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Increasing depth distribution of Arctic kelp with increasing number of open water days with light
Get PDFKelps are a dominant macrophyte group and primary producer in Arctic nearshore waters that provide significant services to the coastal ecosystem. The quantification of these services in the Arctic is constrained, however, by limited estimates of kelp depth extent, which creates uncertainties in the area covered by kelp. Here, we test the environmental drivers of the depth extent of Arctic kelp. We used Southampton Island (SI), Nunavut, Canada, as an example region after an initial survey found deep Arctic kelp (at depths to at least 50 m) with relatively low grazing pressure within diverse hydrographic conditions. We found abundant rocky substrata, but no influence of substratum type on kelp cover. The kelp cover increased with depth until 20 m and then decreased (the median maximum depth for all stations was 37 m). The best predictor of kelp depth extent was the number of annual open (ice-free) water days with light (r2 = 44–52%); combining depth extent data from SI with published data from Greenland strengthened this relationship (r2 = 58–71%). Using these relationships we estimated the maximum kelp-covered area around SI to be 27,000–28,000 km2, yielding potential primary production between 0.6 and 1.9 Tg Cyr−1. Water transparency was a key determinant of the underwater light environment and was essential for explaining cross-regional differences in kelp depth extent in SI and Greenland. Around SI the minimum underwater light required by kelp was 49 mol photons m−2 yr−1, or 1.4% of annual integrated incident irradiance. Future consideration of seasonal variation in water transparency can improve these underwater light estimations, while future research seeking to understand the kelp depth extent relationship with nutrients and ocean dynamics can further advance estimates of their vertical distribution. Improving our understanding of the drivers of kelp depth extent can reduce uncertainties around the role of kelp in Arctic marine ecosystems.publishedVersio
Utvikling og testing av metoder for å redusere uheldige interaksjoner mellom hval / sjøfugl og notfiskeri - Tokt med MS "Vestbris" 6.-10. januar 2023 i Kvænangen fjord
Get PDFToktet hadde som mål å gjøre forsøk og samle inn data til prosjektene "Bifangst av sjøfugler i kystnært notfiske" (FHF 901751) og "Kartlegging og testing av metoder for å redusere interaksjoner mellom fiskeri og hval" (FHF 901681). Det ble gjennomført forsøk med lydeksponering for å holde hvalen unna nota, undersøkelser av interaksjoner mellom sjøfugl og notfangst og noen opportunistiske forsøk med å skremme bort fuglene fra nota med lyd og lys. I tillegg ble overvåking av fangstprosessen i mørket med lyssensitivt kamera og termisk kikkert testet og vurdert og det ble gjort erfaringer med hvordan lydsystemer kan implementeres ombord på fiskebåtene for å redusere interaksjoner mellom hval og fiskeri. Til tross for et kort tokt har vi fått noen foreløpige resultat fra to fangster. Det var få spekkhoggere til stede, og dermed betydelig flere observasjoner av knølhval. Lydsignalene som ble brukt i de to forsøkene hadde liten eller ingen effekt på knølhvalene. Det er dermed behov for å jobbe videre med utvikling av signaler som er effektive, også ved gjentatt og langtidseksponering, uten at de skader hvalen. Det er også behov for å sikre at lydsignalene ikke påvirker sildas atferd før man går videre med implementering i kommersielle fiskerier. Resultatene fra toktet tyder på at risikoen for at måker setter seg fast i nota er størst i siste fasen av innhaling av not og før fangsten blir pumpet ombord. Plutselige lyd og lys skremte effektivt måkene bort fra nota og bør undersøkes videre som mulige avbøtende tiltak. Erfaringene som ble gjort med bruk av lyssensitivt kamera og termisk kikkert til overvåking i mørket var veldig gode. Toktet har gitt oss nyttig erfaring for både gjennomføring av feltforsøk i vinteren 2023 /2024 og videreutvikling av metoder for redusert interaksjon mellom hval og fiskeri.Utvikling og testing av metoder for å redusere uheldige interaksjoner mellom hval / sjøfugl og notfiskeri - Tokt med MS "Vestbris" 6.-10. januar 2023 i Kvænangen fjordpublishedVersio
Mock samples resolve biases in diversity estimates and quantitative interpretation of zooplankton metabarcoding data
Get PDFMetabarcoding is a rapidly developing tool in marine zooplankton ecology, although most zooplankton surveys continue to rely on visual identification for monitoring purposes. We attempted to resolve some of the biases associated with metabarcoding by sequencing a 313-b.p. fragment of the COI gene in 34 “mock” samples from the North Sea which were pre-sorted to species level, with biomass and abundance estimates obtained for each species and taxonomic group. The samples were preserved either in 97% ethanol or dehydrated for 24 h in a drying oven at 65 °C (the routine way of preserving samples for dry weight measurements). The visual identification yielded a total of 59 unique holoplanktonic and 16 meroplanktonic species/taxa. Metabarcoding identified 86 holoplanktonic and 124 meroplanktonic species/taxa, which included all but 3 of the species identified visually as well as numerous species of hard-to-identify crustaceans, hydrozoan jellyfish, and larvae of benthic animals. On a sample-to-sample basis, typically 90–95% of visually registered species were recovered, but the number of false positives was also high. We demonstrate robust correlations of relative sequence abundances to relative biomass for most taxonomic groups and develop conversion factors for different taxa to account for sequencing biases. We then combine the adjusted sequencing data with a single bulk biomass measurement for the entire sample to produce a quantitative parameter akin to species biomass. When examined with multivariate statistics, this parameter, which we call BWSR (biomass-weighed sequence reads) showed very similar trends to species biomass and comparable patterns to species abundance, highlighting the potential of metabarcoding not only for biodiversity estimation and mapping of presence/absence of species but also for quantitative assessment of zooplankton communities.publishedVersio
