| 1. |
- Gräns, Albin, 1979, et al.
(författare)
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A fully implantable multi-channel biotelemetry system for measurement of blood flow and temperature: A first evaluation in the green sturgeon
- 2009
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Ingår i: Hydrobiologia.. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 619:1, s. 11-25
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this study was to evaluate a novel fully implantable radio-based blood flow biotelemetry system which allows simultaneously measurement of blood flow on two channels and temperature on one channel, in fish. These are the first recordings of blood flow from free-swimming fish, showing that the system is capable of recording blood flow in the ventral aorta (cardiac output) and celiacomesenteric artery (gastrointestinal blood flow) in green sturgeon Acipenser medirostris exposed to a series of different stimuli for up to 7 days after implantation. The results showed stable base line recordings and blood flow was used to calculated heart rate (f H) and stroke volume (V s). It was possible to reproduce the same type of responses as has previously been reported during exposure to hypoxia, temperature, stress and feeding. The mass of our implant was less than 2% of the body mass which is well within the recommended sizes for surgically implanted telemetry transmitters and it fitted easily within the abdominal cavity of the sturgeon. A fully implantable system minimizes the risk of infection/expulsion and maximizes the likelihood that the studied fish will behave naturally and be treated normally by surrounding fish. The use of biotelemetry in basic comparative physiology and applied animal ecology could help scientists to collect information that has previously been challenging to obtain and to open the possibility for new types of physiological and ecophysiological studies.
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| 2. |
- Stradmeyer, L, et al.
(författare)
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Competition between brown trout and Atlantic salmon parr over pool refuges during rapid dewatering
- 2008
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Ingår i: Journal of Fish Biology. - : Wiley. - 1095-8649 .- 0022-1112. ; 72:4, s. 848-860
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Tidskriftsartikel (refereegranskat)abstract
- Variations in distributions and behaviours of Atlantic salmon Salmo salar in allopatry (homogeneous) and in sympatry with brown trout Salmo trutta (mixed) were observed before, during and after 2 day periods of dewatering in a large glass-sided indoor stream at densities typical of Scottish upland streams. Brown trout utilized pools more than Atlantic salmon at normal flows and in both species the majority of fishes moved into pools during dewatering. There was no significant effect of brown trout, which was the more dominant species, on the overall ability of Atlantic salmon to use pool habitat as a refuge during dewatering. Within mixed and homogeneous groups, average feeding levels decreased during dewatering. The highest ranking fish, which was always a brown trout in mixed groups, predominantly monopolized the pool and other individuals in pools adopted a more cryptic, stationary behaviour. Dewatering effectively increased local population density with the result that dominance status became much more important in maintaining food intake, and polarization between the top ranking fish and others increased. During the first day of dewatering, there was extreme behavioural polarization such that the dominant fish exhibited most aggression and least feeding within the group. Among dominant fish on the second day of dewatering, aggression had largely abated and feeding had returned to pretreatment levels despite the reduced average feeding within the group. The main difference between mixed and homogeneous groups was in the behaviour of the most dominant Atlantic salmon, which was near-despotic in allopatry and subordinate to brown trout in sympatry.
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| 3. |
- Zavorka, L., et al.
(författare)
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Laboratory captivity can affect scores of metabolic rates and activity in wild brown trout
- 2019
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Ingår i: Journal of Zoology. - : Wiley. - 0952-8369 .- 1469-7998. ; 307:4, s. 249-255
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Tidskriftsartikel (refereegranskat)abstract
- Phenotypic scoring of wild animals under standardized laboratory conditions is important as it allows field ecologists and evolutionary biologists to understand the development and maintenance of interindividual differences in plastic traits (e.g. behaviour and physiology). However, captivity is associated with a shift from a natural familiar environment to an unfamiliar and artificial environment, which may affect estimates of plastic phenotypic traits. In this study, we tested how previous experience with laboratory environments and time spent in captivity affects behavioural (i.e. activity) and metabolic (i.e. standard and maximum metabolic rates) scoring of our model species, wild brown trout Salmo trutta. We found that individuals with previous experience of laboratory captivity (10.5 months earlier) showed higher activity in an open field test than individuals with no prior experience of laboratory captivity. Previous experience with captivity had no significant effect on metabolic rates. However, metabolic rates seemed to increase with increasing time spent in captivity prior to the collection of measurements. Although there are benefits of keeping wild animals in captivity prior to scoring, our results suggest that while allowing for sufficient acclimatization researchers should aim at minimizing time in captivity of wild animals to increase accuracy and ecological relevance of the scoring of plastic phenotypic traits.
