Kids: Catching some zzzzs in the sea
Photo: Jenny Huang
Have you ever wondered if fish sleep?
The answer to that question depends on how you define sleep.
Many fish exhibit resting behavior very much like sleep, but scientists can’t agree on whether this state is the same as sleep in warm-blooded creatures. Mammals and birds exhibit characteristic brainwaves when they sleep, and these brainwaves are different and hard to study in fish.
But if we use a definition of sleep that’s closer to “rest” – that doesn’t depend on brainwave criteria – then, yes, fish do sleep. Perhaps the best example of sleeplike behavior in fish is found in some reef-dwelling parrotfish.
Many parrotfish hole up in a crevice at night and secrete a mucous envelope around themselves. Divers can approach so closely that they can touch and even hold the fish without disturbing it. Lots of other fish – including minnows, butterflyfish, and even sharks – also seem to rest for prolonged periods of time.
Some perch and carp appear to make up for lost rest time by resting more quickly when they have the opportunity – the rough equivalent of you falling asleep faster when you haven’t had enough sleep the night before.
