Viser treff 1358-1377 av 1513

    • Takvatnprosjektet - Forskning og kultivering av en overbefolka røyeberstand 

      Amundsen, Per-Arne; Smalås, Aslak; Knudsen, Rune; Kristoffersen, Roar; Siwertsson, Anna; Klemetsen, Anders (Research report; Forskningsrapport, 2015)
      Overbefolka fiskebestander er et stort problem i mange av våre innsjøer. Det typiske kjennetegnet er en stor tetthet av gammel, småvokst og mager fisk, gjerne med en høy infeksjon av parasitter. Hardt uttynningsfiske har vært foreslått som et mulig botemiddel, men selv om det har vært gjort mange forsøk på å komme problemet til livs, er det få som har lyktes. Denne rapporten ...
    • Tap av tamrein – et kunnskapsgrunnlag 

      Hansen, Inger; Eilertsen, Svein Morten; Sørensen, Ole Jakob; Mørk, Torill; Bråthen, Kari Anne; Johansen, Bernt; Moa, Pål Fossland; Risvoll, Camilla; Sandström, Camilla; Winje, Erlend (Research report; Forskningsrapport, 2019-12-30)
      Tap av dyr er en utfordring og et sentralt tema i norsk tamreindrift. Dette kunnskapsgrunnlaget beskriver status for hva vi vet om tapsomfang, tapsårsaker og tapsammenhenger innen områdene tap av rein til rovvilt, sykdom, klimarelatert tap, påkjørsler og grunnet kumulative effekter. Videre setter den fokus på forebyggende tiltak og hvilke felt man trenger ytterligere kunnskapsbygging på. Gjennomgående ...
    • Taxa-specific activity loss and mortality patterns in freshwater trematode cercariae under subarctic conditions 

      Born-Torrijos, Ana; Van Beest, Gabrielle S.; Vyhlídalová, Tereza; Knudsen, Rune; Kristoffersen, Roar; Amundsen, Per-Arne; Thieltges, David W.; Soldánová, Miroslava (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-11-11)
      Cercarial activity and survival are crucial traits for the transmission of trematodes. Temperature is particularly important, as faster depletion of limited cercarial energy reserves occurs at high temperatures. Seasonal climate conditions in high latitude regions may be challenging to complete trematode life cycle during the 6-month ice-free period, but temperature effects on the activity and ...
    • Taxonomic study on a collection of terrestrial and freshwater gastropods from caves in Bahia state, Brazil, with the description of a new species 

      Salvador, Rodrigo Brincalepe; Silva, Fernanda Santos; Bichuette, Maria Elina (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-02-28)
      Gastropod samples were collected during expeditions to caves in Bahia state, northeastern Brazil, and are studied herein. Collection took place over the past five years, and gastropods were found in 14 caves distributed across six different municipalities: Campo Formoso, Carinhanha, Coribe, Feira da Mata, Central, and Ituaçu. A total of 19 species-level taxa of terrestrial and freshwater gastropods ...
    • Temperature does not influence functional response of amphipods consuming different trematode prey 

      Born-Torrijos, Ana; Paterson, Rachel; van Beest, Gabrielle; Schwelm, Jessica; Vyhlídalová, Tereza; Henriksen, Eirik Haugstvedt; Knudsen, Rune; Kristoffersen, Roar; Amundsen, Per-Arne; Soldánová, Miroslava (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-08-26)
      Direct consumption on free-living cercariae stages of trematodes by non-host organisms interferes with trematode transmission and leads to reduced infections in the next suitable hosts. Consumer functional responses provide a useful tool to examine relationships between consumption rates and ecologically relevant prey densities, whilst also accounting for abiotic factors that likely influence ...
    • Temperature has a major effect on the cuticular wax composition of bilberry (Vaccinium myrtillus L.) fruit 

      Trivedi, Priyanka; Klavins, Linards; Hykkerud, Anne Linn; Kviesis, Jorens; Elferts, Didzis; Martinussen, Inger; Klavins, Maris; Karppinen, Katja; Häggman, Hely; Jaakola, Laura (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-09-20)
      Cuticle is the first layer protecting plants against external biotic and abiotic factors and is responsive to climatic factors as well as determined by genetic adaptations. In this study, the chemical composition of bilberry fruit cuticular wax was investigated through a latitudinal gradient from Latvia (56◦N 24◦E) through Finland (65◦N 25◦E) to northern Norway (69◦N 18◦E) in two seasons 2018 ...
    • Temperature-dependent egg production and egg hatching rates of small egg-carrying and broadcast-spawning copepods Oithona similis, Microsetella norvegica and Microcalanus pusillus 

