Glossary
Note: The FAO Term Portal - Fisheries has some of the definitions in multiple languages.
Absolute Abundance
The total number of a kind of fish in a population; this is rarely known, and usually estimated from the relative abundance.
B0 (Unfished Biomass)
“B0”, unfished biomass or virgin biomass, refers to the average biomass of a stock that has yet not been fished. It is generally calculated as the long-term average biomass value expected in the absence of fishing mortality. In production models, B0 is also known as carrying capacity. It is often used as a reference value to assist the relative health of a stock, monitoring changes in the ratio between current and virgin biomass (B/B0).
Source: Restrepo V. (1999): Annotated Glossary of Terms in Executive Summary Reports of the International Commission for the Conservation of Atlantic Tunas’ Standing Committee on Research and Statistics (SCRS), ICCAT.
Bias
An effect which deprives a statistical result of representativeness by systematically distorting it, as distinct from a random error which may distort on any one occasion but balances out on the average.
Source: OECD Glossary
Biological Overfishing
Catching such a high proportion of one or all age classes in a fishery as to reduce yields and drive stock biomass, and spawning potential below safe levels. Can involve both growth overfishing and recruitment overfishing. With reference to a surplus production model, biological overfishing occurs when fishing levels are higher that those required for extracting the maximum sustainable yield (MSY) of a resource.
Source: Garcia, S.M. (Comp.). 2009. Glossary. In Cochrane, K. and S.M. Garcia. (Eds). A fishery manager’s guidebook. FAO and Wiley-Blackwell:473-505.
Boom and Bust Population Cycle
Species that follow boom-and-bust cycles display high volatility in their population dynamics. This means that their availability is sudden, extreme, and unpredictable.
Source: FishPath Team
Bycatch
Part of a catch of a fishing unit taken incidentally in addition to the target species towards which fishing effort is directed. Some or all of it may be returned to the sea as discards, usually dead or dying
Source: Modified from FAO (1998): Guidelines for the routine collection of capture fishery data
Capital Stuffing
Costly investments in vessel or gear improvements, to outcompete others for a larger share of available fish. This often leads to higher levels of catch than those intended by managers.
Source: Townsend, R. E. (1985). On capital-stuffing in regulated fisheries. Land Economics, 61(2), 195. https://doi.org/10.2307/3145812
via Anderson CM, Krigbaum MJ, Arostegui MC, et al. How commercial fishing effort is managed. Fish Fish. 2018;00:1–18. https://doi.org/10.1111/faf.12339
Carrying Capacity (K)
The maximum population of a species that a specific ecosystem can support indefinitely without deterioration of the character and quality of the resource. It represents the point of balance between reproduction potential and environmental constraints.
Source: Scialabba N. (ed.), 1998. Integrated Coastal Area Management and Agriculture, Forestry and Fisheries. FAO Guidelines, 256p.
Catch-Per-Unit-Effort (CPUE)
Catch-per-unit-effort (CPUE) is the quantity of fish caught (in number or in weight) with one standard unit of fishing effort; e.g. number of fish taken per 1,000 hooks per day or weight of fish, in tons, taken per hour of trawling. CPUE is often considered an index of fish biomass (or abundance). CPUE is sometimes referred to as catch rate, and may be used as a measure of economic efficiency of fishing as well as an index of fish abundance.
Source: Modified from FAO (1998a): Guidelines for the routine collection of capture fishery data. FAO Fisheries Technical Paper. No. 382. Rome, FAO. 113p.
Determinate Growth
Determinate growth means that the species does not grow indefinitely. The species stops growing once reaching a final adult stage.
Source: FishPath Team
Economic Overfishing
Occurs when a fishery is generating no economic rent, primarily because an excessive level of fishing effort is applied in the fishery and does not always imply biological overfishing.
Source: FAO Fisheries and Aquaculture Department, FAO, 2014.
Ecosystem Overfishing
Occurs when the historical species balance (composition and dominance) is significantly modified by fishing (e.g. with reductions of large, long-lived, demersal predators and increases of small, short-lived species at lower trophic levels).
