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The impacts of climate change on marine ecosystems can be seen in the changing distribution, migration, and abundance of species in the oceans. For some species this changing environment may be beneficial and can support population expansions. In the northeast Atlantic (NEA), the Atlantic mackerel (Scomber scombrus) is undergoing an increase in stock size accompanied by changing summer migration patterns, which have resulted in an expansion further north and north west than previously recorded. This study uses microsatellite loci to confirm the differentiation among NEA and northwest Atlantic (NWA) mackerel spawning populations and to assess the level of structuring within these populations. In addition, to enable population-specific exploitation rates to be factored into fisheries management, we identified the origin of individuals composing the expanding feeding aggregations in the central north Atlantic (Greenland, Iceland, Faroes), with all aggregations tested originating from spawning populations in the NEA. This study showed that microsatellite loci were useful to assess the contribution of NEA and NWA populations to mixed feeding aggregations across the north Atlantic for large pelagic fish stocks but were not powerful enough to evaluate the specific contribution of known stocks within NEA and NWA. [ABSTRACT FROM AUTHOR]

The origin and life history of 186 Atlantic salmon caught at sea within Icelandic waters were investigated using microsatellites to assess the origin and scales and otoliths to assess freshwater and sea age. A total of 184 samples were aged using scales or otolithes or both. Most of the samples were from individuals in their first year at sea (72.8%). The freshwater age varied from 1 to 5 years with an average of 2.6 years. The most common freshwater age was 2 years (42%), with a further substantial proportion of 3-year-old fish (28%). Genetic assignment of individual fish to their most likely population of origin was performed using Bayesian genetic individual assignments with a baseline consisting of 284 Eastern Atlantic rivers and 466 sample sites genotyped at the 14 microsatellite. A total of 186 samples of salmon caught at sea were assigned to their origin. Eight samples, from post-smolts and caught close to land, were assigned as having come from Iceland. Of the remaining 178 samples, 121 individuals (68%) were from the Southern Group, i.e. from mainland Europe, the UK, and Ireland, 53 individuals (30%) were from the Northern Group, i.e. Scandinavia and Northern Russia, and 4 individuals were from Iceland (2%). Stock mixture proportions were estimated for four periods using ONCOR and cBAYES. Stock mixture analysis generally supported the individual assignments, but did not suggest a seasonal component to the distribution of salmon stocks. These results indicate that the sea south and east of Iceland are important as feeding areas for migrating Atlantic salmon, particularly for salmon originating in the UK, Ireland, and southern Europe. Furthermore, the lack of adult Icelandic fish so close to Iceland is remarkable and suggests that Atlantic salmon from Icelandic stocks are using different feeding grounds. [ABSTRACT FROM AUTHOR]

Lumpfish, or lumpsucker, Cyclopterus lumpus (Linnaeus, 1758) is widely distributed in the North Atlantic Ocean. It has a considerable economic value and substantial fisheries occur in several North Atlantic regions owing to the use of its fully ripe internal egg masses in the ovaries as an alternative to sturgeon caviar. Despite being intensively fished in several locations, biological knowledge is limited and no genetic structure information is available. In this study, the stock structure of C. lumpus was investigated across the North Atlantic using ten microsatellite loci. Out of ten loci, two exhibited higher level of differentiation but their inclusion/exclusion from the analyses did not drastically change the observed genetic pattern. A total of three distinct genetic groups were detected: Maine–Canada–Greenland, Iceland–Norway and Baltic Sea. These results, discussed in terms of origin of differentiation, gene flow, and selection, showed that gene flow was rather limited among the detected groups, and also between Greenland and Maine–Canada. [ABSTRACT FROM AUTHOR]

Pampoulie, C., Skirnisdóttir, S., Daníelsdóttir, A. K., and Gunnarsson, Á. 2012. Genetic structure of the Atlantic wolffish (Anarhichas lupus L.) at Icelandic fishing grounds: another evidence of panmixia in Iceland? – ICES Journal of Marine Science, 69: 508–515.The stock structure of the Atlantic wolffish was investigated at Icelandic fishing grounds, using 16 microsatellite loci. Despite the potential of the Atlantic wolffish to exhibit genetic structure (lack of eggs/larval dispersal and adults are sedentary), none of the genetic tests applied in this study detected significant genetic differentiation among the contemporary samples as well as among the contemporary and archived samples. The results of this study therefore suggested a lack of genetic structure among the populations of Atlantic wolffish in Icelandic waters and temporal stability over a period of ∼10 years. These results are discussed in terms of biological characteristics of Atlantic wolffish, recent isolation of populations, and their application to sustainable fisheries management issues. [ABSTRACT FROM PUBLISHER]

Pampoulie, C., Skirnisdottir, S., Hauksdottir, S., Olafsson, K., Eiríksson, H., Chosson, V., Hreggvidsson, G. O., Gunnarsson, G. H., and Hjorleifsdottir, S. 2011. A pilot genetic study reveals the absence of spatial genetic structure in Norway lobster (Nephrops norvegicus) on fishing grounds in Icelandic waters. – ICES Journal of Marine Science, 68: 20–25. Stock structure of Norway lobster off southern Iceland was investigated using 12 microsatellite loci. No genetic method detected significant genetic differentiation among the locations sampled, even among Icelandic samples and an out-group from Scotland. Testing the power of resolution of microsatellite loci, the loci and sample sizes used were sufficient to detect significant genetic differentiation with confidence. The lack of genetic structure is discussed in terms of the level of gene flow, recent isolation of populations, and the statistical power of the experimental design. [ABSTRACT FROM PUBLISHER]

