Population genetic studies of the Atlantic halibut in the North Atlantic Ocean

Significant variation in frequency distribution of electrophoretically detectable protein variants between samples of Atlantic halibut Hippoglossus hippoglossus showed that the halibut from northern Norway and from the Faroes–Iceland–Greenland region may not belong to one panmictic population.     

Genetic divergence at the synaptophysin (Syp I) locus among Norwegian coastal and north-east Arctic populations of Atlantic cod

Several nuclear RFLP loci have been discovered recently that exhibit extensive allele frequency variation among Norwegian coastal and north-east Arctic populations of Atlantic cod Gadus morhua. One of these polymorphisms was detected by hybridizing an anonymous cDNA clone (GM798) against genomic DNA digested with the restriction enzyme DraI. This cDNA clone has now been sequenced and identified as synaptophysin (Syp I), an integral synaptic vesicle membrane protein. Primers were constructed that amplify an intron of the Syp I gene that is polymorphic for the DraI site, thus making it possible to use a PCR-based assay to score the polymorphism. A total of 965 individuals sampled from the Barents Sea, coastal areas and fjords in northern Norway have been analysed for this polymorphism. The results confirm that highly significant differences exist between NE Arctic and coastal cod at the Syp I locus. A cluster analysis revealed a deep split between coastal and Arctic populations and hierarchical F-statistics indicated that about 40% of the total variation was attributable to differences between Arctic and coastal groups. The temporal stability of allele frequencies was assessed by comparing Syp I allele frequencies among samples of juveniles (0 group) captured at specific locations in fjords in consecutive years and among samples of adults and juveniles collected from the same fjord. Samples of juveniles collected in 1994 and 1995 in Malangen were genetically indistinguishable whereas juveniles sampled from Dønnesfjord and Ullsfjorden over the same 2-year period exhibited significant differences. Adults and 0-group individuals collected from the same fjord were found to be genetically indistinguishable in Malangen, but not in Balsfjorden. In addition to detecting large differences among Arctic and coastal groups, the Syp I locus suggests that genetic heterogeneity exists among resident populations of cod in different fjords and that gene flow among populations throughout northern Norway may be considerably lower than previously believed.     

Population status of Greenland halibut <Emphasis Type="Italic">Reinhardtius hippoglossoides</Emphasis> (Walbaum, 1793) of the Laptev Sea

This is the first study to perform a comparative genetic analysis of Greenland halibut in the samples from the Atlantic (waters of west and east of Greenland), Arctic (Laptev Sea), and Pacific (the western part of the Bering Sea) ocean basins using seven microsatellite loci. The obtained data clearly demonstrate that the Greenland halibut population in the Laptev Sea belongs to the groups of the Atlantic Ocean basin. Apparently, the Greenland halibut of the Laptev Sea is represented by a dependent population, which is replenished due to the drift of immatures from the spawning grounds in the Barents Sea with the transformed Atlantic water flow along the continental slope. In addition, the Arctic population can be partially replenished due to the breeding of the halibut in local spawning grounds.     

Do Norwegian Atlantic salmon feed in the northern Barents Sea? Tag recoveries from 70 to 78° N

Three tagged Atlantic salmon Salmo salar were recaptured as subadults or adults (1·4–3 kg) between 70·5 and 78° N in the western Barents Sea, two of which originated from the Alta Fjord region in northern Norway and one from the Drammen River, south-eastern Norway. An additional tag was recovered from the stomach of a Greenland halibut Reinhardtius hippoglossoides captured south-west of Bear Island at >600 m depth; this tag was from a smolt released in the River Alta 1 month earlier. These are the northernmost tag recoveries reported for Atlantic salmon, and indicate that Norwegian Atlantic salmon, especially the fish from northern populations, may use the northern Barents Sea as a feeding area during part of their life cycle.     

