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From behaviour to genes: anti-predator responses of brown trout (Salmo trutta) under winter conditions
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013). (River Ecology and Management)ORCID iD: 0000-0003-0762-6551
2020 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Temperature has major effects on the performance of poikilotherms. In encounters with predators, low winter temperatures constrain predator detection and escape capabilities in prey fishes. Most studies of the anti-predator responses of fish under winter conditions focus on endothermic terrestrial predators, whereas effects of piscivorous fish are generally overlooked. The studies presented in this thesis explore behavioural and physiological responses of juvenile brown trout (Salmo trutta) at winter temperatures of 3 and 8 °C in the presence and absence of a winter-active piscivorous fish (burbot, Lota lota). In Paper I, I report behavioural responses of trout in relation to the time of day. At the lower temperature and in the presence of burbot, trout reduced their activity. Trout used overhead shelter the most during the day and in the presence of burbot. Trout also spatially avoided burbot at night and at dawn but not during the day. In Paper II, I examined plasma cortisol and mRNA expression of stress-related genes. A redundancy analysis showed that both temperature and the presence of burbot explained a significant amount of the observed variation. Trout had higher cortisol levels when exposed to the burbot. Analyses of individual gene expressions revealed that trout had higher mRNA expression at 3 than at 8 °C for 11 of the 16 examined genes. Only one gene, RBP1, was expressed to a higher degree in the presence of burbot, but there were also interaction effects between temperature and burbot presence for two genes coding for serotonin and glucocorticoid receptors. My studies show that piscivorous fish shape anti-predator responses of juvenile brown trout, both behaviourally and at the gene level, under winter conditions. The observed thermal effects on mRNA levels underscore the importance of temperature in fish stress responses, with implications for stream salmonids in a warmer climate. 

Abstract [en]

Low winter temperatures constrain physiological performance in stream fishes, with possible consequences for encounters with predators. This thesis explores behavioural and physiological responses of juvenile brown trout (Salmo trutta) at 3 and 8 °C in the presence and absence of a winter-active piscivorous fish (burbot, Lota lota). In Paper I, I report behavioural responses of trout in relation to time of day. Lower temperature and burbot presence reduced trout activity. Use of shelter by trout was greatest during the day and in the presence of burbot. Trout spatially avoided burbot at night and at dawn, but not during the day. In Paper II, I examined plasma cortisol and mRNA levels of stress-related genes. Trout had highest cortisol levels in the presence of burbot. For 11 of the 16 examined genes, trout had higher mRNA expression at 3 than at 8 °C. For one gene, RBP1, trout had higher expression in the presence of burbot, and there were interaction effects between temperature and burbot treatments for genes coding for serotonin and glucocorticoid receptors. Piscivorous fish shape anti-predator responses of juvenile brown trout under winter conditions, and thermal effects underscore the temperature dependence of fish stress responses, with possible effects in a warmer climate.

Place, publisher, year, edition, pages
Karlstad: Karlstads universitet, 2020. , p. 36
Series
Karlstad University Studies, ISSN 1403-8099 ; 2020:11
Keywords [en]
burbot, climate change, cortisol, diel behaviour, gene expression, HPI axis, light, mRNA, piscivorous, poikilotherm, predator, salmonid, stream, stress, temperature, thermal, winter behaviour
National Category
Ecology
Research subject
Biology
Identifiers
URN: urn:nbn:se:kau:diva-76337ISBN: 978-91-7867-094-9 (print)ISBN: 978-91-7867-104-5 (electronic)OAI: oai:DiVA.org:kau-76337DiVA, id: diva2:1387454
Presentation
2020-03-13, Sjöströmsalen, 1B 309, Karlstads universitet, Karlstad, 10:00 (English)
Opponent
Supervisors
Available from: 2020-02-27 Created: 2020-01-21 Last updated: 2020-02-27Bibliographically approved
List of papers
1. Effects of temperature and a piscivorous fish on diel winter behaviour of juvenile brown trout (Salmo trutta)
Open this publication in new window or tab >>Effects of temperature and a piscivorous fish on diel winter behaviour of juvenile brown trout (Salmo trutta)
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2019 (English)In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 64, no 1+, p. 1797-1805Article in journal (Refereed) Published
Abstract [en]

Low winter temperatures constrain predator-detection and escape capabilities, making poikilotherms vulnerable to predation. Investigations of temperature effects on predator-prey interactions can therefore be of special importance in light of ongoing climate change, where winter temperatures are predicted to increase substantially at northern latitudes. Behavioral responses of stream fishes to terrestrial predators in winter are well recognised, whereas responses to predatory fish have received little attention. Using stream flumes, we examined the anti-predator behaviour of one-summer-old brown trout (Salmo trutta) at 3 and 8 degrees C in the presence and absence of burbot (Lota lota) under night, dawn, and daylight conditions. Burbot was placed upstream of the trout, separated by net screens. Lower temperature and the presence of burbot reduced trout activity. Light increased trout shelter use, and trout sheltered more in the presence of burbot. An interaction between the presence of burbot and light conditions affected trout position in the flumes: at night and dawn, trout positioned themselves further downstream when burbot were present than when absent, whereas during the day, trout maintained the same position in the presence or absence of the predator. Our results suggest that piscivorous fish, in addition to terrestrial predators, shape the behaviour of prey fishes in streams during winter. We show how predator avoidance results in altered diel patterns of juvenile brown trout under winter conditions, and that temperature has additional effects on trout behaviour.

Keywords
anti-predator, burbot, climate change, light, predator avoidance
National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-74573 (URN)10.1111/fwb.13371 (DOI)000480404400001 ()
Available from: 2019-08-29 Created: 2019-08-29 Last updated: 2020-01-21Bibliographically approved
2. Manuscript: Temperature and predator-mediated regulation of cortisol and brain gene expression in juvenile brown trout (Salmo trutta)
Open this publication in new window or tab >>Manuscript: Temperature and predator-mediated regulation of cortisol and brain gene expression in juvenile brown trout (Salmo trutta)
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(English)Manuscript (preprint) (Other academic)
National Category
Natural Sciences Biological Sciences
Identifiers
urn:nbn:se:kau:diva-76335 (URN)
Available from: 2020-01-21 Created: 2020-01-21 Last updated: 2020-01-21

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Filipsson, Karl

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