Summary: OIKOS 88: 200­212. Copenhagen 2000
Predator recognition and defence strategies in crucian carp,
Carassius carassius
Lars B. Pettersson, P. Anders Nilsson and Christer Bro¨nmark
Pettersson, L. B., Nilsson, P. A. and Bro¨nmark, C. 2000. Predator recognition and
defence strategies in crucian carp, Carassius carassius. ­ Oikos 88: 200­212.
Crucian carp from populations that lack piscivores are extremely vulnerable to
predation. However, in the presence of piscivores these fish develop an inducible
morphological defence, a deep body. This switch from a vulnerable, shallow-bodied
morph to a morphologically defended morph makes this species very suitable for
investigations of anti-predator strategies, and trade-offs between morphological and
behavioural defences. To address these questions, we performed eight different
experiments. We found that crucian carp exhibited fright responses to chemical cues
from unfamiliar predators (northern pike, perch) when these were fed prey that
contained alarm substance (for northern pike: crucian carp, roach; for perch: crucian
carp). Cues from small pike that were fed prey that lacked alarm substance
(swordtails) caused no significant fright response whereas cues from larger pike with
the same diet did. Perch on a chironomid diet elicited weaker but significant fright
responses. Starved predators caused as strong fright reactions as recently fed ones
did, whereas no response was exhibited towards nonpredatory fish (roach, crucian

Source: Agrell, Jep - Department of Ecology, Lunds Universitet

Collections: Environmental Sciences and Ecology