Source: FAO Fisheries and Aquaculture Department, FAO, 2014.
Effort Creep
Effort creep refers to an increase in effort effectiveness owing to technological progress. These progressions increase the productivity of fishing power, therefore increasing the effective effort. For example, although the number of vessels may be regulated, an increasing number of hooks per vessel or increasing vessel fuel efficiency may demonstrate effort creep.
Source: Squires, Dale, et al. “Effort rights in fisheries management: general principles and case studies from around the world.” Effort rights in fisheries management: General principles and case studies from around the world. Food and Agriculture Organization of the United Nations, 2016.
Fecundity
Fecundity is the potential reproductive capacity of an organism or population expressed in the number of eggs (or offspring) produced during each reproductive cycle. Fecundity usually increases with age and size.
Fishery
A unit determined by an authority or other entity that is engaged in raising and/or harvesting fish. Typically, the unit is defined in terms of some or all of the following: people involved, species or type of fish, area of water or seabed, method of fishing, class of boats and purpose of the activities.
Source: Fletcher, W.J., Chesson, J. Fisher, M., Sainsbury K.J., Hundloe, T. Smith A.D.M., and B. Whitworth (2002): National ESD reporting framework for Australian fisheries: The “How To” guide for wild capture fisheries. FRDC Project 2000/145. Canberra, Australia
Fishery-Dependent Data
Data collected directly on a fish or fishery from commercial or sport fishermen and seafood dealers. Common methods include logbooks, trip tickets, port sampling, fishery observers, and phone surveys.
Fishery-Independent Data
Characteristic of information (e.g. stock abundance index) or an activity (e.g. research vessel survey) obtained or undertaken independently of the activity of the fishing sector. Intended to avoid the biases inherent to fishery-related data.
Fishery Effort
The amount of fishing gear of a specific type used on the fishing grounds over a given unit of time for example 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.
Source: FAO. 1997. Fisheries management. FAO Technical Guidelines for Responsible Fisheries No. 4. Rome, FAO. 82p.
Fishing Mortality (F)
The instantaneous rate of fish deaths due to fishing a component of the fish stock. F reference points may be applied to entire stocks or segments of the stocks.
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. Growth overfishing, by itself, does not affect the ability of a fish population to replace itself.
Source: FAO Fisheries and Aquaculture Department, FAO, 2014.
Harvest Control Rule (HCR)
Also “decision rule”. A formally defined, usually quantitative rule, that is used to adjust a management measure in reponse to some known or inferred status of the fished stock. The strength of adjustment of the management measure is usually some function of a performance measure - that is, the proximity of a performance indicator to a target or limit reference point.
Source: FishPath Team
Harvest Strategy
Also “management strategy”. A harvest (or management) strategy is a formal, pre-specified set of rules designed to achieve the management objectives for the fishery. Harvest strategies (HSs) are formal frameworks for managing exploitation of fisheries, usually applied to the target species (e.g. Sainsbury et al. 2000, Butterworth and Punt 2003). They comprise a fully-specified set of rules for making tactical management decisions including specifications for i) a monitoring (data collection) program, ii) the indicators to be calculated from monitoring data (usually via a stock assessment) and iii) the use of those indicators and their associated reference points in management decisions, through application of decision (or control) rules.
Sources: Butterworth, D.S., and Punt, A.E. 2003. The role of harvest control laws, risk and uncertainty and the precautionary approach in ecosystem-based management. Responsible Fisheries in the Marine Ecosystem: 311-319.
Sainsbury, K.J., Punt, A.E., and Smith, A.D.M. 2000. Design of operational management strategies for achieving fishery ecosystem objectives. ICES Journal of Marine Science 57: 731-741.
Illegal, unregulated, and unreported (IUU) Fishing
Reference to broad activities classified as illegal, unreported and unregulated fishing are included in the IPOA-IUU as follows:
Illegal fishing:
-conducted by national or foreign vessels in waters under the jurisdiction of a State, without the permission of that State, or in contravention of its laws and regulations; -conducted by vessels flying the flag of States that are parties to a relevant regional fisheries management organisation but operate in contravention of the conservation and management measures adopted by that organisation and by which the States are bound, or relevant provisions of the applicable international law; or -in violation of national laws or international obligations, including those undertaken by cooperating States to a relevant regional fisheries management organization.
