| 1. |
- Otero, Jaime, et al.
(författare)
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Basin-scale phenology and effects of climate variability on global timing of initial seaward migration of Atlantic salmon (Salmo salar)
- 2014
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 20:1, s. 61-75
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 2. |
- Jonsson, Bror, 1948-, et al.
(författare)
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Asymmetric competition drives lake use of coexisting salmonids
- 2008
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Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 157:4, s. 553-560
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 3. |
- Jonsson, Bror, 1948-, et al.
(författare)
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Development and Growth
- 2011. - 1
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Ingår i: Ecology of Atlantic salmon and Brown Trout. - Dordrecht : Springer. - 9789400711884 ; , s. 137-209
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Bokkapitel (refereegranskat)
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| 4. |
- Jonsson, Bror, 1948-, et al.
(författare)
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Early environment influences later performance in fishes
- 2014
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Ingår i: Journal of Fish Biology. - : Wiley. - 0022-1112 .- 1095-8649. ; 85:2, s. 155-188
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 5. |
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| 6. |
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| 7. |
- Jonsson, Bror, 1948-, et al.
(författare)
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Farmed Atlantic Salmon in Nature
- 2011. - 1
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Ingår i: Ecology of Atlantic Salmon and Brown Trout. - Dordrecht : Springer. - 9789400711884 ; , s. 517-566
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Bokkapitel (refereegranskat)
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| 8. |
- Jonsson, Bror, 1948-, et al.
(författare)
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Habitat Use
- 2011. - 1
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Ingår i: Ecology of Atlantic Salmon and Brown Trout. - Dordrecht : Springer. - 9789400711884 ; , s. 67-135
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Bokkapitel (refereegranskat)
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| 9. |
- Jonsson, Bror, 1948-, et al.
(författare)
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Habitats as Template for Life Histories
- 2011. - 1
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Ingår i: Ecology of Atlantic Salmon and Brown Trout. - Dordrecht : Springer. ; , s. 1-21
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Bokkapitel (refereegranskat)
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| 10. |
- Jonsson, Bror, 1948-, et al.
(författare)
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Maturation and Spawning
- 2011. - 1
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Ingår i: Ecology of Atlantic Salmon and Brown Trout. - Dordrecht : Springer. - 9789400711884 ; , s. 327-414
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Bokkapitel (refereegranskat)
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| 11. |
- Jonsson, Bror, 1948-, et al.
(författare)
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Migrations
- 2011. - 1
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Ingår i: Ecology of Atlantic Salmon and Brown Trout. - Dordrecht : Springer. - 9789400711884 ; , s. 247-325
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Bokkapitel (refereegranskat)
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| 12. |
- Jonsson, Bror, 1948-, et al.
(författare)
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Naturally and hatchery produced European trout Salmo trutta : do their marine survival and dispersal differ?
- 2014
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Ingår i: Journal of Coastal Conservation. - : Springer Science and Business Media LLC. - 1400-0350 .- 1874-7841. ; 18, s. 79-87
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 13. |
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| 14. |
- Jonsson, Bror, 1948-, et al.
(författare)
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Recruitment, Mortality and Longevity
- 2011. - 1
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Ingår i: Ecology of Atlantic Salmon and Brown Trout. - Dordrecht : Springer. - 9789400711884 ; , s. 473-515
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Bokkapitel (refereegranskat)
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| 15. |
- Jonsson, Bror, 1948-, et al.
(författare)
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Restoration and Enhancement of Salmonid Populations and Habitats with Special Reference to Atlantic Salmon
- 2009
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Ingår i: Challengesfor Diadromous Fishes in a Dynamic Global Environment. - : American Fisheries Society. - 9781934874080
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 16. |
- Jonsson, Bror, 1948-, et al.
(författare)
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Smolts and Smolting
- 2011. - 1
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Ingår i: Ecology of Atlantic Salmon and Brown Trout. - Dordrecht : Springer. - 9789400711884 ; , s. 211-245
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Bokkapitel (refereegranskat)
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| 17. |
- Jonsson, Bror, 1948-, et al.
(författare)
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Species Diversity
- 2011. - 1
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Ingår i: Ecology of Atlantic Salmon and Brown Trout. - Dordrecht : Springer. - 9789400711884 ; , s. 23-66
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Bokkapitel (refereegranskat)
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| 18. |
- Jonsson, Bror, 1948-, et al.
(författare)
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Thinlip grey mullet Liza ramada (Mugilidae) caught in a small Norwegian stream
- 2008
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Ingår i: Fauna Norvegica. - 1502-4873 .- 1891-5396. ; 26/27, s. 31-33
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Tidskriftsartikel (refereegranskat)abstract
- Two individuals of thinlip grey mulletLiza 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 7g in total mass, and most probably in their first year of life. The nearest known spawning area of thespecies is south of the English Channel, meaning that they had probably moved at least 900 km acrossthe North Sea during their first growth season. To our knowledge, this is the first published observationof the catadromous thinlip grey mullet from a Scandinavian freshwater course.
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| 19. |
- Jonsson, Bror, 1948-, et al.
