Danielle Richir, age 12, of Fredericton, New Brunswick, Canada, for her question:

CAN FISH HEAR?

It is impossible, of course, for us to enter the sensory world of fish, but we know they have many of the senses that most other animals have. We know, for example, that many have noise producing devices: some grind their teeth while others have elaborate sound making muscles attached to their gas bladders.

Fish also have highly developed hearing senses. Many bony fish have direct connections from their gas bladders to their inner ears which provide them with the equivalent of a hydrophone. Lateral line organs, associated with the inner ear, can also tell a fish much about the water's turbulence and its currents. And electric organs are used as sonar like organs of detection.