RESUMO
The detection of predation risk without direct engagement with a predator is an important driver of prey movement strategies. Consequently, the application of alarm cues may prove an effective tool in guiding the movements of fishes targeted for control or conservation. However, failure to contemplate the sensory, physiological and cognitive outcomes of repeated or persistent exposure to the cue will likely lead to poor performance of management practices. Using a series of behavioural tests and physiological recordings from the olfactory organ, we examined the timing of onset and recovery of the alarm response in sea lamprey (Petromyzon marinus L.) when exposed continuously or sporadically to its alarm cue. In the laboratory, sea lamprey exhibited short-term, reversible attenuation of the alarm response over 2-4 h with continuous exposure. The alarm response spontaneously recovered after 30-60 min of removal from the cue. In long-duration free-swimming tests, where the animals were allowed to move into and out of the odour plume volitionally, repeated but sporadic encounter with the alarm cue over 5 h did not alter the alarm response. Electro-olfactogram recordings from the main olfactory epithelium indicated that olfactory sensory neurons quickly adapt to alarm cue and recovered within 15 min. Our findings strongly implicate habituation as the mechanism that induces reduction in the alarm response and provide insight into the design of effective management practices that seek to use fish alarm cues as repellents.
