Publications

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sealworm (pseudoterranova decipiens) infection in common seals (phoca vitulina) and potential intermediate fish hosts from the outer oslofjord.infection with pseudoterranova decipiens in 45 common seals (phoca vitulina) from the outer oslofjord was investigated. seals were collected before and during the phocine distemper virus epizootic in 1988 when the seal population in the area was reduced from about 350 to 100. in 1989, cod (gadus morhua) and other fish species were sampled for comparison with earlier investigations on prevalence and abundance of p. decipiens infection in fishes from the outer oslofjord. seventy-two per cent of co ...19957601595
natural selection and the genetic differentiation of coastal and arctic populations of the atlantic cod in northern norway: a test involving nucleotide sequence variation at the pantophysin (pani) locus.to examine the role of contemporary selection in maintaining significant allele frequency differences at the pantophysin (pani) locus among populations of the atlantic cod, gadus morhua, in northern norway, we sequenced 127 pania alleles sampled from six coastal and two barents sea populations. the distributions of variable sites segregating within the pania allelic class were then compared among the populations. significant differences were detected in the overall frequencies of pania alleles a ...200312492878
epidemiology of bacterial diseases in norwegian aquaculture--a description based on antibiotic prescription data for the ten-year period 1991 to 2000.in norway, antibacterial drugs for use in farmed fishes have to be prescribed by a veterinarian. moreover, a national surveillance programme requires that copies of all prescriptions be sent to the directorate of fisheries. the prescriptions give information regarding fish farm and locality, weight and species of fish to be medicated, diagnosis, type and amount of drug prescribed, and date. these prescription data for the 10 yr period 1991 to 2000 have been recorded and systematised. a total of ...200312650244
francisella sp. (family francisellaceae) causing mortality in norwegian cod (gadus morhua) farming.in 2004, a new disease was detected in cod (gadus morhua) in western norway. affected cod had white granulomas in the visceral organs and skin. a species of francisella was isolated on blood agar plates from moribund cod. the bacterium could be grown at temperatures ranging from 6 to 22 degrees c, but did not grow at 37 degrees c. challenge experiments showed that francisella sp. was the cause for the new disease. the 16s rdna gene sequence from francisella sp. showed 99.17% similarity to f. phi ...200616614828
caligus elongatus nordmann genotypes on wild and farmed fish.two mitochondrial genotypes have been described for caligus elongatus nordmann in norway. this article reports on the distribution of c. elongatus mitochondrial cytochrome c oxidase 1 genotypes from wild fish hosts from the se norwegian coast. for comparison, lice from areas with fish farming were included in the study. the genotype distribution of 841 lice from wild coastal (n = 535), wild north sea pelagic (n = 26), farmed (n = 160) and wild hosts in areas of fish farming (n = 89) is presented ...200717298563
accumulation of polychlorinated dibenzo-p-dioxins and furans in atlantic cod (gadus morhua)--cage experiments in a norwegian fjord.polychlorinated dibenzo-p-dioxins (pcdd) and polychlorinated dibenzofurans (pcdf) have been discharged to the frierfjord (eastern norway) for 50 yr. the discharges, dominated by pcdf, were highest in the early 1970s and subsequently reduced 3-4 orders ofmagnitude to 1-2 g toxic equivalents (teq)/yr in 1992-2002. atlantic cod (gadus morhua) and semipermeable membrane devices (spmd) were placed in cages for 6 wk in the frierfjord and at two locations in the adjacent langesundsfjord. the objective ...201121391091
climate and population density drive changes in cod body size throughout a century on the norwegian coast.understanding how populations respond to changes in climate requires long-term, high-quality datasets, which are rare for marine systems. we estimated the effects of climate warming on cod lengths and length variability using a unique 91-y time series of more than 100,000 individual juvenile cod lengths from surveys that began in 1919 along the norwegian skagerrak coast. using linear mixed-effects models, we accounted for spatial population structure and the nested structure of the survey data t ...201121245301
differences in lens optical plasticity in two gadoid fishes meeting in the arctic.arctic and boreal/temperate species are likely to be evolutionary adapted to different light regimes. currently, the boreal/temperate atlantic cod (gadus morhua) is coexisting with the native polar cod (boreogadus saida) in the arctic waters around svalbard, norway. here, we studied light/dark adaptative optical plasticity of their eye lenses by exposing fish to bright light during the polar night. schlieren photography, high-definition laser scanning and ray tracing were used to determine the o ...201425240636
long-term change in a behavioural trait: truncated spawning distribution and demography in northeast arctic cod.harvesting may be a potent driver of demographic change and contemporary evolution, which both may have great impacts on animal populations. research has focused on changes in phenotypic traits that are easily quantifiable and for which time series exist, such as size, age, sex, or gonad size, whereas potential changes in behavioural traits have been under-studied. here, we analyse potential drivers of long-term changes in a behavioural trait for the northeast arctic stock of atlantic cod gadus ...201525336028
spatial ecology of coastal atlantic cod gadus morhua associated with parasite load.acoustic tags and receivers were used to investigate the spatial ecology of coastal atlantic cod gadus morhua (n = 32, mean fork length: 50 cm, range: 33-80 cm) on the norwegian skagerrak coast in 2012. monthly home ranges (hr), swimming activity and depth use varied considerably among individuals and through the months of june, july and august. hr sizes for the period ranged from 0.25 to 5.20 km2 (mean = 2.30 km2. two thirds of the tagged g. morhua were infected with black spot disease cryptoco ...201526177748
species composition and infection dynamics of ascaridoid nematodes in barents sea capelin (mallotus villosus) reflecting trophic position of fish host.capelin (mallotus villosus) is among the most abundant fish species in the barents sea, and represents a critical food source for many predators in the area including atlantic cod and harp seal. in norway, the fish is of economic importance since whole capelin and roe are valuable export products. despite its economic and ecological importance, the parasites of barents sea capelin are poorly known. however, the presence of parasites in the edible parts may adversely affect product quality and co ...201627473836
integrative approach for the reliable detection and specific identification of the microsporidium loma morhua in atlantic cod (gadus morhua).microsporidia are fungal parasites that infect diverse invertebrate and vertebrate hosts. finfish aquaculture supports epizootics due to high host density and the high biotic potential of these parasites. reliable methods for parasite detection and identification are a necessary precursor to empirical assessment of strategies to mitigate the effects of these pathogens during aquaculture. we developed an integrative approach to detect and identify loma morhua infecting atlantic cod. we show that ...201727317934
fine-scale population dynamics in a marine fish species inferred from dynamic state-space models.1.identifying the spatial scale of population structuring is critical for the conservation of natural populations and for drawing accurate ecological inferences. however, population studies often use spatially aggregated data to draw inferences about population trends and drivers, potentially masking ecologically relevant population sub-structure and dynamics. 2.the goals of this study were to investigate how population dynamics models with and without spatial structure affect inferences on popu ...201728393352
effect of a fish stock's demographic structure on offspring survival and sensitivity to climate.commercial fishing generally removes large and old individuals from fish stocks, reducing mean age and age diversity among spawners. it is feared that these demographic changes lead to lower and more variable recruitment to the stocks. a key proposed pathway is that juvenation and reduced size distribution causes reduced ranges in spawning period, spawning location, and egg buoyancy; this is proposed to lead to reduced spatial distribution of fish eggs and larvae, more homogeneous ambient enviro ...201728115694
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