Biomass

The total weight of a group or stock of living organisms (e.g. fish, plankton etc.) or of some defined fraction of it (e.g. spawners) in an area at a particular time.

Bycatch

The unintentional catch of other creatures living near thetarget species. Such creatures may include other fish species, marine mammals, turtles, or even seabirds. Fishermen try to avoid bycatch because it takes time and energy away from catching their target species. Managers try to reduce bycatch and its impacts in a number of ways, such as working with fishermen to develop gear that is more efficient in catching the target species and closing areas to fishing where or when the probability of bycatch is high.

Catchability

In general, the extent to which a stock is susceptible to fishing. In fisheries modelling, the fraction of a fish stock which is caught by a defined unit of the fishing effort, also called the catchability coefficient (q).

Distant water fishing

Catching of fish by vessels outside their own country’s waters under special access agreements, i.e. in all FAO major fishing areas other than those adjacent to the flag State.

Dolphin-safe tuna

A number of labels which denote that the tuna was caught in compliance with various laws or policies designed to minimize fatalities of dolphins during fishing. Some labels impose stricter requirements than others.

Effort

The quantity of fishing gear of a specific type used on the fishing grounds over a given unit of time, e.g. hours trawled per day, number of hooks set per day or number of hauls of a beach seine per day. When two or more kinds of gear are used, the respective efforts must be adjusted to some standard type before being added.

Exclusive Economic Zone (EEZ)

A zone under national jurisdiction (up to 200-nautical miles wide) declared in line with the provisions of the 1982 United Nations Convention on the Law of the Sea, within which the coastal State has the right to explore and exploit, and the responsibility to conserve and manage, the living and non-living resources.

Fecund, fecundity

Fecundity refers to the potential reproductive capacity of an organism or population expressed as the number of eggs (or offspring) produced during each reproductive cycle. Fecundity usually increases with age and size. A highly fecund organism is thus one which produces a large number of eggs or offspring.

Fish aggregating (or aggregation) devices (FADs)

Man-made or natural floating objects placed on the ocean surface, often anchored to the bottom, to attract schooling pelagic fish species such as tuna, marlin and dolphin fish, thus increasing their catchability. They usually consist of buoys or floats tethered to the ocean floor with concrete blocks.

Gillnet

A type of fishing gear which causes the fish to be gilled, entangled or enmeshed in the netting. The nets can be used alone or, as is more common, in large numbers placed in line. They may be used to fish on the surface, in midwater or on the bottom.

Gillrakers

Bony or cartilaginous processes that project from the gill arch of fish and which filter tiny prey as food. They are not to be confused with the gill filaments that make up the bony part of the gill. Rakers are usually present in two rows, projecting from both the anterior and posterior side of each gill arch.

Gonadosomatic index (GSI)

The ratio of gonad weight to total body weight, expressed as a percentage. The GSI is helpful in identifying seasons of spawning, as the ovaries of gravid females rapidly increase in size just prior to spawning.

Growth overfishing

Occurs when too many small fish are being harvested too early, through excessive fishing effort and poor selectivity (e.g. too small mesh sizes) and the fish are not given enough time to grow to the size at which the maximum yield-per-recruit from the stock would be obtained. A reduction of fishing mortality on juveniles, or their outright protection, would lead to an increase in yield from the fishery.

Illegal, unreported and unregulated (IUU) fishing

Fishing that violates national or international law or rules, that hasn’t been reported where reporting is required, or that is inconsistent with relevant international laws or rules. Either the fishing activities are not regulated or the fishing vessels involved are not able to be regulated. Illegal activities can include fishing without a licence or quota for certain species, unauthorized transshipments to cargo vessels, failing to report catches or making false reports, keeping undersized fish that are otherwise protected by regulations, fishing in closed areas or during closed seasons, and using prohibited fishing gear. By dodging conservation and management measures, those engaging in IUU fishing can cut corners and lower their operating costs. As a result, their illegally-caught products provide unfair competition to law-abiding seafood industries in the marketplace.

IUCN Red List

Compiled by the World Conservation Monitoring Centre, the IUCN Red List is the world's most comprehensive inventory of the global conservation status of biological species. Among others, it includes more than 6,000 animal species known to be threatened with extinction.

Long line

Fishing method in which short lines carrying hooks are attached to a longer main line at regular intervals. The horizontal mainline is connected to the surface by floats. The main lines can be as long as 150 km and have several thousand baited hooks (such as in tuna fishing).

Pole and line

A fishing technique in which surface schooling fish, such as yellowfin and skipjack tuna, are attracted to the vessel and driven into a feeding frenzy by throwing live or dead bait into the water and spraying water onto the sea surface to simulate the escape behaviour of small prey. The fish are lured with a line and a hook attached to a pole and pulled off the water by manual or powered devices.

Purse seine

Net characterized by the use of a purse line at the bottom of the net which enables the net to be closed like a purse and retain all the fish caught. Purse seines, which may be very large, are operated by one or two boats.

Recruitment

The process by which fish join the exploitable stock in the fishing area each year, through a process of growth (i.e. the fish grows to size at which it is catchable by the fishing methods being used) or migration (i.e. the fish moves into the fishing area). The process may be short or longer than a year, depending on the biology of the species and the fishing method and gear.

Ring net

Net operated by surrounding a shoal of pelagic fish with a “wall” of netting, often operated by two boats.

Sashimi

Japanese term for sliced fish (especially tuna) and shellfish (scallop, abalone, lobster, squid, or octopus) served raw as a delicacy.

Sustainability

Ability to persist in the long-term.

Swim bladder

A buoyancy organ possessed by most bony fish which enables the fish to stay at a particular water depth without having to waste energy in swimming. Located in the body cavity, it is derived from an out pocketing of the digestive tube. Also called gas bladder, fish maw or air bladder.

Total allowable catch (TAC)

Total annual catch allowed to be taken from a resource in a specified period (usually a year) that, if exceeded, will terminate the fishery for that year. The TAC may be allocated to stakeholders in the form of quotas as specific quantities or proportions.

Troll lines, trolling

Simple lines, provided with natural or artificial bait, trailed near the surface or at a certain depth by a vessel at a speed of 2-10 knots. Several lines are usually towed at the same time, by using outriggers. Trolling is used to catch tuna and tuna-like fish.

Thermocline

Layer below the surface layer of the sea or certain lakes, where the temperature gradient increases abruptly compared to the warmer layer above and the colder layer below (i.e. where temperature decreases rapidly with increasing depth). It is usually an ecological barrier and its oscillations have significant consequences on fish stocks distribution and ocean productivity. Factors that affect the depth and thickness of a thermocline include seasonal weather variations, latitude and longitude, and local environmental conditions.