AGGRESSIVENESS AND THE FORAGING BEHAVIOR OF YOUNG-OF-THE-YEAR BROOK CHARR (SALVELINUS-FONTINALIS)

Aggressive charr were 13% larger than nonaggressive conspecifics observed on the same day in the same area. Aggressive fish had a lateral foraging radius 29% larger than nonaggressive fish and a 45% greater mean distance to neighbours. Aggressive fish of 2 size categories (20-29 and 40-99 mm) made 70 and 55% more feeding attempts per unit time, respectively, than nonaggressive fish of the same size. Number of prey items in stomachs was significantly and positively correlated with feeding attempt rate. Aggressive fish appeared to occupy more preferred sites; their sites were significantly more likely to be reoccupied after their removal than were sites occupied by nonaggressive fish. The hypothesis that defence of a foraging site is a better tactic than ignoring conspecifics is supported. -from Author