Appendix - Acronyms and Units - Glossary

Comparison of stock status classifications between the Fishery status reports (for Commonwealth fisheries) and the Status of Australian fish stocks reports (for all states and territories with wild-capture fisheries)

Fishery status reports

Status of Australian fish stocks reports


Fishing mortality

Stock status

Not overfished


Not subject to overfishing





Not subject to overfishing


Recovering a

Not overfished


Subject to overfishing





Subject to overfishing


Depleted b

Uncertain if overfished


Uncertain if subject to overfishing



a For a stock to be considered ‘recovering’ in the national reports, there must be evidence that the biomass is recovering (that is, increasing). b If the Fishery status reports classify a stock as ‘overfished’ and ‘not subject to overfishing’ but there is no evidence that biomass is recovering, it would be considered as ‘depleted’ in the national reports rather than ‘recovering’.

Note: The Status of Australian fish stocks reports 2018 includes an additional classification of ‘negligible’. This is described as when catches are so low as to be considered negligible and inadequate information exists to determine stock status. In such case, no assessment is conducted unless catches and information increase. No such equivalent classification is used in the Fishery status reports.

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Acronyms and units


Australian Antarctic Division


Australian Bureau of Agricultural and Resource Economics and Sciences


Australian Fisheries Management Authority


Australian Fishing Zone


a stock production model incorporating covariates


Bayesian biomass dynamic model


Bass Strait Central Zone Scallop Fishery


Bayesian state-space production model


Commission for the Conservation of Antarctic Marine Living Resources


Commission for the Conservation of Southern Bluefin Tuna


confidence interval


conservation and management measure




Coral Sea Fishery


Commonwealth Scientific and Industrial Research Organisation


Commonwealth Trawl Sector (of the SESSF)


coefficient of variation


daily egg production method


East Coast Deepwater Trawl Sector (of the SESSF)


Exclusive Economic Zone


Environment Protection and Biodiversity Conservation Act 1999 (Cth)


ecological risk assessment


Eastern Skipjack Tuna Fishery


Eastern Tuna and Billfish Fishery


Food and Agriculture Organization of the United Nations

FM Act

Fisheries Management Act 1991


Fisheries Research and Development Corporation


Great Australian Bight Resource Assessment Group


Great Australian Bight Trawl Sector (of the SESSF)


Gillnet, Hook and Trap Sector (of the SESSF)


gross value of production


Heard Island and McDonald Islands


Heard Island and McDonald Islands Fishery


harvest strategy framework


Commonwealth Fisheries Harvest Strategy Policy


Indian Ocean Tuna Commission


Integrated Scientific Monitoring Program


individual transferable quota


illegal, unreported and unregulated (fishing)


joint authority fisheries


limit reference point


maximum economic yield


Macquarie Island Toothfish Fishery


memorandum of understanding


management strategy evaluation


maximum sustainable yield


multiyear total allowable catch


net economic returns


Northern Prawn Fishery


Northern Prawn Resource Assessment Group


Northern Territory Fisheries Joint Authority


North West Slope Trawl Fishery


Orange Roughy Conservation Programme


Orange Roughy Rebuilding Strategy


Papua New Guinea


Torres Strait Protected Zone Joint Authority


Queensland Fisheries Joint Authority


Resource Assessment Group


recommended biological catch


regional fisheries management organisation


spawning biomass


Southern Bluefin Tuna Fishery


statistical catch-at-age model


standard error


South East Resource Assessment Group


Southern and Eastern Scalefish and Shark Fishery


South East Trawl Fishing Industry Association


statutory fishing right


Shark Gillnet and Shark Hook sectors (of the SESSF)


Shark Resource Assessment Group


Shelf Resource Assessment Group


Scalefish Hook Sector (of the SESSF)


Southern Indian Ocean Fisheries Agreement


Small Pelagic Fishery


spawning potential ratio


South Pacific Regional Fisheries Management Organisation


Stock Synthesis 3


Southern Squid Jig Fishery


small-scale research unit


Skipjack Tuna Fishery


South Tasman Rise


South Tasman Rise Trawl Fishery


south-west Pacific Ocean


total allowable catch


total allowable commercial catch


total allowable effort


Traditional Inhabitant Boat (sector)


