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International audience; Mercury (Hg) pollution in the ocean is an issue of global concern, however bioaccumulation regimes of this ubiquitous pollutant in marine apex predators have important knowledge gaps. Our fish length and stable isotope (δ 15 N and δ 13 C) normalized data of Greenland halibut (GH) (Reinhardtius hippoglossoides) showed that Hg bioaccumulation in fillet tissue decreased by ~35-50 %, over a ten-year period from 2006 to 2015 (n = 7 individual sampling years). Hg was predominantly in the methylmercury form (>77 %). Results from a Bayesian information theoretic model showed that GH Hg concentrations decreased with time and its associated declines in Hg air emissions, estimated trophic position, and a potentially lower degree of demersal prey use as indicated by temporal trend shifts in nitrogen (δ 15 N) and carbon (δ 13 C) stable isotope values. GH trophic shifts accounted for about one third of the observed temporal reduction in Hg. Our study demonstrates the importance of simultaneously considering Hg emissions, food web dynamics and trophic shifts as important drivers of Hg bioaccumulation in a marine, deep water fish species and highlights the effectiveness of Hg regulations on ocean apex predator Hg concentrations and overall seafood safety.

In this contribution, we propose fishery driven predator release as the cause for the largest grazing event ever observed in the NE Atlantic. Based on the evolving appreciation of limits to population connectivity, published and previously unpublished data, we discuss whether overfishing caused a grazer bloom of the sea urchin (Strongylocentrotus droebachiensis) resulting in overgrazing of more than 2000 km2 kelp (Laminaria hyperborea) forest along Norwegian and Russian coasts during the 1970 s. We show that coastal fisheries likely depleted predatory coastal fish stocks through modernization of fishing methods and fleet. These fish were important predators on urchins and the reduction coincided with the urchin bloom. From this circumstantial evidence, we hypothesize that coastal predatory fish were important in regulating sea urchins, and that a local population dynamics perspective is necessary in management of coastal ecosystems.

The present paper presents the practical implementation of the Ecosystem Approach to Fisheries Management (EAFM) in Norway. This involves defining management objectives and developing simple and efficient tools to achieve an overview of management needs and prioritise among these, while integrating broader conservation issues and ensuring stakeholder involvement. A new Marine Resources Act entered into force in Norway in 2009. By integrating conservation and sustainable use as basic principles, the law represents a paradigm shift in the management of Norwegian fisheries. The law indicates which concerns should be addressed, but neither how nor how often evaluations should take place. That is for management to decide. A management principle in the Marine Resources Act confers on the Ministry an obligation to evaluate whether continued fishing at the present scale is justifiable, or whether improved management is required to ensure sustainability. A Stock table, and a table of "Catches of data-poor species" constitute a comprehensive system for monitoring the management principle. Along with a Fisheries table, these tables establish a framework for developing an ecosystem-based fisheries management by providing a basis and tools for prioritising the needs of new and/or revised management measures.

1. Due to globalisation, trade and transport, the spread of alien species is increasing dramatically. Some alien species become ecologically harmful by threatening native biota. This can lead to irreversible changes in local biodiversity and ecosystem functioning, and, ultimately, to biotic homogenisation. 2. We risk-assessed all alien plants, animals, fungi and algae, within certain delimitations, that are known to reproduce in Norway. Mainland Norway and the Arctic archipelago of Svalbard plus Jan Mayen were treated as separate assessment areas. Assessments followed the Generic Ecological Impact Assessment of Alien Species (GEIAA) protocol, which uses a fully quantitative set of criteria. 3. A total of 1519 species were risk-assessed, of which 1183 were species reproducing in mainland Norway. Among these, 9% were assessed to have a severe impact, 7% high impact, 7% potentially high impact, and 49% low impact, whereas 29% had no known impact. In Svalbard, 16 alien species were reproducing, one of which with a severe impact. 4. The impact assessments also covered 319 so-called door-knockers, i.e. species that are likely to establish in Norway within 50 years, and 12 regionally alien species. Of the door-knockers, 8% and 10% were assessed to have a severe and high impact, respectively. 5. The impact category of most species was driven by negative interactions with native species, transformation of threatened ecosystems, or genetic contamination. The proportion of alien species with high or severe impact varied significantly across the different pathways of introduction, taxonomic groups, time of introduction, and the environments colonised, but not across continents of origin. 6. Given the large number of alien species reproducing in Norway and the preponderance of species with low impact, it is neither realistic nor necessary to eradicate all of them. Our results can guide management authorities in two ways. First, the use of quantitative assessment criteria facilitates the prioritisation of management resources across species. Second, the background information collected for each species, such as introduction pathways, area of occupancy and ecosystems affected, helps designing appropriate management measures. 1. Globalisering, handel og transport fører til en dramatisk økning i spredningen av fremmede arter. Noen fremmede arter er skadelige og truer det stedegne naturmangfoldet. Lokalt kan dette medføre irreversible endringer i det lokale biologiske mangfoldet og økosystemenes funksjon; globalt en homogenisering av artssammensetningen. 2. Vi har gjennomført risikovurderinger av alle fremmede planter, dyr, sopper og alger som reproduserer i Norge og oppfyller visse avgrensninger. Svalbard og Jan Mayen ble behandla som et eget vurderingsområde, adskilt fra Fastlands‐Norge. Risikovurderingene ble gjort i tråd med GEIAA (Generic Ecological Impact Assessment of Alien Species), som benytter et rent kvantitativt kriteriesett. 3. Totalt ble 1519 arter risikovurdert, hvorav 1183 reproduserte i Fastlands‐Norge. Av disse ble 9 % vurdert til å utgjøre en svært høy risiko, 7 % en høy risiko, 7 % en potensielt høy risiko, 49 % en lav risiko og 29 % ingen kjent risiko. På Svalbard forekom 16 reproduserende fremmede arter, hvorav én med svært høy risiko. 4. Risikovurderingene omfatta også 319 såkalte dørstokkarter, dvs. fremmede arter som antas å kunne etablere seg i Norge innen 50 år, samt 12 regionalt fremmede arter. Blant dørstokkartene ble 8 % og 10 % vurdert til å utgjøre en svært høy respektive høy risiko. 5. For de fleste arter ble risikokategorien bestemt av artenes interaksjoner med stedegne arter, tilstandsendringer i trua naturtyper eller genetisk forurensning. Andelen av fremmede arter med høy eller svært høy risiko varierte signifikant på tvers av ulike introduksjonsveier, artsgrupper, tidspunkt for introduksjon og koloniserte naturtyper, men ikke på tvers av opphavsområder. 6. Gitt det store antallet av fremmede arter som reproduserer i Norge, og overvekten av arter som har lav risiko, er det verken realistisk eller nødvendig å utrydde alle. Resultatene våre kan hjelpe forvaltningsmyndighetene på to måter. For det første gjør bruken av kvantitative kriterier det lettere å prioritere ressurser på tvers av arter. For det andre kan passende forvaltningstiltak utarbeides på grunnlag av den innsamla bakgrunnsinformasjonen om artene, f.eks. deres spredningsveier, forekomstareal og berørte naturtyper. This is an open access article under the terms of the Creative Commons Attribution License, which permits use,distribution and reproduction in any medium, provided the original work is properly cited.c 2020 The Authors. Ecological Solutions and Evidence published by John Wiley & Sons Ltd on behalf of British Ecological Society

