| 1. |
- Sundström, L. Fredrik, 1972, et al.
(författare)
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Heart rate responses to predation risk in Salmo trutta are affected by the rearing environment
- 2005
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Ingår i: Journal of Fish Biology. - : Wiley. - 1095-8649 .- 0022-1112. ; 67:5, s. 1280-1286
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Tidskriftsartikel (refereegranskat)abstract
- Both wild‐ and hatchery‐reared brown trout Salmotrutta, 18 months of age and of the same genetic origin, responded with increased heart rates (tachycardia) to a simulated predator attack on 2 consecutive days. Brown trout reared in the hatchery showed a more rapidly induced tachycardia compared with wild‐reared fish at day 1, but not day 2. During an undisturbed period several hours after attacks, hatchery‐reared brown trout maintained higher heart rates compared to wild‐reared fish on both days. Behavioural responses to the attack were very low for all fish, although hatchery‐reared fish tended to be more active than wild fish after the attack day 2. The observed differences may have had a genetic background caused by different selection regimes in the hatchery‐ and wild‐rearing environments, or could have been due to different phenotypic responses in the two environments.
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| 2. |
- Aarestrup, K., et al.
(författare)
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Survival and progression rates of anadromous brown trout kelts Salmo trutta during downstream migration in freshwater and at sea
- 2015
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 535, s. 185-195
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Tidskriftsartikel (refereegranskat)abstract
- The marine migration of post-spawning anadromous fish remains poorly understood. The present study examined survival and progression rates of anadromous brown trout Salmo trutta L. after spawning (kelts) during downriver, fjord, and sea migration. Kelts (n = 49) were captured in the Danish River Gudenaa, tagged with acoustic transmitters and subsequently recorded by automatic receivers. Kelts spent on average 25 d moving down the 45 km river and through the brackish fjord. The fish entered the Kattegat Sea between 14 April and 30 May. Eighteen of the 49 kelts disappeared in the river and fjord during outward migration, likely due to mortality. Survival was not significantly related to gill Na+/K+-ATPase activity, suggesting that physiological adaptation to saltwater may be less critical for adults compared to juveniles (smolts). Of the 31 fish that entered the Kattegat Sea, 45% survived and returned to the fjord. The duration of the entire marine migration, from leaving to entering the river, was on average 163 d. The fish returned from the Kattegat Sea to the fjord between 22 July and 21 October. Upon return, the fish spent 1-90 d passing through Randers Fjord, with most individuals completing the reach within 4 d, suggesting that the kelts spent limited time foraging after returning to the fjord. The total survival during the entire marine migration, including the fjord, was a minimum of 29%. Our study provides data that are important for management of anadromous brown trout, and the high survival highlights that kelts may represent a valuable resource for both population reproduction and recreational fisheries.
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| 3. |
- Aas, O., et al.
(författare)
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Salmonid stocking in five North Atlantic jurisdictions: Identifying drivers and barriers to policy change
- 2018
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Ingår i: Aquatic Conservation-Marine and Freshwater Ecosystems. - : Wiley. - 1052-7613. ; 28:6, s. 1451-1464
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Tidskriftsartikel (refereegranskat)abstract
- New knowledge challenges long-established practices of fish stocking and transfer because of increasing scientific consensus that the release of cultivated fish can pose risks to biodiversity; however, stocking can also improve fisheries, creating difficult decision trade-offs regarding its use. Accordingly, controversy persists about fish stocking and transfer. No studies, however, have embraced a multinational perspective to understand the important governance dimensions of the success and failure of salmonid stocking and transfer policies. The present study has analysed the historical development and contemporary governance of the stocking and transfer of native and non-native salmonids of the genera Salmo, Salvelinus, and Oncorhynchus in five legislative units around the North Atlantic Ocean: the Atlantic Provinces of Canada, France, Germany, Norway, and Sweden. The study is based on the analyses of published and unpublished literature, and a survey of experts. Current salmonid stocking policies and practices varied significantly among jurisdictions; the degree of policy change varied, from radical and rapid changes de jure and de facto in Atlantic Canada and Norway to incremental mostly de jure changes in France and Germany. Rapid policy change in Atlantic Canada, Norway, and partly in Sweden can be explained by the socio-political importance of salmonid fisheries, stocking regulations based on policy objectives to conserve wild Atlantic salmon (Salmo salar), well-documented examples of the harmful consequences of transfers of non-native species, and well-developed vertical governance linkages. The policy changes resemble that of the 'punctuated equilibrium policy framework'. By contrast, France and Germany place less socio-political emphasis on salmonids, have stocking regulations less directed at wild salmonids, more local-level decision making, more species-rich fish communities, and little evidence of adverse ecological impacts of the transfer and stocking of salmonids. This has led to small, incremental changes in stocking policy de facto that are reflective of the 'advocacy coalition policy framework'.
