Glossary of seafood terms

Researching seafood can be a minefield of confusing terms. This glossary will help you navigate.

Adapted from Fishonline, published by the Marine Conservation Society.

Aggregating: The behaviour of a group of individuals of a species to form a cluster (ie. in a non-random distribution).

Algal bloom: An abundant growth of phytoplankton, typically triggered by sudden favourable environmental conditions e.g. excess nutrients. Typically seen in the spring in UK waters.

Anadromous: Fish that are born in freshwater rivers and streams but spend most of their adult lives in the marine environment, typically returning to freshwater to spawn, or reproduce.

Aquaculture: The general term given to the farming/cultivation of any aquatic (fresh and marine) species (plant or animal).
Artisanal: Term used to describe small-scale, traditional fisheries.

Beam trawl: In this type of trawl the mouth of the net is kept open by a beam which is mounted at each end on guides or skids which travel along the seabed.

Benthic: Living on or in the seabed.

Benthos: Those organisms attached to, living on, or in the seabed.

Berried: Egg-bearing lobster or crab.

Bioaccumulation: The accumulation of a substance (contaminant) within the tissues of an organism.

Biodiversity: The variability among living organisms from all sources including, among other things, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part.

Biomass: The total weight of living organisms or total weight of a resource or stock.

Bivalve: Having two shells or valves which open and shut.

Boreal: Living near the north; sub Arctic.

Bottom trawl: A large cone-shaped net which is towed across the seabed. Also called an otter or demersal trawl.

Broodstock: A fish which is kept for the purpose of reproduction and supply of juveniles.

Bycatch: Non-target organisms caught in fishing gear.

Catadromous: Fish that are born in the sea then migrate to freshwater to grow and mature.

Catch: Total number or weight of fish and other marine life, including bycatch, taken during a fishing event (as opposed to landings which do not reflect the amount of bycatch discarded).

Caviar: The salted roe (unfertilised eggs) of a female sturgeon. The roe from other fish species, e.g. salmon, is also considered an edible delicacy but in most countries, including the U.K, only sturgeon eggs can legally be called 'caviar.'

Cephalopod: A type of mollusk, have a distinct head and tentacles, e.g. octopus, squid and cuttlefish.

CITES: Convention on International Trade in Endangered Species (CITES). An international agreement which aims to ensure that trade in plants and animals does not threaten their survival.

Cod-end: The rear end of a trawl net where the catch accumulates.

Common Fisheries Policy (CFP): The European Union's policy instrument for the management of fisheries and aquaculture.

Conservation measure: Term applied to legislative methods within the framework of the CFP which regulate fishing activity.

Continental shelf: Sloping undersea shelf of land that extends beyond the shore of the continent.

Copepods: Small (0.5-2mm long) crustacea that form part of the zoo-plankton community and are an important food source for many larger animals.

Coral: A group of marine invertebrate animals that live in colonies, characterised by a calcium carbonate skeleton. Appears in a variety of shapes often forming reefs. (Separately 'coral' is also a term used for some shellfish roe or eggs).

Crustaceans: A group of animals, found in fresh and saltwater, with two pairs of antennae and a calcium carbonate shell, e.g. crab, lobster.

Cultch: Any substrate laid on the seabed with the purpose of encouraging mollusc larvae (spat) settlement. Examples are shell waste, ropes and tiles.

Decommission: Term used to describe the process by which fishing boats are taken out of service or 'scrapped'.

Deep-water species: Those species living in water beyond the continental slope in depths of more than 400 metres.

Demersal: Refers to fish, such as cod, haddock and plaice, which live primarily on or near the seabed.

Depuration: The process of removing pathogens from shellfish by keeping them in clean water for a period of time prior to sale.

Diadromous: Fish that move during their life cycle between fresh and marine waters, e.g. salmon and eels.

Discards: Fish and other organisms caught by fishing gear and then thrown back into the sea for legal, economic or other reasons.

Dredging: A fishing method used along the seabed for catching bivalve molluscs such as oysters, clams and scallops.

Drift net: A gill net suspended vertically in the water that floats unrestrained in the open ocean.

Ecosystem: A community of organisms and their surrounding environment interacting and interconnected with each other.

Ecosystem approach: The ecosystem approach to fisheries management involves a consideration of all the physical, chemical and biological variables within an ecosystem, taking account of their complex interactions.

Ectoparasite: A parasite that attaches itself to and lives off the external surface of an animal (fish).

Elasmobranch: Fish with a cartilaginous, non-bony skeleton (sharks, skates and rays).

Ephemeral: Being present only briefly, as in naturally occurring mussel beds.

Eutrophication: The process whereby waters become hyper-enriched by nutrient inputs, resulting in excessive plant growth and oxygen depletion.

Exclusive Economic Zone (EEZ): An area in which a coastal state has sovereign rights over all the economic resources of the sea, seabed and subsoil. Established in international law by the Law of the Sea treaty.

Extirpation: The loss of a local population (distinct from extinction – the loss of an entire species).