      Barth-Jensen, Coralie; Koski, Marja; Varpe, Øystein; Glad, Peter; Wangensteen, Owen S.; Præbel, Kim; Svensen, Camilla (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-09-07)
      Reproductive rates of copepods are temperature-dependent, but poorly known for small copepods at low temperatures, hindering the predictions of population dynamics and secondary production in high-latitude ecosystems. We investigated egg hatching rates, hatching success and egg production of the small copepods <i>Oithona similis</i> and <i>Microsetella norvegica</i> (sac spawners) and <i>Microcalanus ...
    • Temporal analysis shows relaxed genetic erosion following improved stocking practices in a subarctic transnational brown trout population 

      Klutsch, Cornelya; Maduna, Simo; Polikarpova, Natalia; Forfang, Kristin; Beddari, Benedicte Lissner; Gjelland, Karl Øystein; Aspholm, Paul Eric; Amundsen, Per-Arne; Hagen, Snorre (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-08-30)
      Maintaining standing genetic variation is a challenge in human-dominated landscapes. We used genetic (i.e., 16 short tandem repeats) and morphological (i.e., length and weight) measurements of 593 contemporary and historical brown trout (Salmo trutta) samples to study fine-scale and short-term impacts of different management practices. These had changed from traditional breeding practices, using the ...
    • Temporal and spatial dynamics of the invasive red king crab and native brachyuran and anomuran larvae in Norwegian waters 

      Michelsen, Helena Kling; Nilssen, Einar Magnus; Pedersen, Torstein; Svensen, Camilla (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-01-16)
      This study investigates the temporal and spatial patterns of larval stages of the invasive red king crab <i>Paralithodes camtschaticus</i> (RKC) and co-existing native brachyurans and anomurans in a Norwegian fjord. It is one of few field studies describing the larval stage of native and invasive brachyurans and anomurans in the southern Barents Sea. Larvae were collected at 6 to 18 stations at ...
    • Temporal and spatial variability of sympagic metazoans in a high-Arctic fjord, Svalbard 

      Pitusi, Vanessa; Gradinger, Rolf Rudolf; Søreide, Janne (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-09-08)
      Svalbard is one of the fastest warming regions in the Arctic including massive loss in fjord sea ice both in terms of area coverage, ice thickness and duration. Sea ice is a habitat for a wide variety of microscopic flora and fauna, and we know little about the impact of accelerated loss of sea ice on this unique sea ice community. Here, we present the first study on the seasonal progression and ...
    • Temporal changes and between-host variation in the intestinal parasite community of Arctic charr in a subarctic lake 

      Kuhn, Jesper A.; Knudsen, Rune; Kristoffersen, Roar; Primicerio, Raul; Amundsen, Per-Arne (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-03-16)
      The occurrence of trophically transmitted intestinal parasites in Arctic charr was analyzed from data material collected over two decades from Lake Takvatn, northern Norway. The main objectives were to investigate (i) between-year variation in parasite infracommunity composition, (ii) between-host variation in infracommunity composition, and (iii) possible interspecific interaction between parasites. ...
    • Temporal correlations among demographic parameters are ubiquitous but highly variable across species 

      Fay, Rémi; Hamel, Sandra; Van de Pol, Martijn; Gaillard, Jean Michel; Yoccoz, Nigel; Acker, Paul; Authier, Matthieu; Larue, Benjamin; Le Coeur, Christie; Macdonald, Kaitlin R.; Nicol-Harper, Alex; Barbraud, Christophe; Bonenfant, Christophe; Van Vuren, Dirk H.; Cam, Emmanuelle; Delord, Karine; Gamelon, Marlène; Moiron, Maria; Pelletier, Fanie; Teplitsky, Céline; Visser, Marcel E.; Wells, Caitlin P.; Wheelwright, Nathaniel T.; Jenouvrier, Stéphanie; Sæther, Bernt-Erik (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-05-24)
      Temporal correlations among demographic parameters can strongly influence population dynamics. Our empirical knowledge, however, is very limited regarding the direction and the magnitude of these correlations and how they vary among demographic parameters and species’ life histories. Here, we use long-term demographic data from 15 bird and mammal species with contrasting pace of life to quantify ...
    • Temporal dynamics in zooplankton δ13C and δ15N isoscapes for the North Atlantic Ocean: Decadal cycles, seasonality, and implications for predator ecology 

      Espinasse, Boris Dristan; Sturbois, Anthony; Basedow, Sünnje Linnéa; Hélaouët, Pierre; Johns, David G.; Newton, Jason; Trueman, Clive N. (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-10-17)
      The limited amount of ecological data covering offshore parts of the ocean impedes our ability to understand and anticipate the impact of anthropogenic stressors on pelagic marine ecosystems. Isoscapes, i.e., spatial models of the distribution of stable isotope ratios, have been employed in the recent years to investigate spatio-temporal patterns in biogeochemical process and ecological responses. ...
    • Temporal stability of polymorphic Arctic charr parasite communities reflects sustained divergent trophic niches 

