Endre søk
Begrens søket
1 - 34 of 34
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Treff pr side
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
Merk
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 1.
    Finstad, Anders G.
    et al.
    Norwegian Institute for Nature Research, Trondheim, Norge.
    Forseth, Torbjorn
    Norwegian Institute for Nature Research, Trondheim, Norge.
    Jonsson, Bror
    Norwegian Institute for Nature Research, Oslo, Norge.
    Bellier, Edwige
    Norwegian Institute for Nature Research, Trondheim, Norge.
    Hesthagen, Trygve
    Norwegian Institute for Nature Research, Trondheim, Norge.
    Jensen, Arne J.
    Norwegian Institute for Nature Research, Trondheim, Norge.
    Hessen, Dag O.
    Department of Biology, CEES, University of Oslo, Norge.
    Foldvik, Anders
    Norwegian Institute for Nature Research, Trondheim, Norge.
    Competitive exclusion along climate gradients: energy efficiency influences the distribution of two salmonid fishes2011Inngår i: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 17, nr 4, s. 1703-1711Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We tested the importance of thermal adaptations and energy efficiency in relation to the geographical distribution of two competing freshwater salmonid fish species. Presence–absence data for Arctic char and brown trout were obtained from 1502 Norwegian lakes embracing both temperature and productivity gradients. The distributions were contrasted with laboratory-derived temperature scaling models for food consumption, growth and energy efficiency. Thermal performances of the two species were almost identical. However, Arctic char exhibited double the growth efficiency (per unit of food) and appear to have out-competed brown trout from cold, low-productivity lakes, perhaps by scramble competition. Brown trout, for which previous reports have shown to be aggressive and dominant, have likely excluded the more energy-efficient Arctic char from relatively warm, productive lakes, perhaps by contest competition. Competitive interaction changing in outcome with lake productivity, rather than thermal performance, is likely a major determinant of the range distribution of the two species. Our study highlights the need for more focus on choice of relevant ecophysiological traits in ecological climate impact studies and species distribution modelling.

  • 2.
    Finstad, Anders G.
    et al.
    Norway.
    Jonsson, Bror
    Norway.
    Effect of incubation temperature on growth performance in Atlantic salmon2012Inngår i: Marine Ecology Progress Series, ISSN 0171-8630, E-ISSN 1616-1599, Vol. 454, s. 75-82Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Interspecific variations in thermal growth performance of ectotherms have received considerable recent interest fueled by the focus on ecological climate change effects. Amongpopulation variations in growth are commonly observed in field studies. However, the role of pheno typic plasticity in shaping this variation is largely unexplored in teleost fishes. Here, we tested for the effect of incubation temperature on thermal scaling of growth and maximum growth performance of the anadromous salmonid Atlantic salmon Salmo salar L. Salmon eggs were incubated and reared until the onset of exogenous feeding at either heated or natural temperatures or transferred from natural to heated temperatures at the time of hatching, creating 3 different embryonic temperature treatments (heated, natural or mixed). We subsequently tested for juvenile growth performance of these groups at 8 temperatures ranging from 6 to 24°C. Maximum growth was significantly higher in the heated than the natural and mixed incubation temperature groups, but we did not observe differences in the thermal scaling of growth performance. Neither the upper nor lower thermal limit for growth nor the optimal growth temperature differed be tween the 3 incubation temperature treatments. However, thermal conditions experienced by in cubating embryos affected later growth performance. Although similar results have been observed previously among reptiles, this is to our knowledge the first empirical support for this hypothesis among teleost fishes. Phenotypic plasticity in growth performance can likely explain many of the contrasting findings from previous research on countergradient growth effects in teleost fishes.

  • 3. Forseth, Torbjörn
    et al.
    Larsson, Stefan
    Jensen, Arne J.
    Jonsson, Bror
    Norsk institutt for naturforskning (NINA).
    Naslund, Ingemar
    Berglund, Ingemar
    Thermal growth performance of juvenile brown trout Salmo trutta: no support for thermal adaptation hypotheses2009Inngår i: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 74, nr 1, s. 133-149Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Using thermal growth data from eight populations of anadromous and lake-feeding brown trout Salmo trutta, hypotheses of adaptation to local optima and countergradient variation in growth were tested. The adaptation to local optima hypothesis suggests that natural selection can shift optimal performance temperatures to match the prevailing temperature in a new or changed thermal niche. In contradiction, the countergradient variation hypothesis suggests that populations from hostile environments perform better than conspecifics from benign environments at all temperatures. In this study, growth capacity varied between populations but there was no significant correlation between any of the estimated thermal performance parameters (e.g. lower and upper thermal growth limits, optimal temperature for growth and maximum growth capacity) and natural climatic conditions among populations. Hence, S. trutta growth response to temperature lends no support for either of the two suggested thermal adaptation hypotheses. Instead, growth capacity among populations tended to correlate positively with female size at maturity.