Fecundity: Potential reproductive capacity of an organism or population expressed in number of eggs (fertile or not) produced during each reproductive cycle.

Fresh: A term that can be used to describe fish that have been kept chilled on ice but not deep frozen. The term should not be used to describe previously frozen, thawed fish (FSA advice).

Finfish: A fish with fins, as opposed to shellfish.

Fish: Collective term (includes molluscs and crustaceans) for any aquatic animal that is captured.

Fishery: The sum of all fishing activities on a given resource e.g., shrimp fishery, or activity of catching fish from one or more stocks e.g., North Sea cod fishery, or it may also refer to a single type or style of fishing e.g., trawl fishery.

Fishing: Any activity that involves the catching or taking of fish.

Fishing capacity: The quantity of fish that can be taken by a fishing unit, i.e. individual, community, vessel or fleet.

Fishing effort: The amount of fishing gear of a specific type used over a given unit of time, e.g. hours trawled per day; the overall amount of fishing expressed in units of time e.g. number of hauls per boat per day.

Fishmeal: A fine powder of processed fish (whole fish and bones and offal, which is cooked, dried, and ground). Often used in aquaculture fish feed.

Food and Agriculture Organisation (FAO): Founded in 1945 it has 183 member countries and one member organisation, the European Community. FAO is one of the largest specialised agencies in the United Nations and its programme on fisheries aims to promote their sustainable development through implementation of its Code of Conduct for Responsible Fisheries. The FAO compiles and makes available a number of different statistical data sets related to fish and fisheries, which are available online. FAO also regularly publishes its flagship State of World Fisheries and Aquaculture (SOFIA) report, a 200 page report detailing production and consumption trends and offering analysis and constructive comment.

Food chain: Representation of the passage of energy (food) from producers to the organisms that feed on them (linear predator-prey chain).

Food web: Network of food chains interlocking the organisms in an ecosystem.

Fry: Juvenile fish.

Gadiformes: The taxonomic 'Order' which includes cod, pollack, whiting, coley and haddock.

Gadoid: A cod-like fish, see Gadiformes.

Gear: Any tools used to catch fish, such as hook and line, trawls, traps etc.

Genetic dilution: The process occurring when domestic farmed fish with low variation between individuals interbreed with wild fish of the same species, leading to the subsequent offspring having lower variability when compared to the pure wild strain.

Ghost fishing: The phenomenon whereby lost nets or traps continue to fish.

Gill net: A loosely set and near invisible wall of fine netting (mono or multi-filament nylon) that traps fish by the gill covers.

Grading: The term used to describe the process of sorting fish into similar sizes. Occurs either manually by sweep net or on a grading machine.

Ground fish: American term for demersal fish.

Handlining or hook and lining: Attracts fish by a natural or artificial bait (lures) placed on a hook fixed to the end of a line or snood, on which fish are caught. Hook-and-line units may be used singly or in large numbers.

Hatchery: The place where fertilised eggs are grown on to become fry before being transferred to freshwater tanks.

High-grading: Discarding at sea all or a portion of a vessel’s legal catch, in order to seek a higher or larger grade of fish that brings higher prices.

Industrial fisheries: Fisheries which do not target species for direct human consumption, i.e the capture of fish for reduction into fishmeal and fish oil.

International Council for the Exploration of the Sea (ICES): An international organisation comprising of member countries around the border of the North Atlantic. Established by international convention in 1902, ICES is the intergovernmental marine science organisation developing scientific advice to help manage fisheries.

International Union for Conservation of Nature (IUCN): Every four years IUCN publishes a 'Red List' – an inventory of the current global conservation status of plant and animal species – to raise awareness of species threatened with extinction (Critically Endangered, Endangered or Vulnerable) and promote their conservation.

Invertebrates: Animals without a back-bone, including octopus, shrimp, oysters.

Jig: Lures used on a vertical line that is moved up and down (jigged) by hand or mechanically. Often used at night for fishing oceanic squids.

Landings: The quantity of fish and shellfish brought ashore for sale. This measurement does not include the amount of bycatch incidentally caught and discarded at sea.

Line-caught: A generic term used to describe pole (or rod/hook) and line; hand-line or long-line fisheries.

Long-lining: Uses both vertical and horizontal lines, often a number of miles long, to which short lengths of line (snoods) carrying baited hooks are attached at intervals.

Mangrove forests: Salt-tolerant trees primarily found in the intertidal zone of estuaries along tropical and subtropical coasts. Mangroves are important habitat for fish and protect coastlines from erosion (and contribute fuel, food and fibre to coastal communities).

Mariculture: The farming of a species in sea (marine) water but the term aquaculture is more commonly used.

Maximum Sustainable Yield (MSY): Maximum amount of a species that can be taken by a fishery without diminishing the future take.

Misreporting: False or incorrect reporting of details pertaining to quantity and area of capture of protected species, i.e. those species regulated by quota.

Mixed fishery: Comprising more than one species, e.g. North European demersal fisheries typically comprise cod, haddock, whiting, pollack and saithe.

Mobile gear: Towed or encircling active fishing gears e.g. trawl, dredges or seine.