Genetic structure among continental and island populations of gyrfalcons

Little is known about the possible influence that past glacial events have had on the phylogeography and population structure of avian predators in the Arctic and sub-Arctic. In this study, we use microsatellite and mitochondrial control region DNA variation to investigate the population genetic structure of gyrfalcons (Falco rusticolus) throughout a large portion of their circumpolar distribution. In most locations sampled, the mtDNA data revealed little geographic structure; however, five out of eight mtDNA haplotypes were unique to a particular geographic area (Greenland, Iceland, or Alaska) and the Iceland population differed from others based on haplotype frequency differences (F(ST)). With the microsatellite results, significant population structure (F(ST), principal components analysis, and cluster analysis) was observed identifying Greenland and Iceland as separate populations, while Norway, Alaska and Canada were identified as a single population consistent with contemporary gene flow across Russia. Within Greenland, differing levels of gene flow between western and eastern sampling locations was indicated with apparent asymmetric dispersal in western Greenland from north to south. This dispersal bias is in agreement with the distribution of plumage colour variants with white gyrfalcons in much higher proportion in northern Greenland. Lastly, because the mtDNA control region sequence differed by only one to four nucleotides from a common haplotype among all gyrfalcons, we infer that the observed microsatellite population genetic structure has developed since the last glacial maximum. This conclusion is further supported by our finding that a closely related species, the saker falcon (Falco cherrug), has greater genetic heterogeneity, including mtDNA haplotypes differing by 1-16 nucleotide substitutions from a common gyrfalcon haplotype. This is consistent with gyrfalcons having expanded rapidly from a single glacial-age refugium to their current circumpolar distribution. Additional sampling of gyrfalcons from Fennoscandia and Russia throughout Siberia is necessary to test putative gene flow between Norway and Alaska and Canada as suggested by this study.     

Genetic variation at enzyme loci in North Atlantic minke whales,Balaenoptera acutorostrata

Electrophoretic variation within and between North Atlantic minke whale samples(Balaenoptera acutorostrata) from West Greenland, Iceland, and Norway was investigated. In the West Greenland samples, 28 enzyme systems were examined, representing 36 loci, of which 6 were found to be polymorphic. In Icelandic and Norwegian samples, 22 enzyme systems were examined, representing 29 loci, of which 6 and 5 were found to be polymorphic, respectively. The average heterozygosity was 0.058 (SE=0.024) in samples from West Greenland, 0.074 (SE=0.028) in samples from Iceland, and 0.054 (SE=0.023) in samples from Norway. No significant deviations from the expected Hardy—Weinberg genotypic frequencies, within samples taken from the same area, were found. Significant differences in allele frequencies were observed, however, between samples from the three different areas. The average Nei's genetic distance was 0.014 and the averageF _st value was 0.126. The genetic differences between the samples from the different areas indicate that those from West Greenland, Iceland, and Norway represented different breeding populations.     

Ovary development in Greenland halibut Reinhardtius hippoglossoides in west Greenland waters

Maturity in adult female Greenland halibut Reinhardtius hippoglossoides was studied in three areas in west Greenland waters: the inshore area in Disko Bay and two offshore areas, Baffin Bay and Davis Strait. The aim was to monitor maturity changes in the inshore fjords of Disko Bay over an extended period from winter to autumn and compare these findings with specimens from Baffin Bay and the presumed spawning area in Davis Strait. A significant difference in maturity level was observed in and between the three areas. In Disko Bay maturity indices increased significantly in August and September both with respect to the gonado‐somatic index ( I _G) and the size in the leading oocyte cohort. In the period February to May no significant changes were observed. Mature ovaries were only observed among fish >80 cm total length and only among a fraction of these large fish. Offshore areas of Baffin Bay, even though poorly sampled, showed similar signs in the maturity indices as in Disko Bay. Relative to Disko Bay and Baffin Bay, female fish in Davis Strait had more progressed maturity indices. Furthermore, almost all fish in Davis Strait showed signs of progressed maturity contrary to Disko and Baffin Bay. A large proportion of the Greenland halibut in Disko and Baffin Bay apparently did not begin the maturation cycle until very late in their life history or were repeat spawners with a multi‐year maturation cycle. These observations could thus support the hypothesis that Greenland halibut have a prolonged adolescent phase. Atresia was highest in the early phases of maturation in Greenland halibut but relatively high levels of atresia were also observed in fish in more advanced maturity phase. The first was ascribed to fecundity regulation while the latter could be linked to the fish's fitness condition but it was not possible to show this with the available condition index.     

Melanophore comparisons in different forms of ambicoloration in the flatfish Pseudopleuronectes americanus and Reinhardtius hippoglossoides

The melanophores associated with contrasting manifestations of ambicoloration in two species, winter flounder ( Pseudopleuronectes americanus ) and Greenland halibut ( Reinhardtius hippoglossoides ), from the Pleuronectidae are compared microscopically. Winter flounder is a benthic inshore species, whilst Greenland halibut is a deep water species considered to spend the greater part of its life away from the sea floor, although the relatively thick blind-side epidermis associated with a benthic life occurs in both species. Various forms of abnormal ambicoloration occur in some specimens of winter flounder. Melanophores from the flounder blind side are morphologically similar to those from the ocular side in the different forms of ambicoloration, although there are differences in melanophore densities. In Greenland halibut, ambicoloration is a normal characteristic which is considered to be secondarily acquired. The melanophores of the ocular side of Greenland halibut are similar to the melanophores of other Pleuronectidae, whereas those of the blind side are very different in morphology and size.     

