English
norskBlar i forfatter "Gjelland, Karl Øystein"
Viser treff 1-16 av 16
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Contrasting Population and Life History Responses of a Young Morph-Pair of European Whitefish to the Invasion of a Specialised Coregonid Competitor, Vendace
(Journal article; Tidsskriftartikkel; Peer reviewed, 2013)Invasions of non-native species represent a global problem of great scientific interest. Here we study in detail the response in population and life history characteristics of closely related native species, with divergent habitat preferences, that are impacted by an invading species over a sufficient time period to allow a new stable state to become established. A time series of 20 years starting ... -
Forsøk med trål og ekkolodd i Mjøsa, 2012
(Research report; Forskningsrapport, 2013)Trål har i liten grad vore brukt ved undersøkingar av fiskesamfunn i norske innsjøar. Gjennom innføringa av Vanndirektivet har Norge forplikta seg til meir regulær oppfølging av den økologiske tilstanden i større vassførekomstar. Tettleik, rekruttering, artsfordeling og vekst hjå fisk er alle parametrar der ein kan forvente relativt rask respons på miljøendringar. Det er derfor viktig å ha ... -
Havbruksnæringens konsekvenser for økosystemtjenester og samfunn i nordområdene. Forprosjekt Balsfjorden
(Research report; Forskningsrapport, 2017)Utviklingen av havbruksnæringen styres etter prinsippet om bærekraftig utvikling; sosial, økonomisk og miljømessig. Forvaltningen trenger mer kunnskap om hvilke effekter merdbasert havbruk har på økosystemtjenester og samfunn. Balsfjorden gir en unik mulighet til å studere hvordan anleggsetablering påvirker miljø og samfunn, der status for systemet i stor grad er kjent før etablering, og det kan ... -
Invader population speeds up life history during colonization
(Journal article; Tidsskriftartikkel; Peer reviewed, 2012)We explore the long-term developments in population biology and life history during the invasion and establishment of the fish species vendace Coregonus albula in a subarctic watercourse by comparing life-history traits and molecular genetic estimates between the source and the colonist population. The two populations exhibited highly contrasting life-history strategies. Relative to the source ... -
Invasion genetics of vendace (Coregonus albula (L.)) in the Inari-Pasvik watercourse: revealing the origin and expansion pattern of a rapid colonization event
(Journal article; Tidsskriftartikkel; Peer reviewed, 2013)Species invasions can have wide-ranging biological and socio-economic effects and are generally unwanted by legislation. Identification of the source population as well as the ecology and genetics of both the invader population and the receiving community is of crucial importance. The rapid invasion of a small coregonid fish vendace (Coregonus albula) in a major northern European subarctic watercourse ... -
Is coexistence mediated by microhabitat segregation? An in-depth exploration of a fish invasion
(Journal article; Tidsskriftartikkel; Peer reviewed, 2007)Vendace <i>Coregonus albula</i> has invaded the subarctic Pasvik hydrosystem, northern Norway and Russia, after being translocated from its native Finnish range into Lake Inari (Finland), upstream of Pasvik. The development of the invader and the effects on two native lake communities in the upstream and downstream part of the hydrosystem, respectively, have been monitored since 1991. In the upstream ... -
Lagesilda i Pasvikvassdraget : langtidseffekter av en biologisk invasjon
(Research report; Forskningsrapport, 2012)Pasvikvassdraget har siden 1991 vært gjenstand for omfattende økologiske studier i regi av Ferskvannsøkologisk faggruppe ved Universitetet i Tromsø. Undersøkelsene har særlig vært rettet mot å undersøke effektene av at lagesilda, en fremmed fiskeart for Nord-Norge, kom inn i vassdraget på slutten av 1980-tallet. For å få en grundig forståelse av økologien i vassdraget har studiene også omfattet ... -
Movement diversity and partial sympatry of coastal and Northeast Arctic cod ecotypes at high latitudes
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-07-24)Movement diversity within species represent an important but often neglected, component of biodiversity that affects ecological and genetic interactions, as well as the productivity of exploited systems. By combining individual tracking data from acoustic telemetry with novel genetic analyses, we describe the movement diversity of two Atlantic cod Gadus morhua ecotypes in two high-latitude fjord ... -
Planktivore vertical migration and shoaling under a subarctic light regime
(Journal article; Tidsskriftartikkel; Peer reviewed, 2009-03-20)Visually foraging planktivorous fish are prey of visual predators, and their foraging behaviour may be affected by light levels both in terms of gain and risk. The large seasonal change in day length throughout a subarctic summer at 69°N was used to show the influence of light on diel vertical migration (DVM) and shoaling patterns in a planktivorous fish assemblage consisting of two species (<i>Coregonus ... -
The role of gill raker number variability in adaptive radiation of coregonid fish
(Journal article; Tidsskriftartikkel; Peer reviewed, 2010-07-27)Gill raker divergence is a general pattern in adaptive radiations of postglacial fish, but few studies have addressed the adaptive significance of this morphological trait in foraging and eco-evolutionary interactions among predator and prey. Here, a set of subarctic lakes along a diversifying gradient of coregonids was used as the natural setting to explore correlations between gill raker numbers ... -
Salmon louse infestation levels on sea trout can be predicted from a hydrodynamic lice dispersal model
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-12-13)1. The abundance of the parasitic salmon louse has increased with the growth in aquaculture of salmonids in open net pens. This represents a threat to wild salmonid populations as well as a key limiting factor for salmon farming. The Norwegian ‘traffic light’ management system for salmon farming aims to increase aquaculture production while securing sustainable wild salmonid populations. However, ... -
Sea trout adapt their migratory behaviour in response to high salmon lice concentrations
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-11-21)Sea trout face growth–mortality trade-offs when entering the sea to feed. Salmon lice epizootics resulting from aquaculture have shifted these trade-offs, as salmon lice might both increase mortality and reduce growth of sea trout. We studied mortality and behavioural adaptations of wild sea trout in a large-scale experiment with acoustic telemetry in an aquaculture intensive area that was fallowed ... -
Speciation reversal in European whitefish (Coregonus lavaretus (L.)) caused by competitor invasion
(Journal article; Tidsskriftartikkel; Peer reviewed, 2014)Invasion of exotic species has caused the loss of biodiversity and imparts evolutionary and ecological changes in the introduced systems. In northern Fennoscandia, European whitefish (Coregonus lavaretus (L.)) is a highly polymorphic species displaying adaptive radiations into partially reproductively isolated and thus genetically differentiated sympatric morphs utilizing the planktivorous and ... -
Temporal analysis shows relaxed genetic erosion following improved stocking practices in a subarctic transnational brown trout population
(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 ... -
Timing is everything: Survival of Atlantic salmon Salmo salar postsmolts during events of high salmon lice densities
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-04-07)<ol> <li>Atlantic salmon in aquaculture act as reservoir hosts and vectors of parasites like salmon lice and this parasite is shown to harm wild salmonid populations.</li> <li>In this study, <i>n</i> = 29,817 tagged Atlantic salmon were studied in four release trials. Half of the released fish were given prophylactic treatment against lice, the other half represented sham control fish. We used ... -
Transmission dynamics of the monogenean Gyrodactylus salaris under seminatural conditions
(Journal article; Tidsskriftartikkel; Peer reviewed, 2014-07-12)Tracking individual variation in the dynamics of parasite infections in wild populations is often complicated by lack of knowledge of the epidemiological history of hosts. Whereas the dynamics and development of Gyrodactylus salaris Malmberg, 1957, on Atlantic salmon, Salmo salar L., are known from laboratory studies, knowledge about infection development on individual wild fishes is currently sparse. ...
