Background - March 25, 2014
What are they talking about?

What are they talking about? Sometimes the technical jargon makes it impossible to understand what is going on. We have included the most common terms that are regularly used in "technical talk" about the oceans. If there are other terms you come across that you think could be included – tweet us and let us know.

Shark Mural in Wellington. 09/12/2013 © Greenpeace / Phil Crawford


Aquaculture - Cultivation or farming of any aquatic species – marine or freshwater, plant or animal.

Beam trawl - A type of bottom trawl in which the horizontal opening of the net is provided by a heavy beam mounted at each end on guides or skids which travel along the seabed. On sandy or muddy bottoms, a series of ‘tickler’ chains are strung between the skids ahead of the net to stir up the fish from the seabed and chase them into the net. On rocky grounds, these tickers are replaced with chain matting. Used mainly for flatfish and shrimp fishing.

Benthic - Bottom-dwelling.

Biomass - The total weight of a group (or stock) of living organisms or of some defined fraction of it (e.g. spawners), in a given area, at a particular time.

BMSY - Biomass corresponding to maximum sustainable yield (MSY). Often used as a biological reference point in fisheries management, it is the long-term average biomass expected if fishing at the rate of FMSY (see Fishing mortality).

Bottom trawl - A trawl designed to work at the sea bottom. The lower edge of the net opening drags along the seabed, and is normally protected by a thick ground rope and ballasted with chains, sinkers, rubber discs, bobbins, etc. Bottom trawls include low-opening trawls for demersal species such as beam trawls and shrimp trawls, and high-opening demersal otter trawls for semi-demersal or pelagic species.

Brood stock - Eggs, juveniles or adults of a species, from which a first or subsequent generation may be produced in captivity, whether for growing in aquaculture or for release to the wild for stock enhancement.

Bycatch - The part of a catch other than the adults of the target species, which is taken incidentally. Some or all of it may be returned to the sea as discards, usually dead or dying.

Cetacean - A marine mammal of the order Cetacea, including whales, dolphins and porpoises.

CITES - Convention on International Trade in Endangered Species of Wild Fauna and Flora.

Common Fisheries Policy (CFP) - The policy under which the EU manages all fisheries within the European EEZ.

Cold seep - An area of the seabed where hydrogen sulphide, methane and other hydrocarbon-rich fluid-seepage occurs, often in the form of a brine pool.

Critically Endangered - Facing an extremely high risk of extinction in the wild in the immediate future (IUCN definition).

Danish seine - A fishing net with a conical net bag with two relatively long wings. Two long heavy ropes, one attached to each wing, are used to encircle a large area of the seabed to herd the fish into the net and then to haul the net in. Used for benthic fish such as flatfish.

Data Deficient - Presumed to be at some risk of extinction, but there is inadequate information to make a direct, or indirect assessment of this risk based on its distribution and/or population status (IUCN definition).

Demersal - Of a fish or other organism: living near or on the seabed. Of a fishery, etc: operating within this zone. Demersal fish include species such as haddock and cod and flatfish.

Demersal otter trawl - A type of bottom trawl with rectangular 'doors' or 'otterboards' to keep the mouth of the cone-shaped net open horizontally while the net is being towed. A vertical opening is maintained by weights on the bottom and floats on the top. The net is dragged along the sea bed with the aid of bobbins, rollers and ‘rockhoppers’, which can roll across or dig into the bottom or bounce over obstacles.

Dredge - Gear used in fishing for shellfish, consisting of a rugged triangular steel frame and tooth-bearing bar, behind which a mat of linked steel rings is secured. A heavy netting cover joins the sides and back of this mat to form a bag in which the catch is retained. Shellfish such as scallops are raked out of sand or gravel and swept into the bag. Several dredges are towed together from a tow bar and larger vessels generally tow two bars.

Endangered - Not Critically Endangered, but facing a very high risk of extinction in the wild in the near future (IUCN definition).

EU - European Union.

Exclusive economic zone (EEZ) - The maritime zone under national jurisdiction (up to 200 nautical miles from the coast), within which a coastal state has the right to explore and exploit, and the responsibility to conserve and manage, the living and non-living natural resources.

FAO - Food and Agriculture Organisation of the United Nations.

Fishing mortality(F) - The total rate of deaths of fish directly due to fishing. Usually expressed as the proportion of the entire population caught in a year. FMSY is the rate which, if applied constantly, results in the maximum sustainable yield (MSY) of fish. Flim is the rate above which recruitment will decline substantially, usually set as the FMSY. Fpa is the precautionary approach limit set to allow for uncertainty in survey data and to ensure Flim is not reached accidentally.

Fishmeal - Protein-rich meal derived from processing whole fish (usually small pelagic forage fish, and bycatch) as well as by-products from fish processing plants. Used mainly as feeds for poultry, livestock, and aquaculture species.