      Rochat, Eloïse Coralie; Paterson, Rachel; Costa, Isabel Blasco; Power, Michael; Adams, Colin E.; Greer, Ron; Knudsen, Rune (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-11-05)
      Polymorphic Arctic charr Salvelinus alpinus populations frequently display distinct differences in habitat use, diet, and parasite communities. Changes to the relative species densities and composition of the wider fish community have the potential to alter the habitat niche of sympatric Arctic charr populations. This study evaluated the temporal stability of the parasite community, diet, and stable ...
    • Temporal trend of mercury in relation to feeding habits and food availability in arctic foxes (Vulpes lagopus) from Svalbard, Norway 

      Hallanger, Ingeborg G.; Fuglei, Eva; Yoccoz, Nigel Gilles; Pedersen, Åshild Ønvik; König, Max; Routti, Heli Anna Irmeli (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-03-20)
      We investigated the temporal trend of mercury (Hg) in arctic foxes from Svalbard, Norway sampled in the period 1997–2014 (<i>n</i> = 109, from 11 trapping seasons). We used linear models to investigate the effect of trapping season, feeding habits (δ<sup>13</sup>C), food availability from marine and terrestrial ecosystems (reindeer carcasses and sea ice cover), sex, age and body condition on liver ...
    • Temporal Trends of Organochlorine and Perfluorinated Contaminants in a Terrestrial Raptor in Northern Europe Over 34 years (1986–2019) 

      Bustnes, Jan Ove; Bårdsen, Bård-Jørgen; Herzke, Dorte; Bangjord, Georg; Bourgeon, Sophie; Fritsch, Clémentine; Eulaers, Igor (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-03-21)
      Fourteen legacy organochlorine (OC) contaminants and 12 perfluoroalkyl substances (PFASs) were measured in eggs of tawny owls (Strix alueco) in central Norway (1986–2019). We expected OCs to have reached stable equilibrium levels due to bans, and that recent phase-out of some PFASs would have slowed the increase of these compounds. ∑OC comprised on average approximately 92% of the measured compounds, ...
    • Temporal trends of persistent organic pollutants in Barents Sea polar bears (Ursus maritimus) in relation to changes in feeding habits and body condition 

      Lippold, Anna; Bourgeon, Sophie; Aars, Jon; Andersen, Magnus; Polder, Anuschka; Lyche, Jan Ludvig; Bytingsvik, Jenny; Jenssen, Bjørn Munro; Derocher, Andrew E.; Welker, Jeffrey Martin; Routti, Heli (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-12-14)
      Temporal trends of persistent organic pollutants (POPs: PCBs, OH-PCBs, <i>p,p′</i>-DDE, HCB, β-HCH, oxychlordane, BDE-47, and 153) in relation to changes in feeding habits and body condition in adult female polar bears (<i>Ursus maritimus</i>) from the Barents Sea subpopulation were examined over 20 years (1997–2017). All 306 samples were collected in the spring (April). Both stable isotope values ...
    • Temporal variability in surface water pCO2 in Adventfjorden (West Spitsbergen) with emphasis on physical and biogeochemical drivers 

      Ericson, Ylva; Falck, Eva; Chierici, Melissa; Fransson, Agneta; Kristiansen, Svein; Platt, Stephen Matthew; Hermansen, Ove; Myhre, Cathrine Lund (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-06-26)
      Seasonal and interannual variability in surface water partial pressure of CO<sub>2</sub> (<i>p</i>CO2) and air‐sea CO<sub>2</sub> fluxes from a West Spitsbergen fjord (IsA Station, Adventfjorden) are presented, and the associated driving forces are evaluated. Marine CO<sub>2</sub> system data together with temperature, salinity, and nutrients, were collected at the IsA Station between March 2015 and ...
    • Temporally stable population-specific differences in run timing of one-sea-winter Atlantic salmon returning to a large river system 

      Vähä, Juha-Pekka; Erkinaro, Jaakko; Niemelä, Eero; Primmer, Craig R.; Saloniemi, Irma; Johansen, Morten; Svenning, Martin; Brørs, Sturla (Journal article; Tidsskriftartikkel; Peer reviewed, 2010-12-06)
      The understanding of migration patterns can significantly contribute to conservation and management. The spawning migrations of Atlantic salmon (<i>Salmo salar</i>) cover thousands of kilometers from the feeding areas at sea to their natal rivers to reproduce. Migrating salmon are exposed to intensive harvest, but little is known of the population‐specific differences in migration behavior. In this ...
    • Terrestrial Inputs Shape Coastal Bacterial and Archaeal Communities in a High Arctic Fjord (Isfjorden, Svalbard) 

      Delpech, Lisa-Marie; Vonnahme, Tobias; Mcgovern, Maeve; Gradinger, Rolf; Præbel, Kim; Poste, Amanda (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-26)
      The Arctic is experiencing dramatic changes including increases in precipitation, glacial melt, and permafrost thaw, resulting in increasing freshwater runoff to coastal waters. During the melt season, terrestrial runoff delivers carbon- and nutrient-rich freshwater to Arctic coastal waters, with unknown consequences for the microbial communities that play a key role in determining the cycling and ...