  • 4.
    Guenard, G.
    et al.
    Département de Sciences Biologiques, Université de Montréal, Canada.
    Boisclair, D.
    De´partement de sciences biologiques, Universite´ de Montre´al, Canada.
    Ugedal, O.
    Norwegian Institute for Nature Research, Trondheim, Norway.
    Forseth, T.
    Norwegian Institute for Nature Research, Trondheim, Norway.
    Jonsson, Bror
    Norwegian Institute for Nature Research, Norway.
    Fleming, I. A.
    Memorial University of Newfoundland .
    An experimental study of the multiple effects of brown trout Salmo trutta on the bioenergetics of two Arctic charr Salvelinus alpinus morphs2012Inngår i: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 81, nr 4, s. 1248-1270Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study investigated the importance of competition with brown trout Salmo trutta as a driver of the morphological and behavioural divergence of two morphs of Arctic charr Salvelinus alpinus. The morphs originated from two lakes differing in absence or presence of the competitor. The bioenergetics and behaviour of S. alpinus were quantified in replicate experimental enclosures (mean volume: 150 m(3)) stocked with 15 S. alpinus of one morph or the other and in the absence or presence of nine S. trutta. The presence of S. trutta decreased growth rate, affected food consumption and increased activity costs in S. alpinus, but provided little support for the hypothesis that competition with S. trutta is a major driver of the divergence of the two S. alpinus morphs. Both morphs responded similarly in terms of mean growth and consumption rates per enclosure, but the association between individual morphology and growth rate reversed between allopatric and sympatric enclosures. While the activity patterns of the two morphs were unaffected by the presence of S. trutta, their swimming speed and activity rate differed. Since the profound differences in the structure of the physical habitat of the source lakes provided a more likely explanation for the difference observed among these two morphs than interspecific competition, it is hypothesized that physical habitat may sometimes be a significant driving force of the phenotypic divergence.

  • 5. Guenard, G.
    et al.
    Boisclair, Daniel
    Ugedal, Ola
    Forseth, Torbjörn
    Fleming, Ian A.
    Jonsson, Bror
    The bioenergetics ofdensity-dependent growth in Arctic char (Salvelinus alpinus L.)2012Inngår i: Canadian Journal of Fisheries and Aquatic Sciences, ISSN 0706-652X, E-ISSN 1205-7533, Vol. 69, s. 1651-1662Artikkel i tidsskrift (Fagfellevurdert)
  • 6.
    Guenard, Guillaume
    et al.
    Université de Montréal, Canada.
    Boisclair, Daniel
    Université de Montréal, Canada.
    Ugedal, Ola
    Norwegian Institute for Nature Research, Trondheim, Norway.
    Forseth, Torbjorn
    Norwegian Institute for Nature Research, Trondheim, Norway.
    Jonsson, Bror
    Norwegian Institute for Nature Research, Oslo, Norge.
    Comparison between activity estimates obtained using bioenergetic and behavioural analyses2008Inngår i: Canadian Journal of Fisheries and Aquatic Sciences, ISSN 0706-652X, E-ISSN 1205-7533, Vol. 65, nr 8, s. 1705-1720Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Activity rate of Arctic char (Salvelinus alpinus) held in 90 m2 littoral enclosures were estimated using bioenergetic (with consumption estimated using stable caesium, 133Cs) and behavioural approaches (with fish movements quantified using video cameras). We found no statistically significant difference between values of activity rate obtained using the two approaches for three of the six experiments we performed. However, there was no relationship between estimates of activity rate obtained using the two approaches. Discrepancies may arise from the difficulty to meet assumptions regarding the temporal stability of the concentration of 133Cs in fish diet and of the assimilation coefficient of this tracer. When fish remain in an area where their behaviour can be well described (e.g., enclosure, habitat patches of littoral zones, coral reefs), the behavioural approach appears more robust to estimate activity rate because it depends most on a variable that is easiest to estimate (the number of movements performed). When these conditions are not met (low fish densities or major fish migrations), a reliable assessment of the concentration and assimilation of 133Cs in stomach contents appears critical to implement the bioenergetic approach based on this tracer.

  • 7.
    Guenard, Guillaume
    et al.
    De´partement de sciences biologiques, Universite´ de Montre´al,.
    Boisclair, Daniel
    De´partement de sciences biologiques, Universite´ de Montre´al,.
    Ugedal, Ola
    Norwegian Institute for Nature Research, Trondheim, Norway..
    Forseth, Torbjorn
    Norwegian Institute for Nature Research, Trondheim, Norway..
    Jonsson, Bror
    Norwegian Institute for Nature Research, Oslo, Norway..
    Fleming, Ian A.
    Ocean Sciences Centre, Memorial University of Newfoundland, Canada..
    Experimental assessment of the bioenergetic and behavioural differences between two morphologically distinct populations of Arctic char (Salvelinus alpinus)2010Inngår i: Canadian Journal of Fisheries and Aquatic Sciences, ISSN 0706-652X, E-ISSN 1205-7533, Vol. 67, s. 580-595Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

     

    A common environment experiment was conducted to assess the magnitude of the difference in growth, consumption,

    activity rate, and spatial and temporal patterns of habitat use between morphologically different populations of