Tropical Rock Lobster Resource Assessment Group


Torres Strait Bêche-de-mer Fishery


Torres Strait Finfish Fishery


Torres Strait Finfish (Reef Line) Fishery


Torres Strait Prawn Fishery


Torres Strait Protected Zone


Torres Strait Spanish Mackerel Fishery


Torres Strait Trochus Fishery


Torres Strait Tropical Rock Lobster Fishery


Tropical Tuna Resource Assessment Group


Transferable Vessel Holder


United Nations Convention on the Law of the Sea


Union of Soviet Socialist Republics


vulnerable marine ecosystem


Western Australia Joint Authority Northern Shark Fishery


West Coast Demersal Gillnet and Demersal Longline Managed Fishery


Western and Central Pacific Fisheries Commission


western and central Pacific Ocean


Western Deepwater Trawl Fishery


Western Skipjack Fishery


Western Tuna and Billfish Fishery



minutes of latitude or longitude (for example, 34˚20'S)


degrees Celsius

˚E, ˚N, ˚S, ˚W

degrees east, north, south, west











square kilometre






nautical mile


tonne (1,000 kg)

Year ranges


financial year or season

2017 or 2018;

calendar year



Acoustic survey. Systematic method of gathering information on the abundance of a species in a water body with the help of echo sounders and sonar, which use ultrasonic sound to detect the fish.

Aerial survey. Method of gathering information on movements and density of fish near the surface by visual observation and photography from low-flying aircraft.

Age–length (age–length key or curve). Relationship between age and length.

Age-structured assessment. Assessment of the status of a fish stock based on the relative abundances of fish of different ages in the stock.

Aggregation. Group of fish that come together, often to feed or spawn.

Aquaculture. Commercial growing of marine or freshwater animals and aquatic plants. Often called ‘fish farming’.

Area closure. Closure of a given area or fishing ground, often for a defined period. Used as a tool in the management of a fishery.

Artisanal fishing. Fishing for subsistence using traditional methods.

Australian Fishing Zone (AFZ). The area extending seaward of coastal waters (3 nautical miles from the territorial sea baseline) to the outer limits of the Exclusive Economic Zone (EEZ). In the case of external territories, such as Christmas Island, the AFZ extends from the territorial sea baseline to the outer limit of the EEZ. The AFZ is defined in the Fisheries Management Act 1991, which also specifies a number of ‘excepted waters’, notably in Antarctica and Torres Strait, that are excluded from the AFZ.

Autonomous adjustment. An ongoing structural adjustment process that occurs in all fisheries. As technologies and prices change, the characteristics of the fishing fleet required to maximise the net value from the fishery will also change. As a result, fishery fleet behaviour tends to change in line with market signals. The primary role for government in structural adjustment is to establish a management regime that removes any incentives that lead to overcapacity, and that facilitates autonomous adjustment in response to changing economic and biological conditions.


B (biomass). Total weight or volume of a stock or a component of a stock.

B0 (mean equilibrium unfished biomass). Average biomass level if fishing had not occurred.

BLIM (biomass limit reference point). Point beyond which the risk to the stock is regarded as unacceptably high.

BMEY (biomass at maximum economic yield). Average biomass that corresponds to maximum economic yield.

BMSY (biomass at maximum sustainable yield). Average biomass that corresponds to maximum sustainable yield.

BTARG (target biomass). Desired biomass of the stock.

Beach price. A price that would be received by fishers or aquaculture farmers per unit of whole-weight fish at the point of landing or farm gate. It excludes any margins for freight, marketing and processing.

Benthic. Associated with the bottom of a water body.

Beverton–Holt. Mathematical function that describes the relationship between stock size and recruitment.

Biodiversity. Biological diversity; variety among living organisms, including genetic diversity, diversity within and between species, and diversity within ecosystems.

Buyback. Purchase of fishing entitlements by the government to increase structural adjustment in a fishery.

Bycatch. A species that is incidentally (a) taken in a fishery and returned to the sea, or (b) killed or injured as a result of interacting with fishing equipment in the fishery, but not taken. Bycatch can include species listed under the Environment Protection and Biodiversity Conservation Act 1999.

Bycatch reduction device. A device that allows fish and other animals to escape immediately after being taken in or with fishing gear (for example, a trawl net).

Byproduct. A species taken incidentally in a fishery while fishing for another species but retained for sale because it has some commercial value, although less value than key commercial species.


Carapace. The exoskeleton covering the upper surface of the body of a crustacean.

