10 results on '"Westgaard, Jon‐Ivar"'
Search Results
2. Taxonomic and genetic confirmed findings of snow crab (Chionoecetes opilio) larvae in the Barents Sea
- Author
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Hjelset, Ann Merete, Danielsen, Hanna Ellerine Helle, Westgaard, Jon-Ivar, and Agnalt, Ann-Lisbeth
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- 2021
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3. Scrutinizing the current management units of the greater argentine in the light of genetic structure.
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Quintela, María, Seljestad, Gaute W, Dahle, Geir, Hallfredsson, Elvar H, Enberg, Katja, Langbehn, Tom J, Jansson, Eeva, Glover, Kevin A, and Westgaard, Jon-Ivar
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FISH food ,PROCESSED foods ,SINGLE nucleotide polymorphisms ,LOCUS (Genetics) ,COASTS - Abstract
The greater argentine is a benthopelagic fish with a northern amphi-Atlantic and southern Arctic distribution. Landings of this species have been steadily increasing since the early 2000s, mainly for ultra-processed fish food. The rising economic importance of this species begs for an accurate delineation of the management units needed to ensure the sustainability of the fishery. The alignment between management and biological units was investigated on three of the ICES stocks in the NE Atlantic (123a4, 5a14, and 5b6a) by genotyping 88 ad hoc- developed SNPs on 1299 individuals sampled along the Norwegian coast, north of Shetland, around the Faroe Islands, and in the Denmark Strait within Icelandic waters. Candidate loci to positive selection were particularly crucial for units' delineation and supported the current ICES 5b6a and 5a14 stocks around the Faroe Islands and Iceland, respectively. However, within the third stock investigated, 123a4, which corresponded mainly to the Norwegian coast, the sample from area 3a (Skagerrak) was significantly different from all the remaining in the same stock. This differentiation advocates for reconsideration of the present policy and suggests considering ICES Area 3a (Skagerrak) as an independent management unit. The environmental conditions in the Skagerrak area have left a genetic print on other marine taxa, which could putatively be the case in the greater argentine. [ABSTRACT FROM AUTHOR]
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- 2024
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4. Maximizing sampling efficiency to detect differences in fish community composition using environmental DNA metabarcoding in subarctic fjords.
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Guri, Gledis, Westgaard, Jon‐Ivar, Yoccoz, Nigel, Wangensteen, Owen S., Præbel, Kim, Ray, Jessica Louise, Kelly, Ryan P., Shelton, Andrew Olaf, Hanebrekke, Tanja, and Johansen, Torild
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- 2024
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5. Contaminants reach everywhere: Fish dietary samples should be surface decontaminated prior to molecular diet analysis.
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Rijal, Dilli Prasad, Hanebrekke, Tanja, Arneberg, Per, Johansen, Torild, Sint, Daniela, Traugott, Michael, Skern‐Mauritzen, Mette, and Westgaard, Jon‐Ivar
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POLLUTANTS ,ECOSYSTEM dynamics ,GASTROINTESTINAL contents ,DIET ,ECOLOGICAL disturbances ,FECAL contamination ,DECONTAMINATION (From gases, chemicals, etc.) - Abstract
Knowledge of trophic interaction is necessary to understand the dynamics of ecosystems and develop ecosystem‐based management. The key data to measure these interactions should come from large‐scale diet analyses with good taxonomic resolution. To that end, molecular methods that analyze prey DNA from guts and feces provide high‐resolution dietary taxonomic data. However, molecular diet analysis may also produce unreliable results if the samples are contaminated by external sources of DNA. Employing the freshwater European whitefish (Coregonus lavaretus) as a tracer for sample contamination, we studied the possible route of whitefish in beaked redfish (Sebastes mentella) guts sampled in the Barents Sea. We used whitefish‐specific COI primers for diagnostic analysis, and fish‐specific 12S and metazoa‐specific COI primers for metabarcoding analyses of intestine and stomach contents of fish samples that were either not cleaned, water cleaned, or bleach cleaned after being in contact with whitefish. Both the diagnostic and COI metabarcoding revealed clear positive effects of cleaning samples as whitefish were detected in significantly higher numbers of uncleaned samples compared to water or bleach‐cleaned samples. Stomachs were more susceptible to contamination than intestines and bleach cleaning reduced the frequency of whitefish contamination. Also, the metabarcoding approach detected significantly more reads of whitefish in the stomach than in intestine samples. The diagnostic analysis and COI metabarcoding detected contaminants in a higher and comparable number of gut samples than the 12S‐based approach. Our study underlines thus the importance of surface decontamination of aquatic samples to obtain reliable diet information from molecular data. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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6. Genetic population structure in Norway lobster (Nephrops norvegicus): management regime under panmixia.