    Arctic char (Salvelinus alpinus) originating from two Norwegian lakes. These two lakes contrasted sharply in terms of surface

    area, depth, elevation, length of the winter period, and fish community structure (presence–absence of brown trout,

    Salmo trutta). The experimental framework encompassed four littoral enclosures (average volume, 146 m3) stocked with

    char from either of the two populations with duplicated treatments. Char morphology was quantified with numerical image

    analysis, food consumption was estimated using caesium analysis (133Cs), and activity cost and patterns were determined

    using video cameras. Char populations were morphologically distinct and reacted differently in growth (1.9-fold difference

    between populations), food consumption (3-fold difference), and spatial activity patterns (20-fold difference) to the conditions prevailing in the enclosures. The results highlight that functional differences between morphologically distinct char

    may drive important differences in their bioenergetic and behavioural responses when exposed to similar environmental

    conditions. Such functional differences should be incorporated when developing habitat or trophic cascade models.

  • 8. Jonsson, Bror
    et al.
    Finstad, Anders G.
    Jonsson, Nina
    Winter temperature and food quality affect age and size at maturity in ectotherms: an experimentaltest with Atlantic salmon2012Inngår i: Canadian Journal of Fisheries and Aquatic Sciences, ISSN 0706-652X, E-ISSN 1205-7533, Vol. 69, nr 11, s. 1817-1826Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Field studies have revealed that many ectotherms mature younger and smaller in warmer environments although they grow faster. This has puzzled ecologists because the direct effect of factors that accelerate growth is expected to be larger, not smaller size. We tested this experimentally for Atlantic salmon (Salmo salar) at two winter temperatures and diets. Logistic regression revealed that the probability of maturation during the second year in sea water, relative to the probability of older maturation, increased with temperature and growth rate during the first winter. Also, large size and high condition factor 1 year prior to maturation stimulated maturation. In females, a high lipid diet increased the probability of maturation as one-sea-winter fish, and there were significant interactions between winter temperature and food quality and between body size and condition factor the first autumn in sea water. Thus, if the direct effect of temperature on growth rate is the main effect of warming, salmon are likely to attain maturity younger and smaller. Also, richer food decreased age at maturation in females. This finding has consequences for interpretations of climate change impacts on age at maturity in Atlantic salmon and may also hold for many other ectotherm species.

    Salmo salar) at two winter temperatures and

    diets. Logistic regression revealed that the probability of maturation during the second year in sea water, relative to the

    probability of older maturation, increased with temperature and growth rate during the first winter. Also, large size and

    high condition factor 1 year prior to maturation stimulated maturation. In females, a high lipid diet increased the probability of

    maturation as one-sea-winter fish, and there were significant interactions between winter temperature and food quality and

    between body size and condition factor the first autumn in sea water. Thus, if the direct effect of temperature on growth rate is

    the main effect of warming, salmon are likely to attain maturity younger and smaller. Also, richer food decreased age at

    maturation in females. This finding has consequences for interpretations of climate change impacts on age at maturity in Atlantic salmon and may also hold for many other ectotherm species.

  • 9. Jonsson, Bror
    et al.
    Jonsson, Nina
    A review of the likely effects of climate change on anadromous Atlantic salmon Salmo salar and brown trout Salmo trutta, with particular reference to water temperature and flow2009Inngår i: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 75, s. 2381-2447Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The present paper reviews the effects of water temperature and flow on migrations, embryonic development, hatching, emergence, growth and life-history traits in light of the ongoing climate change with emphasis on anadromous Atlantic salmon Salmo salar and brown trout Salmo trutta. The expected climate change in the Atlantic is for milder and wetter winters, with more precipitation falling as rain and less as snow, decrease in ice-covered periods and frequent periods with extreme weather. Overall, thermal limits for salmonids are species specific. Scope for activity and growth and optimal temperature for growth increase with temperature to an optimal point before constrain by the oxygen content of the water. The optimal temperature for growth decreases with increasing fish size and varies little among populations within species, whereas the growth efficiency may be locally adapted to the temperature conditions of the home stream during the growth season. Indirectly, temperature influences age and size at smolting through its effect on growth. Time of spawning, egg hatching and emergence of the larvae vary with temperature and selective effects on time of first feeding. Traits such as age at first maturity, longevity and fecundity decrease with increasing temperature whilst egg size increases with temperature. Water flow influences the accessibility of rivers for returning adults and speed of both upstream and downstream migration. Extremes in water flow and temperature can decrease recruitment and survival. There is reason to expect a northward movement of the thermal niche of anadromous salmonids with decreased production and population extinction in the southern part of the distribution areas, migrations earlier in the season, later spawning, younger age at smolting and sexual maturity and increased disease susceptibility and mortality. Future research challenges are summarized at the end of the paper.