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| 4. |
- Aldvén, David, 1986, et al.
(författare)
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Environmental cues and downstream migration of anadromous brown trout (Salmo trutta) and Atlantic salmon (Salmo salar) smolts
- 2015
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Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 20:1, s. 35-44
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Tidskriftsartikel (refereegranskat)abstract
- Several environmental cues have been suggested to govern the initiation of the downstream migration of smolts (e.g. light, temperature and discharge). Here we investigated the effect of these cues on the initiation of the downstream migration in anadromous brown trout and Atlantic salmon in a small river on the Swedish west coast during two consecutive years. The total smolt production was assessed using a smolt trap and by modelling data from standardized electrofishing. The results show that it is possible to estimate smolt numbers using electrofishing, but that the model had a tendency to overestimate the number of smolts from electrofishing as compared with that from captures with the smolt trap. Discharge had the greatest effect on downstream migration, but temperature was also important when there was no increase in discharge. These results reveal that discharge and temperature govern the initiation of downstream migration but their effect may depend on the amount of precipitation
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| 5. |
- Aldvén, David, 1986, et al.
(författare)
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Migration speed, routes, and mortality rates of anadromous brown trout Salmo trutta during outward migration through a complex coastal habitat
- 2015
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 541, s. 151-163
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Tidskriftsartikel (refereegranskat)abstract
- Little is known about migratory routes and habitat use of anadromous brown trout Salmo trutta at sea. We therefore conducted a 2 yr study (2011-2012) on sea trout in the River Himlean system (a river, an estuary, and a coastal sea environment) in western Sweden. The main objectives were to investigate migration speed, migration routes, and mortality both for adult brown trout returning to the sea (kelts) and smolts (generally 2 yr old trout migrating to the sea for the first time). Brown trout were captured and tagged with hydro-acoustic transmitters, after which they were released and monitored during their initial migration. Migration was primarily nocturnal in the river and estuary, whereas no tendency for nocturnal migration was observed along the coast. Migration speed tended to decrease as individuals progressed from the river through the estuary and along the coast, and we found no differences in absolute migration speed between kelts and smolts. Smolts and kelts showed similar mortality. Mortality during the initial part of the migration ranged between 5 and 51% and was significantly higher in 2011, for both smolts and kelts. Our study is the first to compare migratory patterns and mortality rates between sea trout kelts and smolts during the transition from freshwater into an open coastal system.
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| 6. |
- Bekkevold, D., et al.
