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Winter Behavior of Juvenile Brown Trout in a Changing Climate: How Do Light and Ice Cover Affect Encounters with Instream Predators?
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).ORCID iD: 0000-0003-0762-6551
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).ORCID iD: 0000-0002-3191-7140
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).ORCID iD: 0000-0001-6758-5857
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2023 (English)In: Fishes, E-ISSN 2410-3888, Vol. 8, no 10, article id 521Article in journal (Other academic) Published
Abstract [en]

During winter, stream fishes are vulnerable to semi-aquatic predators like mammals and birds and reduce encounters by being active in darkness or under surface ice. Less is known about the behavior of fishes towards instream piscivorous fishes. Here, we examined how surface ice and light affected the anti-predator behavior of juvenile brown trout (Salmo trutta Linnaeus, 1758) in relation to piscivorous burbot (Lota lota Linnaeus, 1758) and northern pike (Esox lucius Linnaeus, 1758) at 4 degrees C in experimental flumes. Trout had lower foraging and swimming activity and spent more time sheltering when predators were present than when absent. In daylight, trout's swimming activity was not affected by predators, whereas in darkness trout were less active when predators were present. Trout consumed more drifting prey during the day when ice was present, and they positioned themselves further upstream when under ice cover, regardless of light conditions. Trout stayed closer to conspecifics under ice, but only in the presence of pike. Piscivorous fishes thus constitute an essential part of the predatory landscape of juvenile trout in winter, and thus loss of ice cover caused by climate warming will likely affect trout's interactions with predators.

Place, publisher, year, edition, pages
2023. Vol. 8, no 10, article id 521
Keywords [en]
anti-predator, global changer, diel behavior, foraging, piscivores, predators
National Category
Ecology Zoology
Research subject
Biology
Identifiers
URN: urn:nbn:se:kau:diva-88204DOI: 10.3390/fishes8100521ISI: 001089943500001Scopus ID: 2-s2.0-85175046960OAI: oai:DiVA.org:kau-88204DiVA, id: diva2:1632092
Funder
Karlstad University
Note

This paper was included as a manuscript in doctoral thesis entitled "Early life stages of brown trout - Anti-predator responses under warming winters" 2022:2

Available from: 2022-01-26 Created: 2022-01-26 Last updated: 2023-11-28Bibliographically approved
In thesis
1. Early life stages of brown trout - Anti-predator responses under warming winters
Open this publication in new window or tab >>Early life stages of brown trout - Anti-predator responses under warming winters
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

During winter, juvenile salmonids in boreal streams are vulnerable to predation, mainly from mammals and birds. Encounters with terrestrial predators can be reduced or avoided if fish limit activity to the darker periods of the day or to periods with surface ice. As piscivorous fish also are active in winter, they may be a threat under low light conditions when juvenile salmonids do not avoid terrestrial predators. Abiotic conditions, especially temperature, have major effects on fish in winter. High temperatures alter ice conditions in winter and lead to increased metabolism and physiological performance of fish. Water temperature also influences embryogenesis, with repercussions for fish throughout their life. Considering the rapid warming of winters in boreal regions, insights into how salmonids are adapted to winter conditions can aid in efforts to predict and mitigate anthropogenic effects that alter the winter environment.

In this doctoral thesis, I explore anti-predator responses of brown trout (Salmo trutta) during its early life stages. I have examined the effects of predators, temperature, light and ice on the behaviour and physiology of juvenile trout during winter. In addition, I have studied how temperature and predators affect embryogenesis and the behaviour of fry after hatching. Anti-predator responses were evident in both the behaviour and physiology of juveniles and during embryogenesis. Trout exhibited diel behavioural changes when piscivorous fish were present, and were more vigilant towards piscivorous fish in darkness. Furthermore, temperature affected trout behaviour and physiology, with higher activity levels and lower mRNA expression of stress-related genes at higher temperatures. Trout also behaved differently depending on the temperature they experienced as eggs, as increased egg-incubation temperatures resulted in trout being more active and prone to risk taking.

Abstract [en]

This thesis explores how winter conditions affect anti-predator responses of brown trout (Salmo trutta) during its early life stages. Salmonids in streams are vulnerable to predation from mammals, birds and piscivorous fish in winter. Abiotic conditions such as water temperature also affect the fish, and winters in boreal regions are getting warmer as a result of global change. Warmer winters are expected to increase the metabolism of fish, but also change the physical environment by reducing ice cover and altering light conditions. Eggs of salmonids are affected by warmer winters as well, with direct effects on embryos and indirect effects on the fish after hatching.  

I have examined how predators, temperature, light and ice affect juvenile brown trout during winter, and how temperature and predators affect embryos and the behaviour of fry after hatching. Anti-predator responses were evident in juveniles and during embryogenesis. Juvenile trout exhibited diel behavioural changes when piscivorous fish were present, and increased their vigilance towards piscivorous fish in darkness. Trout exhibited higher activity and lower expression of stress-related genes at higher temperatures. Increased egg-incubation temperatures resulted in trout being more active and risk taking.

Place, publisher, year, edition, pages
Karlstad: Karlstads universitet, 2022
Series
Karlstad University Studies, ISSN 1403-8099 ; 2022:2
Keywords
behaviour, climate, cortisol, development, egg incubation, embryo, gene expression, ice, light, mRNA, piscivorous, poikilotherm, salmonid, stress, temperature
National Category
Ecology Zoology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-88207 (URN)978-91-7867-255-4 (ISBN)978-91-7867-265-3 (ISBN)
Public defence
2022-03-18, Sjöströmssalen, 1B 309, Karlstads universitet, Karlstad, 10:00 (English)
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Supervisors
Note

Abstract 2 är baksidestext.

Available from: 2022-02-25 Created: 2022-01-26 Last updated: 2022-03-01Bibliographically approved

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Filipsson, KarlGreenberg, LarryÖsterling, MartinWatz, JohanBergman, Eva

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