a process for locating distant or hard-to-see objects using the reflection of sound waves. The distance of objects or depth of the seafloor can be determined by measuring the time it takes for reflected sound waves (echoes) to return to the sound source. Some whales and dolphins use echolocation to identify underwater objects and to help find food.

A hard outer structure, such as the carapace of a lobster or crab, that provides protection or support for an organism (especially invertebrates).

relatively small organisms that drift or float passively in the water and are carried wherever currents and tides take them. Plankton are often microscopic and are an important food source for other aquatic organisms. There are two types of plankton- phytoplankton (plants and autotrophs) and zooplankton (animals).

containing or operated by air or gas under pressure.

Sprattus sprattus

an instrument, such as a side scan sonar, that is towed behind a ship

a pattern of movement that some marine organisms undertake each day. Usually organisms move to shallow waters at night and return to deeper waters during the day.

relative frequencies of vital occurrences that affect changes in the size and composition of a population, such as birth rate or death rate

the most commonly used frequency weighting function for humans that accounts for the fact that human hearing is less sensitive to low frequencies; units dB(A) or dBA.

the conversion of acoustic energy to heat energy