This is a post-peer-review, pre-copyedit version of an article published in Biological Invasions. The final authenticated version is available online at: https://doi.org/10.1007/s10530-019-02058-x. We present the results of an inventory and status assessment of alien species in Norway. The inventory covered all known multicellular neobiota, 2496 in total, 1039 of which were classified as naturalised. The latter constitute c. 3% of all species known to be stably reproducing in Norway. These figures are higher than expected from Norway’s latitude, which may be due a combination of climatic and historical factors, as well as sampling effort. Most of the naturalised neobiota were plants (71%),followed by animals (21%) and fungi (8%). The main habitat types colonised were open lowlands (79%), urban environments (52%) and woodlands (42%). The main areas of origin were Europe (67%), North America (15%) and Asia (13%). For most taxa, the rate of novel introductions seems to have been increasing during recent decades. Within Norway, the number of alien species recorded per county was negatively correlated with latitude and positively correlated with human population density. In the high-Arctic territories under Norwegian sovereignty, i.e. Svalbard and Jan Mayen, 104 alien species were recorded, of which 5 were naturalised.

In the Barents Sea and adjacent water, fishing grounds are closed for shrimp fishing by the Norwegian Directorate of Fisheries Monitoring and Surveillance Service (MSS) if the expected number of juvenile fish caught are predicted to exceed a certain limit per kilogram shrimp (Pandalus borealis). Today, a simple ratio estimator, which does not fully utilize all data available, is in use. In this paper, we construct a Bayesian hierarchical spatiotemporal model for improved prediction of the bycatch ratio in the Barents Sea shrimp fishery. More predictable bycatch will be an advantage for the MSS because of more correct decisions and better resource allocation and also for the fishermen because of more predictable fishing grounds. The model assumes that the occurrence of shrimp and juvenile Atlantic cod (Gadus morhua) can be modeled by linked regression models containing several covariates (including 0-group abundance estimates) and random effects modeled as Gaussian fields. Integrated nested Laplace approximations is applied for fast calculation. The method is applied to prediction of the bycatch ratio for Atlantic cod.

The aim of this paper is to evaluate the food safety of the red king crab from Norwegian waters and obtain information on possible geographical and gender differences. Samples of claw and leg meat of 185 red king crabs (Paralithodes camtschaticus), collected from 23 positions in the Barents Sea, were analysed for dioxins, furans, non-ortho and mono-ortho PCBs, non dioxin-like PCBs, polybrominated diphenyl ethers, and perfluorinated alkyl substances and elements, such as arsenic, cadmium, mercury and lead. The concentrations of persistent organic pollutants and metals were low compared to maximum levels laid down in European regulations. Hence, red king crab is a safe food. Significant differences in the concentrations of metals among different areas, and between male and female crabs, were found. Positive correlations were found between carapace length and mercury, methylmercury and cadmium concentrations, and between fat and arsenic and inorganic arsenic concentrations.

Europe has a long tradition of exploiting marine fishes and is promoting marine economic activity through its Blue Growth strategy. This increase in anthropogenic pressure, along with climate change, threatens the biodiversity of fishes and food security. Here, we examine the conservation status of 1,020 species of European marine fishes and identify factors that contribute to their extinction risk. Large fish species (greater than 1.5 m total length) are most at risk; half of these are threatened with extinction, predominantly sharks, rays and sturgeons. This analysis was based on the latest International Union for Conservation of Nature (IUCN) European regional Red List of marine fishes, which was coherent with assessments of the status of fish stocks carried out independently by fisheries management agencies: no species classified by IUCN as threatened were considered sustainable by these agencies. A remarkable geographic divergence in stock status was also evident: in northern Europe, most stocks were not overfished, whereas in the Mediterranean Sea, almost all stocks were overfished. As Europe proceeds with its sustainable Blue Growth agenda, two main issues stand out as needing priority actions in relation to its marine fishes: the conservation of marine fish megafauna and the sustainability of Mediterranean fish stocks. Marine fishes exhibit high biodiversity 1,2 and have been culturally and nutritionally important throughout human history 3 . Europe, in particular, has a well-documented history of exploiting marine fish populations, written records of which commence in the classical works of ancient Greece. Although this historical exploitation has undoubtedly altered populations 4,5 and changed many seascapes 6 , marine defaunation in the region has not been as great as in terrestrial systems 7 . However, the use of ocean space and resources is increasing due to Europe’s Blue Growth strategy 8 , the nutritional requirements of an expanding human population are growing 9,10 and marine ecosystems will experience unusually rapid changes in future due to climate change 11,12 . Consequently there are imminent threats both to European marine biodiversity and fish resources 13 . It is important, therefore, to assess the threats of extinction to fish species and to ensure consistency in the management approach by the various agencies involved. We analysed data on the conservation status of 1,020 species of Europe’s marine fishes from the recent International Union for Conservation of Nature (IUCN) Red List assessments 14 to identify characteristics that make Europe’s fishes most susceptible to extinction risk. We then compared the Red List with 115 fish stock assessments (of 31 species) made by intergovernmental agencies charged with providing advice on the exploitation of commercial fishes. Previous comparisons of this sort applied criteria under various modelling assumptions 15,16, 17 or limited the comparison to biomass reference points 18 .