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Westgaard, Jon-Ivar, Søvik, Guldborg, and Johansen, Torild
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MICROSATELLITE repeats , *LOBSTERS , *OCEAN currents , *GENETIC markers , *GENETIC testing - Abstract
Investigations of genetic stock structure sometimes reveal a mismatch between management units and biological units. In Scandinavian waters, Norway lobster (Nephrops norvegicus) is divided into two management units (the Skagerrak–Kattegat and the Norwegian Deep). We have tested the population genetic structure of Nephrops within this region using microsatellite DNA markers, and compared the structure with the present management units. Our study suggests no population genetic structure of Nephrops within the Skagerrak, Kattegat, and Norwegian Deep region, whereas a shallow genetic structure was detected on a larger geographical scale when comparing outgroup samples from Scotland and Iceland. We found indications of sex-biased dispersal as the overall genetic differences were larger for females. Ocean current patterns suggest that Nephrops stocks in the region may be connected by larval drift. The two areas differ in fishing pressure, monitoring, assessment, and regulations, which is an argument for maintaining the present two-areas management regime despite the evidence for one biological population. [ABSTRACT FROM AUTHOR]
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- 2023
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7. Benthic invertebrates in Svalbard fjords--when metabarcoding does not outperform traditional biodiversity assessment.
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Willassen, Endre, Westgaard, Jon-Ivar, Kongsrud, Jon Anders, Hanebrekke, Tanja, Buhl-Mortensen, Pål, and Holte, Børge
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GENETIC barcoding ,FJORDS ,EUPHOTIC zone ,MARINE sciences ,INVERTEBRATES ,BIODIVERSITY - Abstract
To protect and restore ecosystems and biodiversity is one of the 10 challenges identified by the United Nations's Decade of the Ocean Science. In this study we used eDNA from sediments collected in two fjords of the Svalbard archipelago and compared the taxonomic composition with traditional methods through metabarcoding, targeting mitochondrial CO1, to survey benthos. Clustering of 21.6 mill sequence reads with a d value of 13 in swarm, returned about 25 K OTU reads. An identification search with the BOLD database returned 12,000 taxonomy annotated sequences spanning a similarity range of 50% to 100%. Using an acceptance filter of minimum 90% similarity to the CO1 reference sequence, we found that 74% of the ca 100 taxon identified sequence reads were Polychaeta and 22% Nematoda. Relatively few other benthic invertebrate species were detected. Many of the identified sequence reads were extra-organismal DNA from terrestrial, planktonic, and photic zone sources. For the species rich Polychaeta, we found that, on average, only 20.6% of the species identified from morphology were also detected with DNA. This discrepancy was not due to missing reference sequences in the search database, because 90-100% (mean 96.7%) of the visually identified species at each station were represented with barcodes in Boldsystems. The volume of DNA samples is small compared with the volume searched in visual sorting, and the replicate DNA-samples in sum covered only about 2% of the surface area of a grab. This may considerably reduce the detection rate of species that are not uniformly distributed in the sediments. Along with PCR amplification bias and primer mismatch, this may be an important reason for the limited congruence of species identified with the two approaches. However, metabarcoding also identified 69 additional species that are usually overlooked in visual sample sorting, demonstrating how metabarcoding can complement traditional methodology by detecting additional, less conspicuous groups of organisms. [ABSTRACT FROM AUTHOR]
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- 2022
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8. Geographic variation in gene flow from a genetically distinct migratory ecotype drives population genetic structure of coastal Atlantic cod (Gadus morhua L.).
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Breistein, Bjoerghild, Dahle, Geir, Johansen, Torild, Besnier, Francois, Quintela, Maria, Jorde, Per Erik, Knutsen, Halvor, Westgaard, Jon‐Ivar, Nedreaas, Kjell, Farestveit, Eva, and Glover, Kevin Alan
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ATLANTIC cod ,GENE flow ,LIFE history theory ,SUSTAINABLE fisheries ,POPULATION differentiation ,FISHERY management - Abstract
Identifying how physical and biotic factors shape genetic connectivity among populations in time and space is essential to our understanding of the evolutionary trajectory as well as the management of marine species. Atlantic cod is a widespread and commercially important marine species displaying several ecotypes with different life history strategies. Using three sets of SNPs: neutral, informative, and genome‐inversion linked, we studied population genetic structure of ~2500 coastal Atlantic cod (CC) from 40 locations along Norway's 2500 km coastline, including nine fjords. We observed: (1) a genetic cline, suggesting a mechanism of isolation by distance, characterized by a declining FST between CC and North East Arctic Cod (NEAC—genetically distinct migratory ecotype) with increasing latitude, (2) that in the north, samples of CC from outer‐fjord areas were genetically more similar to NEAC than were samples of CC from their corresponding inner‐fjord areas, (3) greater population genetic differentiation among CC sampled from outer‐fjord areas along the coast, than among CC sampled from their corresponding inner‐fjord areas, (4) genetic differentiation among samples of CC from both within and among fjords. Collectively, these results permit us to draw two main conclusions. First, that differences in the relative presence of the genetically highly distinct, migratory ecotype NEAC, declining from north to south and from outer to inner fjord, plays the major role in driving population genetic structure of the Norwegian CC. Second, that there is limited connectivity between CC from different fjords. These results suggest that the current management units implemented for this species in Norway should be divided into smaller entities. Furthermore, the situation where introgression from one ecotype drives population genetic structure of another, as is the case here, may exist in other species and geographical regions, thus creating additional challenges for sustainable fisheries management. [ABSTRACT FROM AUTHOR]
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- 2022
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9. Genetic differentiation between inshore and offshore populations of northern shrimp (Pandalus borealis).