Cadrin, S. X., Bernreuther, M., Daníelsdóttir, A. K., Hjörleifsson, E., Johansen, T., Kerr, L., Kristinsson, K., Mariani, S., Nedreaas, K., Pampoulie, C., Planque, B., Reinert, J., Saborido-Rey, F., Sigurðsson, T., and Stransky, C. 2010. Population structure of beaked redfish, Sebastes mentella: evidence of divergence associated with different habitats. – ICES Journal of Marine Science, 67: 1617–1630.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. [ABSTRACT FROM PUBLISHER]

Pampoulie, C., Gíslason, D., and Daníelsdóttir, A. K. 2009. A “seascape genetic” snapshot of Sebastes marinus calls for further investigation across the North Atlantic. – ICES Journal of Marine Science, 66: 2219–2222.A collection of 376 golden redfish (Sebastes marinus) from several fishing grounds in the North Atlantic in late 2001 was genotyped at nine microsatellite loci to provide preliminary information on the possible genetic structure in this species. Landscape genetic analysis revealed the presence of two distinct genetic pools within the North Atlantic, suggesting that S. marinus might be structured within the North Atlantic and should be the subject of more investigation. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM PUBLISHER]

Most studies of the genetic structure of Atlantic cod have focused on small geographical scales. In the present study, the genetic structure of cod sampled on spawning grounds in the North Atlantic was examined using eight microsatellite loci and the Pan I locus. A total of 954 cod was collected from nine different regions: the Baltic Sea, the North Sea, the Celtic Sea, the Irish Sea and Icelandic waters during spring 2002 and spring 2003, from Norwegian waters and the Faroe Islands (North and West spawning grounds) in spring 2003, and from Canadian waters in 1998. Temporal stability among spawning grounds was observed in Icelandic waters and the Celtic Sea, and no significant difference was observed between the samples from the Baltic Sea and between the samples from Faroese waters. F-statistics showed significant differences between most populations and a pattern of isolation-by-distance was described with microsatellite loci. The Pan I locus revealed the presence of two genetically distinguishable basins, the North-west Atlantic composed of the Icelandic and Canadian samples and the North-east Atlantic composed of all other samples. Permutation of allele sizes at each microsatellite locus among allelic states supported a mutational component to the genetic differentiation, indicating a historical origin of the observed variation. Estimation of the time of divergence was approximately 3000 generations, which places the origin of current genetic pattern of cod in the North Atlantic in the late Weichselian (Wisconsinian period), at last glacial maximum. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 94, 315–329. [ABSTRACT FROM AUTHOR]

Pampoulie, C., Steingrund, P., Stefánsson, M. Ö., and Daníelsdóttir, A. K. 2008. Genetic divergence among East Icelandic and Faroese populations of Atlantic cod provides evidence for historical imprints at neutral and non-neutral markers. – ICES Journal of marine Science, 65: 65–71.During the past decade, genetic markers have been used increasingly to improve stock discrimination and to aid fisheries management. Today, the Icelandic and Faroese Plateau cod (Gadus morhua) are managed as separate units, belonging to ICES Subareas Va and Vb1, respectively. There is little information on the genetic connectivity of the two units, however, except in terms of tagging experiments which revealed limited adult migration between the two areas, and few genetic studies describing genetic differentiation among Faroese and East Icelandic cod. Here, previously published data on the genetic structure of Icelandic cod were combined with new data from the Faroe Plateau to assess the level and the source of genetic variability of Atlantic cod around the Iceland–Faroe Ridge and the potential sources of genetic variation. In all, 771 cod were genotyped at nine microsatellite loci and at the Pantophysin locus (Pan I). The genetic markers employed were congruent and showed that South Icelandic and East Icelandic–Faroese Plateau populations have limited genetic connectivity. Diversifying selection associated with restricted gene flow is likely to explain the observed pattern with the Pan I locus. Further analyses detected historical imprints in the microsatellite data, suggesting that the divergence could be due to isolation of different cod populations during the last glacial maximum. [ABSTRACT FROM PUBLISHER]

Cadrin, S. X., Mariani, S., Pampoulie, C., Bernreuther, M., Daníelsdóttir, A. K., Johansen, T., Kerr, L., Nedreaas, K., Reinert, J., Sigurðsson, Þ., and Stransky, C. 2011. Counter-comment on: Cadrin et al. (2010) “Population structure of beaked redfish, Sebastes mentella: evidence of divergence associated with different habitats. ICES Journal of Marine Science, 67: 1617–1630.” – ICES Journal of Marine Science, 68: 2016–2018.A one-stock hypothesis for S. mentella in the Irminger Sea was rejected in favour of one involving depth-segregated stock structure based on the best scientific information available, including recent genetic results. The depth-based hypothesis is maintained and supported, despite the criticisms by Makhrov et al. (2011), which can all be explained and refuted. [ABSTRACT FROM PUBLISHER]