• The association between parasite infection and growth rates in Arctic charr: do fast growing fish have more parasites? 

      Henriksen, Eirik Haugstvedt; Smalås, Aslak; Strøm, John Fredrik; Knudsen, Rune (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-01-01)
      Trophically transmitted parasites are known to impair fish growth in experimental studies, but this is not well documented in natural populations. For Arctic charr [<i>Salvelinus alpinus</i> (L.)], individual growth is positively correlated with food consumption. However, increased food consumption will increase the exposure to trophically transmitted parasites. Using a correlative approach, we ...
    • Cercarial behaviour alters the consumer functional response of three-spined sticklebacks 

      Born-Torrijos, Ana; Paterson, Rachel; van Beest, Gabrielle; Vyhlídalová, Tereza; Henriksen, Eirik Haugstvedt; Knudsen, Rune; Kristoffersen, Roar; Amundsen, Per-Arne; Soldánová, Miroslava (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-01-22)
      <ol> <li>Free-living parasite life stages may contribute substantially to ecosystem biomass and thus represent a significant source of energy flow when consumed by non-host organisms. However, ambient temperature and the predator's own infection status may modulate consumption rates towards parasite prey.</li> <li>We investigated the combined effects of temperature and predator infection status ...
    • Contrasting associations between breeding coloration and parasitism of male Arctic charr relate to parasite species and life cycle stage 

      Johansen, Ida Beitnes; Henriksen, Eirik Haugstvedt; Shaw, Jenny Carolyn; Mayer, Ian; Amundsen, Per-Arne; Øverli, Øyvind (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-07-23)
      Conspicuous carotenoid ornamentation is considered a signal of individual “quality” and one of the most intensely studied traits found to co-vary with parasitism. Since it has been suggested that only “high quality” individuals have enough resources to express excessive sexual ornaments and resist parasites, current theory struggles to explain cases where the brightest individuals carry the most ...
    • Ectoparasites population dynamics are affected by host body size but not host density or water temperature in a 32-year long time series 

      Henriksen, Eirik Haugstvedt; Frainer, André; Poulin, Robert; Knudsen, Rune; Amundsen, Per-Arne (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-11-22)
      Host density, host body size and ambient temperature have all been positively associated with increases in parasite infection. However, the relative importance of these factors in shaping long-term parasite population dynamics in wild host populations is unknown due to the absence of long-term studies. Here, we examine long-term drivers of gill lice (Copepoda) infections in Arctic charr (Salmonidae) ...
    • The effect of inter- and intraspecific competition on individual and population niche widths: a four-decade study on two interacting salmonids 

      Prati, Sebastian; Henriksen, Eirik Haugstvedt; Smalås, Aslak; Knudsen, Rune; Klemetsen, Anders; Sanchez-Hernandez, Javier; Amundsen, Per-Arne (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-07-12)
      Competition is assumed to shape niche widths, affecting species survival and coexistence. Expectedly, high interspecific competition will reduce population niche widths, whereas high intraspecific competition will do the opposite. Here we test in situ how intra- and interspecific competition affects trophic resource use and the individual and population niche widths of two lacustrine fish species, ...
    • Fish culling reduces tapeworm burden in Arctic charr by increasing parasite mortality rather than by reducing density-dependent transmission 

      Henriksen, Eirik Haugstvedt; Frainer, André; Knudsen, Rune; Kristoffersen, Roar; Kuris, Armand M.; Lafferty, Kevin D.; Amundsen, Per-Arne (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-02-25)
      <ol> <li>Two common <i>Dibothriocephalus</i> (formerly <i>Diphyllobothrium</i>) tapeworm species were significantly reduced by experimental culling of their fish host Arctic charr (<i>Salvelinus alpinus</i>) in a subarctic lake.</li><p> <p><li>Between 1984 and 1991, funnel traps were used to cull ~35 metric tons of Arctic charr, reducing charr density by ~80%. As charr densities decreased, ...
    • High parasite diversity in the amphipod Gammarus lacustris in a subarctic lake 

      Shaw, Jenny Carolyn; Henriksen, Eirik Haugstvedt; Knudsen, Rune; Kuhn, Jesper Andreas; Kuris, Armand M.; Lafferty, Kevin D.; Siwertsson, Anna; Soldánová, Miroslava; Amundsen, Per-Arne (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-10-05)
      Amphipods are often key species in aquatic food webs due to their functional roles in the ecosystem and as intermediate hosts for trophically transmitted parasites. Amphipods can also host many parasite species, yet few studies address the entire parasite community of a gammarid population, precluding a more dynamic understanding of the food web. We set out to identify and quantify the parasite ...
    • Impacts of ontogenetic dietary shifts on the food-transmitted intestinal parasite communities of two lake salmonids 