Nature Ecology & Evolution 1, 0170 (2017); published 26 May 2017; corrected 12 June 2017. In the original version of this Article, the European Commission was mistakenly included as an affiliation for Christos D. Maravelias. His contribution to this work was exclusively completed while at the Hellenic Centre for Marine Research.

Beaked redfish inhabits North Atlantic waters in the depth range 100–950 m, over the continental shelf, slope and the open ocean. Individuals can live demersal or pelagic, at various stages of their life cycle. The geographical distribution of the species extends to most of the Atlantic waters from Newfoundland and the Labrador basin in the west to the Barents Sea in the east. Monitoring beaked redfish is challenging because of the species wide geographical distribution and large scale migrations; deep distribution, which complicates trawling and hydroacoustic surveys; difficulties with tagging; and persistent difficulties in taxonomic identification. These challenges make it a particularly problematic species to observe with conventional research methods. We review these key challenges and provide recommendations for the coordinated observation of Sebastes mentella in the North Atlantic that would best contribute to the assessment and ecological research on this species.

This study is one of several baseline studies that will provide basic and reliable information about the content of undesirable substances in important species of fish caught in Norwegian waters. Concentrations of metals in the muscle and livers of 516 cod caught at 22 positions in the North Sea were analysed. An additional 687 cod were caught from 13 fjords and coastal areas along the coast of Norway. Three out of 1203 samples of muscle exceeded the maximum limit of 0.5 mg Hg kg −1 wet weight set by the EU for foodstuffs. The mercury concentration in cod muscle was higher and the cadmium concentration in the liver was lower in the North Sea and coastal areas in the southern part of Norway than in the Barents Sea and coastal areas in the northern part of Norway. These differences are perhaps caused by differences in the cod diet.

Knowledge about how many fish that have been killed due to bycatch is an important aspect of ensuring a sustainable ecosystem and fishery. We introduce a Bayesian spatio-temporal prediction method for historical bycatch that incorporates two sources of available data sets, fishery data and survey data. The model used assumes that occurrence of bycatch can be described as a log-linear combination of covariates and random effects modeled as Gaussian fields. Integrated Nested Laplace Approximations (INLA) is used for fast calculations. The method introduced is general, and is applied on bycatch of juvenile cod ( Gadus morhua ) in the Barents Sea shrimp ( Pandalus borealis ) fishery. In this fishery we compare our prediction method with the well known ratio and effort methods, and make a strong case that the Bayesian spatio-temporal method produces more reliable historical bycatch predictions compared to existing methods.

With the decline of many of the world’s fisheries, increased regulation, including marine protected areas (MPA), forms an increasingly important role in promoting sustainable resource use. Here, we present a novel “real-time” genetic monitoring programme used to protect the depleted Norwegian coastal cod stock (NCC) in an MPA during the spawning season, while a fishery targeted at the sustainable Northeast Arctic cod stock (NEAC) operates immediately outside. In the period 2009–2016, >6800 cod from the fishery were genotyped with the PanI locus that is discriminatory between these two stocks. The estimated fraction of NEAC increased during the study period until 2014; however, it did not exceed 70% for any sustained period. Therefore, the MPA remained closed for commercial harvest. Genetic analysis of eggs revealed a distinctly lower fraction of NEAC than in the catch from the adult stock, both immediately outside and within the MPA itself. We suggest that this discrepancy is likely to reflect differences in spawning areas used by NCC and NEAC. Estimated fractions of NEAC/NCC using PanI, otolith classification, and 39 single nucleotide polymorphisms were similar, thus validating the use of PanI to estimate NEAC/NCC composition.

The contents of total arsenic and inorganic arsenic were determined in fillet samples of Northeast Artic cod, herring, mackerel, Greenland halibut, tusk, saithe and Atlantic halibut. In total, 923 individual fish samples were analysed. The fish were mostly caught in the open sea off the coast of Norway, from 40 positions. The determination of total arsenic was carried out by inductively coupled plasma mass spectrometry following microwave-assisted wet digestion. The determination of inorganic arsenic was carried out by high-performance liquid chromatography-ICP-MS following microwave-assisted dissolution of the samples. The concentrations found for total arsenic varied greatly between fish species, and ranged from 0.3 to 110 mg kg(-1) wet weight. For inorganic arsenic, the concentrations found were very low (0.006 mg kg(-1)) in all cases. The obtained results question the assumptions made by the European Food Safety Authority (EFSA) on the inorganic arsenic level in fish used in the recent EFSA opinion on arsenic in food.