Preliminary assessment of Greenland halibut diet in Cumberland Sound using stable isotopes

We provide preliminary carbon (δ¹³C) and nitrogen (δ¹⁵N) stable isotope assessment of the Greenland halibut (Reinhardtius hippoglossoides) diet in Cumberland Sound, with focus on two possible prey sources: pelagic represented by capelin (Mallotus villosus) and epibenthic represented by shrimp (Lebbeus polaris). The δ¹³C for the Greenland halibut stock indicated a pelagic carbon source in Cumberland Sound while stable isotope mixing models, IsoSource and MixSIR, indicated a 99% dietary composition of capelin relative to the shrimp. The δ¹⁵N did not vary across Greenland halibut size ranges and placed them at a fourth trophic position relative to a primary herbivore. This study provides the starting point for more elaborate Cumberland Sound research on the local Greenland halibut feeding ecology by confirming pelagic feeding and establishing relative trophic position as well as identifying stable isotopes as a useful tool for the study of diet in cold water fish species.     

Catching of Greenland halibut <Emphasis Type="Italic">Reinhardtius hippoglossoides</Emphasis> (Pleuronectidae) on the shelf edge of the Laptev and East Siberian Seas

The first capture of the Greenland (or Black) halibut Reinhardtius hippoglossoides in the Arctic Ocean on the border with the East Siberian Sea (79°03′–79°08′ N 139°59′–141°16′ E, 259–277 m) and the repeated findings of the species in the Laptev Sea (78°03′–78°04′ N 132°56′–133°04′ E, 307 m; 78°33′–78°35′ N 138°44′–138°48′ E, 125 m) are reported. Fish (79 specimens with the length of 15.0–44.5 cm) were caught during four bottom trawlings on the edge of the continental shelf of the two seas in the transformed waters of Atlantic origin, as evidenced by the discovery of the indicator species of these waters—the Glacier lanternfish Benthosema glaciale (Myctophidae)—in one of the stomachs of halibut. The other captures of Greenland halibut in the Arctic were also reviewed.     

Oogenesis and the spawning pattern in Greenland halibut from the North-west Atlantic

Gametogenesis in Greenland halibut Reinhardtius hippoglossoides from the North-west Atlantic is not synchronous between individuals of the same population suggesting that the spawning season is not well defined. Differences in oocyte size–frequency distributions in prespawning, spawning and spent conditions suggest that Greenland halibut are capable of de novo vitellogenesis prior to and during spawning, indicating that the spawning pattern is not determinate. Greenland halibut may be capable of fast-tracking oocytes to maturity, whereby during the spawning season oocyte batches may be brought quickly through vitellogenesis so as to increase the fish's yearly reproductive output. 1999 The Fisheries Society of the British Isles     

Distribution,prevalence and mean numbers of larvalAnisakis simplex (Nematoda: Ascaridoidea) in Atlantic salmon,Salmo salar L. and their use as biological indicators of host stocks

Synopsis An estimate of the arithmetic mean number of larvalAnisakis simplex per salmon,Salmo salar, in the north Atlantic was obtained from data collected off west Greenland where salmon from both sides of the Atlantic intermingle. An average of 5.34 larvae was found in the body cavity or associated viscera of 771 age 1 salmon representing some 60.8% of the total number of larvae present. LarvalA. simplex were found at all sampling stations throughout the north Atlantic. In most samples prevalence varied only slightly from area to area.The mean numbers of larvae in the body cavity and on associated organs of salmon in samples from North America were significantly different between samples. Comparisons of the mean numbers of larvae with several known variables in the data were, therefore, considered: host's sex, host's sea-age, geographic locality, year and season of capture.There was evidence that the mean number of larvae per host was greater in salmon from Europe than in those from North America, but the data could not be used to providereliable estimates of the mean numbers of larvae from each area because of heterogeneity within areas. Thus the data from west Greenland and from continental home waters could net be used in calculations to determine the percentage composition of North American and European salmon in the Greenland fishery although they supported earlier findings of mixing of salmon stocks off west Greenland.The use of parasitological data in the identification of different Atlantic salmon stocks is discussed.     

