Ricky Hunsakar, age 7, of Sioux City, Iowa, for his question:

Do fish sleep?

Fishes do not sleep as we do. They do not go to bed at night, close their eyes and dream until morning. In fact, they cannot close their eyes at all. Their eyelids are windows of glassy skin and they are sealed shut. So if fishes do any kind of sleeping, they must do it with their eyes staring wide open. As a rule, they take only short naps and scientists think that they almost never sink into a deep sleep. But sometimes they hibernate through a long winter or estivate through a hot summer drought.

Naturally the fishes get tired from all the swimming they do. Some take a few short rest periods during the night. Other types are busy all night and rest a few times during the day. During his nap, a fish may rest on the bottom or lean against a rock or a waterweed. Or he may just float beside a lot of other fishes, gently waving his fins. No matter how he takes a nap, a slight sound or touch brings him wide awake in a flash. Nobody gets a chance to sneak up on a dozing fish.