Unreported fishing:
-which have not been reported, or have been misreported, to the relevant national authority, in contravention of national laws and regulations; or -are undertaken in the area of competence of a relevant regional fisheries management organisation which have not been reported or have been misreported, in contravention of the reporting procedures of that organisation.
Unregulated fishing:
-in the area of application of a relevant regional fisheries management organization that are conducted by vessels without nationality, or by those flying the flag of a State not party to that organization, or by a fishing entity, in a manner that is not consistent with or contravenes the conservation and management measures of that organization; or -in areas or for fish stocks in relation to which there are no applicable conservation or management measures and where such fishing activities are conducted in a manner inconsistent with State responsibilities for the conservation of living marine resources under international law.
Source: http://www.fao.org/iuu-fishing/background/what-is-iuu-fishing/en/
Indicators
A variable, pointer, or index. Its fluctuation reveals the variations in key elements of a system. The position and trend of the indicator in relation to reference points or values indicate the present state and dynamics of the system. Indicators provide a bridge between objectives and action.
Source: FAO (1999): Indicators for sustainable development of marine capture fisheries. FAO Technical Guidelines for Responsible Fisheries, 8: 68 p. Rome, FAO
Intrinsic growth rate (r)
A value that quantifies how much a population can grow between successive time periods. The intrinsic growth rate is often estimated with production models and plays an important role in evaluating the sustainability of different harvest levels and the capacity to recover after depletion.
Source: Restrepo V. (1999): Annotated Glossary of Terms in Executive Summary Reports of the International Commission for the Conservation of Atlantic Tunas Standing Committee on Research and Statistics (SCRS). ICCAT.
Latent effort
Fishing capacity that is authorised for use but not currently being used. Depending on how a fishery is managed, latency might appear in effort (for example, unused vessel statutory fishing rights [SFRs], gear SFRs, quota SFRs, permits or nights fishing) or in quota (for example, where total allowable catches [TACs] are not fully caught in a quota-managed fishery). It can be an indicator of fishers’ views about the profitability of a fishery, with high levels of latency suggesting that low expected profits in the fishery do not justify fishing.
Length-weight relationship
A mathematical formula for calculating the weight of a fi sh in terms of its length. When only one is known, the formula can determine the other
Limit reference point
Indicates the limit beyond which the state of a fishery and / or a resource is not considered desirable. Fishery development should be stopped before reaching it. If a LRP is inadvertently reached, management action should severely curtail or stop fishery development, as appropriate, and corrective action should be taken.
Source: Garcia S.M. (1996)The precautionary approach to fisheries and its implications for fishery research, technology and management: An updated review. FAO Fisheries Technical Paper, 350.2: 1-76
“Live” Fishery
A “live” fishery refers to a fishery where species are captured or harvested alive. This may be done for human consumption or the aquarium trade, for example.
Source: FishPath Team
Management Strategy
See Harvest Strategy
Maturity ogive
The curve resulting from the proportion of mature fish at a given size or length.
Source: FishPath Team
Maximum sustainable yield (MSY)
The highest theoretical equilibrium yield that can be continuously taken (on average) from a stock under existing (average) environmental conditions without affecting significantly the reproduction process.
Source: FAO Fisheries and Aquaculture Department, FAO, 2014.
Metapopulation
A population that consists of a series of physically separate subpopulations linked by dispersal. Metapopulations persist as a result of a balance between extinctions of subpopulations and recolonization of habitat patches (and hence reestablishment of subpopulations).
Multispecies fishery
A multispecies fishery is a fishery in which more than one species is caught at the same time. Because of the imperfect selectivity of most fi shing gears, most fisheries are “multispecies.” The term is often used to refer to fisheries where more than one species is intentially sought and retained.