THE MIGRATION PATTERNS OF THE PURPLE SANDPIPER CALIDRIS MARITIMA

Summers, R. W. 1994. The migration patterns of the Purple Sandpiper Calidris maritima. Ostrich 65: 167–173.

The Purple Sandpiper breeds largely in the Arctic, and winters (boreal season) on the rocky shores of the north Atlantic, further north than any other sandpiper. As the populations from Canada, Greenland, Iceland, Svalbard, Norway and Russia differ in wing and bill lengths it is possible to match measurements taken from breeding birds with samples of birds caught in winter. Ringing recoveries, especially from colour marked birds, have also helped to determine migration routes and wintering areas. Four populations move to the nearest ice-free coast. Two populations move south of the nearest ice-free coast, being replaced by larger birds from a more northerly population (“chain migration”). Only the north Canadian population is believed to migrate a long distance, “leap-frogging” other winter populations. These patterns are discussed in relation to theories for the migration patterns of waders.     

Microarray analysis of defined Mycobacterium tuberculosis populations using RNA amplification strategies

Background

Halibuts are commercially important flatfish species confined to the North Pacific and North Atlantic Oceans. We have determined the complete mitochondrial genome sequences of four specimens each of Atlantic halibut (Hippoglossus hippoglossus), Pacific halibut (Hippoglossus stenolepis) and Greenland halibut (Reinhardtius hippoglossoides), and assessed the nucleotide variability within and between species.

Results

About 100 variable positions were identified within the four specimens in each halibut species, with the control regions as the most variable parts of the genomes (10 times that of the mitochondrial ribosomal DNA). Due to tandem repeat arrays, the control regions have unusually large sizes compared to most vertebrate mtDNAs. The arrays are highly heteroplasmic in size and consist mainly of different variants of a 61-bp motif. Halibut mitochondrial genomes lacking arrays were also detected.

Conclusion

The complexity, distribution, and biological role of the heteroplasmic tandem repeat arrays in halibut mitochondrial control regions are discussed. We conclude that the most plausible explanation for array maintenance includes both the slipped-strand mispairing and DNA recombination mechanisms.     

Population structure and gene flow of the Atlantic walrus (Odobenus rosmarus rosmarus) in the eastern Atlantic Arctic based on mitochondrial DNA and microsatellite variation

The population structure of the Atlantic walrus, Odobenus rosmarus rosmarus , was studied using 11 polymorphic microsatellites and restriction fragment length polymorphism detected in the NADH-dehydrogenase ND1, ND2 and ND3/4 segments in mtDNA. A total of 105 walrus samples were analysed from northwest (NW) Greenland, east (E) Greenland, Svalbard and Franz Joseph Land. Two of the 10 haplotypes detected in the four samples were diagnostic for the NW Greenland sample, which implied that the group of walruses in this area is evolutionary distinct from walruses in the other three areas. One individual sampled in E Greenland exhibited a Pacific haplotype, which proved a connection between the Pacific walrus and walruses in eastern Greenland. The Franz Joseph Land, Svalbard and E Greenland samples shared the most common haplotype, indicating very little differentiation at the mtDNA level. Gene flow ( Nm ) estimates among the four areas indicated a very restricted exchange of female genes between NW Greenland and the more eastern Atlantic Arctic samples, and a closer relationship between the three samples composing the eastern Atlantic Arctic. The genetic variation at 11 polymorphic microsatellite loci grouped individuals into three populations, NW Greenland, E Greenland and a common Franz Joseph Land–Svalbard population, which were connected by moderate gene flow.     

Step‐less models for regional environmental variation in Norway

Aim To assess the scale of variation for major environmental gradients in Norway. To obtain a step‐less model for this variation and to use this model to evaluate the extent to which the consensus expert classification of Norway into vegetation regions can be predicted from environmental variables. To discuss the potential of step‐less models for understanding natural variation at regional scales, for stratification and for predictive modelling of species distributions and land‐cover types. Location The mainland of Norway. Methods Fifty‐four climatic, topographical, hydrological and geological variables were recorded for grid cells with spatial resolution (grain size) of 1 × 1, 5 × 5 and 10 × 10 km, spanning the entire mainland of Norway. Principal components analyses (PCA) were used to summarize variation in three primary data matrices and three random subsets of these. Results The first four principal components explained between 75% and 85% of the variation in the data sets. All PCAs revealed four consistent environmental gradients, in order of decreasing importance: (1) regional variation (gradient) from coast to inland and from oceanic/humid to continental areas; (2) regional variation from north to south and from high to low altitudes; (3) regional variation from north to south and from inland to coast, related to solar radiation; and (4) topographic (terrain relief) variation on finer scales than (1–3). The first two PCA axes corresponded to the two bioclimatic gradients used in expert classifications of Norway into biogeographical regions: vegetation sections (from highly oceanic to slightly continental) and vegetation zones (from nemoral to alpine). Main conclusions Our PCA analyses substantiate the current view of bioclimatic regional vegetation variation in Norway, provide an explicit characterization of this variation in terms of climatic variables, and show that environmental variability can be reproduced as GIS layers in step‐less models. These models have the potential to become important tools for future predictive modelling within resource management, conservation planning and biogeographical (and other ecological) research.     

