• Environmental regulation of individual depth on a cod spawning ground 

      Meager, Justin J.; Skjæraasen, Jon Egil; Karlsen, Ørjan; Løkkeborg, Svein; Mayer, Ian; Michalsen, Kathrine; Nilsen, Trygve; Fernö, Anders (Journal article; Peer reviewed, 2012-12-13)
      Fine-scale characteristics of spawning grounds may provide the opportunity for cod Gadus morhua L. to regulate their external environment by adjusting their depth. Ultrasonic telemetry was used to study how the environment ...
    • From “where” and “when” to “what” and “why”: archival tags for monitoring “complex” behaviours in fish. 

      Metcalfe, Julian D.; Wilson, R.P.; Kjesbu, Olav Sigurd; Challiss, M.J.; Gleiss, A.; Skjæraasen, Jon Egil; Clarke, S. (ICES CM documents;2009/B:04, Working paper, 2009)
      Understanding the movements (“where” and “when”) and behaviour (“what” and, hopefully, “why”) of individuals and populations is key to answering fundamental questions in fish ecology. The use of archival tags in telemetry ...
    • Highly mixed impacts of near-future climate change on stock productivity proxies in the North East Atlantic 

      Kjesbu, Olav Sigurd; Sundby, Svein; Sandø, Anne Britt; Alix, Maud; Hjøllo, Solfrid Sætre; Tiedemann, Maik; Skern-Mauritzen, Mette; Junge, Claudia; Fossheim, Maria; Broms, Cecilie; Søvik, Guldborg; Zimmermann, Fabian; Nedreaas, Kjell Harald; Eriksen, Elena; Höffle, Hannes; Hjelset, Ann Merete; Kvamme, Cecilie; Reecht, Yves; Knutsen, Halvor; Aglen, Asgeir; Albert, Ole Thomas; Berg, Erik; Bogstad, Bjarte; Durif, Caroline; Halvorsen, Kim Aleksander Tallaksen; Høines, Åge Sigurd; Hvingel, Carsten; Johannesen, Edda; Johnsen, Espen; Moland, Even; Myksvoll, Mari Skuggedal; Nøttestad, Leif; Olsen, Erik Joel Steinar; Skaret, Georg; Skjæraasen, Jon Egil; Slotte, Aril; Staby, Arved; Stenevik, Erling Kåre; Stiansen, Jan Erik; Stiasny, Martina H.; Sundet, Jan Henry; Vikebø, Frode Bendiksen; Huse, Geir (Peer reviewed; Journal article, 2021)
      Impacts of climate change on ocean productivity sustaining world fisheries are predominantly negative but vary greatly among regions. We assessed how 39 fisheries resources—ranging from data-poor to data-rich stocks—in the ...
    • Large annual variation in the amount of skipped spawning for female Northeast Arctic haddock Melanogrammus aeglefinus 

      Skjæraasen, Jon Egil; Korsbrekke, Knut; Dingsør, Gjert Endre; Langangen, Øystein; Opdal, Anders Frugård; Jørgensen, Christian (Peer reviewed; Journal article, 2020)
      Although the phenomenon of skipped spawning has been described in numerous fishes, time-series are scarce. We used the presence of post-ovulatory follicles in histological gonad slides from females not developing oocytes ...
    • Liver energy, atresia and oocyte stage influence fecundity regulation in Northeast Arctic cod 

      Skjæraasen, Jon Egil; Nash, Richard D.M.; Kennedy, James; Thorsen, Anders; Nilsen, Trygve; Kjesbu, Olav Sigurd (Journal article; Peer reviewed, 2010-04-08)
      Marine ecosystems are changing; global warming-induced increases in water temperatures and fishing have caused truncated age structures and small sizes at maturity in many stocks. This may affect both populations’ total ...
    • Making use of Johan Hjort's “unknown” legacy: reconstruction of a 150-year coastal time-series on northeast Arctic cod (Gadus morhua) liver data reveals long-term trends in energy 