Life-history theory suggests that animals may skip reproductive events after initial maturation to maximize lifetime fitness. In iteroparous teleosts, verifying past spawning history is particularly difficult; the degree of skipped spawning at the population level therefore remains unknown. We unequivocally show frequent skipped spawning in Northeast Arctic cod (NEAC) in a massive field and laboratory effort from 2006 to 2008. This was verified by postovulatory follicles in temporarily arrested ovaries close to the putative spawning period. At the population level, “skippers” were estimated to be approximately equally abundant as spawning females in 2008, constituting ∼24% of the females 60–100 cm. These females never truly started vitellogenesis and principally remained on the feeding grounds when spawners migrated southward, avoiding any migration costs. The proximate cause of skipping seems to be insufficient energy to initiate oocyte development, indicating that skipped spawning may partly be a density-dependent response important in population regulation. Our data also indicate more skipping among smaller females and potential tradeoffs between current and future reproductive effort. We propose that skipped spawning is an integral life-history component for NEAC, likely varying annually, and it could therefore be an underlying factor causing some of the currently unexplained large NEAC recruitment variation. The same may hold for other teleosts.

In January 2006 it was reported from Russia that Greenland halibut (Reinhardtius hippoglossoides) caught in the Barents Sea had shown mercury levels exceeding the European Union's upper limit of 0.5 mg/kg wet weight (ww) for this species. These findings were confirmed in a small study from the same area. To gain more knowledge, a larger study was initiated to investigate the levels of mercury in Greenland halibut caught off the coast of northern Norway. A total of 320 Greenland halibut were caught in this area in May 2006. Individual fish were filleted and analysed for mercury, arsenic, cadmium and lead. Round weight of the fish varied between 1.1 and 8.1 kg. Fish age varied between 12 and 29 years. The highest mercury concentration measured in muscle tissue was 1.1 mg/kg ww. The highest concentrations were found in female fish. Mercury concentration was positively correlated with fish size and negatively correlated with fat content. Fish captured in the easternmost part of the investigated area ...

For 16 years (1992–2007) comparative age-reading studies for cod were carried out by the two national laboratories: Polar Research Institute of Marine Fisheries and Oceanography (PINRO), Murmansk, Russia, and Institute of Marine Research (IMR), Bergen, Norway. Pairs (6786) of Northeast Arctic cod otoliths were read and compared to assess the precision of age estimation between the two laboratories. Cod otoliths which provide basic information for stock assessment were re-analysed to determine if there were any discrepancies since additional information on fish length may or may not have been available. Two groups of otoliths which were sampled during 1992 and 1994 were analysed in parallel: 285 otoliths with known length data and 661 otoliths without length data available. Knowing the length of the cod appeared to increase the discrepancies between the two laboratories. Analysis of long-term discrepancies in cod age determinations between two laboratories showed that variability of ageing is infl...

Vølstad, J. H., Korsbrekke, K., Nedreaas, K. H., Nilsen, M., Nilsson, G. N., Pennington, M., Subbey, S., and Wienerroither, R. 2011. Probability-based surveying using self-sampling to estimate catch and effort in Norway's coastal tourist fishery. – ICES Journal of Marine Science, 68: 1785–1791. Recreational fishing as a tourist activity has become an increasingly important part of the Norwegian travel industry and may contribute significantly to the fishing mortality on Norwegian coastal cod (Gadus morhua). Quantifying catches in the tourist fishery is made difficult by Norway's intricate and long coastline, and the lack of a fishing licence system, a registry of businesses catering for fishing tourists, and a registry of charter boats. A probability-based survey was used to estimate annual catch and effort by boat for anglers associated with 445 tourist-fishing businesses during 2009. From a stratified random sample of businesses, fishing tourists were recruited systematically over time to record their daily catch and effort in diaries. Cod dominated the reported landed catch (harvest) north of 62°N, and saithe and mackerel dominated south of 62°N. The estimated total landed catch of all species taken by tourist fishers in the business sector during 2009 was 3335 t (relative standard error, RSE = 17%), of which 1613 t (RSE = 22%) were cod. It is concluded that surveys based on self-sampling can yield accurate estimates of catch and effort accounted for by the business sector of the Norwegian tourist fishery and that the tourist catch of coastal cod is insignificant compared with the commercial and recreational catch by local residents.

Aanes, S., Nedreaas, K., and Ulvatn, S. 2011. Estimation of total retained catch based on frequency of fishing trips, inspections at sea, transhipment, and VMS data. – ICES Journal of Marine Science, 68: 1598–1605. The satellite-based vessel monitoring system in the Norwegian Economic Zone provides detailed information about individual trips by vessels. Vessel sizes are available through official registries, and the storage capacity for fish is estimated using the established conversion factors as a function of the vessel's gross registered tonnage. Scientists have had access to the database of both transport and fishing vessels, with records for individual trips, in addition to information about the total round weight (whole fish) of cod and haddock for trips inspected by the coastguard. The analysis assumes that trips with complete documentation of the fish on board are a random sample, so allowing estimation of the mean amount of both cod and haddock per trip, and annual totals give the number of trips per vessel annually. ICES has accepted this methodology for estimating illegal, unregulated, and unreported (IUU) catches, which has resulted in 15 000–166 000 t (3–35%) being added to the officially reported landings of Northeast Arctic cod during the years 2002–2008. IUU landings have decreased in recent years, but are so important for assessment and management that estimates continue to be made annually.

Geffen, A. J., Høie, H., Folkvord, A., Hufthammer, A. K., Andersson, C., Ninnemann, U., Pedersen, R. B., and Nedreaas, K. 2011. High-latitude climate variability and its effect on fisheries resources as revealed by fossil cod otoliths. – ICES Journal of Marine Science, 68: 1081–1089. Cod (Gadus morhua) otoliths from archaeological sites in northern Norway were analysed to reconstruct the temperature regime and determine the age structure, growth, and population identity of the fish harvested. Otoliths were selected from late- and post-medieval sites (700–300 years ago) to evaluate historical changes in the geographic region that matches the present-day stocks of Northeast Arctic cod (NEAC) and Norwegian coastal cod (NCC). Seasonal temperature cycles were reconstructed from stable isotope (δ18O) measurements along transects representing fish ages 1.5–3 years old. Reconstructions of the size, age, and growth characteristics of individual fish were based on otolith growth increments. The geographical source and stock identity of the individuals were estimated based on otolith elemental composition and otolith growth features. Both NCC and NEAC fish were represented at Måsøy and Vanna. The results indicate that fishing at Vanna exploited NEAC during their spawning migration, compared with fishing at Måsøy, which was restricted to more coastal fish. Fish growth patterns appeared to be affected by changes in the temperature regimes as estimated from otolith δ18O and back-calculated fish length-at-age, with evident differences between pre- and post-1600 periods.