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| 4. |
- 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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| 5. |
- 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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| 6. |
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| 7. |
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| 8. |
- Höjesjö, Johan, 1967, et al.
(författare)
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Movement and home range in relation to dominance; a telemetry study on brown trout Salmo trutta
- 2007
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Ingår i: Journal of Fish Biology. - : Wiley. - 0022-1112 .- 1095-8649. ; 70:1, s. 257-268
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Tidskriftsartikel (refereegranskat)abstract
- By combining behavioral observations on adult resident brown trout Salmo trutta in the laboratory with radio telemetry studies in a natural stream. information on movement and space use in relation to social status was obtained. Dominant individual longer distances and also tended to have larger home ranges than subordinates during the summer. In general. home ranges were larger during daytime than at night. Fish were not strictly territorial since the average overlap in interquartile range was 36%. during the summer. During the spawning period, the brown trout moved to specific spawning areas resulting in an increased overlap (89%) in space Use. Subordinate individuals now tended to increase both home range and interquartile range and were also less frequently observed in spawning areas relative to dominants.
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| 9. |
- Höjesjö, Johan, 1967, et al.
(författare)
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Size-related habitat use in juvenile Atlantic salmon: the importance of intercohort competition
- 2016
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Ingår i: Canadian Journal of Fisheries and Aquatic Sciences. - : Canadian Science Publishing. - 0706-652X .- 1205-7533. ; 73:8, s. 1182-1189
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Tidskriftsartikel (refereegranskat)abstract
- In stream-living salmonids, an underlying mechanism for the critical period after emergence has generally been assumed to be size-dependent swimming capacity constraining fry (age-0) to low-velocity habitats with reduced food availability and intense competition. A further plausible mechanism is that intercohort habitat exclusion confines fry to marginal habitats. This possibility was tested using a seminatural stream with 16 test arenas, each comprising one high-velocity, deep habitat and one low-velocity, shallow habitat. We observed groups of newly emerged Atlantic salmon (Salmo salar) fry, either alone or in sympatry with one or two age-1 salmon. Salmon fry used high-velocity areas (42.2 +/- 0.4 cm.s(-1)) most extensively in the absence of intercohort competition, where they obtained more food than in low-velocity areas (3.3 +/- 0.3 cm.s(-1)), even though foraging efficiency was lower (though not significantly so). In sympatry with older cohorts, fry increased their use of the low-velocity habitat, with a reduced foraging activity, suggesting that strong older cohorts in natural populations may have the potential to influence the strength of the recruiting cohort by negative density dependence due to interference competition for habitat.
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| 10. |
- Höjesjö, Johan, 1967, et al.
(författare)
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Sneaky feeding by salmon in sympatry with dominant brown trout.
- 2004
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Ingår i: Animal Behaviour. - : Elsevier BV. - 0003-3472. ; 69:5, s. 1037-1041
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Tidskriftsartikel (refereegranskat)abstract
- We compared the feeding performance and overt aggressive behaviour of two closely related salmonids occupying the same food patches. Foraging competition between pairs of Atlantic salmon, Salmo salar, and brown trout, Salmo trutta, in which trout were the larger and predicted to be the more dominant species, was investigated in a controlled stream channel environment. Trout held station by swimming actively in the central regions of food patches, whereas salmon occupied the margins, generally remaining stationary on the stream bed. There was little overt aggression, but the direction of attacks was consistent, with trout being dominant over salmon. Trout made significantly more foraging attempts (61.4% of food items presented) than salmon (28.9%). However, efficiency of food capture was higher in salmon (97%) than in trout (78%) and there was no significant difference between species in food intake. Salmon fed by briefly invading the space occupied for most of the time by trout. This behaviour has similarities to the ‘sneaky’ behaviours often shown by subordinate male salmonids during spawning, when gametes rather than food are the contested resource.
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