title: Ice cover affects the growth of a stream-dwelling fish.
abstract: Protection provided by shelter is important for survival and affects the time and energy budgets of animals. It has been suggested that in fresh waters at high latitudes and altitudes, surface ice during winter functions as overhead cover for fish, reducing the predation risk from terrestrial piscivores. We simulated ice cover by suspending plastic sheeting over five 30-m-long stream sections in a boreal forest stream and examined its effects on the growth and habitat use of brown trout (Salmo trutta) during winter. Trout that spent the winter under the artificial ice cover grew more than those in the control (uncovered) sections. Moreover, tracking of trout tagged with passive integrated transponders showed that in the absence of the artificial ice cover, habitat use during the day was restricted to the stream edges, often under undercut banks, whereas under the simulated ice cover condition, trout used the entire width of the stream. These results indicate that the presence of surface ice cover may improve the energetic status and broaden habitat use of stream fish during winter. It is therefore likely that reductions in the duration and extent of ice cover due to climate change will alter time and energy budgets, with potentially negative effects on fish production.
authors.affiliation: River Ecology and Management, Department of Environmental and Life Sciences, Karlstad University, Universitetsgatan 2, 651 88, Karlstad, Sweden. johan.watz@kau.se.
authors.forename: Johan
authors.initials: J
authors.lastname: Watz
authors.affiliation: River Ecology and Management, Department of Environmental and Life Sciences, Karlstad University, Universitetsgatan 2, 651 88, Karlstad, Sweden.
authors.forename: Eva
authors.initials: E
authors.lastname: Bergman
authors.affiliation: River Ecology and Management, Department of Environmental and Life Sciences, Karlstad University, Universitetsgatan 2, 651 88, Karlstad, Sweden.
authors.forename: John J
authors.initials: JJ
authors.lastname: Piccolo
authors.affiliation: River Ecology and Management, Department of Environmental and Life Sciences, Karlstad University, Universitetsgatan 2, 651 88, Karlstad, Sweden.
authors.forename: Larry
authors.initials: L
authors.lastname: Greenberg
mesh_terms: D063147:Animal Distribution; D000818:Animals; D001823:Body Composition; D046448:Ice Cover; D045483:Rivers; D012621:Seasons; D013548:Sweden; D014337:Trout / Q000254:growth & development / Q000502:physiology*
keywords: Climate change; Energy budget; Global warming; Salmonid; Winter