(författare)
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Northern European Salmo trutta (L.) populations are genetically divergent across geographical regions and environmental gradients
- 2020
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Ingår i: Evolutionary Applications. - : Wiley. - 1752-4571. ; 13:2, s. 400-416
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Tidskriftsartikel (refereegranskat)abstract
- The salmonid fish Brown trout is iconic as a model for the application of conservation genetics to understand and manage local interspecific variation. However, there is still scant information about relationships between local and large-scale population structure, and to what extent geographical and environmental variables are associated with barriers to gene flow. We used information from 3,782 mapped SNPs developed for the present study and conducted outlier tests and gene-environment association (GEA) analyses in order to examine drivers of population structure. Analyses comprised >2,600 fish from 72 riverine populations spanning a central part of the species' distribution in northern Europe. We report hitherto unidentified genetic breaks in population structure, indicating strong barriers to gene flow. GEA loci were widely spread across genomic regions and showed correlations with climatic, abiotic and geographical parameters. In some cases, individual loci showed consistent GEA across the geographical regions Britain, Europe and Scandinavia. In other cases, correlations were observed only within a sub-set of regions, suggesting that locus-specific variation was associated with local processes. A paired-population sampling design allowed us to evaluate sampling effects on detection of outlier loci and GEA. Two widely applied methods for outlier detection (pcadapt and bayescan) showed low overlap in loci identified as statistical outliers across sub-sets of data. Two GEA analytical approaches (LFMM and RDA) showed good correspondence concerning loci associated with specific variables, but LFMM identified five times more statistically significant associations than RDA. Our results emphasize the importance of carefully considering the statistical methods applied for the hypotheses being tested in outlier analysis. Sampling design may have lower impact on results if the objective is to identify GEA loci and their population distribution. Our study provides new insights into trout populations, and results have direct management implications in serving as a tool for identification of conservation units.
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| 7. |
- Bour, Agathe, et al.
(författare)
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Microplastic Vector Effects: Are Fish at Risk When Exposed via the Trophic Chain?
- 2020
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Ingår i: Frontiers in Environmental Science. - : Frontiers Media SA. - 2296-665X. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- In aquatic organisms, trophic transfer is a relevant exposure route for microplastics (MPs). Despite their relevance, effect studies on fish exposed via trophic chains are currently very scarce. MPs are known to contain many chemicals that could be transferred to organisms and induce deleterious effects. However, there is currently no consensus on whether MPs represent a significant exposure pathway to chemicals in contaminated habitats. Here, we exposed three-spined sticklebacks (Gasterosteus aculeatus) to polyethylene MPs via prey ingestion, in a one-month experiment. MPs were either pristine or spiked with chlorpyrifos (CPF), and a CPF control was included tocompare vector effects of MPs and natural prey. Following exposure, we assessed AChE activity and fish behavior (feeding, locomotion, environment exploration and reaction to the introduction of a novel object). No effect was observed in fish exposed to pristine MPs. CPF accumulation was observed in fish exposed to CPF-spiked MPs (MP-CPF), confirming the vector potential of MPs. However, CPF accumulation was more important in fish exposed to CPF via prey. In fish exposed to MP-CPF, we observed significant AChE inhibition and hyperactivity, which could result in increased vulnerability to predation. CPF organ distribution differed between groups, suggesting that chemical exposure via MPs could alter organ distribution of chemicals. This can result in a change in the organs most at risk, likely increasing intestine exposure.
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| 8. |
- Filipsson, Karl, et al.
(författare)
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Encystment of parasitic freshwater pearl mussel (Margaritifera margaritifera) larvae coincides with increased metabolic rate and haematocrit in juvenile brown trout (Salmo trutta)
- 2017
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Ingår i: Parasitology Research. - : Springer Science and Business Media LLC. - 0932-0113 .- 1432-1955. ; 116, s. 1353-1360
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Tidskriftsartikel (refereegranskat)abstract
- © 2017 The Author(s)Gill parasites on fish are likely to negatively influence their host by inhibiting respiration, oxygen transport capacity and overall fitness. The glochidia larvae of the endangered freshwater pearl mussel (FPM, Margaritifera margaritifera (Linnaeus, 1758)) are obligate parasites on the gills of juvenile salmonid fish. We investigated the effects of FPM glochidia encystment on the metabolism and haematology of brown trout (Salmo trutta Linnaeus, 1758). Specifically, we measured whole-animal oxygen uptake rates at rest and following an exhaustive exercise protocol using intermittent flow-through respirometry, as well as haematocrit, in infested and uninfested trout. Glochidia encystment significantly affected whole-animal metabolic rate, as infested trout exhibited higher standard and maximum metabolic rates. Furthermore, glochidia-infested trout also had elevated levels of haematocrit. The combination of an increased metabolism and haematocrit in infested fish indicates that glochidia encystment has a physiological effect on the trout, perhaps as a compensatory response to the potential respiratory stress caused by the glochidia. When relating glochidia load to metabolism and haematocrit, fish with low numbers of encysted glochidia were the ones with particularly elevated metabolism and haematocrit. Standard metabolic rate decreased with substantial glochidia loads towards levels similar to those of uninfested fish. This suggests that initial effects visible at low levels of encystment may be countered by additional physiological effects at high loads, e.g. potential changes in energy utilization, and also that high numbers of glochidia may restrict oxygen uptake by the gills.