  • 10.
    Jonsson, Bror
    et al.
    Norsk institutt for naturforskning (NINA).
    Jonsson, Nina
    Norsk institutt for naturforskning (NINA).
    Climatic Effects on Atlantic Salmon and Brown Trout: Habitat as a Template for Life Histories2011Inngår i: Ecology of Atlantic salmon and Brown Trout, Dordrecht: Springer, 2011, 1, s. 415-471Kapittel i bok, del av antologi (Fagfellevurdert)
  • 11.
    Jonsson, Bror
    et al.
    Norsk institutt for naturforskning (NINA).
    Jonsson, Nina
    Norsk institutt for naturforskning (NINA).
    Development and Growth2011Inngår i: Ecology of Atlantic salmon and Brown Trout: Habitat as aTemplate for Life Histories, Dordrecht: Springer, 2011, 1, s. 137-209Kapittel i bok, del av antologi (Fagfellevurdert)
  • 12.
    Jonsson, Bror
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013). Norwegian Institute for Nature Research, Oslo, Norway.
    Jonsson, Nina
    Early environment influences later performance in fishes2014Inngår i: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 85, nr 2, s. 155-188Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Conditions fish encounter during embryogenesis and early life history can leave lasting effects not only on morphology, but also on growth rate, life-history and behavioural traits. The ecology of offspring can be affected by conditions experienced by their parents and mother in particular. This review summarizes such early impacts and their ecological influences for a variety of teleost species, but with special reference to salmonids. Growth and adult body size, sex ratio, egg size, lifespan and tendency to migrate can all be affected by early influences. Mechanisms behind such phenotypically plastic impacts are not well known, but epigenetic change appears to be one central mechanism. The thermal regime during development and incubation is particularly important, but also early food consumption and intraspecific density can all be responsible for later life-history variation. For behavioural traits, early experiences with effects on brain, sensory development and cognition appear essential. This may also influence boldness and other social behaviours such as mate choice. At the end of the review, several issues and questions for future studies are given.

  • 13.
    Jonsson, Bror
    et al.
    Norsk institutt for naturforskning (NINA).
    Jonsson, Nina
    Norsk institutt for naturforskning (NINA).
    Farmed Atlantic Salmon in Nature2011Inngår i: Ecology of Atlantic Salmon and Brown Trout: Habitat as a Template for Life Histories, Dordrecht: Springer, 2011, 1, s. 517-566Kapittel i bok, del av antologi (Fagfellevurdert)
  • 14.
    Jonsson, Bror
    et al.
    Norsk institutt for naturforskning (NINA).
    Jonsson, Nina
    Norsk institutt for naturforskning (NINA).
    Habitat Use2011Inngår i: Ecology of Atlantic Salmon and Brown Trout: Habitat as a Template for Life Histories, Dordrecht: Springer, 2011, 1, s. 67-135Kapittel i bok, del av antologi (Fagfellevurdert)
  • 15.
    Jonsson, Bror
    et al.
    Norsk institutt for naturforskning (NINA).
    Jonsson, Nina
    Norsk institutt for naturforskning (NINA).
    Habitats as Template for Life Histories2011Inngår i: Ecology of Atlantic Salmon and Brown Trout: Habitat as a Template for life Histories, Dordrecht: Springer, 2011, 1, s. 1-21Kapittel i bok, del av antologi (Fagfellevurdert)
  • 16.
    Jonsson, Bror
    et al.
    Norsk institutt for naturforskning (NINA).
    Jonsson, Nina
    Norsk institutt for naturforskning (NINA).
    Maturation and Spawning2011Inngår i: Ecology of Atlantic Salmon and Brown Trout: Habitat as a Template for life Hstories, Dordrecht: Springer, 2011, 1, s. 327-414Kapittel i bok, del av antologi (Fagfellevurdert)
  • 17.
    Jonsson, Bror
    et al.
    Norsk institutt for naturforskning (NINA).
    Jonsson, Nina
    Norsk institutt for naturforskning (NINA).
    Migrations2011Inngår i: Ecology of Atlantic Salmon and Brown Trout: Habitat as a Template for Life Histories, Dordrecht: Springer, 2011, 1, s. 247-325Kapittel i bok, del av antologi (Fagfellevurdert)
  • 18. Jonsson, Bror
    et al.
    Jonsson, Nina
    Migratory timing, marine survival and growth of anadromous brown trout Salmo trutta in the River Imsa, Norway2009Inngår i: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 74, nr 3, s. 621-638Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of the paper was to study sea migration, growth and survival of brown trout Salmotrutta of the River Imsa, 1976–2005. The migratory S. trutta were individually tagged and fishleaving or entering the river were monitored daily in traps located near the river mouth. Themean annual duration of the sea sojourn was 6–9 months for first-time migrants moving to seabetween January and June. It was 8–18 months for those migrating to sea between July andDecember. Veteran migrants stayed 12 months or less at sea and most returned to the river inAugust. Early ascending fish stayed the longest in fresh water because most returned to sea inApril to May. The day number of 50% cumulative smolt descent correlated negatively withmean water temperature in February to March and the February North Atlantic Oscillationindex (NAOI). Mean annual sea growth during the first 2 years after smolting was higher for S.trutta spending the winter at sea than those wintering in the River Imsa. First year's sea growthwas lower for S. trutta descending in spring than autumn. For first-time migrants, it correlatednegatively with the February NAOI of the smolt year. Sea survival was higher for spring thanautumn descending first-time migratory S. trutta with a maximum in May (149%). Number ofanadromous S. trutta returning to the river increased linearly with the size of the cohort movingto sea, with no evidence of density-dependent sea mortality. Sea survival of S. trutta smoltsmoving to sea between January and June correlated positively both with the annual number ofAtlantic Salmo salar smolts, the specific growth rate at sea, and time of seaward migration inspring. This is the first study indicating how environmental factors at the time of seawardmigration influence the sea survival of S. trutta.

