Glossary of Fishery Terms - E

E

• Echinoderms - a group of marine animals that includes seastars, sea urchins and sea cucumbers, abundant on the floor of the deep sea, as well as in shallower seas.

• Ecologically sustainable development - in the context of fisheries, using, conserving and enhancing fishery resources so that the ecological processes, on which the fish depend, are not degraded.

• Economic rent - the profit that could be earned from a fishery owned by an individual. Individual ownership maximizes profit, but an open entry policy usually results in so many fishermen that profit barely matches opportunity cost. See maximum economic yield.

• Ectothermic - animals that control body temperature through external means, using the sun, or flowing air or water.

• Ekman transport - resultant flow at right angles to and to the right of the wind direction in the northern hemisphere, to the left in the southern hemisphere.

• Elasmobranch - cartilaginous fish that includes sharks, skates and rays. Compare bony fish.

• Electrophoresis - A technique used by fisheries scientists. Tissue samples are taken from fish, and electrophoresis is used to separate proteins such as enzymes, based on their different mobilities in an electric field. This information is used to differentiate between morphologically similar species and to distinguish sub-populations or stocks.

• El Niño - large scale, cyclical (generally three to seven years), ocean warming and cooling episodes across the equatorial Pacific. Warm water pools in the east in El Niño conditions and in the west during La Niña conditions. It begins around Christmas (El Niño means Christ child). These changes disrupt weather patterns and the migration habits of fish.

• Endangered species - An endangered species is a population of an organism which is at risk of becoming extinct. The IUCN has calculated the percentage of endangered species as 40 percent of all organisms based on the sample of species that have been evaluated through to 2006.

• Endemic - native to a certain region, often a fairly small local area.

• Endothermic - animals which maintain a body temperature which is above ambient temperature. See Ectothermic.

• Epibenthos - invertebrates that live on top of the seabed. Compare benthos.

• Epipelagic - The top layer of the ocean from the surface down to about 200 metres. This is the illuminated zone where there is enough light for photosynthesis. Nearly all primary production in the ocean occurs here. See photic zone.

• Escapement - the percentage of a spawning anadromous fish population that survives all obstacles during their migration, including fishing pressure and predation, and successfully reach their spawning grounds.

• Estuary - a semi-enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Healthy estuaries can have high rates of biological productivity.

• Eulittoral zone - another name for the intertidal zone or foreshore, extending from the spring high tide line to the neap low tide line.

• Euryhaline - fish that are tolerant to a wide range of salinities.

• Eutrophication - an increase in chemical nutrients – typically compounds containing nitrogen or phosphorus – in an ecosystem. Eutrophication in water often results in an increase in algae growth and decay, which can lead to decreased levels of oxygen and fish populations.

• Exclusive Economic Zone (EEZ) - a seazone under the law of the sea over which a state has special rights to the exploration and use of marine resources. Generally a state's EEZ extends to a distance of 200 nautical miles (370 km) out from its coast.