Otter board: (Or otter door) a paired device used to spread the trawl mouth laterally, when towed by one vessel.

Otter trawl: A large cone-shaped net, which is towed across the seabed. Also called a bottom trawl.

Overcapacity: A state of saturation or an excess of catching capability, i.e. more boats/gear/investment in a fishery than is efficient/sustainable.

Overfishing: The rate/intensity of fishing reduces the breeding stock levels to such an extent that they will no longer support a sufficient quantity of fish for sport or commercial capture. i.e. overfishing occurs when a population of fish is caught faster than it can replenish itself through reproduction.

Pelagic: The upper layers of the ocean. This is where food is relatively plentiful. Pelagic fish include herring, sardine and pilchard.

Plankton: Tiny plants and animals that spend at least part of their time on the sea surface. Primarily distributed by oceans currents. Plankton form the basis of ocean food webs.

Phytoplankton: The microscopic plant component of plankton.

Pinger: Acoustic device designed to deter marine mammals from entanglement in fishing nets.

Pole and line: Hand held or mechanically operated rod with baited hook or lure.

Pollution: The introduction by man, directly or indirectly, of substances or energy to the marine environment with negative effects.

Polyculture and integrated aquaculture: The farming of two or more species (animals and/or plants) in the same aquaculture system. Waste from one species is taken up by a second species, instead of discharged into the environment.

Pond system: One of the earliest forms of aquaculture, ponds can be either natural or artificially constructed. Catfish, carp and tilapia are commonly cultured in ponds.

Population: A biological unit representing the individuals of a species living in a specific area.

Pot: A trap used to capture fish, especially crustaceans.

Protected name: Protected designation of origin (PDO), protected geographical indication (PGI) and Protected Geographical Status (PGS) are geographical indications defined in European Union law to pro-tect the names of regional foods, including Arbroath Smokies and Scottish Salmon.

Purse seining: The general name given to the method of encircling a school of pelagic fish with a large wall of net.

Quota: A share of the Total Allowable Catch (TAC) allocated to a country, vessel, company or individual fishermen.

Raceway: A straight-sided artificial channel (usually concrete) in which farmed fish are raised.

Round fish: Demersal fish that are rounded in transverse section, e.g. cod, haddock and whiting (as opposed to flat fish e.g. plaice or flounder).

Safe biological limits: Limits (reference points) for fishing mortality rates and spawning stock biomass beyond which, the fishery is unsustainable. Other criteria that indicate when a stock is outside safe biological limits include age structure, distribution of the stock and exploitation rates. A fishery that maintains stock size within a precautionary range (a range within which the probability of reaching any limits is very small) would be expected to be sustainable.

Selectivity: Ability to target and capture fish by size and species, allowing by-catch of juvenile and non-target species to escape unharmed.

Shellfish: As opposed to finfish. A collective term used to describe molluscs and crustacea.

Smoltification: The physical transformation undergone by salmonid (salmon and trout) fish to enable them to migrate from freshwater to seawater as part of their lifecycle.

Smolts: Juvenile fish that have undergone smoltification.

Spat: The stage in a mollusc's lifecycle in which it goes from being free swimming to attaching itself to a substrate.

Spawn: Release of eggs into the water, either fertilised or to be fertilised.

Spawning stock: The mature fish responsible for reproduction in a population(s).

Spawning Stock Biomass (SSB): The total weight of all sexually mature fish in a population.

Static or fixed gears: Refers to fishing gears that are fixed to or on the seabed e.g pots, traps or nets. These types of gears are passive as opposed to mobile gears, e.g. trawl nets, which are referred to as active gears.

Stock: Term given to a group of individuals or populations in a species occupying a well-defined spatial range independent of other stocks of the same species. Fisheries are often managed by 'stocks'.

Stocking density: The amount of fish in a farmed area. Usually expressed at the weight of fish per volume of water, for example 15kg/m3.

Straddling stocks: Fish stocks that migrate through more than one country's Exclusive Economic Zone (EEZ).

Sweep: The rope (usually wire) between the otter board and trawl net.

Tangle net: A type of bottom set gill net used to capture flatfish, crustaceans and other species.

Target species: The species, or assemblage of species, which are primarily sought in a fishery.

Teleost: Fish with a bony skeleton, as opposed to cartilaginous fish (elasmobranchs).

Total Allowable Catch (TAC): Maximum tonnage of a fish species that may be caught each year within a certain area.

Trawl: A sock-shaped net with a wide mouth tapering to a small, pointed end (the cod end) that is towed behind a vessel at any depth.

Trolling: A type of hook-and-line method in which several unconnected lines, each hooked and baited, are slowly dragged behind the vessel.

Trophic: The different levels in a food chain.

Turtle Excluding Device (TED): Turtles can be excluded from trawl nets by fitting solid grids of various kinds into the net. These 'trap doors' are designed to reduce turtle bycatch, particulary in tropical prawn fisheries.

Zooplankton: The animal component of plankton; animals suspended or drifting in the water column including larvae of many fish and benthic invertebrates.