Predation risk and reduced foraging activity in fish: experiments with parasitized and non‐parasitized three‐spined sticklebacks, <i>Gasterosteus aculeatus</i> L.

Abstract

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.