Natural mortality (M)
Deaths of fish from all causes except fishing (e.g. ageing, predation , cannibalism, disease and perhaps increasingly pollution). It is often expressed as a rate that indicates the percentage of fish dying in a year; for example a natural mortality rate of 0.2 implies that approximately 20% of the population will die in a year from causes other than fishing.
Source: FAO Fisheries and Aquaculture Department, FAO, 2014.
No-take reserve
Areas where extractive activities are prohibited
Sala, E., and Giakoumi, S. 2017. No-take marine reserves are the most effective protected areas in the ocean. – ICES Journal of Marine Science, 75: 1166–1168.
Nursery
Nursery refers to the part of a fish’s or animal’s habitat where the young develop and grow.
Open Access
Any fishery that does not limit effort or inclusion in the fishery. A fishery without permits or one with unlimited permits are both examples of an open access fishery.
Source: FishPath Team
Overfished
A stock is considered overfished when exploited beyond an explicit limit beyond which its abundance is considered “too low” to ensure safe reproduction. In many fisheries fora the term is used when biomass has been estimated to be below a limit biological reference point that is used as the signpost defining an “overfished condition”.
Source: Mace, P.M. 1998. The status of ICCAT species relative to optimum yield and overfishing criteria recently proposed in the United States, also with consideration of the precautionary approach. ICCAT SCRS/97/074.
Overfishing
A generic term used to refer to the state of a stock subject to a level of fishing effort or fishing mortality such that a reduction of effort would, in the medium term, lead to an increase in the total catch. Often referred to as overexploitation and equated to biological overfishing, it results from a combination of growth overfishing and recruitment overfishing and occurs often together with ecosystem overfishing and economic overfishing.
Source: Garcia, S.M. (Comp.). 2009. Glossary. In Cochrane, K. and S.M. Garcia. (Eds). A fishery manager’s guidebook. FAO and Wiley-Blackwell:473-505.
Periodic strategist
Periodic strategists are characterized by large body size, late maturation, high fecundity, and low juvenile survivorship and are likely to be favored in highly periodic (seasonal) environments
Source: Mims, M.C. and Olden, J.D., 2012. Life history theory predicts fish assemblage response to hydrologic regimes. Ecology, 93(1), pp.35-45.
Recruitment
The number of fish added to the exploitable stock, in the fishing area, each year, through a process of growth (i.e. the fish grows to a size where it becomes catchable) or migration (i.e. the fish moves into the fishing area).
Source: Garcia, S.M. (Comp.). 2009. Glossary. In Cochrane, K. and S.M. Garcia. (Eds). A fishery manager’s guidebook. FAO and Wiley-Blackwell:473-505.
Recruitment Overfishing
A situation in which the rate of fishing is (or has been) such that annual recruitment to the exploitable stock has become significantly reduced. The situation is characterized by a greatly reduced spawning stock, a decreasing proportion of older fish in the catch, and generally very low recruitment year after year. If prolonged, recruitment overfishing can lead to stock collapse, particularly under unfavourable environmental conditions.
Source: Restrepo, V. 1999. Annotated Glossary of Terms in Executive Summary Reports of the International Commission for the Conservation of Atlantic Tunas Standing Committee on Research and Statistics SCRS). ICCAT, Madrid, Spain.
Reference Points
An estimated value derived from an agreed scientific procedure and/or model, which corresponds to a specific state of the resource and of the fishery, and that can be used as a guide for fisheries management. Reference points may be general (applicable to many stocks) or stock-specific.
Source: Garcia, S.M. 1997. Indicators for sustainable development in fisheries. In: FAO (1997). Land Quality indicators and their use in sustainable agriculture and rural development, 131-162.
Relative abundance
Relative abundance is an estimate of actual or absolute abundance; usually stated as some kind of index; for example, as bottom trawl survey stratified mean catch per tow.
