| 1. |
- Johnsson, Jörgen I, 1959, et al.
(författare)
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Environmental effects on behavioural development: consequences for fitness of captive-reared fishes in the wild
- 2014
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Ingår i: Journal of Fish Biology. - : Wiley. - 0022-1112 .- 1095-8649. ; 85, s. 1946-1971
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Tidskriftsartikel (refereegranskat)abstract
- Why do captive-reared fishes generally have lower fitness in natural environments than wild conspecifics, even when the hatchery fishes are derived from wild parents from the local population? A thorough understanding of this question is the key to design artificial rearing environments that optimize post-release performance, as well as to recognize the limitations of what can be achieved by modifying hatchery rearing methods. Fishes are generally very plastic in their development and through gene–environment interactions, epigenetic and maternal effects their phenotypes will develop differently depending on their rearing environment. This suggests that there is scope for modifying conventional rearing environments to better prepare fishes for release into the wild. The complexity of the natural environment is impossible to mimic in full-scale rearing facilities. So, in reality, the challenge is to identify key modifications of the artificial rearing environment that are practically and economically feasible and that efficiently promote development towards a more wild-like phenotype. Do such key modifications really exist? Here, attempts to use physical enrichment and density reduction to improve the performance of hatchery fishes are discussed and evaluated. These manipulations show potential to increase the fitness of hatchery fishes released into natural environments, but the success is strongly dependent on adequately adapting methods to species and life stage-specific conditions.
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| 2. |
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| 3. |
- Näslund, Joacim, 1985, et al.
(författare)
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Early enrichment effects on brain development in hatchery-reared Atlantic salmon (Salmo salar): no evidence for a critical period
- 2012
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Ingår i: Canadian Journal of Fisheries and Aquatic Sciences. - : Canadian Science Publishing. - 0706-652X .- 1205-7533. ; 69:9, s. 1481-1490
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Tidskriftsartikel (refereegranskat)abstract
- In hatcheries, fish are normally reared in barren environments, which have been reported to affect their phenotypic development compared with wild conspecifics. In this study, Atlantic salmon (Salmo salar) alevins were reared in conventional barren hatchery trays or in either of two types of structurally enriched trays. We show that increased structural complexity during early rearing increased brain size in all investigated brain substructures. However, these effects disappeared over time after transfer to barren tanks for external feeding. Parallel to the hatchery study, a group of salmon parr was released into nature and recaptured at smoltification. These stream-reared smolts developed smaller brains than the hatchery reared smolts, irrespective of initial enrichment treatment. These novel findings do not support the hypothesis that there is a critical early period determining the brain growth trajectory. In contrast, our results indicate that brain growth is plastic in relation to environment. In addition, we show allometric growth in brain substructures over juvenile development, which suggests that comparisons between groups of different body size should be made with caution. These results can aid the development of ecologically sound rearing methods for conservational fish-stocking programs.
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| 4. |
- Näslund, Joacim, 1985, et al.
(författare)
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Effects of early rearing environment on brain devlopment in Atlantic salmon
- 2011
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Ingår i: Oikos meeting 2011.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The brain size of animals has previously been shown to be affected by environmental complexity. In an experiment we show that hatchery environment experienced early in life can affect the brain size in salmonid fish. Atlantic salmon were subjected to three different structural treatments during the alvelin stage: (1) stones scattered on the botton, (2) an artificial substrate grid, or (3) conventional barren hatchery trays. Our results show that stone treatment produce fish with larger brains than fish reared in barren trays, with grid treatment being intermediary. These effects were gradually reduced when the fish were moved to a standard barren hatchery environment. In addition, fish released into nature a half year prior to smoltification showed a higher degree of brain growth than age-matched-fish kept in the hatchery. The results show that brain growth in alvelins and parr is plastic and that enrichment affects brain development and thereby potentially fitness and behaviour.
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| 5. |
- Sundström, L. Fredrik, 1972, et al.