Barents Sea Shrimp - stock assessment report 2022/23
Get PDFSince the 1980s, the Barents Sea has gone from a situation with high fishing pressure, cold conditions and low demersal fish stock levels, to the current situation with high levels of demersal fish stocks, reduced fishing pressure and warm conditions.Barents Sea Shrimp - stock assessment report 2022/23publishedVersio
Report of the Joint Russian-Norwegian Working Group on Arctic Fisheries (JRN-AFWG) 2023
Get PDFOn 30 th March 2022 all Russian participation in ICES was temporally suspended. Although the announcement of the suspension stressed the role of ICES as a “multilateral science organization”, this suspension applied not only to research activities, but also to the ICES work providing fisheries advice for the sustainable management of fish stocks and ecosystems. As a result of the suspension, the ICES AFWG provided advice only for saithe, coastal cod north, coastal cod south, and golden redfish ( Sebastes norvegicus ). Northeast Arctic (NEA) cod, haddock and Greenland halibut assessments have been conducted outside of ICES in a newly constituted Joint Russian-Norwegian Working Group on Arctic Fisheries (JRN-AFWG). Although this work has been conducted independently of ICES, the methodologies agreed at ICES benchmarks and agreed HCRs (Harvest Control Rules) have been followed in providing this advice.
The Greenland halibut model has been revised at an ICES benchmark in 2023. The JRN-AFWG has agreed to use the new ICES model, with the addition of revising the Russian survey tuning index (as was recommended at the benchmark). Although the overall biomass level in the model has been revised, the trends and advice are similar to the old model. The Greenland halibut advice is for one year to bring the timing back in line with the slope survey, after this a two-year advice cycle will resume. The main worry with that stock is a history of TACs and catches well above advice. Given that the model is now indicating that the stock will drop below B pa by the end of 2023, continuing to set quota above advice poses a risk of serious harm to the stock.publishedVersio
An evolutionary explanation of female-biased sexual size dimorphism in North Sea plaice, Pleuronectes platessa L.
Get PDFSexual size dimorphism (SSD) is caused by differences in selection pressures and life-history trade-offs faced by males and females. Proximate causes of SSD may involve sex-specific mortality, energy acquisition, and energy expenditure for maintenance, reproductive tissues, and reproductive behavior. Using a quantitative, individual-based, eco-genetic model parameterized for North Sea plaice, we explore the importance of these mechanisms for female-biased SSD, under which males are smaller and reach sexual maturity earlier than females (common among fish, but also arising in arthropods and mammals). We consider two mechanisms potentially serving as ultimate causes: (a) Male investments in male reproductive behavior might evolve to detract energy resources that would otherwise be available for somatic growth, and (b) diminishing returns on male reproductive investments might evolve to reduce energy acquisition. In general, both of these can bring about smaller male body sizes. We report the following findings. First, higher investments in male reproductive behavior alone cannot explain the North Sea plaice SSD. This is because such higher reproductive investments require increased energy acquisition, which would cause a delay in maturation, leading to male-biased SSD contrary to observations. When accounting for the observed differential (lower) male mortality, maturation is postponed even further, leading to even larger males. Second, diminishing returns on male reproductive investments alone can qualitatively account for the North Sea plaice SSD, even though the quantitative match is imperfect. Third, both mechanisms can be reconciled with, and thus provide a mechanistic basis for, the previously advanced Ghiselin–Reiss hypothesis, according to which smaller males will evolve if their reproductive success is dominated by scramble competition for fertilizing females, as males would consequently invest more in reproduction than growth, potentially implying lower survival rates, and thus relaxing male–male competition. Fourth, a good quantitative fit with the North Sea plaice SSD is achieved by combining both mechanisms while accounting for sex-specific costs males incur during their spawning season. Fifth, evolution caused by fishing is likely to have modified the North Sea plaice SSD.publishedVersio
Novel tag-based method for measuring tailbeat frequency and variations in amplitude in fish
