to respond to stress (i.e. response capacity). An indicator of community response diversity is the diversity of different traits associated with their capacity to be resistant to stress, to recover and to regulate ecosystem functions. We conducted a network analysis of traits using benthic macroinvertebrate community data from a large-scale field experiment to explore the loss of response diversity along environmental gradients. We elevated sediment nutrient concentrations (a process that occurs with eutrophication) at 24 sites (in 15 estuaries) with varying environmental conditions (water column turbidity and sediment properties). Macroinvertebrate community response capacity to nutrient stress was dependent on the baseline trait network complexity in the ambient community (i.e. non-enriched sediments). The greater the complexity of the baseline network, the less variable the network response to nutrient stress was; in contrast, more variable responses to nutrient stress occurred with simpler networks. Thus, stressors or environmental variables that shift baseline network complexity also shift the capacity for these ecosystems to respond to additional stressors. Empirical studies that explore the mechanisms responsible for loss of resilience are essential to inform our ability to predict changes in ecological states.publishedVersio
Alkyl-phenanthrenes in early life stage fish: differential toxicity in Atlantic haddock (Melanogrammus aeglefinus) embryos
No full textTricyclic polycyclic aromatic hydrocarbons (PAHs) are believed to be the primary toxic components of crude oil. Such compounds including phenanthrene are known to have direct effects on cardiac tissue, which lead to malformations during organogenesis in early life stage fish. We tested a suite of 13 alkyl-phenanthrenes to compare uptake and developmental toxicity in early life stage haddock (Melanogrammus aeglefinus) embryos during gastrulation/organogenesis beginning at 2 days post fertilization via passive dosing. The alkyl-phenanthrenes were tested at their solubility limits, and three of them also at lower concentrations. Measured body burdens were linearly related to measured water concentrations. All compounds elicited one or more significant morphological defects or functional impairment, such as decreased length, smaller eye area, shorter jaw length, and increased incidence of body axis deformities and eye deformities. The profile of developmental toxicities appeared unrelated to the position of alkyl substitution, and gene expression of cytochrome 1 a (cyp1a) was low regardless of alkylation. Mortality and sublethal effects were observed below the expected range for baseline toxicity, thus indicating excess toxicity. Additionally, PAH concentrations that resulted in toxic effects here were far greater than when measured in whole crude oil exposures that cause toxicity. This work demonstrates that, while these phenanthrenes are toxic to early life stage fish, they cannot individually account for most of the developmental toxicity of crude oil, and that other compounds and/or mixture effects should be given more consideration.publishedVersio
Evolutionary history and seascape genomics of Harbour porpoises (Phocoena phocoena) across environmental gradients in the North Atlantic and adjacent waters
Get PDFThe Harbour porpoise (Phocoena phocoena) is a highly mobile cetacean species primarily occurring in coastal and shelf waters across the Northern hemisphere. It inhabits heterogeneous seascapes broadly varying in salinity and temperature. Here, we produced 74 whole genomes at intermediate coverage to study Harbour porpoise's evolutionary history and investigate the role of local adaptation in the diversification into subspecies and populations. We identified ~6 million high quality SNPs sampled at eight localities across the North Atlantic and adjacent waters, which we used for population structure, demographic and genotype–environment association analyses. Our results suggest a genetic differentiation between three subspecies (P.p. relicta, P.p. phocoena and P.p. meridionalis), and three distinct populations within P.p. phocoena: Atlantic, Belt Sea and Proper Baltic Sea. Effective population size and Tajima's D suggest population contraction in Black Sea and Iberian porpoises, but expansion in the P.p. phocoena populations. Phylogenetic trees indicate post-glacial colonization from a southern refugium. Genotype–environment association analysis identified salinity as major driver in genomic variation and we identified candidate genes putatively underlying adaptation to different salinity. Our study highlights the value of whole genome resequencing to unravel subtle population structure in highly mobile species, shows how strong environmental gradients and local adaptation may lead to population differentiation, and how neutral and adaptive markers can give different perspectives on population subdivision. The results have great conservation implications as we found inbreeding and low genetic diversity in the endangered Black Sea subspecies and identified the critically endangered Proper Baltic Sea porpoises as a separate population.publishedVersio
Refined mackerel oil increases hepatic lipid accumulation and reduces choline and choline-containing metabolites in the liver tissue in mice fed a Western diet
Get PDFIn this study, we aimed to evaluate the impact of consuming refined mackerel oil (MO) from rest raw material on hepatic fat accumulation, glucose tolerance, and metabolomic changes in the liver from male C57BL/6N mice. The mice were fed either a Western diet (WD) or a chow diet, with 30 g or 60 g MO per kg of diet (3% or 6%) for 13 weeks. Body weight, energy intake, and feed efficiency were monitored throughout the experiment. A glucose tolerance test was conducted after 11 weeks, and metabolomic analyses of the liver were performed at termination.publishedVersio
Quantifying diets for small pelagic fish: effects of weight versus occurrence methods and sampling effort