  • 19.
    Jonsson, Bror
    et al.
    Norsk institutt for naturforskning (NINA).
    Jonsson, Nina
    Norsk institutt for naturforskning (NINA).
    Naturally and hatchery produced European trout Salmo trutta: do their marine survival and dispersal differ?2014Inngår i: Journal of Coastal Conservation, ISSN 1400-0350, E-ISSN 1874-7841, Vol. 18, s. 79-87Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We tested whether marine survival and migration pattern differed between naturally and hatchery produced European trout Salmo trutta of different origins. The hatchery fish were released 150 m above the river estuary of the southwestern, Norwegian River Imsa, the home of the local population. Recaptures were used as proxy for survival. Wild and local hatchery fish survived better than transplanted hatchery stocks. Trout that were 1 year at release survived less well than 2-year olds, and small individuals less well than larger ones. Relative to their body size at release, populations that originated most distant from the River Imsa, the Baltic River Emån and the Norwegian mountain Lake Tunhovd, exhibited the poorest sea survival. At sea, trout chiefly moved less than 240 km from the river of release, but there were significant differences in dispersal among populations. Hatchery-produced River Emån and Lake Tunhovd trout moved farther from the River Imsa than the south Norwegian sea trout populations, and the marine distributions of the former were similar to that of the natural River Imsa trout. Large fish moved farther from the river than smaller ones. Straying to other rivers was low among wild and local hatchery-produced fish, and significantly lower than among most transplanted populations, and River Emån trout in particular. Thus, the River Imsa trout appeared better adapted to survival under the local conditions than non-local trout with consequences for optimal population management.

  • 20.
    Jonsson, Bror
    et al.
    Norsk institutt for naturforskning (NINA).
    Jonsson, Nina
    Norsk institutt for naturforskning (NINA).
    Population Enhancement and Population Restoration2011Inngår i: Ecology of Atlantic Salmon and Brown Trout: Habitat as a Template for Life Histories / [ed] Bror Jonsson and Nina Jonsson, Dordrecht: Springer, 2011, 1, s. 567-632Kapittel i bok, del av antologi (Fagfellevurdert)
  • 21.
    Jonsson, Bror
    et al.
    Norsk institutt for naturforskning (NINA).
    Jonsson, Nina
    Norsk institutt for naturforskning (NINA).
    Recruitment, Mortality and Longevity2011Inngår i: Ecology of Atlantic Salmon and Brown Trout: Habitat as a Template for Life Histories, Dordrecht: Springer, 2011, 1, s. 473-515Kapittel i bok, del av antologi (Fagfellevurdert)
  • 22.
    Jonsson, Bror
    et al.
    Norsk institutt for naturforskning (NINA).
    Jonsson, Nina
    Norsk institutt for naturforskning (NINA).
    Restoration and Enhancement of Salmonid Populations and Habitats with Special Reference to Atlantic Salmon2009Inngår i: Challengesfor Diadromous Fishes in a Dynamic Global Environment, American Fisheries Society , 2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Based on a 2007 international symposium, this book reviews the biology, ecology, human importance, and management and conservation of diadromous fishes with the goal of providing innovative interpretations and opportunities for sustainability. Because diadromous fishes use different environments and migration corridors to complete their life history in ocean and freshwater environments, they are particularly vulnerable to direct and indirect consequences of human development and global climate change.

    Also presents new ecological and evolutionary concepts and experimental and modeling tools that advance understanding of the significance and the resilience of the diadromy life history strategies within ecosystems. Considers creative approaches for habitat protection and restoration to sustain stocks in the future.

  • 23.
    Jonsson, Bror
    et al.
    Norsk institutt for naturforskning (NINA).
    Jonsson, Nina
    Norsk institutt for naturforskning (NINA.
    Smolts and Smolting2011Inngår i: Ecology of Atlantic Salmon and Brown Trout: Habitat as a Template for Life Histories, Dordrecht: Springer, 2011, 1, s. 211-245Kapittel i bok, del av antologi (Fagfellevurdert)
  • 24.
    Jonsson, Bror
    et al.
    Norsk institutt for naturforskning (NINA).
    Jonsson, Nina
    Norsk institutt for naturforskning (NINA).
    Species Diversity2011Inngår i: Ecology of Atlantic Salmon and Brown Trout: Habitat as a Template for Life Histories, Dordrecht: Springer, 2011, 1, s. 23-66Kapittel i bok, del av antologi (Fagfellevurdert)
  • 25.
    Jonsson, Bror
    et al.
    Norsk institutt for naturforskning (NINA).
    Jonsson, Nina
    Norsk institutt for naturforskning (NINA).
    Thinlip grey mullet Liza ramada (Mugilidae) caught in a small Norwegian stream2008Inngår i: Fauna Norvegica, ISSN 1502-4873, E-ISSN 1891-5396, Vol. 26/27, s. 31-33Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Two individuals of thinlip grey mullet