Carapace length. In prawns, the distance from the posterior margin of the orbit to the mid-caudodorsal margin of the carapace; in lobster, the distance from the tip of the rostrum to the mid-caudodorsal margin of the carapace.

Catch. In relation to fishing, means capture, take or harvest.

Catch-at-age data. Data on the number of fish of each age group in the catch, usually derived from representative samples of the catch.

Catch curve. Method for estimating average recent fishing mortality, based on the age structure of the catch, biology of the species, total catch weight and selectivity of the fishing gear.

Catch-per-unit-effort (CPUE). The number or weight of fish caught by a unit of fishing effort. Often used as a measure of fish abundance.

Catch rate. See Catch-per-unit-effort (CPUE).

Catchability. The extent to which a stock is susceptible to fishing; quantitatively, the proportion of the stock removed by one unit of fishing effort.

Chondrichthyans. Fishes that have skeletons made of cartilage rather than bone. This group includes sharks and rays (elasmobranchs), and chimaeras (holocephalans).

Coastal waters. The waters extending 3 nautical miles from the territorial sea baseline. The states and the Northern Territory have jurisdiction over the coastal waters adjacent to them.

Codend. The closed end of a trawl net.

Cohort. Individuals of a stock born in the same spawning season.

Conservation-dependent species. The Environment Protection and Biodiversity Conservation Act 1999 dictates that a native species is eligible to be included in the conservation-dependent category at a particular time if, at that time, (a) the species is the focus of a specific conservation program the cessation of which would result in the species becoming vulnerable, endangered or critically endangered; or (b) the following subparagraphs are satisfied: (i) the species is a species of fish; (ii) the species is the focus of a plan of management that provides for management actions necessary to stop the decline of, and support the recovery of, the species so that its chances of long-term survival in nature are maximised; (iii) the plan of management is in force under a law of the Commonwealth or of a state or territory; and (iv) cessation of the plan of management would adversely affect the conservation status of the species.

Continental shelf. Either the area of relatively shallow water that fringes a continent from the shoreline to the top of the continental slope (the top of the continental slope is often defined by the 200 m isobath), or a defined maritime zone that comprises the continental shelf where it extends beyond the limit of the Exclusive Economic Zone to the limit of the continental margin. The defined maritime zone is also sometimes referred to as the ‘extended continental shelf’, and its limit is determined by the United Nations Commission on the Limits of the Continental Shelf.

Continental slope. Region of the outer edge of a continent between the relatively shallow continental shelf and the abyssal depths; often characterised by a relatively steep slope.

Control rules. See Harvest control rules.


Daily egg production method (DEPM). A method of estimating the spawning biomass of a fish population from the abundance and distribution of eggs and/or larvae.

Danish-seining. A trawling method used by relatively small vessels in shallow waters (up to about 200 m). Lengths of weighted ropes of up to 2,800 m are laid out on the sea floor in a diamond pattern, with the vessel at one end of the diamond and the net at the other. As the vessel moves forward, bringing in the net, the diamond becomes elongated, allowing the fish to be herded into the path of the net (c.f. Purse seining).

Decision rules. See Harvest control rules.

Delay-difference model. Type of population model that incorporates age structure.

Demersal. Found on or near the benthic habitat (c.f. Pelagic).

Demersal trawling. Trawling with gear designed to work on or near the seabed. Such gear is used to take demersal species of fish and prawns.

Depletion (stock depletion). Reduction in the biomass of a fish stock.

Discarding. The practice of returning any part of the catch, whether dead or alive, to the sea. In Commonwealth fisheries, the term ‘discard’ is predominantly used to refer to commercial species that are not retained.

Domestic fishery. Fishery within the Australian Fishing Zone operated by Australian-flagged vessels.

Driftnet. Gillnet suspended by floats so that it fishes the top few metres of the water column. See also Gillnet.

Dropline. Fishing line with one or more hooks, held vertically in the water column with weights.


EMSY. Effort that supports maximum sustainable yield.

Ecologically sustainable development. Using, conserving and enhancing the community’s resources so that ecological processes are maintained and the total quality of life, now and in the future, can be increased.

Economic efficiency. A fishery is economically efficient when fishery-level efficiency and vessel-level efficiency are achieved, and management costs are as low as they can be while still providing the necessary level of management. Fishery-level and vessel-level efficiency means that effort is restricted to the point where the difference between fishing revenue and cost is greatest, and fishers are applying that level of effort at least cost.

