Behavioral syndromes in salmonid fish: Ecological and evolutionary implications

Variation in the physiological stress response has been correlated to a number of major axes of variation in behavior, including activity, shyness-boldness, and aggression. Sih and co-workers recently coined the term behavioral syndromes for this phenomen on, and pointed out several important ecological and evolutionary implications. One of the questions to be addressed is how variation in correlated traits is maintained in a population. In the current project we aim to address the occurrence and fitness c onsequences of behavioral syndromes in two salmonid fish model systems: Genetically selected rainbow trout lines expressing correlated differences in behavior and physiology, and wild lake-migratory brown trout from a river system where migratory behavior , density and growth differ between two nearby stream sections. Behavior and performance of fish with these backgrounds will be compared under both laboratory conditions designed to identify individual profiles in salmonid fish, and in semi-natural artifi cial streams. Fish with consistently low cortisol concentrations under stress are characterized by enhanced competitiveness and a strong tendency to become socially dominant, a more rapid recovery of food intake after transfer to a novel environment, and a reduced panic response under acute stress. We aim to verify that these trait associations represent selection for behavioral syndromes that are also present in wild-type salmonid populations. We will also study whether the frequency distribution of diff erent behavioral syndromes differ between brown trout populations from two nearby localities that appear to incur different selective pressures. Thereafter we will investigate whether different behavioral syndromes are associated with altered fitness in fluctuating vs stable environments.