Get PDFIn the Norwegian Sea, assessment of diet composition relies on annual cruise activity combined with visual identification and weight determination of prey from fish stomachs. This weight-based method is labour intensive, and suggestions to reduce cost include moving from the weight-based to the occurrence-based method and/or reducing sampling effort. Studies have suggested that the occurrence-based method may be more robust while providing similar results as the weight-based method. Here we re-analyse data from >14.000 stomachs for herring, mackerel, and blue whiting. We compare diet composition estimates and quantify the uncertainty using both methods. We also quantify the impact of reducing sampling effort (number of trawl stations and fish per station) on the diet uncertainties. Our results confirm that occurrence-based estimates are more precise than those based on weight. In addition, they are better at capturing year-to-year fluctuations. The occurrence-based method provides similar results to the weight-based method. Differences between methods arise primarily from disparities in the mean weight of prey in stomachs. Decreasing the number of stations sampled leads to increased uncertainty, while reducing the sampling effort from 10 to 5 fish per station has little impact on uncertainty estimates. These results provide quantified insights to guide future diet monitoring programmes.publishedVersio
Fish assemblages at the Yermak Plateau and in northern Svalbard waters during the period 2012–2020
Get PDFDuring several surveys covering the north-western and northern Svalbard waters, and the deeper Yermak Plateau north of Svalbard during the period 2012–2020, 291 standardized hauls with a demersal trawl were made. All fishes in the catches were identified to the lowest possible taxonomic level, mostly to species. In addition to the data generated from the trawl catches, bottom temperature, salinity, and depth were recorded at each trawl station. The eelpouts were the most species rich family, with 15 species, followed by codfishes and sculpins with six species each. The other 13 families were represented with one to four species each. Atlantic cod (Gadus morhua) dominated by weight in the catches, while polar cod (Boreogadus saida) dominated by numbers. In the deeper areas including the Yermak Plateau, Greenland halibut (Reinhardtius hippoglossoides) dominated by weight. Zoogeographically, 23 species were Arctic, 5 were Mainly Arctic, 4 Arctoboreal, 25 Mainly Boreal, 9 Boreal, and 2 Widely Distributed. The Arctic species dominated in the deeper areas (Yermak Plateau and slope > 500 m) and on the shallow eastern shelf, whereas the Mainly Boreal species dominated along the slope and on the western and northern shelves < 500 m. A hierarchical cluster analysis revealed three prominent station clusters consistent with the zoogeographical classifications which reflected the oceanographic conditions, water masses and sea ice. The hierarchical cluster analysis additionally separated the cold-water species into two groups consistent with the bathymetry of the region. Diet studies of Atlantic cod revealed that it mainly fed on hyperiids, and that its preferred food further south, capelin, was not prominent in the diet.publishedVersio
Bioavailability of iodine from a meal consisting of sushi and a wakame seaweed salad—A randomized crossover trial
Get PDFThe consumption of seaweed is on the rise in the Western world. Seaweeds may contain substantial amounts of iodine, and some species could serve as a potential dietary iodine source. However, limited data on the iodine content and in vivo bioavailability of iodine from seaweeds exist. The objective was to assess whether iodine from a meal consisting of sushi with nori, (Porphyra spp) and a wakame seaweed salad (Undaria pinnatifida) had similar bioavailability as a potassium iodide reference supplement of similar iodine content. A randomized 2 × 2 crossover trial (AB/BA model) was conducted in 20 healthy young women. One intervention arm consisted of a meal with sushi and wakame salad (231 μg iodine), and the other of potassium iodide (KI) supplement (225 μg iodine). Urinary iodine concentration (UIC) was measured at 11 different time points for 48 h after the interventions. The UIC increased after consumption of both the sushi and wakame meal and the KI supplement, but the median UIC was higher after ingestion of the KI supplement. The estimated bioavailability of iodine during the first 24 h was 75% from sushi with wakame and 97% from the KI supplement. The bioequivalence analyses confirmed that the KI supplement had higher estimated bioavailability than the sushi and wakame meal, however, with small margins. Our findings on iodine bioavailability imply that sushi and wakame could be potential iodine sources in the diet, which may be favorable for population groups at risk for iodine deficiency. However, further research is needed to account for the variability of iodine content in seaweeds by different locations and degree of processing, to assure that the iodine levels are stable and predictable for the consumers.Bioavailability of iodine from a meal consisting of sushi and a wakame seaweed salad—A randomized crossover trialpublishedVersio
Rømt oppdrettslaks – risikovurdering og kunnskapsstatus 2023 — Ytterligere genetisk endring hos villaks som følge av innkryssing av rømt oppdrettslaks
Get PDFRømming av oppdrettslaks fra oppdrettsanlegg utgjør en trussel mot den genetiske integriteten til de ville laksebestandene. Undersøkelser viser at det er en sammenheng mellom andel rømt oppdrettslaks i et vassdrag og genetisk endring målt som innkryssing med genetiske markører. Det betyr at jo flere rømte oppdrettslaks det er på gyteplassen, desto høyere er sannsynligheten for genetisk endring. I tillegg til andel rømt oppdrettslaks på gyteplassen, kan villaksbestandenes robusthet påvirke nivået av innkryssing. Dette fordi tallrike villaksbestander uten tidligere genetisk innkryssing antakelig er mer robuste overfor rømt oppdrettslaks, siden den rømte oppdrettslaksen der møter større konkurranse fra bedre tilpassete, ville individer. Disse faktorene danner grunnlaget for risikovurderingen for ytterligere genetisk endring hos villaks som følge av innkryssing av rømt oppdrettslaks.Rømt oppdrettslaks – risikovurdering og kunnskapsstatus 2023 — Ytterligere genetisk endring hos villaks som følge av innkryssing av rømt oppdrettslakspublishedVersio