(författare)
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Winter temperature and food quality affect age and size at maturity in ectotherms: an experimentaltest with Atlantic salmon
- 2012
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Ingår i: Canadian Journal of Fisheries and Aquatic Sciences. - : Canada. Dept. of Fisheries and Oceans; National Research Council Canada, National Research Council Canada. - 0706-652X .- 1205-7533. ; 69:11, s. 1817-1826
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Tidskriftsartikel (refereegranskat)abstract
- 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 anddiets. Logistic regression revealed that the probability of maturation during the second year in sea water, relative to theprobability of older maturation, increased with temperature and growth rate during the first winter. Also, large size andhigh condition factor 1 year prior to maturation stimulated maturation. In females, a high lipid diet increased the probability ofmaturation as one-sea-winter fish, and there were significant interactions between winter temperature and food quality andbetween body size and condition factor the first autumn in sea water. Thus, if the direct effect of temperature on growth rate isthe main effect of warming, salmon are likely to attain maturity younger and smaller. Also, richer food decreased age atmaturation 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.
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| 20. |
- Jonsson, Nina, et al.
(författare)
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Time and size at seaward migration influence the sea survival of Salmo salar
- 2014
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Ingår i: Journal of Fish Biology. - : Wiley. - 0022-1112 .- 1095-8649. ; 84:5, s. 1457-1473
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 21. |
- Finstad, Anders G., et al.
(författare)
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Competitive exclusion along climate gradients : energy efficiency influences the distribution of two salmonid fishes
- 2011
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 17:4, s. 1703-1711
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 22. |
- Forseth, Torbjörn, et al.
(författare)
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Thermal growth performance of juvenile brown trout Salmo trutta : no support for thermal adaptation hypotheses
- 2009
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Ingår i: Journal of Fish Biology. - : Wiley. - 0022-1112 .- 1095-8649. ; 74:1, s. 133-149
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 23. |
- Guenard, G., et al.
(författare)
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An experimental study of the multiple effects of brown trout Salmo trutta on the bioenergetics of two Arctic charr Salvelinus alpinus morphs
- 2012
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Ingår i: Journal of Fish Biology. - : Wiley. - 0022-1112 .- 1095-8649. ; 81:4, s. 1248-1270
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 24. |
- Guenard, Guillaume, et al.
(författare)
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Experimental assessment of the bioenergetic and behavioural differences between two morphologically distinct populations of Arctic char (Salvelinus alpinus)
- 2010
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Ingår i: Canadian Journal of Fisheries and Aquatic Sciences. - 0706-652X .- 1205-7533. ; 67, s. 580-595
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Tidskriftsartikel (refereegranskat)abstract
- 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 ofArctic char (Salvelinus alpinus) originating from two Norwegian lakes. These two lakes contrasted sharply in terms of surfacearea, 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 withchar from either of the two populations with duplicated treatments. Char morphology was quantified with numerical imageanalysis, food consumption was estimated using caesium analysis (133Cs), and activity cost and patterns were determinedusing video cameras. Char populations were morphologically distinct and reacted differently in growth (1.9-fold differencebetween 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 charmay drive important differences in their bioenergetic and behavioural responses when exposed to similar environmentalconditions. Such functional differences should be incorporated when developing habitat or trophic cascade models.
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| 25. |
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| 26. |
- Nicola, Graciela G., et al.
(författare)
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Recruitment variability of resident brown trout in peripheral populations from southern Europe
- 2008
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Ingår i: Freshwater Biology. - : Wiley. - 0046-5070 .- 1365-2427. ; 53, s. 2364-2374
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Tidskriftsartikel (refereegranskat)abstract
- 1. Population regulation was studied for seven consecutive years (1992–98) in five rivers atthe periphery of the distribution of Salmo trutta, where the fish were living underenvironmental constraints quite different from those of the main distribution area.2. Recruitment is naturally highly variable and the populations had been earlier classifiedas overexploited. Thus we expected that densities of young trout in most populationswould be too low for density-dependent mortality to operate. We tested this by fitting theabundance of recruits to egg densities over seven consecutive years (stock–recruitmentrelationship), and used the results to judge whether exploitation should be restricted in theinterests of conserving the populations.3. The density of 0+ trout in early September, as well as the initial density of eggs andparents, varied greatly among localities and years. The data for all populations fitted theRicker stock–recruitment model. The proportion of variance explained by the populationcurves varied between 32% and 51%. However, in most cases the observations were in thedensity-independent part of the stock–recruitment curve, where densities of the recruitsincreased proportionally with egg densities.4. Our findings suggest that recruitment densities in most rivers and years were below thecarrying capacity of the habitats. Although density-dependent mechanisms seemed toregulate fish abundance in some cases, environmental factors and harvesting appearedgenerally to preclude populations from reaching densities high enough for negativefeedbacks to operate. The findings thus lend support to Haldane’s (1956) secondhypothesis that changes in population density are primarily due to density-independentfactors in unfavourable areas and areas with low density due to exploitation. Exploitationshould be reduced to allow natural selection to operate more effectively.
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