Economic profit (profitability). See Profit, economic.

Ecosystem. A complex of plant, animal and microorganism communities that, together with the non-living components, interact to maintain a functional unit.

Effort. A measure of the resources used to harvest a fishery’s stocks. The measure of effort appropriate for a fishery depends on the methods used and the management arrangements. Common measures include the number of vessels, the number of hooks set, and the number of fishing days or nights.

Effort restriction. Restriction of the permitted amount of fishing effort (for example, total number of hooks) in a fishery; used as a management tool.

Egg survey. Systematic gathering of information on the occurrence and abundance of fish eggs and larvae by collecting them in nets and traps.

Endangered species. Species in danger of extinction because of its low numbers or degraded habitat, or likely to become so unless the factors affecting its status improve. The Environment Protection and Biodiversity Conservation Act 1999 dictates that a native species is eligible to be included in the endangered category at a particular time if, at that time, (a) it is not critically endangered, and (b) it is facing a very high risk of extinction in the wild in the near future, as determined in accordance with the prescribed criteria.

Endemic species. Species that occurs naturally and exclusively in a given place.

Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act). The central piece of Commonwealth environmental legislation. It provides a legal framework to protect and manage nationally and internationally important flora, fauna, ecological communities and heritage places—defined in the EPBC Act as matters of national environmental significance. Parts 10, 13 and 13A relate specifically to aspects of fisheries.

EPBC Act–listed species. All species protected under part 13 of the EPBC Act, including whales and other cetaceans, and listed threatened, marine and migratory species (except for conservation-dependent species, which are managed through rebuilding strategies under the Harvest Strategy Policy).

Escapement. The number, expressed as a percentage, of fish that survive an event (for example, predation, natural mortality, fishing mortality), often to spawn.

Exclusive Economic Zone (EEZ). The area that extends from the limit of the territorial sea, which is 12 nautical miles offshore from the territorial sea baseline, to a maximum of 200 nautical miles, measured from the territorial sea baseline. The EEZ is less than 200 nautical miles in extent where it coincides with the EEZ of another country. In this case, the boundaries between the two countries are defined by treaty. Within its EEZ, Australia has sovereign rights and responsibilities over the water column and the seabed, including the exploration and exploitation of natural resources.

Exploitation rate. The fraction of total animal deaths caused by fishing, usually expressed as an annual value. Can also be defined as the proportion of a population caught during a year.


F (fishing mortality). The instantaneous rate of fish deaths due to fishing a designated component of the fish stock. F reference points may be applied to entire stocks or segments of stocks and should match the scale of management unit. Instantaneous fishing mortality rates of 0.1, 0.2 and 0.5 are equivalent to 10%, 18% and 39% of deaths of a stock due to fishing. See also M (natural mortality), Mortality.

FCurr. Current level of fishing mortality.

FLIM (fishing mortality limit reference point). Point above which the removal rate from the stock is too high.

FMEY (fishing mortality at maximum economic yield). Fishing mortality rate that corresponds to maximum economic yield.

FMSY (fishing mortality at maximum sustainable yield). Fishing mortality rate that achieves maximum sustainable yield.

FTARG (fishing mortality target). Target fishing mortality rate.

Farm-gate value. See Beach price.

Fecundity. Number of eggs an animal produces each reproductive cycle; the potential reproductive capacity of an organism or population.

Fisheries Management Act 1991. One of two main pieces of legislation (the other is the Fisheries Administration Act 1991) that details the responsibilities and powers of the Australian Fisheries Management Authority. The Act sets out, among other things, fisheries management objectives and arrangement for regulating, permitting and taking enforcement action with respect to fishing operations.

Fishery-independent survey. Systematic survey by research vessels or contracted commercial fishing vessels to gather information independently of normal commercial fishing operations.

Fishing capacity. Total fishing effort that can be expended by a fleet operating in a fishery.

Fishing down (fish-down). Fishing mortality above FMSY for a stock that is above a biomass target, with the intention of reducing the biomass to the target.

Fishing effort. Amount of fishing taking place, usually described in terms of gear type and the frequency or period of operations (for example, hooks, trawl-hours, net length).

Fishing power. Effectiveness of a vessel’s fishing effort relative to that of other vessels or in other periods of time.

Fishing season. The period during which a fishery can be accessed by fishers. Sometimes referred to as a fishing year.

