Predation risk and reduced foraging activity in fish: experiments with parasitized and non-parasitized three-spined sticklebacks, Gasterosteus aculeatus L.
After varying periods of food deprivation the foraging behaviour of parasitized and non-parasitized sticklebacks was measured in both undisturbed and recently frightened fish. Parasitized sticklebacks forage significantly more actively and recover more quickly after a frightening stimulus than do control fish. They also react more quickly to food deprivation than do uninfected control fish. Seventy-two hours without food is sufficient to suppress the fright response in parasitized fish, and causes them to forage at the same rate as when undisturbed. Non-infected controls failed to forage successfully after a frightening stimulus, even when they had been without food for 96 h. Frightening stimuli can affect profoundly the normal foraging behaviour of hungry fish.