(författare)
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Density-Dependent Compensatory Growth in Brown Trout (Salmo trutta) in Nature
- 2013
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Ingår i: Plos One. - : Public Library of Science (PLoS). - 1932-6203. ; 8:5
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Tidskriftsartikel (refereegranskat)abstract
- Density-dependence is a major ecological mechanism that is known to limit individual growth. To examine if compensatory growth (unusually rapid growth following a period of imposed slow growth) in nature is density-dependent, one-year-old brown trout (Salmo trutta L.) were first starved in the laboratory, and then released back into their natural stream, either at natural or at experimentally increased population density. The experimental trout were captured three times over a one-year period. We found no differences in growth, within the first month after release (May-June), between the starved fish and the control group (i.e. no evidence of compensation). During the summer however (July-September), the starved fish grew more than the control group (i.e. compensation), and the starved fish released into the stream at a higher density, grew less than those released at a natural density, both in terms of weight and length (i.e. density-dependent compensation). Over the winter (October-April), there were no effects of either starvation or density on weight and length growth. After the winter, starved fish released at either density had caught up with control fish in body size, but recapture rates (proxy for survival) did not indicate any costs of compensation. Our results suggest that compensatory growth in nature can be density-dependent. Thus, this is the first study to demonstrate the presence of ecological restrictions on the compensatory growth response in free-ranging animals.
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| 6. |
- Tinoco, Ana B, et al.
(författare)
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Ghrelin increases food intake, swimming activity and growth in juvenile brown trout (Salmo trutta)
- 2014
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Ingår i: Physiology and Behavior. - : Elsevier BV. - 0031-9384 .- 1873-507X. ; 124, s. 15-22
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Tidskriftsartikel (refereegranskat)abstract
- Several key functions of ghrelin are well conserved through vertebrate phylogeny. However, some of ghrelin's effects are contradictory and among teleosts only a limited number of species have been used in functional studies on food intake and foraging-related behaviors. Here we investigated the long-term effects of ghrelin on food intake, growth, swimming activity and aggressive contest behavior in one year old wild brown trout (Salmo trutta) using intraperitoneal implants. Food intake and swimming activity were individually recorded starting from day 1, and aggressive behavior was tested at day 11, after ghrelin implantation. Body weight and growth rate were measured from the beginning to the end of the experiment. Triglycerides and lipase activity in muscle and liver; monoaminergic activity in the telencephalon and brainstem; and neuropeptide Y (NPY) mRNA levels in the hypothalamus were analyzed. Ghrelin treatment was found to increase food intake and growth without modifying lipid deposition or lipid metabolism in liver and muscle. Ghrelin treatment led to an increased foraging activity and a trend towards a higher swimming activity. Moreover, ghrelin-treated fish showed a tendency to initiate more conflicts, but this motivation was not reflected in a higher ability to win the conflicts. No changes were observed in monoaminergic activity and NPY mRNA levels in the brain. Ghrelin is therefore suggested to act as an orexigenic hormone regulating behavior in juvenile wild brown trout. These actions are accompanied with an increased growth without the alteration of liver and muscle lipid metabolism and they do not seem to be mediated by changes in brain monoaminergic activity or hypothalamic expression of NPY.
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| 7. |
- Tinoco, Ana Belén, et al.
(författare)
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Regulación de la ingesta, el crecimiento y el comportamiento por ghrelina en ejemplares salvajes de trucha marrón (Salmo trutta)
- 2011
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Ingår i: Libro de actas: XIII Congreso Nacional Acuicultura, Barcelona 2011.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Studies in teleosts reveal that several key functions of ghrelin have been conserved during vertebrate evolution. However, results in rainbow trout (Oncorhynchus mykiss) showed different effects of this hormone. Our aim was to clarify if these results are representative for salmonids, or reflect domestication effects, since rainbow trout has been artificially selected for rapid growth. Thus, the long-term effect of ghrelin implants in wild brown trout (S. trutta) parr was studied. Ghrelin significantly increased food intake and specific growth rate. Moreover, an increase tendency was observed in swim activity and aggressive behavior in ghrelin treated fish. Therefore, ghrelin seems to have the same functions in wild salmonids as in other fish, and the altered ghrelin actions in rainbow trout are likely due to domestication effects, although species-specific effects cannot be ruled out. Additional studies are necessary to clarify if ghrelin affect swim activity and aggressive behavior in salmonids.
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