CONTEST-DEPENDENT FRIGHT REACTIONS IN CAPTIVE EUROPEAN MINNOWS - THE IMPORTANCE OF NATURALNESS IN LABORATORY EXPERIMENTS

The responses of ostariophysan fish to alarm substance (Schreckstoff) have been investigated extensively in the laboratory but there have be en few tests of its role under natural conditions. Furthermore, existi ng studies of the efficacy of Schreckstoff as an alarm substance in th e wild have typically employed indirect approaches and have failed to document specific behaviour in a quantitative manner. European minnows , Phoxinus phoxinus, were exposed to Schreckstoff in small aquaria. Th ey responded with a suite of behavioural changes that are consistent w ith the explanation that they perceive danger. Fish from the same popu lation were then exposed to Schreckstoff under conditions that more cl osely resembled their natural habitat. Under these near-natural condit ions they showed a small decrease in feeding rate and a slight increas e in group size, both effects being transitory and independent of stim ulus concentration. These data reveal that the ostariophysan fright re action is context-dependent and highlight the importance of quantifyin g the behaviour of fish exposed to Schreckstoff under fully natural co nditions. (C) 1997 The Association for the Study of Animal Behaviour.