    Liza ramada were collected in a southern Norwegian brook

    (58° 22’ N, 8° 37’ E) on 12th September 2007. The fish were 8.7 and 9.0 cm in total length, 6 and 7

    g in total mass, and most probably in their first year of life. The nearest known spawning area of the

    species is south of the English Channel, meaning that they had probably moved at least 900 km across

    the North Sea during their first growth season. To our knowledge, this is the first published observation

    of the catadromous thinlip grey mullet from a Scandinavian freshwater course.

  • 26. Jonsson, Bror
    et al.
    Jonsson, Nina
    Finstad, Anders G.
    Effects of temperature and food quality on age at maturity of ectotherms: an experimentaltest of Atlantic salmon2013Inngår i: Journal of Animal Ecology, ISSN 0021-8790, E-ISSN 1365-2656, Vol. 82, nr 1, s. 201-210Artikkel i tidsskrift (Fagfellevurdert)
  • 27.
    Jonsson, Bror
    et al.
    Norwegian Institute for Nature Research, CIENS, Oslo, Norge.
    Jonsson, Nina
    Norsk institutt for naturforskning (NINA).
    Hindar, Kjetil
    Northcote, Thomas Gordon
    Engen, Steinar
    Asymmetric competition drives lake use of coexisting salmonids2008Inngår i: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 157, nr 4, s. 553-560Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To what degree are population differences in resource use caused by competition and the occupation of adjacent positions along environmental gradients evidence of competition? Habitat use may be the result of a competitive lottery, or restricted by competition. We tested to what extent population differences in habitat use of two salmonids, cutthroat trout (Oncorhynchus clarki) and Dolly Varden charr (Salvelinus malma) were influenced by interspecific competition. We hypothesized that the depth distribution of Dolly Varden charr would be affected by competition from the more littoral and surface-oriented cutthroat trout, and that the depth distribution of cutthroat trout would be little affected by competition from Dolly Varden charr. Sympatric populations of cutthroat trout and Dolly Varden charr were created by reciprocal transfers of previously allopatric populations in two experimental lakes. We found evidence of asymmetric competition, as Dolly Varden charr were displaced from littoral habitats when sympatric with cutthroat trout, whereas cutthroat trout remained unaffected by the presence of Dolly Varden charr. Evolved differences between the species, and differences between experimental lakes, also contributed to population differences in habitat use, but asymmetric competition remained as the main driver of different depth distributions in sympatry.

  • 28.
    Jonsson, Bror
    et al.
    Norway.
    Jonsson, Nina
    Norway.
    Ugedal, Ola
    Norway.
    Production of juvenile salmonids in small Norwegian streams is affected by agricultural land use2011Inngår i: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 56, s. 2529-2542Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    1. We estimated the biomass and production of juvenile anadromous brown trout (Salmotrutta) and Atlantic salmon (Salmo salar) (parr) in 12 streams in the Skagerrak area ofNorway to identify controlling environmental factors, such as land-use and waterchemistry.2. Production estimates correlated positively with fish density in early summer, but notwith the size of the catchment. The summer biomass of age-0 brown trout and Atlanticsalmon was smaller than that of age-1 and constituted 27.4 and 25.7%, respectively, of thetotal biomass of the two groups.3. Mean production of brown trout from July to September varied between streams, but inmost cases it was below 2 g 100 m)2 day)1. Yearly cohort production from age-0 in July toage-1 in July was 10 g m)2 or less, with mean annual production of 1.32 g 100 m)2 day)1,equivalent to 4.8 g m)2 year)1. The corresponding annual cohort production of Atlanticsalmon was 0.38 g 100 m)2 day)1 or 1.4 g m)2 year)1. Annual production to biomass ratio(P⁄B) for brown trout of the same cohort in the various streams was between 1.47 and 4.37;the overall mean (±SD) for all streams was 2.25 ± 0.94. Mean turnover rate of Atlanticsalmon was 2.73 ± 0.24.4. Production of 0+ brown trout during the summer correlated significantly with thepercentage of agricultural land and forest⁄bogs in the catchment, with maxima at 20 and75%, respectively. Age-0 brown trout production also correlated with concentration ofnitrogen and calcium in the water, with maxima at 2.4 and 14 mg L)1, respectively.5. The results support the hypothesis that brown trout parr production reflects the qualityof their habitat, as indicated by the dome-shaped relationship between percentage ofagricultural land and the concentration of nitrogen and calcium in the water.