Diets of hooded seals (Cystophora cristata) in coastal waters and drift ice waters along the east coast of Greenland

To provide data on the diets of hooded seals (Cystophora cristata) in the Greenland Sea, seals were collected for scientific purposes on expeditions conducted in the pack ice belt east of Greenland in September/October 1999, 2002 and 2003 (autumn), July/August in 2000 (summer), and February/March in 2001 and 2002 (winter). The results from analyses of stomach and intestinal contents from captured seals revealed that their diet was comprised of relatively few prey taxa. The squid Gonatus fabricii and polar cod (Boreogadus saida) were particularly important, whereas capelin (Mallotus villosus) and sand eels (Ammodytes spp.) occasionally contributed more. These four prey items constituted 60-97% of the diet biomass. Gonatus fabricii was the most important food item in autumn and winter, whereas polar cod dominated the summer diet, with important contributions from G. fabricii and sand eels. The latter was only observed on the hooded seal menu during the summer period, whereas polar cod, which was an important component during the autumn survey, was almost absent from the winter samples. During the latter survey, capelin also contributed to the hooded seal diet. Samples obtained from hooded seals in more coastal waters indicated a more varied diet based on fish such as polar cod, redfish (Sebastes sp.) and Greenland halibut (Reinhardtius hippoglossoides).     

Feeding of Greenland halibut <Emphasis Type="Italic">Reinhardtius hippoglossoides</Emphasis> (Pleuronectidae) in the Kara Sea

Feeding of Greenland halibut Reinhardtius hippoglossoides in the northern Kara Sea was studied based on data collected in summer–autumn 2007–2013. The main food of all size groups of halibut were fish—up to 98% of weight of the food bolus. Larger individuals had lower intensity of feeding as compared to juveniles, which was probably owing to the lack of suitable food for large fish and, along with gonad maturation process, could be one of the reasons of their migration to the Barents Sea. The northern part of the Kara Sea, as well as the adjacent areas of Barents Sea, can be considered as an important area of habitation of juvenile Greenland halibut of the Norwegian–Barents Sea population.     

WINTER FEEDING INTENSITY OF NARWHALS (MONODON MONOCEROS)

Stomach contents from 121 narwhals ( Monondon monoceros ) harvested in the eastern Canadian High Arctic and West Greenland were used to quantify seasonal changes in feeding activity and prey selection. Stomachs collected from summer harvests were mostly empty with little evidence of recent feeding. Stomachs collected in late fall and winter harvests had considerable amounts of undigested material with evidence of recent feeding. In summer, Arctic cod ( Arctogadus glacialis ), polar cod ( Boreogadus saida ), and Gonatus squid spp. constituted the narwhal diet. In fall, Gonatus fabricii was the only prey item observed. In late fall and winter, Greenland halibut ( Reinhardtius hippoglossoides ) and G. fabricii were the dominant prey items, observed in 51% and 73% of stomachs collected, respectively. Greenland halibut taken by narwhals were on average 39 cm (SD 8) and 556 g (306) and G. fabricii were on average 23 g (15) with mean mantle lengths of 85 mm (24). The low diversiry of prey species indicates narwhals have a restricted diet across all seasons. This study presents the first information on the winter diet of the narwhal and suggests Baffin Bay and Davis Strait are heavily utilized for feeding, in contrast to limited food intake during the summer period.     

Inter- and Intra-Species Relationships of Greenland Halibut Reinhardtius hippoglossoides (Pleuronectidae) Based on the Analysis of Nuclear and Mitochondrial Genetic Markers

Journal of Ichthyology - Samples of Greenland halibut Reinhardtius hippoglossoides (Jordan and Snyder, 1901) from the Atlantic, Arctic, and Pacific Oceans were compared using eight microsatellite...