Jan Mayen Island was already the focus of science during the First International Polar Year in 1882–1883, even though fish biodiversity played only a minor role. Marine investigations were conducted at irregular intervals until the area was covered by the routine research activities of the Institute of Marine Research (IMR). The objective of this paper is to present an annotated list of species recorded in the Fisheries Zone around Jan Mayen, and to give an overview of the change in species composition and distribution. The data are based on scientific collections, literature citings and the IMR database. Between 1877 and 2009, 71 fish species have been recorded in the area, of which 43 are documented by voucher specimens. The zoarcid species Lycenchelys platyrhina is endemic to the area. Results show an increase in the number of species over the last 40 years, 40 of the 71 species were registered for the first time after 1970. This, on the one hand, is due to complete catch registration and better species identification, and on the other hand, to an enlargement of the species’ distribution area and immigration into the Jan Mayen area of other species. The data provides basic information for future monitoring of the area, especially as the polar regions may be strongly affected by climate change, which may have an impact on species abundance and distribution.

Stefánsson, M. Ö., Reinert, J., Sigurðsson, Þ., Kristinsson, K., Nedreaas, K., and Pampoulie, C. 2009. Depth as a potential driver of genetic structure of Sebastes mentella across the North Atlantic Ocean. – ICES Journal of Marine Science, 66: 680–690. A primary question that remains to be answered about the fishery for Sebastes mentella is whether it exploits several stocks within the North Atlantic Ocean. To address this issue, 1240 redfish were collected from several fishing grounds in late 2006 and early 2007 and genotyped at 12 microsatellite loci. Contemporary allele frequencies were compared with archived data to examine the temporal stability of the genetic structure. The analyses all revealed the presence of three genetically distinguishable clusters, which persisted throughout the study period, suggesting that the genetic structure detected is genuine. Cluster D included fish from the deep Irminger Sea and west Faroe Islands, and Cluster I included fish only from the Icelandic shelf. All other fish grouped in a third cluster (S). Further analyses revealed that the genetic pattern observed was not primarily attributable to isolation by distance, but rather to depth distribution.

Seasonality of otolith zone formation can vary between fish species, and between populations within the same species. Although information on otolith zone formation is important for fish age estimation, there is incomplete knowledge of factors influencing variation in otolith opacity. In this study, marginal increment types (opaque or translucent) of two spatially distinct Atlantic cod stocks were assessed. Cod otoliths from the southern North Sea, where the fish experience high temperatures were compared with cod otoliths from the Barents Sea, where the fish experience much lower temperatures. There was approximately a shift of 5 months for deposition of translucent otolith material between the two areas. Cod from the southern North Sea deposited translucent otolith material in the period July–November, while it occurred in the period December–April in the Barents Sea. Inter-annual differences within areas were minor compared to differences between the two areas.

Norwegian and Russian Marine Research Institutes have investigated the possibility that biases in age determination from otoliths may have contributed to the long-term trends observed in the Northeast Arctic cod stock productivity: changes in growth, maturation rate, fecundity, etc. To determine the effects of changes in age reading protocols between contemporary and historical practices, randomly chosen material from each decade for the period 1940–1980s was re-read by experts. The quality of old otoliths stored in paper bags for more than 50 years was also assessed. Although some year-specific differences in age determination were seen between historical and contemporary readers, there was no significant effect on length at age for the historical time period. A small systematic bias in the number spawning zones detection was observed, demonstrating that the age at first maturation in the historic material as determined by the contemporary readers is younger than that determined by historical re...

Determining the population age structure of important fish species with high accuracy and precision is fundamental to age-based fish stock assessment. Otoliths sampled for independent age reading by Russian and Norwegian specialists have routinely been exchanged twice annually since 1992. In total, 6386 pairs of otoliths were exchanged during 1992–2006; to verify techniques, 1331 of these were read repeatedly by experts attending annual joint age readers’ meetings. Important lessons have been learned during these 15 years of collaborative, regular, and systematic age reading. Consistency between the two laboratories in reading cod ages appears to have increased. The scientific, biological, and hence economic effect, of this work is easily observed. The need for regular meetings to tune and coordinate age-reading procedures is ongoing.

In January 2006 it was reported that Greenland halibut (Reinhardtius hippoglossoides) caught in the Barents Sea contained mercury levels that exceeded the EU's upper limit of 0.5 mg/kg wet weight for this species. To further investigate this finding, the National Institute of Nutrition and Seafood Research (NIFES) in Norway recently undertook a study to quantify the levels of mercury in Greenland halibut caught in the same area of the Barents Sea. A total of 120 Greenland halibut were caught in this area between the 28th and the 30th of January 2006. The fish were immediately frozen and shipped to the laboratory; individual fish were coded, weighed, defrosted, filleted and skinned before their mercury content was determined. Analyses were carried out on 65 individuals of Greenland halibut weighing from 0.81 kg to 7.1 kg, and 40 fish weighing more than 3 kg. The lowest mercury concentration found in muscle tissue (skinless and boneless fillet) was 0.019 mg/kg wet weight, in a fish that weighed 0.81 kg. The highest mercury concentration measured in muscle tissue was 1.1 mg/kg wet weight, from a fish that weighed 4.2 kg. Of the 65 fish analysed, 15 individuals with weight exceeding 3 kg had mercury concentrations in their muscle tissue exceeded the EU's upper limit.

