Human beings and animals use sounds is many ways. We use sound when we talk to each other, or when we alert others of danger.
Many marine animals rely on sound for survival and depend on unique adaptations that enable them to communicate, protect themselves, locate food, navigate underwater, and/or understand their environment. They may both produce sounds and listen to the sounds around them.
Sounds are particularly useful for communication because they can be used to convey a great deal of information quickly and over long distances. Changes in rate, pitch, and/or structure of sounds communicate different messages. In particular, fishes and marine mammals use sound for communications associated with reproduction and territoriality. Some marine mammals also use sound for the maintenance of group structure.
Similar to sonar systems on ships, some whales use sound to detect, localize, and characterize objects. By emitting clicks, or short pulses of sound, these marine mammals can listen for echoes and detect objects underwater. This is called echolocation. Some whales and dolphins use echolocation to locate food. They send out pulsed sounds that are reflected back when they strike a target. The analysis of the echoes helps the animals determine the size and shape of an object, its location, whether it is moving, and how far away it is. Echolocation is an effective way to locate prey and also helps whales and dolphins analyze their environment.
Many species of fish and aquatic invertebrates also use sound. Fishes produce various sounds, including grunts, croaks, clicks, and snaps, that are used to attract mates as well as ward off predators.
The life history of many coral reef fishes includes a pelagic larval stage that metamorphoses to the juvenile stage. Late stage larvae and transforming juveniles need to reach suitable reef habitats to mature. There is some evidence that underwater reef sounds may be detected by coral reef fish (and invertebrate) larvae guiding them to coastal areas and allowing them to identify suitable settlement habitats Different coastal habitat types have been found to produce different ambient sounds over short distances.