  • 29.
    Jonsson, Bror
    et al.
    Norsk institutt for naturforskning (NINA).
    Nina, Jonsson
    Norsk institutt for naturforskning (NINA).
    Ecology of Atlantic Salmon and Brown Trout: Habitat as a template for life histories2011 (oppl. 1)Bok (Fagfellevurdert)
  • 30.
    Jonsson, Bror
    et al.
    Norsk institutt for naturforskning (NINA).
    Nina, Jonsson
    Norsk institutt for naturforskning (NINA).
    Ecology of Atlantic Salmon and Brown Trout Habitat as a Template for Life Histories General Conclusions and Research Tasks2011Inngår i: Ecology of Atlantic Salmon and Brown Trout: Habitat as a template for Life Histories, Dordrecht: Springer, 2011, 1, s. 633-655Kapittel i bok, del av antologi (Fagfellevurdert)
  • 31.
    Jonsson, Nina
    et al.
    Norwegian Institute for Nature Research, Oslo, Norway.
    Jonsson, Bror
    Norsk institutt for naturforskning (NINA).
    Time and size at seaward migration influence the sea survival of Salmo salar2014Inngår i: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 84, nr 5, s. 1457-1473Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Whether time of seaward migration of young Atlantic salmon Salmo salar influences their subsequent survival and growth was investigated in the River Imsa, south-western Norway. Salmo salar were tagged when moving downstream through a trap near the outlet between 1976 and 2010 and recaptured on their adult return. Most descended as smolts in April and May, but some descended during the other months of the year. Annual variation in timing of the smolt migration was significantly correlated with variation in water temperature during spring. Mean total body length of the descending S. salar varied with month of seaward migration. The sea survival of S. salar emigrating from the River Imsa between January and May was 2·8 times higher than for those descending between June and December. The sea survival of the various cohorts decreased with increasing river temperature in April to May, prior to the smolt migration, and decreasing day number when the smolts moved to sea. The size of smolts descending the river between April and May did not affect the survival at sea as much as it affected the survival of migrants descending in any other month of the year. The majority of the downstream migrating S. salar were 2 years old, but proportionally, more 1 year olds moved downstream in the autumn than in the rest of the year. Mean duration between downstream migration of the young and the return migration of the grilse was shortest (12·7 months) for those descending in July and August and longest for those descending in October (21 months). Mean monthly specific growth rate was highest for those migrating downstream between May and July and lowest for those emigrating in September. Based on the present results, it was hypothesized that S. salar emigrating between April and August migrated directly out into the ocean, while those that emigrated between October and March stayed in the estuary until the subsequent spring.

  • 32.
    Nicola, Graciela G.
    et al.
    Department of Environmental Sciences, University of Castilla-La Mancha, Toledo, Spain.
    Almodovar, Ana
    Department of Zoology, Complutense University of Madrid, Madrid, Spain.
    Jonsson, Bror
    Norwegian Institute for Nature Research, Oslo, Norway.
    Elvira, Benigno
    Department of Zoology, Complutense University of Madrid, Madrid, Spain.
    Recruitment variability of resident brown trout in peripheral populations from southern Europe2008Inngår i: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 53, s. 2364-2374Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    1. Population regulation was studied for seven consecutive years (1992–98) in five rivers at

    the periphery of the distribution of Salmo trutta, where the fish were living under

    environmental constraints quite different from those of the main distribution area.

    2. Recruitment is naturally highly variable and the populations had been earlier classified

    as overexploited. Thus we expected that densities of young trout in most populations

    would be too low for density-dependent mortality to operate. We tested this by fitting the

    abundance of recruits to egg densities over seven consecutive years (stock–recruitment

    relationship), and used the results to judge whether exploitation should be restricted in the

    interests of conserving the populations.

    3. The density of 0+ trout in early September, as well as the initial density of eggs and

    parents, varied greatly among localities and years. The data for all populations fitted the

    Ricker stock–recruitment model. The proportion of variance explained by the population

    curves varied between 32% and 51%. However, in most cases the observations were in the

    density-independent part of the stock–recruitment curve, where densities of the recruits

    increased proportionally with egg densities.

    4. Our findings suggest that recruitment densities in most rivers and years were below the

    carrying capacity of the habitats. Although density-dependent mechanisms seemed to

    regulate fish abundance in some cases, environmental factors and harvesting appeared

    generally to preclude populations from reaching densities high enough for negative

    feedbacks to operate. The findings thus lend support to Haldane’s (1956) second

    hypothesis that changes in population density are primarily due to density-independent

    factors in unfavourable areas and areas with low density due to exploitation. Exploitation

    should be reduced to allow natural selection to operate more effectively.

