Glossary - E
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E

echinoderm
marine invertebrates with tube feet and five-part radially symmetrical bodies. The group includes sea urchins, sea stars, sea cucumbers, brittle stars, and crinoids.
echo ranging
Determining the distance to an object by measuring the time between transmitting a sound signal and hearing its echo.
echo signature
a unique sonar return (reflection) that can be used to identify individual species of marine organisms, such as fish, or other submerged objects
echolocation
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.
echosounding
the technique of measuring the depth of a body of water by means of an echosounder, an electrical depth sounder that uses sound echoes. The instrument emits sound waves that travel to the bottom of the ocean and are reflected back. Depth is determined by timing how long it takes the sound pulse to leave the instrument, travel to the seafloor, and return to the receiver on the ship.
ecological risk assessment
the process of calculating the probability of adverse ecological effects
ecology
the scientific study of the relationship between organisms and their environment.
ecotype
Ecologically distinct groups or communities; in this case, groups exhibiting different dietary specializations and corresponding behavioral adaptions, such as hunting techniques and acoustic repertoires.
elasmobranch
a group of cartilaginous fish that comprises the sharks, rays, and skates.
elasmobranchs
a group of fishes, including sharks, rays and skates, that has a skeleton made of cartilage rather than bone; they also do not have a swim bladder.
electro-physiological response
the electrical activity of neurons when stimulated (see auditory brainstem response (ABR)).
elephant seal
Mirounga
endangered
any species that is in danger of extinction
endemic
Native to or prevalent in a particular area or region; not found in other places.
entanglement
whales, seals, sea lions, and other marine animals may come into contact with lost or active fishing gear, causing the gear to become twisted around their bodies and/or snagged on different body parts. When this occurs, the animal is considered entangled.
epicenter
the point on the earth's surface (on land or underwater) vertically above the focus of an earthquake.
equal energy hypothesis
assumption that sounds of equal SELcum produce an equal risk for hearing loss (i.e., if the SELcum of two sources are similar, a sound from a lower level source with a longer exposure duration may have similar risks to a shorter duration exposure from a higher level source).
equal latency
the assumption in hearing studies that sounds that are perceived to be equally loud result in equal response times, thereby allowing response time to be a proxy for perceived loudness.
equal loudness curve
a graph of the perceived intensity (loudness) of sounds. The loudness of a sound is different for different frequencies.
equilibrium
the rest position of the particles in a medium
essential fish habitat (EFH)
those waters and substrate necessary for fish for spawning, feeding, or growth to maturity.
estuary
a coastal body of water formed when freshwater from rivers and streams flows into the ocean, mixing with the seawater. Estuaries and the lands surrounding them are places of transition from land to sea, and from freshwater to saltwater. Although influenced by the tides, estuaries are protected from the full force of ocean waves, winds, and storms by the reefs, barrier islands, or fingers of land, mud, or sand that surround them.
euphausiids
small, shrimp-like invertebrates (also called krill ) that swarm in dense patches within the water column or at the sea surface. They have hard mouths and tail parts that reflect sound. Krill is an important food source for many marine organisms including whales and seals.
European perch
Perca fluviatilis
European spiny lobster
Palinurus elephas
exoskeleton
A hard outer structure, such as the carapace of a lobster or crab, that provides protection or support for an organism (especially invertebrates).
expendable bathythermograph
A probe which is dropped from a ship and measures the temperature as it falls through the water. Two very small wires transmit the temperature data to the ship where it is recorded for later analysis. The probe is designed to fall at a known rate, so that the depth of the probe can be inferred from the time since it was launched. By plotting temperature as a function of depth, the scientists can get a picture of the temperature profile of the water.
explosive sound source
a device that uses explosive material to generate controlled acoustic energy.
extinction
The end of an organism or group of taxa. The moment of extinction is generally considered to be the death of the last individual of that species (although the capacity to reproduce and recover may have been lost before this point).
extirpation
the movement of an entire population out of a region
extrapolate
to estimate or expand unknown data based on known facts and/or observations.
extrapolation
using evidence and inferences from a similar situation to project information about a related event or process. Extrapolation can also be used to apply or transfer experimental observations from a model to the real world.