Get PDFThe tailbeat frequency (TBF) together with tailbeat amplitude (TBA) of fish are tightly correlated with swimming speed. In addition, these parameters can be used as indicators of metabolic rate and general activity level, provided that appropriate calibration studies have been performed in the laboratory. If an implantable bio-logger could measure TBF and TBA, it would, therefore, have great potential as a tool to monitor swimming behaviours and bioenergetics over extended periods of time in free roaming fish within natural or farm environments. The purpose of this study was, therefore, to establish a method for deriving accurate TBF and variations in TBA from activity tags that log high-resolution acceleration data. We used 6 tagged Atlantic salmon (Salmo salar) of ≈1 kg and subjected them to two types of swim trials in a large swim tunnel system. Test speeds were either incrementally increased in 20-min intervals until steady swimming ceased, or constant speed of 60 cm s−1 was given in a 4-h sustained test. The TBFs were visually observed by camera and compared with computed values from the activity tags. In the incremental trials the TBF increased linearly with swimming speed, while it remained constant during the 4 h of sustained swimming. The TBFs measured by activity tags were within ± 0.1 beat s−1 of the visual measurements across the swim speeds tested between 30 to 80 cm s−1. Furthermore, TBF and its corresponding relative swim speed were consistent between trial type. The relative TBA increased with swimming speed as a power function, showing that the fish relies on changes in both amplitude and frequency of tail movements when swimming at higher speeds, while adjustments of amplitude only play a minor part at lower speeds. These results demonstrate that TBFs can be measured accurately via activity tags, and thus be used to infer swimming activities and bioenergetics of free roaming fish. Furthermore, it is also possible to estimate changes in TBA via activity tags which allows for more nuanced assessments of swimming patterns in free roaming fish.publishedVersio
Key physical processes and their model representation for projecting climate impacts on subarctic Atlantic net primary production: A synthesis
Get PDFOceanic net primary production forms the foundation of marine ecosystems. Understanding the impact of climate change on primary production is therefore critical and we rely on Earth System Models to project future changes. Stemming from their use of different physical dynamics and biogeochemical processes, these models yield a large spread in long-term projections of change on both the global and regional scale. Here we review the key physical processes and biogeochemical parameterizations that influence the estimation of primary production in Earth System Models and synthesize the available projections of productivity in the subarctic regions of the North Atlantic. The key processes and modelling issues we focus on are mixed layer depth dynamics, model resolution and the complexity and parameterization of biogeochemistry. From the model mean of five CMIP6 models, we found a large increase in PP in areas where the sea ice retreats throughout the 21st century. Stronger stratification and declining MLD in the Nordic Seas, caused by sea ice loss and regional freshening, reduce the vertical flux of nutrients into the photic zone. Following the synthesis of the primary production among the CMIP6 models, we recommend a number of measures: constraining model hindcasts through the assimilation of high-quality long-term observational records to improve physical and biogeochemical parameterizations in models, developing better parameterizations for the sub-grid scale processes, enhancing the model resolution, downscaling and multi-model comparison exercises for improved regional projections of primary production.publishedVersio
Functional Evolution of Clustered Aquaporin Genes Reveals Insights into the Oceanic Success of Teleost Eggs
Get PDFAquaporin-mediated oocyte hydration is considered important for the evolution of pelagic eggs and the radiative success of marine teleosts. However, the molecular regulatory mechanisms controlling this vital process are not fully understood. Here, we analyzed >400 piscine genomes to uncover a previously unknown teleost-specific aquaporin-1 cluster (TSA1C) comprised of tandemly arranged aqp1aa-aqp1ab2-aqp1ab1 genes. Functional evolutionary analysis of the TSA1C reveals a ∼300-million-year history of downstream aqp1ab-type gene loss, neofunctionalization, and subfunctionalization, but with marine species that spawn highly hydrated pelagic eggs almost exclusively retaining at least one of the downstream paralogs. Unexpectedly, one-third of the modern marine euacanthomorph teleosts selectively retain both aqp1ab-type channels and co-evolved protein kinase-mediated phosphorylation sites in the intracellular subdomains together with teleost-specific Ywhaz-like (14-3-3ζ-like) binding proteins for co-operative membrane trafficking regulation. To understand the selective evolutionary advantages of these mechanisms, we show that a two-step regulated channel shunt avoids competitive occupancy of the same plasma membrane space in the oocyte and accelerates hydration. These data suggest that the evolution of the adaptive molecular regulatory features of the TSA1C facilitated the rise of pelagic eggs and their subsequent geodispersal in the oceanic currents.publishedVersio
Metabolic effects of diet containing blue mussel (Mytilus edulis) and blue mussel-fed salmon in a mouse model of obesity
Get PDFAlternative 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