Dægursveiflur í virkni bleikju í íslenskum ám / Diel activity in stream-dwelling Arctic charr

Fréttatilkynning verkefnisstjóra


In general, Arctic charr exhibited vast variability in the overall level and the timing of activity.

Diel activity provides insights into the way animals use, compete for and share habitats in time, and can have direct consequences for individuals and populations. Thus, flexibility in diel activity, and the degree to which individuals modify this behaviour across ecological situations, remains an important research topic. In this research project, we conducted one observational study and a series of field experiments, using individually-tagged juvenile Arctic charr placed in semi-natural stream enclosures, to test for the effect of key ecological factors on diel activity and growth. In general, Arctic charr exhibited vast variability in the overall level and the timing of activity.

Heiti verkefnis: Dægursveiflur í virkni bleikju í íslenskum ám / 

Diel activity in stream-dwelling Arctic charr
Verkefnisstjóri: Stefán Óli Steingrímsson, Háskólanum á Hólum
Tegund styrks: Verkefnisstyrkur
Styrkár: 2012-2014
Fjárhæð styrks: 18,054 millj. kr. alls
Tilvísunarnúmer Rannís: 12023502

First, as expected, individuals increased their overall activity from colder to warmer streams. Second, when shelters were limited, Arctic charr switched from nocturnal to diurnal activity. Third, at high population density, fish increased their overall activity, in part via increased activity at crepuscular times. Fourth, when exposed to abrupt fluctuations in water flow, fish seized activity at high water level but showed a temporary burst of feeding activity when water flow was reduced. Finally, when fish where exposed to higher water current velocity over a longer period of time, they increased their activity and grew faster than in slow-running habitats.

Across most of the experiments, however, flexible diel activity patterns appear to enable Arctic charr to maintain comparable growth rates under suboptimal conditions, although in some cases this may result in increased exposure to predators. Our findings systematically highlight that freshwater fish exhibit extremely flexible diel activity patterns, which predictably respond to a range of ecological and environmental changes, and thus mediate the effect of these changes on individual fitness and population ecology. 

Information on how the results will be applied 

In terms of management and conservation our findings e.g., provide insights into potential individual and population consequences of (i) rising water temperatures, (ii) increased competition, e.g. via fish enhancement programs, and (iii) altered stream-flow conditions in regulated rivers. Hence, improved knowledge on how individual fish respond to ecological and environmental changes, can improve management and conservation decision, which focus on reducing negative effects of these changes. 

A list of the projects output (reports, journal articles or manuscripts) 

1. Larranaga N. & Steingrímsson S.Ó. (2015) Shelter availability alters diel activity and space use in a stream fish. Behav. Ecol., 26(2): 578-586. doi.10.1093/ beheco/aru234. Free access on the publishers site following a 1 year embargo. 

2. Fingerle A., Larranaga N. & Steingrímsson S.Ó. (under review) Density-dependent diel activity in stream-dwelling Arctic charr Salvelinus alpinus. Ecol. and Evol. (open access). Awaiting decision. 

3. Larranaga N. & Steingrímsson S.Ó. (In preparation) Diel activity and aggregation in Arctic charr in streams with different temperature profiles. Will be submitted to an international peer-reviewed fish/freshwater journal. The title is preliminary. 

4. Larranaga N., Fingerle A. & Steingrímsson S.Ó. (In preparation) Repeatability and ecological correlates of foraging mode in a stream-dwelling fish. Will be submitted to a peer-reviewed behavioural journal. 

5. Larranaga N., Hadi F., Grant J.W.A. & Steingrímsson S.Ó.. (In preparation) Diel activity and growth of Arctic charr in contrasting stream habitats. Soon submitted to Can. J. Fish. Aquat. Sci. Order of authors may change based on eventual contribution. 

6. Larranaga N., Valdimarsson S.K., Linnansaari T.P. & Steingrímsson S.Ó. (In preparation). Fluctuations in water flow: Effects on diel activity and growth in juvenile Arctic charr. Soon submitted to a fish ecology journal. Title and order of authors are preliminary. 

Other papers can be envisioned e.g. on the effect of (i) population density on space use patterns, (ii) habitat availability on foraging and swimming behaviour, (iii) fluctuations in water flow on foraging and swimming behaviour. The data collected also allows us to explore how individuals differ in their response (e.g. personality) to temporal changes in ecological conditions in streams. Finally, a summary paper on diel activity in Arctic charr will be written in Icelandic for Náttúrufræðingurinn.


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