      Kjesbu, Olav Sigurd; Opdal, Anders Frugård; Korsbrekke, Knut; Devine, Jennifer A.; Skjæraasen, Jon Egil (Journal article; Peer reviewed, 2014-03-11)
      Hidden within the seminal 1914 publication by Johan Hjort, we find what is probably one of the first comprehensive teleost time-series ever published. The series is liver size and fat content of northeast Arctic (NEA) cod ...
    • Mating competition between farmed and wild cod Gadus morhua 

      Skjæraasen, Jon Egil; Meager, Justin J.; Karlsen, Ørjan; Mayer, Ian; Dahle, Geir; Rudolfsen, Geir; Fernö, Anders (Journal article; Peer reviewed, 2010-08-18)
      Increasing numbers of hatchery-produced fish entering marine environments has caused concern over potential fitness depressions in wild populations, yet no study has addressed the likelihood of hybridisation between farmed ...
    • Mechanisms regulating oocyte recruitment and skippedspawning in Northeast Arctic cod (Gadus morhua L.) 

      Skjæraasen, Jon Egil; Kennedy, James; Thorsen, Anders; Fonn, Merete; Strand, Bente; Mayer, Ian; Kjesbu, Olav Sigurd (Journal article; Peer reviewed, 2009-09)
      To examine mechanisms that affect fecundity, atresia and skipped spawning in Northeast Arctic cod (Gadus morhua L.), we conducted an experiment where wild-caught cod (>60 cm) kept under restricted food regimes were subjected ...
    • Mechanisms regulating oocyte recruitment and skippedspawning in Northeast Arctic cod (Gadus morhua L.) 

      Skjæraasen, Jon Egil; Kennedy, James; Thorsen, Anders; Fonn, Merete; Strand, Bente; Mayer, Ian; Kjesbu, Olav Sigurd (Journal article; Peer reviewed, 2009-09)
      To examine mechanisms that affect fecundity, atresia and skipped spawning in Northeast Arctic cod (Gadus morhua L.), we conducted an experiment where wild-caught cod (>60 cm) kept under restricted food regimes were subjected ...
    • Skipped spawning in Northeast Arctic haddock Melanogrammus aeglefinus 

      Skjæraasen, Jon Egil; Korsbrekke, Knut; Nilsen, Trygve; Fonn, Merete; Kjesbu, Olav Sigurd; Dingsør, Gjert Endre; Nash, Richard David Marriott (Journal article; Peer reviewed, 2015-04-22)
    • Sluttrapport fra ICOD-prosjektet - Arbeidspakke 2: Egg- og yngelundersøkelser på gyte- og oppvekstområder på Smøla og i Aure i forbindelse med etablering av oppdrettsanlegg nær lokale gyteområder for kysttorsk 

      van der Meeren, Terje; Meier, Sonnich; Myksvoll, Mari Skuggedal; Dahle, Geir; Karlsen, Ørjan; Staby, Arved; Mjanger, Hildegunn; Engevik, Annhild; Dunlop, Katherine Mary; Bannister, Raymond; Skjæraasen, Jon Egil (Rapport fra havforskningen;2021 - 32, Research report, 2021)
      ICOD-prosjektet ble etablert for å undersøke mulige interaksjoner mellom oppdrettsanlegg og nærliggende gyteområder for kysttorsk. Rapporten presenterer resultater fra ICOD som omfatter egg- og yngelundersøkelser foretatt ...
    • Sperm characteristics and competitive ability in farmed and wild cod 

      Skjæraasen, Jon Egil; Mayer, Ian; Meager, Justin J.; Rudolfsen, Geir; Karlsen, Ørjan; Haugland, Thomas; Kleven, Oddmund (Journal article; Peer reviewed, 2009-01-27)
      The development of cod aquaculture has raised concerns about its effect on wild stocks. One risk is hybridisation between escapees and wild cod, causing genetic introgression, and, potentially, fitness depressions in wild ...
    • Synergies between climate and management for Atlantic cod fisheries at high latitudes 