Forage fish - Abundant, schooling species (such as sardines, herrings, Alaska pollock, menhaden, krill, and squid) that are described as ‘fuel for the food web’ because they are the food that sustains diverse assemblages of larger predators higher up in the ocean food chain – seabirds, marine mammals, and other fish species. Although highly abundant, their populations fluctuate widely under various environmental influences. Forage fish were once a relatively small share of the global marine fisheries, but industrial fishing technologies have enabled the removal of ever-growing quantities from the oceans, with little thought as to the impacts on marine ecosystems. The Peruvian anchoveta fishery is now the largest in the world (10.7 million tonnes in 2004), and seven of the top ten fisheries (by weight) target forage fish. Most of these fish are processed directly into fishmeal and fish oil to be used in poultry, livestock, and aquaculture feeds.

Hydrothermal vent - A fissure in the seabed from which geothermally heated water issues.

ICES - International Council for the Exploration of the Sea. Scientists working through ICES gather information about the marine ecosystem. ICES Advisory Committee develops this information into advice which is used by the 20 member countries to help them manage resources in the North Atlantic Ocean and adjacent seas.

Industrial fisheries - Fleets of large vessels, using highly mechanised means to catch and process fish and shellfish, particularly for purposes other than human consumption (e.g. fishmeal, fertiliser).

IUCN - World Conservation Union (formerly the International Union for Conservation of Nature and Natural Resources).

IUCN Redlist - The world's most comprehensive inventory of the global conservation status of plant and animal species. It is widely considered to be the most objective and authoritative system for classifying species in terms of the risk of extinction. Classification groups are: Data Deficient, Near Threatened, Vulnerable, Endangered, Critically Endangered, Extinct in the Wild, or Extinct.

IUU fishing - Illegal, unreported and unregulated fishing. Also known as pirate fishing.

Minimum landing size (MLS) - A fishery management control on size at landing (or in the market). Intended to minimize the catch of small fish or juveniles to give them a better chance to grow and reproduce before being vulnerable to fishing.

Maximum sustainable yield (MSY) - The highest theoretical yield that can be continuously taken from a stock under existing environmental conditions without significantly affecting recruitment.

NAFO - Northwest Atlantic Fisheries Organization. NAFO is an intergovernmental fisheries science and management body. NAFO Scientific Council gives advice on the status of fish stocks in the NAFO Convention Area to the Fisheries Commission and Coastal States.

Near Threatened - At a lower risk of extinction in the wild but close to qualifying for the Vulnerable category (IUCN definition).

Nursery - An area where juvenile fish live and grow.

OSPAR - Oslo and Paris Convention for the Protection of the Marine Environment of the North-East Atlantic

Overfished - In fisheries science, a stock is considered to be in an overfished state when it has reached an explicit limit set by management, below which the population may fall to a level too low to ensure reproduction at a rate sufficient to maintain it. (Exact definitions vary between management systems).

Overfishing - In fisheries science, overfishing is occurring when the fishing mortality has reached an explicit limit set by management, above which the stock is expected to decline towards an overfished state. (Exact definitions vary between management systems).

Pair trawl - A large pelagic trawl towed between two boats. Associated with bycatch of marine mammals.

Pelagic - Of a fish or other organism: spending most of its life in the mid-water, with little contact with or dependency on the seabed. Of a fishery, etc: operating within this zone. Pelagic fish include species such as herring and sardine.

Pelagic trawl -  A trawl designed to work in mid-water, targeting pelagic fish. The front net sections are often made of very large meshes or ropes, which herd the fish towards the back of the funnel-shaped net. Pelagic trawls may be towed by one or two (pair trawl) boats. Associated with bycatch of cetaceans and other marine mammals.

Quota -  A share of the total allowable catch (TAC) for a given fishery, allocated to an operating unit such as a country, a vessel, a company or an individual fisherman (individual quota), depending on the system of allocation. Quotas may or may not be transferable, inheritable or tradable.

Recruitment - The rate at which a population is added to each year. Recruitment to an exploitable (i.e. mature) stock is generally through growth of juvenile individuals and/or migration into the stock area.

Reproductive capacity (RC) - A measure of a stock’s ability to maintain its SSB at a level below which recruitment will decline substantially. RC is determined by comparing the SSB to the biomass limit reference point (Blim) and the biomass precautionary approach reference point (Bpa).

Spawning stock biomass (SSB) - The total weight of all fish in the population which contribute to reproduction.

Seamount - A mountain rising from the seabed that does not reach to the water's surface.

 Stock - A population from which catches are taken by a fishery. A stock is usually defined in terms of a particular population more or less isolated from other populations of the same species and hence self-sustaining.

Stock status - Assessment of the situation of a stock. The FAO express this as: protected, under-exploited, intensively exploited, fully exploited, over-exploited, depleted, extinct or commercially extinct.

Suction/hydraulic dredge - Water is shot into sediments and displaced shellfish are collected the in a mesh bag (hydraulic) or sucked to the surface through a pipe (suction).

Total allowable catch (TAC) - The catch allowed to be taken from a resource in a specified period (usually a year), as defined in the management plan. The TAC may be allocated to the stakeholders in the form of quotas, as specific quantities or proportions of the TAC.

Trawl - A funnel-shaped net that is towed through the water by one or more vessels.

Tropic level - The position that an organism occupies in a food chain, i.e. what it eats, and what eats it.

Vulnerable - Not Critically Endangered or Endangered, but facing a high risk of extinction in the wild in the medium-term future (IUCN definition).