| 1. |
- Nevoux, M., et al.
(författare)
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Environmental influences of life history strategies in partial anadromous brown trout (Salmo trutta, Salmonidae)
- 2019
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Ingår i: Fish and Fisheries. - : Wiley. - 1467-2960 .- 1467-2979. ; 20:6, s. 1051-1082
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Tidskriftsartikel (refereegranskat)abstract
- This paper reviews the life history of brown trout and factors influencing decisions to migrate. Decisions that maximize fitness appear dependent on size at age. In partly anadromous populations, individuals that attain maturity at the parr stage typically become freshwater resident. For individual fish, the life history is not genetically fixed and can be modified by the previous growth history and energetic state in early life. This phenotypic plasticity may be influenced by epigenetic modifications of the genome. Thus, factors influencing survival and growth determine life-history decisions. These are intra- and interspecific competition, feeding and shelter opportunities in freshwater and salt water, temperature in alternative habitats and flow conditions in running water. Male trout exhibit alternative mating strategies and can spawn as a subordinate sneaker or a dominant competitor. Females do not exhibit alternative mating behaviour. The relationship between growth, size and reproductive success differs between sexes in that females exhibit a higher tendency to migrate than males. Southern populations are sensitive to global warming. In addition, fisheries, aquaculture with increased spreading of salmon lice, introduction of new species, weirs and river regulation, poor water quality and coastal developments all threaten trout populations. The paper summarizes life-history data from six populations across Europe and ends by presenting new research questions and directions for future research.
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| 2. |
- Thorstad, E. B., et al.
(författare)
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Reduced marine survival of hatchery-reared Atlantic salmon post-smolts exposed to aluminium and moderate acidification in freshwater
- 2013
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Ingår i: Estuarine Coastal and Shelf Science. - : Elsevier BV. - 0272-7714. ; 124, s. 34-43
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Tidskriftsartikel (refereegranskat)abstract
- Short-term Al-exposure and moderate acidification increased initial marine mortality in migrating post-smolts, and can thereby reduce viability of Atlantic salmon stocks. The delayed impact of short-term aluminium (Al) exposure on hatchery-reared Atlantic salmon smolt in moderately acidified freshwater (pH 5.88–5.98) was investigated during the first 37 km of the marine migration. Smolts were tagged with acoustic tags and exposed to low (28.3 ± 4.6 μg l−1 labile Al, 90 h) or high (48.5 ± 6.4 μg l−1 labile Al, 90 or 48 h) Al concentrations within the hatchery. Thereafter their movements, together with a control group, were monitored throughout the marine fjord. Al-exposure resulted in increased gill-Al and compromised hypoosmoregulatory capacity, as shown by elevated mortality in laboratory seawater challenge tests and reduced Na+, K+-ATPase activity levels. Further, Al-exposure resulted in decreased plasma concentrations of growth hormone (GH), while the insulin-like growth factor (IGF-I) was unaffected. There was a significant mortality in the 90 h high-Al group during exposure, and those surviving until release died during the first 3.6 km of the marine migration. Physiological stress and mortality were not only a result of the Al-concentrations, but also dependent on exposure duration, as shown by results from the 48 h high-Al group. Elevated mortality was not recorded in freshwater or after entering the sea for this group, which highly contrasts to the 100% mortality in the 90 h high-Al group, despite both groups having similarly high gill-Al levels. The low-Al group showed a 20% higher mortality compared to the control group during the first 10 km of the marine migration, but during the next 28 km, mortality rates did not differ. Hence, post-smolts surviving the first 10 km subsequently showed no differences in mortality compared to controls. At least one third of the mortality in both the low-Al and control groups were due to predation by marine fishes, indicating that the proximate cause for elevated mortality due to Al-exposure may have been predation. Migration speeds over 3.6, 9.6 or 37.1 km from the release site was not affected by Al-exposure.
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| 3. |
- Mes, D., et al.
(författare)
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Effects of environmental enrichment on forebrain neural plasticity and survival success of stocked Atlantic salmon
- 2019
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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 222:23
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Tidskriftsartikel (refereegranskat)abstract
- Fish reared for stocking programmes are severely stimulus deprived compared with their wild conspecifics raised under natural conditions. This leads to reduced behavioural plasticity and low post-release survival of stocked fish. Environmental enrichment can have positive effects on important life skills, such as predator avoidance and foraging behaviour, but the neural mechanisms underpinning these behavioural changes are still largely unknown. In this study, juvenile Atlantic salmon (Salmo safer) were reared in an enriched hatchery environment for 7 weeks, after which neurobiological characteristics and post-release survival were compared with those of fish reared under normal hatchery conditions. Using in situ hybridization and qPCR, we quantified the expression of brain derived neurotrophic factor (bdnf) and the neural activity marker dos in telencephalic subregions associated with relational memory, emotional learning and stress reactivity. Aside from lower expression of bdnf in the Dlv (a region associated with relational memory) of enriched salmon, we observed no other significant effects of enrichment in the studied regions. Exposure to an enriched environment increased postrelease survival during a 5 month residence in a natural river by 51%. Thus, we demonstrate that environmental enrichment can improve stocking success of Atlantic salmon parr and that environmental enrichment is associated with changes in bdnf expression in the fish's hippocampus-equivalent structure.
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