This paper describes the pelagic fishery for deep-sea redfish, Sebastes mentella, in the Irminger Sea and adjacent waters, from the start of commercial exploitation of the resource in 1982. The information prior to 1990 is mostly based on ICES reports and unpublished data, but from 1990, logbook data from a joint database on a haul-by-haul basis from the Faroe Islands, Germany, Greenland, Iceland, Norway, and Russia are used to describe the fishery. The nations listed are the main ones operating on the resource, catching about 80% of the total reported catches in recent years. The logbook data include inter alia information on positions, catch, and trawling time. Additionally, some nations also include information on gear type and size of gear used, and in some cases also trawling depth. Length distributions of commercial catches from various fleets for the whole period have also been collected, and are shown along with information on the mean lengths in the catches for the whole period. The paper therefore provides a detailed overview of the fishery in terms of area, season, depth, and size composition of the catches from the start of the pelagic fishery to the present, allowing better understanding of the behaviour of the fishery and, in turn, providing improved background for assessment of the resource in the future.

Age determination of Atlantic redfish (Sebastes spp.) has proven difficult and has led to inconsistent age and growth estimates in the past. Using otoliths of the two major commercial species, golden redfish (Sebastes marinus) and deep-sea redfish (S. mentella), a series of exchange schemes was carried out to assess bias and precision of age readings between four readers and between two preparation methods. Considerable bias between readers and moderate precision were observed for the S. marinus readings, especially for ages >20 years, with coefficients of variation (CV) of 7.7–12.0% and average percent error (APE) of 5.4–8.5%. Agreement between readers increased from 17–28% to 45–61% when allowing deviations of ±1 year, and to 80–92% with ±3 years tolerance. The age of S. marinus determined from broken and burnt otoliths was estimated to be slightly lower than when the age of the same individuals was determined from thin-sectioned otoliths. The bias and precision estimates obtained from the S. mentella material were generally poorer than for S. marinus (CV 8.2–19.1%, APE 5.8–13.5%), but similar to reported values for other long-lived fish species. Better than 50% agreement was only achieved with ±3 years tolerance. Growth rates differed significantly between species, confirming slower growth for S. mentella. For S. marinus, only one reader comparison revealed significantly different growth functions, whereas almost all S. mentella reader pairs showed significant differences in growth curves. Section and break-and-burn readings of S. marinus did not differ significantly. Average ages of around 9–10 years were determined for juvenile S. mentella 24–30 cm long, which were likely to have migrated from East Greenland into the Irminger Sea, based on earlier observations. As some of the error in the age determinations presented could be attributed to interpretation differences between readers, further intercalibration of redfish ageing is urgently needed in order to provide consistent input data for stock assessment.

Since the late 1980s there has been considerable uncertainty in recruitment levels of the north-east Arctic stock of Greenland halibut (Reinhardtius hippoglossoides). The abundance of several year classes, originally considered very low at 0–3 yr age, appeared higher than expected at the age of 6+. This may be due to poor targeting of recruitment surveys of the younger year classes. The present work considers the transport and dispersion of eggs and larvae of Greenland halibut by numerical modelling in order to predict the locations of the initial recruitment grounds. Current fields from a 3D baroclinic hydrodynamic model are fed into a Lagrangian particle-tracking model developed for the Barents Sea area. The particles are released into the current at the spawning field along the shelf slope from Lofoten to Bear Island (69– 75� N). Vertically, the particles can follow a predefined depth-by-age curve or be kept at a fixed depth. This model system is used for different years to examine changes in the drift pattern. The results indicate that spawning location, transport depth and inflowing activity to the Barents Sea are important factors influencing the distribution of juveniles.

During an international acoustic survey on pelagic redfish (Sebastes mentella) in the Irminger Sea in June–July 2001, a deep-towed vehicle carrying a dual-frequency SIMRAD EK60 Mk1 echosounder was used experimentally to observe and estimate redfish abundance at depths greater than 500 m. Comparison was made with the hull-mounted SIMRAD EK500 echosounder. The deep-towed echosounder improved the spatial resolution of fish in scattering layers as well as the ability to scrutinize and interpret fish echoes. The signal-to-noise ratio was better than that of the hull-mounted system. The fish abundance measured by the deep-towed sounder was consistently high compared to the hull-mounted sounder, particularly, at greater depths. For redfish within the deep scattering layer (DSL), the abundance was, on average, 5% higher, increasing to 55% for redfish below the DSL. From these findings it is concluded that a deep-towed echosounder is superior to hull-mounted ones for estimating the abundance of fish swimming in deep water.

Steven X. Cadrin1*, Stefano Mariani2, Christophe Pampoulie3, Matthias Bernreuther4, Anna Kristin Danielsdottir5, Torild Johanssen6, Lisa Kerr1, Kjell Nedreaas7, Jakup Reinert8, Þorsteinn Sigurðsson3, and Christoph Stransky4 School for Marine Science and Technology, University of Massachusetts, 200 Mill Road, Fairhaven, MA 02719, USA School of Biology and Environmental Science, University College Dublin, Dublin 4, Ireland Marine Research Institute, Skulagata 4, Reykjavik121, Iceland Institute of Sea Fisheries, Johann Heinrich von Thunen-Institute, Bundesallee 50, Braunschweig 38116, Germany Matis, Vinlandsleið 12, Reykjavik113, Iceland Institute of Marine Research, PO Box 6404, Tromso 9294, Norway Institute of Marine Research, PO Box 1870, Nordnes, Bergen 5817, Norway Faroe Marine Research Institute, PO Box 3051 Noatun 1, Torshavn FO-110, Faroe Islands *Corresponding Author: tel: +1 508 910 6358; fax: +1 508 910 6396; e-mail:scadrin@umassd.edu.

