Behavioural response of roach (Cyprinidae) to different doses of chemical alarm cues (Schreckstoff)

Abstract

In laboratory experiments several types of behavioural responses of roach to different dilutions of alarm substance (Schreckstoff) were determined. The pattern of behaviour consisted of hiding in a refuge and at its border, inspection of the tank and the feeding plate, swimming throughout the aquarium and feeding. The higher the dose of the warning cue was, the longer the time spent hiding in the refuge, and the shorter the time spent on swimming. Different dilutions of alarm substance, probably reflecting variation in predation danger, did not alter the sequence of responses but changed the time period for which each of its constituent elements was performed. Generally, intermediate dilutions elicited higher fish activity, while the highest and lowest doses elicited lower activity, practically limited to hiding (highest concentration) or swimming (lowest concentration). The reaction to alarm substance, seems to be gradual, not a yes or no reaction consisting of subtle but repeatable changes in fish behaviour over the concentration gradient of the cue.