Do fish sleep? And if they do, how? Do they lay down? — Jessica of Wetumpka, AL

Dear Jessica,

Most fish spend part of every day asleep. Being asleep can mean different things to different fish. Some fish (like herring and tuna) are motionless in the water during the night. Other fish, like rockfish and grouper, don't appear to sleep at all. They rest against rocks, bracing themselves with their fins. Also, some freshwater fish (like catfish) swim up under a log or river bank for shelter during the day. By the way, fish can't close their eyes when they sleep; they don't have eyelids.