      Kjesbu, Olav Sigurd; Bogstad, Bjarte; Devine, Jennifer A.; Gjøsæter, Harald; Howell, Daniel; Ingvaldsen, Randi; Nash, Richard D.M.; Skjæraasen, Jon Egil (Journal article; Peer reviewed, 2014-02-18)
      The widespread depletion of commercially exploited marine living resources is often seen as a general failure of management and results in criticism of contemporary management procedures. When populations show dramatic and ...
    • Timecourse of oocyte development in saithe Pollachius virens 

      Skjæraasen, Jon Egil; Devine, Jennifer Ann; Godiksen, Jane Aanestad; Fonn, Merete; Otterå, Håkon Magne; Kjesbu, Olav Sigurd; Norberg, Birgitta; Langangen, Øystein; Karlsen, Ørjan (Journal article; Peer reviewed, 2017)
      Wild caught North Sea saithe Pollachius virens were monitored for growth, sex steroid profiles and oocyte development pre-spawning and measured for egg size and group fecundity during the spawning season in the laboratory. ...
    • Timing and determination of potential fecundity in Atlantic cod (Gadus morhua) 

      Skjæraasen, Jon Egil; Nilsen, Trygve; Kjesbu, Olav Sigurd (Journal article; Peer reviewed, 2005)
      Studies using annual averages of lipid storage or estimated quality of the feeding season have shown that energy reserves influence egg production in Atlantic cod (Gadus morhua). However, vitellogenesis starts months ...
    • Trade-offs between growth and reproduction in wild Atlantic cod 

      Folkvord, Arild; Jørgensen, Christian; Korsbrekke, Knut; Nash, Richard D.M.; Nilsen, Trygve; Skjæraasen, Jon Egil (Journal article; Peer reviewed, 2014-04-08)
      Animals partition and trade off their resources between competing needs such as growth, maintenance, and reproduction. Over a lifetime, allocation strategies should result in distinct trajectories for growth, survival, and ...
    • Triploid Atlantic salmon and triploid Atlantic salmon × brown trout hybrids have better freshwater and early seawater growth than diploid counterparts 

      Fraser, Thomas; Lerøy, Hilde; Hansen, Tom Johnny; Skjæraasen, Jon Egil; Tronci, Valentina; Pinto Pedrosa, Cindy; Fjelldal, Per Gunnar; Nilsen, Tom Ole (Peer reviewed; Journal article, 2021)
      The use of reproductively sterile triploid salmonids would enhance the environmental sustainability of the aquaculture industry by preventing genetic exchange between escapees and wild conspecifics. To this end, we assessed ...
    • Vertical dynamics and reproductive behaviour of farmed and wild Atlantic cod Gadus morhua 

      Meager, Justin J.; Skjæraasen, Jon Egil; Fernö, Anders; Karlsen, Ørjan; Løkkeborg, Svein; Michalsen, Kathrine; Utskot, Stig Ove (Journal article; Peer reviewed, 2009-09-04)
      Rapid development of fish mariculture and efforts to restock depleted populations have raised concerns about the effects on wild populations and the risk of genetic introgression from hybridisation. Reproduction of many ...
    • Vertical dynamics and reproductive behaviour of farmed and wild Atlantic cod Gadus morhua 

      Meager, Justin J.; Skjæraasen, Jon Egil; Fernö, Anders; Karlsen, Ørjan; Løkkeborg, Svein; Michalsen, Kathrine; Utskot, Stig Ove (Journal article; Peer reviewed, 2009-09-04)
      Rapid development of fish mariculture and efforts to restock depleted populations have raised concerns about the effects on wild populations and the risk of genetic introgression from hybridisation. Reproduction of many ...
    • Vertical dynamics and reproductive behaviour of farmed and wild Atlantic cod Gadus morhua 

      Meager, Justin J.; Skjæraasen, Jon Egil; Fernö, Anders; Karlsen, Ørjan; Løkkeborg, Svein; Michalsen, Kathrine; Utskot, Stig Ove (Journal article; Peer reviewed, 2009-09-04)
      Rapid development of fish mariculture and efforts to restock depleted populations have raised concerns about the effects on wild populations and the risk of genetic introgression from hybridisation. Reproduction of many ...