Albert, O. T., Nilssen, E. M., Nedreaas, K. H., and Gundersen, A. C. 2001. Distribution and abundance of juvenile Northeast Arctic Greenland halibut (Reinhardtius hippoglossoides) in relation to survey coverage and the physical environment. – ICES Journal of Marine Science, 58: 1053–1062. Based on annual bottom-trawl surveys in the Barents Sea and Svalbard area in 1983–2000, variations in distribution and abundance of age 1 Greenland halibut (Reinhardtius hippoglossoides Walbaum) are described. The surveys showed high contrasts in abundance during the period, with extremely low abundance in 1990–1995 associated with a northerly displacement of the distribution within the survey area. A reduced abundance was not reflected in VPA-based estimates of total abundance of 1-group halibut. We conclude that the survey covered a varying proportion of the total distribution area. Survey abundance, the range of distribution within the survey area, and the proportion covered by the surveys were all negatively correlated with temperature in the Atlantic Water of the Spitsbergen Current. Possible mechanisms linking survey results to the physical environment are discussed. 2001 International Council for the Exploration of the Sea

The maturation and spawning of Greenland halibut ( Reinhardtius hippoglossoides Walbaum) is described from six trawl surveys in the spawning area along the continental slope between North-Norway and Svalbard from October 1997 to May 1998. Different maturity classes were identified with frequency analyses of logarithmic classes of the Gonadosomatic Index. The main spawning period started in November, peaked in December and ended in late January. Mature females appeared at the spawning area in the early autumn and left during the first months of the year. Males were recorded after this with residual milt, indicating that some spawning may occur several months after the main spawning season. Observations from the fishery indicated spawning concentrations near the coast half a year after the main spawning period. Sex differences in spawning behaviour were discussed and related to the problem of representative sampling.

Age validation exercises clearly established the expected modal size of 0-group Greenland halibut specific to the study area and time of sampling. Subsequently, the modal sizes of at least ages 1–3 (and sometimes 4) were determined and indicated that at these ages Greenland halibut will grow on average about 6–8 cm per year. It is emphasized, however, that validation work is specific for the years and areas in which the data are collected. Female Greenland halibut have a longer lifespan than males. It is shown that the difference between the maximum age of males and females differ by as much as 8 years in the Northwest Atlantic but the difference declined in recent years. In most instances for both the northwest and northeast Atlantic growth rates for females are slightly higher than for males after about age 5–6. For the northwest Atlantic data the apparent differences are greater in earlier years but show little difference since mid 1980s. Greenland halibut in the northeast Atlantic are general...

Radiocarbon measured in seawater dissolved inorganic carbon (DIC) can be used to investigate ocean circulation, atmosphere/ocean carbon flux, and provide powerful constraints for the fine-tuning of general circulation models (GCMs). Time series of 14C in seawater are derived most frequently from annual bands of hermatypic corals. However, this proxy is unavailable in temperate and polar oceans. Fish otoliths, calcium carbonate auditory, and gravity receptors in the membranous labyrinths of teleost fishes, can act as proxies for 14C in most oceans and at most depths. Arcto-Norwegian cod otoliths are suited to this application due to the well-defined distribution of this species in the Barents Sea, the ability to determine ages of individual Arcto-Norwegian cod with a high level of accuracy, and the availability of archived otoliths collected for fisheries research over the past 60 years. Using measurements of 14C derived from Arcto-Norwegian cod otoliths, we present the first pre- and post-bomb time series (1919–1992) of 14C from polar seas and consider the significance of these data in relation to ocean circulation and atmosphere/ocean flux of 14C. The data provide evidence for a minor Suess effect of only 0.2‰ per year between 1919 and 1950. Bomb 14C was evident in the Barents Sea as early as 1957 and the highest 14C value was measured in an otolith core from a cod with a birth date of 1967. The otolith 14C data display key features common to records of 14C obtained from a Georges Bank mollusc and corals from the tropical and subtropical North Atlantic.

Because of indications of recruitment failures and a historic low spawning stock, the Northeast Arctic Greenland halibut ( Reinhardtius hippoglossoides Walbaum) stock has been strongly regulated in the 1990s. Fecundity is a link between the spawning stock and the following recruitment. This paper describes relationships between fecundity and total length for Northeast Arctic Greenland halibut for 1997 and 1998, based on samples taken in autumn on the continental slope west of the Barents Sea. A previous study describes a similar relationship for 1996. Individual fecundity is raised to a population level using stock data from XSA, and sex composition data, maturity oogives, and mean length at age from surveys covering the area of distribution. Total egg production (TEP) varied slightly around 1.0×10 11 , during 1996–1998, with the highest TEP in 1998. A back-calculating exercise estimated annual TEP during 1980–1998 in the range 0.9–3.4×10 11 , and revealed that age groups 9–12 were the main contributors to TEP.

11 pages, 9 figures, 5 tables., At present there is considered to be only one management unit of Sebastes mentella in the Northeast Arctic. A morphometric analysis was conducted to compare specimens from different locations and different times of the year. Residuals of the regression between each morphometric variable and standard length were used as input in a stepwise discriminant analysis, which revealed morphometric differences between three main regions: Svalbard, the Barents Sea and the Norwegian Sea, with the Lofoten area being an intermediate area where fish from the other three areas are present during some of the year. A previously described spawning migration pattern can also be derived from this analysis; the implications on survey design in this region are discussed., This study was supported by the European Union (ERBFMBICT 960772).

Greenland halibut (Reinhardtius hippoglossoides (Walbaum)) are widely distributed over extensive geographic areas of both the Northwest and Northeast Atlantic Ocean with no break in the continuity of the respective distributions. Although the entire Greenland halibut resource in the North Atlantic is genetically homogeneous they mainly comprise a single interbreeding stock in each of the two regional areas investigated. Both stocks show similar distribution patterns over depth. Generally, larger fish become more abundant and smaller fish less abundant in progressively deeper water with peak abundance occurring over a depth range of 400-1000 m. Greenland halibut in the Northwest Atlantic were observed to be most abundant in bottom temperatures mainly between 2 °C and 6 °C compared to 0 °C to 4 °C in the Northeast Atlantic. The fishery for Greenland halibut in the Northeast Atlantic was unregulated until 1992 although since 1995 catches substantially exceed those advised. The spawning stock size re...