Removals
All of the fish “removed” from a stock by fishing, including the catch and any fish killed but not caught
Source: Gough, J. and T. Kenchington (1995), A Glossary of Fisheries Science. Communications Branch, DFO, Nova Scotia
Sector/Fleet
A physical group of vessels and/or fishers sharing similar characteristics in terms of technical features and/or major activity
Source: https://www.ices.dk/community/Documents/Advice/Acronyms_and_terminology.pdf
Selectivity
Ability to target and capture fish by size and species during harvesting operations, allowing by-catch of juvenile fish and non-target species to escape unharmed. In stock assessment, conventionally expressed as a relationship between retention and size (or age) with no reference to survival after escapement.
Source: Garcia, S.M. (Comp.). 2009. Glossary. In Cochrane, K. and S.M. Garcia. (Eds). A fishery manager’s guidebook. FAO and Wiley-Blackwell:473-505.
Steepness
Stock recruitment steepness is a measure of fish productivity. It is used in the stock-recruitment function, the relationship between the stock’s adult spawning biomass and the corresponding production of young fish (recruitment). Steepness is the ratio of 2 recruitment levels: the recruitment obtained when the spawning stock is at 20% of its virgin level, and the recruitment at the virgin population level (e.g. the population in the absence of fishing). The higher the steepness, the more resilient the population is, the more robust the stock is to harvesting, and the sooner the stock is likely to rebuild after fishing pressure is relaxed.
Source: https://www.pifsc.noaa.gov/qrb/2011_06/article_08.php
Stock
A group of individuals in a species occupying a well defined spatial range independent of other stocks of the same species. Random dispersal and directed migrations due to seasonal or reproductive activity can occur. Such a group can be regarded as an entity for management or assessment purposes. Some species form a single stock (e.g. southern bluefin tuna) while others are composed of several stocks (e.g. albacore tuna in the Pacific Ocean comprises separate Northern and Southern stocks). The impact of fishing on a species cannot be determined without knowledge of this stock structure.
In theory, a Unit Stock comprises all the individuals of fish in an area, which are part of the same reproductive process. It is self-contained, with no emigration or immigration of individuals from or to the stock. On practical grounds, however, a fraction of the unit stock is considered a ““stock”” for management purposes (or a management unit), as long as the results of the assessments and management remain close enough to what they would be on the unit stock.
Source: Comonwealth of Australia (1997): http://www.brs.gov.au/fish/gloss.html
Stock Abundance
Degree of plentifulness. The total number of fish in a population or on a fishing ground. Can be measured in absolute or relative terms.
Source: FAO Fisheries and Aquaculture Department, FAO, 2014.
Target reference point
Corresponds to a state of a fishery and / or a resource which is considered desirable. Management action, whether during a fishery development or a stock rebuilding process should aim at bringing and maintaining the fishery system at this level.
Source: Garcia S.M. (1996)The precautionary approach to fisheries and its implications for fishery research, technology and management: An updated review. FAO Fisheries Technical Paper, 350.2: 1-76
Trigger reference point
Trigger reference points (TRPs) are levels of an indicator, usually a stock status indicator, at which a change in management is considered or adopted. Trigger reference points play a particularly important role in harvest decision rules, where they identify a point (such as a biomass level) at which a substantial change in the exploitation rate occurs (Sloan et al. 2014). Trigger points can be used in two ways in harvest strategies. Where useful indicators have been identified, they are values of those indicators that correspond to some important change in how the fishery is managed (a change in the decision rule). The second use of trigger points is in fisheries where it has not been possible to identify useful indicators (Dichmont et al. 2011). These triggers would be levels of catch or effort that signal the need to collect more information on the fishery to allow the development of useful indicators.
Sources: Dichmont, C.M., Dowling, N.A., Smith, A.D.M., Smith, D.C., and Haddon, M. 2011. Guidelines on developing harvest strategies for data-poor fisheries. CSIRO Marine and Atmospheric Research, Hobart, Australia. 27pp
Sloan, S., Smith, T., Gardner, C., Crosthwaite, K., Triantafillos, L., Jeffries, B. and Kimber, N. 2014. National guidelines to develop fishery harvest strategies. FRDC Report – Project 2010/061. Primary Industries and Regions, South Australia, Adelaide, March. CC BY 3.0