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Hansen, Agneta, Westgaard, Jon-Ivar, Søvik, Guldborg, Hanebrekke, Tanja, Nilssen, Einar Magnus, Jorde, Per Erik, Albretsen, Jon, and Johansen, Torild
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SHRIMP populations , *FISHERIES , *SMALL-scale fisheries , *FJORDS , *SHRIMPS - Abstract
Many marine organisms have a permanent presence both inshore and offshore and spawn in multiple areas, yet their status as separate populations or stocks remain unclear. This is the situation for the northern shrimp (Pandalus borealis) around the Arctic Ocean, which in northern Norway represents an important income for a small-scale coastal fishery and a large-vessel offshore fleet. In Norwegian waters, we uncovered two distinct genetic clusters, viz. a Norwegian coastal and a Barents Sea cluster. Shrimps with a mixed heritage from the Norwegian coastal and the Barents Sea clusters, and genetically different from both, inhabit the fjords at the northernmost coast (Finnmark). Genetic structure between fjords did not display any general trend, and only the Varangerfjord in eastern Finnmark displayed significant genetic structure within the fjord. Shrimps in the Finnmark fjords differed in some degree from shrimps both in the adjacent Barents Sea and along the rest of the coast and should probably be considered a separate management unit. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
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10. Inter-fjord variations in species composition in Svalbard as revealed by eDNA metabarcoding : evidence of 'Atlantification'?
- Author
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Ødegaard, Thea-Elise Kjempengren, Haugen, Thrond Oddvar, and Westgaard, Jon-Ivar
- Abstract
Marin ecosystems faces mass extinction from climate change, and the Arctic marine ecosystems have experienced non-linear change the last decade. “Atlantification”, movement of warm and saline water being moved northward by the West Spitsbergen Current (WSC), has led to alteration of the Arctic marine environment and northward movement of Atlantic and sub-Arctic fish species. Knowledge of species distribution is critical to ecological management and conservation biology. Effective management requires the detection of populations, and biodiversity monitoring is necessary to provide baselines for policies. Recently, there has been considerable interest in the detection of short species-specific environmental DNA (eDNA) fragments to allow aquatic species monitoring within different environments due to the potential of greater sensitivity over traditional survey methods which can be invasive, time-consuming and costly. As well as have limitations in detecting species of low densities and is usually based on visual detection and counting. Water was sampled from two distant fjords in Svalbard, the high-Arctic Rijpfjorden and the sub-Arctic Kongsfjorden to compare patterns of fish biodiversity between the areas. Because of the distant location of the fjord there was expected to be observed difference in species composition, and “Atlantification” was expected to have had a larger impact on the species composition in Kongsfjorden than in Rijpfjorden, whereas Rijpfjorden was expected to be dominated by Arctic species. eDNA was isolated from 1 L per 3 replicates of seawater sampled close to the sea floor from a total of seven stations divided into three sampling groups, three in Kongsfjorden, three in Rijpfjorden and one north of Rijpfjorden. A 170 bp fragment of the mitochondrial 12S ribosomal RNA (rRNA) was used as target region for species detection. Using next-generation DNA sequencing of PCR amplicons, 46 Molecular Operational Taxonomic Units (MOTUs) and 13 fish species were detected. There was found significant differences between temperature, salinity, and depth between all three sampling groups. Although, the significant difference in temperature and salinity was between Rijpfjorden Inner and the two other groups, while significant difference in depth was found between Kongsfjorden and the two Rijpfjorden groups. Despite this there was found no significant difference in biodiversity between the three sampling groups, neither for within- group dispersal or for the mean of the groups. This shows that there was considerable species overlap between the sampling groups, but Atlantic and sub-Arctic species were more dominating in Kongsfjorden than in Rijpfjorden, while the inner parts of Rijpfjorden were dominated by Arctic species. The data supports the hypothesis that the fish community in Kongsfjorden was dominated by north Atlantic and sub-polar species, while in Rijpfjorden it was more dominated by Arctic species. This indicates that Rijpfjorden might be more isolated from the “Atlantification” processes, but Kongsfjorden may serve as an analogue for the future of the northern fjords in Svalbard. M-ECOL
- Published
- 2022
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