  • 33. Otero, Jaime
    et al.
    L'Abee-Lund, Jan Henning
    Castro-Santos, Ted
    Leonardsson, Kjell
    Storvik, Geir O.
    Jonsson, Bror
    Karlstads universitet, Fakulteten för samhälls- och livsvetenskaper, Avdelningen för biologi. Norsk institutt for naturforskning (NINA).
    Dempson, Brian
    Russell, Ian C.
    Jensen, Arne J.
    Bagliniere, Jean-Luc
    Dionne, Melanie
    Armstrong, John D.
    Romakkaniemi, Atso
    Letcher, Benjamin H.
    Kocik, John F.
    Erkinaro, Jaakko
    Poole, Russell
    Rogan, Ger
    Lundqvist, Hans
    MacLean, Julian C.
    Jokikokko, Erkki
    Arnekleiv, Jo Vegar
    Kennedy, Richard J.
    Niemela, Eero
    Caballero, Pablo
    Music, Paul A.
    Antonsson, Thorolfur
    Gudjonsson, Sigurdur
    Veselov, Alexey E.
    Lamberg, Anders
    Groom, Steve
    Taylor, Benjamin H.
    Taberner, Malcolm
    Dillane, Mary
    Arnason, Fridthjofur
    Horton, Gregg
    Hvidsten, Nils A.
    Jonsson, Ingi R.
    Jonsson, Nina
    McKelvey, Simon
    Naesje, Tor F.
    Skaala, Oystein
    Smith, Gordon W.
    Saegrov, Harald
    Stenseth, Nils C.
    Vollestad, Leif Asbjorn
    Basin-scale phenology and effects of climate variability on global timing of initial seaward migration of Atlantic salmon (Salmo salar)2014Inngår i: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 20, nr 1, s. 61-75Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Migrations between different habitats are key events in the lives of many organisms. Such movements involve annually recurring travel over long distances usually triggered by seasonal changes in the environment. Often, the migration is associated with travel to or from reproduction areas to regions of growth. Young anadromous Atlantic salmon (Salmo salar) emigrate from freshwater nursery areas during spring and early summer to feed and grow in the North Atlantic Ocean. The transition from the freshwater ('parr') stage to the migratory stage where they descend streams and enter salt water ('smolt') is characterized by morphological, physiological and behavioural changes where the timing of this parr-smolt transition is cued by photoperiod and water temperature. Environmental conditions in the freshwater habitat control the downstream migration and contribute to within- and among-river variation in migratory timing. Moreover, the timing of the freshwater emigration has likely evolved to meet environmental conditions in the ocean as these affect growth and survival of the post-smolts. Using generalized additive mixed-effects modelling, we analysed spatio-temporal variations in the dates of downstream smolt migration in 67 rivers throughout the North Atlantic during the last five decades and found that migrations were earlier in populations in the east than the west. After accounting for this spatial effect, the initiation of the downstream migration among rivers was positively associated with freshwater temperatures, up to about 10 °C and levelling off at higher values, and with sea-surface temperatures. Earlier migration occurred when river discharge levels were low but increasing. On average, the initiation of the smolt seaward migration has occurred 2.5 days earlier per decade throughout the basin of the North Atlantic. This shift in phenology matches changes in air, river, and ocean temperatures, suggesting that Atlantic salmon emigration is responding to the current global climate changes.

  • 34.
    Watz, Johan
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper (from 2013).
    Bergman, Eva
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper (from 2013).
    Calles, Olle
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper (from 2013).
    Enefalk, Åsa
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper (from 2013).
    Gustafsson, Stina
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper (from 2013).
    Hagelin, Anna
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper (from 2013).
    Nilsson, P. Anders
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper (from 2013).
    Norrgård, Johnny
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper (from 2013). Fortum generation.
    Nyqvist, Daniel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper (from 2013).
    Österling, Martin
    Karlstads universitet, Fakulteten för samhälls- och livsvetenskaper, Avdelningen för biologi.
    Piccolo, John J.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper (from 2013).
    Schneider, Lea Dominique
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper (from 2013).
    Greenberg, Larry
    Karlstads universitet, Fakulteten för samhälls- och livsvetenskaper, Avdelningen för biologi.
    Jonsson, Bror
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper (from 2013). Norsk institutt for naturforskning, Oslo.
    Ice cover alters the behavior and stress level of brown trout Salmo trutta2015Inngår i: Behavioral Ecology, ISSN 1045-2249, E-ISSN 1465-7279, Vol. 26, nr 3, s. 820-827Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Surface ice in rivers and lakes buffers the thermal environment and provides overhead cover, protecting aquatic animals from terrestrial predators. We tested if surface ice influenced the behavior (swimming activity, aggressive encounters, and number of food items eaten) and stress level (coloration of eyes and body) of stream-living brown trout Salmo trutta at temperatures of 3–4 °C in indoor experimental flumes. We hypothesized that an individual’s resting metabolic rate (RMR, as measured by resting ventilation rate) would affect winter behavior. Therefore, groups of 4 trout, consisting of individuals with high, low, or mixed (2 individuals each) RMR, were exposed to experimental conditions with or without ice cover. Ice cover reduced stress responses, as evaluated by body coloration. Also, trout in low RMR groups had a paler body color than those in both mixed and high RMR groups. Trout increased their swimming activity under ice cover, with the highest activity found in high RMR groups. Ice cover increased the number of aggressive encounters but did not influence the number of drifting food items taken by each group. In mixed RMR groups, however, single individuals were better able to monopolize food than in the other groups. As the presence of surface ice increases the activity level and reduces stress in stream-living trout, ice cover should influence their energy budgets and production. The results should be viewed in light of ongoing global warming that reduces the duration of ice cover, especially at high latitudes and altitudes.

1 - 34 of 34
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf