Genetic population structure in Norway lobster (Nephrops norvegicus): management regime under panmixia

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.publishedVersio

Farming of Atlantic cod Gadus morhua in the vicinity of major spawning sites for Norwegian coastal cod populations - is it hazardous?

Waters along and adjacent to the coast of northern Norway are unique in housing two major populations of Atlantic cod with very di erent life histories. The Northeast Arctic cod (NEAC) has its nursery and feeding grounds in the Barents Sea but migrates to the coast of northern Norway to spawn. Norwegian coastal cod (NCC) is more stationary, spawns mainly at local sites in individual ords but to some degree also overlap with the spawning sites of NEAC (Fig.1). These distinctive patterns in life history are re ected in a clear-cut genetic divergence between the two populations. Various molecular genetic markers (scnDNA, microsatellites and SNPs) have displayed genetic di erences between NEAC and NCC which are remarkable for marine sh with a comparable gene ow potential (cf. Sarvas and Fevolden 2005, Wennevik et al. 2008, and Westgaard and Fevolden 2008 for recent updates)

Genetic management of mixed-stock fisheries "real-time": The case of the largest remaining cod fishery operating in the Atlantic in 2007-2017

Fish stocks represent fundamental units in fisheries management, and their identification, especially in mixed-fisheries, represents one of the primary challenges to sustainable harvest. Here, we describe the first “real-time” genetic management program used to manage a mixed-stock fishery of a non-salmonid and commercially significant marine fish, the Atlantic cod (Gadus morhua L). Based upon the analysis of >18 000 fish sampled from the commercial catch in Lofoten (Norway), which represents the largest remaining cod fishery in the Atlantic, we estimated the fraction of North East Arctic cod (NEAC), and Norwegian Coastal cod (NCC), just 24 h post-landing. These estimates, based upon the analysis of the Pantophysin gene, were performed weekly in the winter and spring of each year in the period 2007–2017. The program has successfully permitted the Norwegian Directorate of Fisheries to actively manage the commercial exploitation of the highly abundant NEAC stock, while simultaneously limiting exploitation of the fragile NCC stock, both of which overlap at the spawning grounds. Data from this program have also revealed a distinct temporal increase in the fraction of NEAC on the spawning grounds in this region, which is consistent with the overall increased abundance of this stock as estimated by ICES.publishedVersio

Benthic invertebrates in Svalbard fjords—when metabarcoding does not outperform traditional biodiversity assessment

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.publishedVersio

Taxonomic and genetic confirmed findings of snow crab (Chionoecetes opilio) larvae in the Barents Sea

The snow crab (Chionoecetes opilio) is an Arctic cold-water species native to the northwestern Atlantic Ocean and the northern Pacific Ocean. During the recent decades, a population has established in the Barents Sea. Several aspects of the snow crabs’ biology in this area have not been described, including time of hatching, intermoult duration of the different larval stages and larval distribution. Insight into the early-life stages might increase the understanding of the population's dynamics and further spreading in the Barents Sea as well as inform basis for making monitoring and management decisions. The present study investigated the presence and developmental stage of snow crab larva in plankton samples obtained in the central Barents Sea during a research survey in June and July 2019. Presence of snow crab larvae was confirmed through taxonomic and genetic identification. All larvae were identified as zoea I, which gives an indication of the timing of the hatching period. Morphological measurements coincide well with those reported in studies from the species native distribution range. No larvae of native Hyas spp. were found and overlap in temporal and spatial distribution is discussed. The study provides important information for development of further research into the biology of the snow crab in the Barents Sea.publishedVersio

Genetic differentiation between inshore and offshore populations of northern shrimp (Pandalus borealis)

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

Contaminants reach everywhere: Fish dietary samples should be surface decontaminated prior to molecular diet analysis

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.publishedVersio

Geographic extent of introgression in Sebastes mentella and its effect on genetic population structure

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Genetic structuring in Atlantic haddock contrasts with current management regimes

The advent of novel genetic methods has made it possible to investigate population structure and connectivity in mobile marine fish species: knowledge of which is essential to ensure a sustainable fishery. Haddock (Melanogrammus aeglefinus) is a highly exploited marine teleost distributed along the coast and continental shelf on both sides of the North Atlantic Ocean. However, little is known about its population structure. Here, we present the first study using single-nucleotide polymorphism (SNP) markers to assess the genetic population structure of haddock at multiple geographic scales, from the trans-Atlantic to the local (fjord) level. Genotyping 138 SNP loci in 1329 individuals from 19 locations across the North Atlantic revealed three main genetic clusters, consisting of a Northwest Atlantic cluster, a Northeast Arctic cluster, and a Northeast Atlantic cluster. We also observed a genetically distinct fjord population and a pattern of isolation by distance in the Northeast Atlantic. Our results contrast with the current management regime for this species in the Northeast Atlantic, as we found structure within some management areas. The study adds to the growing recognition of population structuring in marine organisms in general, and fishes in particular, and is of clear relevance for the management of haddock in the Northeast Atlantic.publishedVersionPaid open acces

Isolation and characterization of nuclear microsatellite loci in the northern shrimp, Pandalus borealis

Published version of an article published in the journal: Conservation Genetics Resources. Also available from the publisher at: http://dx.doi.org/10.1007/s12686-011-9486-4We developed and characterized 20 microsatellite primer loci for the northern shrimp Pandalus borealis. All 20 loci were polymorphic with number of alleles ranging from 3 to 36 and with observed heterozygosity between 0.04 and 0.93. In addition, we tested the utility of these markers in three related shrimp species, P. montagui, Atlantopandalus propinqvus and Dichelopandalus bonnieri. These new markers will prove useful in the identification of stock structure and hence, assessment of the commercially important species P. borealis