Relationships between fecundity (thousands) and total length (cm), F = 1.155 × 10-7 × L4.598 and fecundity (thousands) and round weight (g) (F = 2.539 × 10-4 × W1.439) were established for Greenland halibut in the Northeast Atlantic, based on a total of 95 ovaries collected near the Bear Island in the Barents Sea, in September 1996. The potential fecundity ranged from 6 800 to 70 500 eggs per female. The Greenland halibut were in the total length range 48–80 cm. The Greenland halibut were maturing with ovaries containing vitellogenic oocyte sized about 2–4 mm in diameter, visual to the naked eye.

The early development of the Greenland halibut (Reinhardtius hippoglossoides) has not been described. This study presents some preliminary notes on the egg development of the Northeast Arctic Greenland halibut. Buoyancy and morphometric characteristics of artificially spawned eggs are compared with field sampled eggs, in order to identify these to species. The eggs in the ovary of ripening females were large (about 4 mm), transparent, almost equal in size and stuck to the walls of the ovary. In running, artificially spawned females the ovulated eggs were all easily released in one batch. This may indicate that Greenland halibut has a comparatively long period between each egg batch delivered. Artificially spawned eggs of the Greenland halibut had a diameter varying from 3.3 to 4.2 mm and a neutral buoyancy in seawater of ca. 33‰ (c. 5°C) during the first four days of development. During gastrulation the egg density increased until closure of blastopore. Eggs from field surveys had a diameter raging from 3.9 to 4.7 mm and a neutral buoyancy in seawater of 35.2‰ (ca. 5°C). This corresponds to a density near 1.0279 g/cm3. This density is found at depths around 650 m (34.9‰ salinity and 1.8°C) in the spawning

This study is one of several baseline studies on commercially important Norwegian wild fish species that will provide information concerning metals and persistent organic pollutants (POPs) and food safety. The cod liver is a traditional food product in Norway and a potential source for POPs in the diet. The concentrations of dioxins and furans (PCDD/Fs), dioxin-like PCBs (DL-PCBs), non-dioxin-like PCBs (NDL-PCBs, PCB 6 ) and polybrominated flame retardants (PBDEs) were determined in the liver of 784 individual Northeast Arctic cod caught at 32 positions in the Barents Sea in the period from 2009–2010. In addition, muscle samples from 30 individual cod were analysed for the same substances. The mean concentration of the sum of PCDD/Fs and DL-PCBs for all samples was 14.2 ng TEQ who-2005 /kg ww with a variation between 1.0 and 151 ng TEQ/kg ww. The concentrations of POPs in the fillet samples were very low.

This study is one of several baseline studies that will provide basic and reliable information about the content of undesirable substances in important species of fish caught in Norwegian waters. Concentrations of metals in the muscle and liver of more than 800 Northeast Arctic cod caught at 32 sites in the Barents Sea are reported. The highest concentration of both mercury in the muscle and cadmium in the liver was found in cod caught in the western part of the Barents Sea, while the highest concentration of total arsenic was found in cod from the eastern part. The arsenic concentrations varied greatly among individual fish, ranging from 0.3 to 170 mg kg−1 wet weight in the muscle. Such high levels of total arsenic have never previously been reported in any fish, and the primary factor for these high concentrations is likely to be the shrimp in the cod diet.

Graham, N., Grainger, R., Karp, W. A., MacLennan, D. N., MacMullen, P., and Nedreaas, K. 2011. An introduction to the proceedings and a synthesis of the 2010 ICES Symposium on Fishery-Dependent Information. – ICES Journal of Marine Science, 68: 1593–1597. Current problems and issues concerning the collection and use of fishery-dependent information are reviewed and selected papers in the pages following highlight emergent findings in the field. Key issues include relationships between stakeholders, especially fishers and scientists, and how to develop these constructively, the increasing demands on the quality and range of data on fishing activities and exploitation rates needed to promote the ecosystem approach to fishery management, and technological advances that have allowed new approaches and insights.

Samples of blue mouth, Helicolenus dactylopterus (De La Roche, 1809). were collected in the areas between Shetland and the Faroe Islands, and analysed by starch gel electrophoresis and isoelectric focusing of haemoglobins and tissue enzymes. Moderate intraspecific variation was found, but most enzyme patterns were diagnostic for this species compared to the Sebastes species. The haemoglobin patterns were similar to the pattern of Sebastes marinus and S. viviparus, and thus diagnostic in relation to S. mentella. The estimated genetic distances between blue mouth and the Sebastes species were high (0.92–1.05) compared to corresponding values within the latter genus (0.03–0.13).

14 páginas, 4 figuras.--Steve Cadrin ... et al.-- Acceso avanzado online., Throughout their range, Sebastes spp. are adapted to a diversity of ecological niches, with overlapping spatial distributions of different species that have little or no morphological differences. Divergence of behavioural groups into depth-defined adult habitats has led to reproductive isolation, adaptive radiation, and speciation in the genus Sebastes. Recent genetic research, supported by life-history information, indicates four biological stocks of Sebastes mentella in the Irminger Sea and adjacent waters: a western stock, a deep-pelagic stock, a shallow-pelagic stock, and an Iceland slope stock. Congruent differences in fatty acids and parasites suggest that these genetically distinct populations are adapted to disparate trophic habitats in pelagic waters (shallower and deeper than the deep-scattering layer) and in demersal habitats on the continental slope. Morphology of pelagic forms is also more streamlined than demersal forms. Although genetic differences and evidence for reproductive isolation are clear, these populations appear to share common nursery habitats on the Greenland shelf. We propose a redefinition of practical management units near the Irminger Sea based on geographic proxies for biological stocks and minimizing mixed-stock catches according to the spatial patterns of the recent fishery.