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| 9. |
- Filipsson, Karl, et al.
(författare)
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Heavy loads of parasitic freshwater pearl mussel (Margaritifera margaritifera L.) larvae impair foraging, activity and dominance performance in juvenile brown trout (Salmo trutta L.)
- 2018
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Ingår i: Ecology of Freshwater Fish. - : Wiley. - 0906-6691 .- 1600-0633. ; 27:1, s. 70-77
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Tidskriftsartikel (refereegranskat)abstract
- © 2016 John Wiley & Sons A/S.The life cycle of the endangered freshwater pearl mussel (Margaritifera margaritifera) includes a parasitic larval phase (glochidia) on the gills of a salmonid host. Glochidia encystment has been shown to affect both swimming ability and prey capture success of brown trout (Salmo trutta), which suggests possible fitness consequences for host fish. To further investigate the relationship between glochidia encystment and behavioural parameters in brown trout, pairs (n = 14) of wild-caught trout (infested vs. uninfested) were allowed to drift feed in large stream aquaria and foraging success, activity, agonistic behaviour and fish coloration were observed. No differences were found between infested and uninfested fish except for in coloration, where infested fish were significantly darker than uninfested fish. Glochidia load per fish varied from one to several hundred glochidia, however, and high loads had significant effects on foraging, activity and behaviour. Trout with high glochidia loads captured less prey, were less active and showed more subordinate behaviour than did fish with lower loads. Heavy glochidia loads therefore may negatively influence host fitness due to reduced competitive ability. These findings have implications not only for management of mussel populations in the streams, but also for captive breeding programmes which perhaps should avoid high infestation rates. Thus, low levels of infestation on host fish which do not affect trout behaviour but maintains mussel populations may be optimal in these cases.
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| 10. |
- Griffiths, S. W., et al.
(författare)
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Coping with divided attention: the advantage of familiarity
- 2004
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Ingår i: Proceedings of the Royal Society of London Series B-Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 271:1540, s. 695-699
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Tidskriftsartikel (refereegranskat)abstract
- The ability of an animal to perform a task successfully is limited by the amount of attention being simultaneously focused on other activities. One way in which individuals might reduce the cost of divided attention is by preferentially focusing on the most beneficial tasks. In territorial animals where aggression is lower among familiar individuals, the decision to associate preferentially with familiar conspecifics may therefore confer advantages by allowing attention to be switched from aggression to predator vigilance and feeding. Wild juvenile brown trout were used to test the prediction that familiar fishes respond more quickly than unfamiliar fishes to a simulated predator attack. Our results confirm this prediction by demonstrating that familiar trout respond 14% faster than unfamiliar individuals to a predator attack. The results also show that familiar fishes consume a greater number of food items, foraging at more than twice the rate of unfamiliar conspecifics. To the best of our knowledge, these results provide the first evidence that familiarity-biased association confers advantages through the immediate fitness benefits afforded by faster predator-evasion responses and the long-term benefits provided by increased feeding opportunities.
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