TRADING OFF SAFETY AGAINST FOOD - STATE-DEPENDENT HABITAT CHOICE AND FORAGING IN CRUCIAN CARP

The influence of hunger level and predation risk on habitat choice and foraging in crucian carp, Carassius carassius, were studied in a labo ratory experiment. Experiments were carried out in aquaria with or wit hout a predator (pike, Esox lucius). Habitat use and foraging activity of three-fish foraging groups of either fed or hungry crucian carp we re studied. Fish were allowed to choose between an open (risky) habita t with Tubifex worms and a habitat with dense vegetation (safe) withou t food. Habitat use was significantly affected by both risk of predati on and hunger level. Crucian carp spent less time in the open habitat when there was a predator present and they also spent less time there when fed than when hungry. Furthermore, there was a significant intera ction between risk of predation and hunger level, indicating a state-d ependent trade-off between food acquisition and predator avoidance.