While fish do not sleep in the same way that land mammals sleep, most fish do rest. Research shows that fish may reduce their activity and metabolism while remaining alert to danger. Some fish float in place, some wedge themselves into a secure spot in the mud or coral, and some even locate a suitable nest.

Do deep sea fish come to surface at night?

EVERY EVENING as sunset rolls across the Earth, vast numbers of ocean creatures emerge from the depths to flutter and fin their way toward the surface. Most of them are small, translucent crustaceans called copepods.

How do you know if a fish is sleeping?

It's pretty easy to tell when fish are sleeping: they lie motionless, often at the bottom or near the surface of the water. They are slow to respond to things going on around them, or may not respond at all (see some sleeping catfish here). If you watch their gills, you'll notice they're breathing very slowly.