A systematic gathering of information on fish availability and abundance using underwater sound.
The use of underwater sound to map underwater topography and the contents of the sea.
- A method of gathering information on surface fish movement and density by visual observation and photography from low-flying aircraft.
- Воздушное фотографирование; воздушная разведка...
Surplus water from agricultural land, often draining into rivers and then into the sea, and often enriched with nutrients, sediment, and agricultural chemicals.
A rapid excessive growth of algae, generally caused by high nutrient levels, particularly phosphorus. when the algae die, algal blooms can deplete oxygen to the point where fish cannot survive.
A gel substance extracted from brown algae and used industrially as a thickening agent for food and paint.
Fish that live their adult lives in the ocean but migrate up fresh water rivers to spawn. examples are pacific salmon. fish that migrate in the opposite direction are called catadromous.
|anoxic sea water|
Sea water depleted of oxygen. see hypoxia.
Sediments depleted of oxygen.
A line encircling antarctica where cold, northward-flowing antarctic waters meet and sink beneath the sub-antarctic waters, creating an upwelling zone which is very high in marine productivity, es...
The farming of freshwater and saltwater organisms including molluscs, crustaceans and aquatic plants. see also fish farming and mariculture.
A term sometimes used to describe small scale commercial or subsistence fishing practices. the term particularly applies to coastal or island ethnic groups using traditional techniques and traditi...
The open ocean or pelagic zone that extends from a depth of 1000 to 4000 meters below the ocean surface. батипелагический;
The simplest method of bottom trawling. the mouth of the trawl net is held open by a solid metal beam attached to two solid metal plates, welded to the ends of the beam, which slide over and distu...
The ecological region at the lowest level of a body of water such as an ocean or a lake, including the sediment surface and some sub-surface layers. organisms living in this zone are called bentho...
- Aquatic organisms which live on or in the seabed, also known as the benthic zone. included are both mobile animals, such as crabs and abalone, and non mobile animals, such as corals and sponge...
Large, predatory fish characterised by their long sword-like bill. billfish include the sailfish, marlin and swordfish. they are important apex predators feeding on a wide variety of smaller fish ...
- A bimodal distribution is a distribution with two different modes which appear as distinct peaks. an example in fisheries is the length of fish in a fishery, which might show two or more modes...
In underwater acoustics and fisheries acoustics this term is used to mean the effect of plants and animals on sound propagated underwater, usually in reference to the use of sonar technology for b...
- Is the variation of life forms within an area. in the context of fisheries the number and variety of organisms found within a fishery.
- Biodiversity is the variety of all life forms:...
- The total weight of a fish species in a given area. can be measured as the total weight in tons of a stock in a fishery, or are be measured per square metre or square kilometre. the most succe...
A region where a distinctive transition from one set of biota to another occurs. an example is the region where tropical and temperate waters mix.
Natural toxins produced by organisms, often for use as a defence mechanism.
Fish that have a bony skeleton and belong to the class osteichthyes. basically, this is all fish except for sharks, rays, skates, hagfish and lampreys.
A fishing method that involves towing trawl nets along the sea floor. bottom trawling can cause serious damage to sea floor habitats.
- Water that has more salinity than fresh water, but not as much as seawater. it may result from mixing seawater with fresh water, as in estuaries.
- Water containing bacteria between 1...
Bycatch is the harvest of marine life and seabirds during fishing operations when other fish were the target. for example, bycatch might consist of a species which was not the targeted species, su...
A calcified protective cover on the upper frontal surface of crustaceans. it is particularly well developed in lobsters and crabs. каранакс;
capacidad de carga; несущая способность; предельная численность;
- The supportable population of a species, given the food, habitat conditions and other resources available within a fishery.
- Of an electric cable or wire,
Fish that live their adult lives in fresh water lakes or rivers but migrate down rivers to spawn in the sea. an example are freshwater eels of genus anguilla, whose larvae drift on the open ocean,...
(from the greek for "head-feet") animals such as squid and octopus where tentacles converge at the head. cephalopods are the most intelligent of the invertebrates with well developed senses and la...
Member of the group of marine mammals that includes whales, dolphins and porpoises. they are the mammals most fully adapted to aquatic life and are noted for their high intelligence.
The incidental capture of non-target cetacean species by fisheries. bycatch can be caused by entanglement in fishing nets and lines, or direct capture by hooks or in trawl nets.
Variation in the earth's global climate or in regional climates over time. climate change involves changes in the variability or average state of the atmosphere over time periods ranging from deca...
поток context (учащихся); когорта;
- Those individuals of a stock born in the same spawning season. for annual spawners, a year's recruitment of new individuals to a stock is a single cohort or year-class. see brood.
An umbrella term covering fisheries resources and the whole process of catching and marketing fish, molluscs and crustaceans. it includes the fishermen and their boats, and all activities and reso...
Organisms or populations that belong to the same species. organisms that don't belong to the same species are heterospecific. coespecífico (no conespecífico); принадлежащий к тому же в;
The zone of the ocean floor that separates the thin oceanic crust from the thick continental crust. continental margins constitute about 28% of the oceanic area.
Is below the slope, but landward of the abyssal plains. extending as far as 500 kilometres from the slope, it consists of thick sediments which have cascaded down the slope and accumulated as a pi...
- The seabed from the shore to the edge of the continental slope, covered by relatively shallow seas (known as shelf seas) and gulfs.
- Portions of the continental land masses covered b...
The slope which starts, usually abruptly at about a 200 metre depth, at the outer edge of the continent shelf and dips more steeply down to the deep-ocean floor (abyssal plain).
Due to the earth's rotation, freely moving objects on the surface of the earth veer right in the northern hemisphere and left in the southern hemisphere. this effect is called the coriolis effect,...
Small, locally owned businesses usually associated in fishing with traditional methods and low relative yield.
|crab pot fishery|
A fishing technique where crabs are lured by bait into portable traps, sometimes called pots.
A group of freshwater and saltwater animals having no backbone, with jointed legs and a hard shell made of chitin. includes crabs, lobsters, crayfish, shrimp and krill.
A widely used commercial fishing technique which uses a small trawl net with long wire warps. the seine boat drags the warps and the net in a circle around the fish. the motion of the warps herds ...
An area in an ocean or large lake where oxygen levels are extremely low, often due to eutrophication. dead zones have been increasing since the 1970s.
|deep ocean currents|
Currents in the deep ocean, also known as thermohaline circulation or the "conveyor belt", are driven by density and temperature gradients. they can be contrasted with surface ocean currents, whic...
A species which is no longer listed under the esa. see also recovered species.
Fish that live in the demersal zone. examples are cod, flounder and snapper. compared to pelagic fish, demersal fish contain little oil. see also bottom feeder.