      Prati, Sebastian; Henriksen, Eirik Haugstvedt; Knudsen, Rune; Amundsen, Per-Arne (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-10)
      Ontogenetic dietary shifts are common in fish and often impact trophically transmitted parasite communities. How parasite species composition and relative abundances change among size classes, and at what rate these changes occur, is rarely examined. Hosts with a broad trophic niche are potentially exposed to a large variety of parasite species. The degree of ontogenetic changes in parasite species ...
    • Long-term dynamics of metazoan parasites in an age- and size-structured host population 

      Henriksen, Eirik Haugstvedt (Doctoral thesis; Doktorgradsavhandling, 2021-10-29)
      <p>Parasites negatively affect hosts and may constitute serious management problems. At the same time, parasites are integral components of ecosystems and represent a substantial part of the biodiversity on earth. Understanding the ecological factors that influence the abundance and distribution of parasite populations is therefore important from a management perspective, but also to understand the ...
    • Long-term ecological studies in northern lakes – challenges, experiences, and accomplishments 

      Amundsen, Per-Arne; Primicerio, Raul; Smalås, Aslak; Henriksen, Eirik Haugstvedt; Knudsen, Rune; Kristoffersen, Roar; Klemetsen, Anders (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-08-15)
      We review three long‐term research programs performed over the last four decades on the ecology and management of oligotrophic lake systems with different fish communities at 69&deg; N in Norway. Through whole‐lake perturbation experiments, intensive culling of stunted fish removed 35 tons (1984–1991) of Arctic charr <i>Salvelinus alpinus</i> in Takvatn (15 km<sup>2</sup>) and 153 tons (1981–1983, ...
    • Long-term population dynamics of Diphyllobothrium ditremum and D. dendriticum (Cestoda: Pseudophyllidea) in their salmonid hosts following a fish removal experiment 

      Henriksen, Eirik Haugstvedt (Master thesis; Mastergradsoppgave, 2014-02-15)
      Parasite-host interactions are important in understanding ecosystem processes, for instance by using trophically transmitted parasites as indicators of host ecology. Parasite infections are expected to correlate with host density, habitat choice and feeding behaviour. The importance of long-term data and perturbation experiments has been emphasized for advancing our knowledge of the parasite-host ...
    • Molecular analyses reveal high cryptic diversity of trematodes in a sub-Arctic lake 

      Soldánová, Miroslava; Georgieva, Simona; Roháčová, Jana; Knudsen, Rune; Kuhn, Jesper A.; Henriksen, Eirik Haugstvedt; Siwertsson, Anna; Shaw, Jenny C.; Kuris, Armand M.; Amundsen, Per-Arne; Scholz, Tomas; Lafferty, Kevin D.; Kostadinova, Aneta (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-03-14)
      To identify trematode diversity and life-cycles in the sub-Arctic Lake Takvatn, Norway, we characterised 120 trematode isolates from mollusc first intermediate hosts, metacercariae from second intermediate host fishes and invertebrates, and adults from fish and invertebrate definitive hosts, using molecular techniques. Phylogenies based on nuclear and/or mtDNA revealed high species richness (24 ...
    • Ontogenetic dynamics of infection with Diphyllobothrium spp. cestodes in sympatric Arctic charr Salvelinus alpinus (L.) and brown trout Salmo trutta L. 

      Henriksen, Eirik Haugstvedt; Knudsen, Rune; Kristoffersen, Roar; Kuris, Armand M.; Lafferty, Kevin D.; Siwertsson, Anna; Amundsen, Per-Arne (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-12-23)
      The trophic niches of Arctic charr and brown trout differ when the species occur in sympatry . Their trophically transmitted parasit es are expected to reflect these differences. Here , we investigate how the infections of Diphyllobothrium dendriticum and Diphyllobothrium ditremum differ between charr and trout. These tapeworms use copepods ...
    • Seasonal dietary shifts enhance parasite transmission to lake salmonids during ice cover 

      Prati, Sebastian; Henriksen, Eirik Haugstvedt; Knudsen, Rune; Amundsen, Per-Arne (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-04-08)
      Changes in abiotic and biotic factors between seasons in subarctic lake systems are often profound, potentially affecting the community structure and population dynamics of parasites over the annual cycle. However, few winter studies exist and interactions between fish hosts and their parasites are typically confined to snapshot studies restricted to the summer season whereas host‐parasite dynamics ...
    • 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 ...
    • Transmission dynamics of the monogenean Gyrodactylus salaris under seminatural conditions 

      Hendrichsen, Ditte Katrine; Kristoffersen, Roar; Gjelland, Karl Øystein; Knudsen, Rune; Kusterle, Stefan; Rikardsen, Audun H.; Henriksen, Eirik Haugstvedt; Smalås, Aslak; Olstad, Kjetil (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. ...