Javascript is not activated in your browser. This website needs javascript activated to work properly.
You are here

Ice cover alters the behavior and stress level of brown trout Salmo trutta

  • Johan Watz
  • Eva Bergman
  • Olle Calles
  • Asa Enefalk
  • Stina Gustafsson
  • Anna Hagelin
  • Anders Nilsson
  • Johnny R. Norrgard
  • Daniel Nyqvist
  • E. Martin Osterling
  • John J. Piccolo
  • Lea D. Schneider
  • Larry Greenberg
  • Bror Jonsson
Publishing year: 2015
Language: English
Pages: 820-827
Publication/Series: Behavioral Ecology
Volume: 26
Issue: 3
Document type: Journal article
Publisher: Oxford University Press

Abstract english

Surface ice in rivers and lakes buffers the thermal environment and provides overhead cover, protecting aquatic animals from terrestrial predators. We tested if surface ice influenced the behavior (swimming activity, aggressive encounters, and number of food items eaten) and stress level (coloration of eyes and body) of stream-living brown trout Salmo trutta at temperatures of 3-4 degrees C in indoor experimental flumes. We hypothesized that an individual's resting metabolic rate (RMR, as measured by resting ventilation rate) would affect winter behavior. Therefore, groups of 4 trout, consisting of individuals with high, low, or mixed (2 individuals each) RMR, were exposed to experimental conditions with or without ice cover. Ice cover reduced stress responses, as evaluated by body coloration. Also, trout in low RMR groups had a paler body color than those in both mixed and high RMR groups. Trout increased their swimming activity under ice cover, with the highest activity found in high RMR groups. Ice cover increased the number of aggressive encounters but did not influence the number of drifting food items taken by each group. In mixed RMR groups, however, single individuals were better able to monopolize food than in the other groups. As the presence of surface ice increases the activity level and reduces stress in stream-living trout, ice cover should influence their energy budgets and production. The results should be viewed in light of ongoing global warming that reduces the duration of ice cover, especially at high latitudes and altitudes.


  • Zoology
  • aggression
  • climate change
  • energy budget
  • metabolic rate
  • winter


  • ISSN: 1045-2249
Anders Nilsson
E-mail: anders [dot] nilsson [at] biol [dot] lu [dot] se


Aquatic ecology

+46 46 222 83 65

+46 70 346 25 66



Research group

Aquatic Ecology


Doctoral students and postdocs

Main supervisor

Varpu Pärssinen

Assistant supervisor

Downloads & links