Effects of body size, body condition, and breeding state on responses to alarm cues by fathead minnows

There is often considerable variation in the intensity of behavioural responses of prey to predation cues. The purpose of the current study was to determine the role of standard length (a correlate of age), body condition (a measure of energy reserves, calculated by mass/(standard length)3), and gonadosomatic index (state of reproduction, calculated by gonad mass / body mass) in the responses of fathead minnows (Pimephales promelas Rafinesque, 1820) to damage-release alarm cues. Our data indicate that during the nonbreeding season longer/older minnows exhibited significantly increased antipredator responses compared with younger individuals. However, the significance of these correlations ceased during the breeding season. Data from the same trials failed to reveal a significant correlation between the intensity of antipredator behaviour and the body condition before or during the breeding season; the intensity of a minnow’s antipredator response was also not significantly correlated with its gonadosomati...