Repeated antipredator conditioning: a pathway to habituation or to better avoidance?

Abstract

Hatchery-reared juveniles of Arctic charr Salvelinus alpinus were conditioned to the odours of Arctic charr-fed pikeperch Sander lucioperca in the absence of any other cues. Accordingly, there was no physical threat of capture for the Arctic charr. It was evident from the subsequent survival tests that a single exposure to predator odours was enough to increase Arctic charr survival compared to predator-naı¨ve control fish whist under direct threat from live predators. Instead of habituating to predator odours, the fish conditioned repeatedly (four times) improved their spatial avoidance of predator cues in the course of training. The repeated conditioning also further enhanced the survival of the test fish as compared to the singly conditioned fish. The economical and ethical advantages of training with chemical cues, combined with its high reliability, could promote the success of fish reintroductions especially through repeated antipredator conditioning.

Conclusions: Aquaculture and Behaviour

“…Knowledge of the specific effects of learning has formed the basis of programmes of 'life skills training' for cultured fish of various species. For example, predator-naive Arctic charr exposed to the odour of a piscivorous fish followed by an encounter with a predator become more responsive to the odour alone, especially if they have observed a trained conspecific respond to predator odour (Vilhunen et al 2005; Chapter 8).…”

Learning about Danger: Chemical Alarm Cues and Threat‐Sensitive Assessment of Predation Risk by Fishes

“…The question remains if repeated exposure over time results in enhanced learning opportunities in which the learned response is greater (stronger) than that resulting from a single conditioning event or if the retention is extended, or both. Vilhunen (2006) conditioned hatchery-reared Arctic charr juveniles to the odour of pikeperch (Sander lucioperca, Percidae) which had been fed a diet of Arctic charr once or four times (with 4 days between each conditioning). Vilhunen (2006) reports stronger antipredator responses (relative to unconditioned controls) by charr exposed four times to the predator.…”

“…Vilhunen (2006) conditioned hatchery-reared Arctic charr juveniles to the odour of pikeperch (Sander lucioperca, Percidae) which had been fed a diet of Arctic charr once or four times (with 4 days between each conditioning). Vilhunen (2006) reports stronger antipredator responses (relative to unconditioned controls) by charr exposed four times to the predator. In addition, when exposed to a live predator during staged encounters, those that received multiple exposures had a higher probability of survival than did those conditioned a single time.…”

Social Learning in Fishes

“…These populations are fully maintained by reintroductions from hatchery stocks after hydroelectric schemes destroyed their primary spawning grounds. Initial studies revealed that socially acquired avoidance of predator odours is particularly effective means of training naïve fishes to recognise predators (Vilhunen et al 2005) and these early exposures to predators do lead to improved survival upon subsequent contact with live predators (Vilhunen 2006). …”