Early environmental effects on dominance in juvenile Atlantic salmon (Salmo salar L.)

Sammanfattning: The earth’s climate is rapidly changing. With climate change currently altering the environment, water temperature is an important environmental factor that will have various effects on fishes since they are ectotherms. As the changes are expected to be greatest during winter, when salmonid fishes incubate their eggs, one might expect substantial effects on egg development. In this experiment pairs of fish, matched by length, were compared. For each pair, one fish had experienced ambient cold temperatures (cold treatment) during embryogenesis and the other elevated temperatures (warm treatment, ca. 4-5 oC). The fish were tested in stream. Aggressive interactions were recorded and dominance was determined by scoring each fish’s position relative to where food was delivered from and the amount of food taken. Salmon from the cold treatment had a strong tendency to have a higher dominance score than salmon from the warm treatment. The individual with the highest dominance score was not consistently larger or smaller than the individual with the lower dominance score. The results support the hypothesis that salmonids exposed to a cold environment during embryogenesis will be more dominant. Due to climate change, it is expected that water temperature will continue to rise in the future, which in turn will alter the fish’s behaviour.