Effects of Thyroid Hormones on Behavior of Yearling Atlantic Salmon (<i>Salmo salar</i>)

Abstract

Swimming activity, aggressive behavior, and upstream orientation of yearling Atlantic salmon (Salmo salar) treated with 6.43 × 10 −11 M thyroxine were significantly lower than those of control fish injected with solvent alone. Two concentrations of triiodothyronine (7.43 × 10 −11 M; 7.43 × 10 −10 M) caused similar but less pronounced effects.Because similar behavioral modifications accompany smolt migration, we hypothesize that thyroid hormones may play a role in arousing migratory tendencies in Atlantic salmon.