Fishmeal. Protein-rich animal feed made of fish or fish waste.

Free-diving. Diving without the assistance of breathing apparatus. Gear used may include a snorkel, face mask, flippers, weight belt and wetsuit.


Gear restriction. Restriction on the amount and/or type of fishing gear that can be used by fishers in a fishery; used as a management tool.

Generation time. Average time taken for an individual animal to replace itself in a population.

Gillnet. Type of passive fishing gear consisting of panels of net held vertically in the water column, either in contact with the seabed or suspended from the sea surface, such that fish attempting to swim through the net are entangled. The mesh size of the net determines the size range of fish caught, because smaller fish can swim through the meshes and larger fish are not enmeshed. See also Driftnet.

Gross value of production (GVP). A value obtained by multiplying the volume of catch (whole-weight equivalent) by the average per-unit beach price. In the case of a multispecies fishery, the fishery’s GVP is the sum of the GVPs of each species.

Grow-out cage. Pontoons supporting cages in which wild-caught fish are fattened until they reach marketable size.

Growth overfishing. Occurs when fish are harvested at an average size that is smaller than the size that would produce the maximum yield per recruit. This makes the total yield less than it would be if the fish were allowed to grow to an appropriate size. The annual yield is therefore smaller than the maximum sustainable yield.


Handline. Hand-held lines of various types used to catch fish.

Harvest control rules. Predetermined rules that control fishing activity according to the biological and economic conditions of the fishery (as defined by monitoring or assessment). Also called ‘decision rules’ or ‘control rules’. Harvest control rules are a key element of a harvest strategy.

Harvest strategy. Strategy outlining how the catch in a fishery will be adjusted from year to year depending on the size of the stock, the economic or social conditions of the fishery, conditions of other interdependent stocks or species, and uncertainty of biological knowledge. Well-managed fisheries have an unambiguous (explicit and quantitative) harvest strategy that is robust to the unpredictable biological fluctuations to which the stock may be subject.

Headrope (headline). In a trawl, the length of rope or wire to which the top wings and cover netting are attached.

High grading. A type of discarding motivated by an output control system. Depending on the costs of fishing, and price differences between large and small fish of the same species, fishers may have an incentive to discard small, damaged or relatively low-value catch so that it does not count against their quota. They then hope to fill the quota with higher-value fish.

High seas. Waters outside national jurisdictions—that is, outside Exclusive Economic Zones.

Highly migratory stock. Refers to fish species or stocks that carry out extensive movement or migrations and can occur in both Exclusive Economic Zones and high seas. This term is usually used to denote tuna and tuna-like species, marlins and swordfish.

Hookah. Underwater breathing apparatus consisting of an onboard air compressor and an air-supply tube attached to a diver’s mouthpiece or helmet.


Index of abundance. Relative measure of the abundance of a stock (for example, catch per unit of effort).

Individual transferable effort. Shares of a total allowable effort that are allocated to individuals. They can be traded permanently or temporarily. Analogous to individual transferable quotas in a fishery managed with a total unit allowable catch. Usually issued at the start of a fishing season.

Individual transferable quota (ITQ). Management tool by which portions of the total allowable catch quota are allocated to fishers (individuals or companies). The fishers have long-term rights over the quota but can trade quota with others. See also Quota.

Input controls. Management measures that place restraints on who fishes (licence limitations), where they fish (closed areas), when they fish (closed seasons) or how they fish (gear restrictions).

Inshore waters. Waters of the shallower part of the continental shelf, usually less than 3 nautical miles from the coast.

Isobath. Contour line linking points of the same depth.


Jig. Vertical line with lures, which is moved up and down, or jigged, by hand or machine.

Joint authority. An Offshore Constitutional Settlement arrangement whereby a fishery is managed jointly by the Australian Government and one or more states or territories under a single (Commonwealth, or state or territory) jurisdiction.

Joint venture. Collaborative fishing operation, usually involving two companies from different countries.


Key commercial species. A species that is, or has been, specifically targeted and is, or has been, a significant component of a fishery.

Key threatening process. Defined under the Environment Protection and Biodiversity Conservation Act 1999 as a process that threatens the survival, abundance or evolutionary development of a native species or ecological community, requiring the formal development of a threat abatement plan. A threatening process is eligible to be treated as a key threatening process if (a) it could cause a native species or an ecological community to become eligible for listing in any category, other than conservation-dependent, or (b) it could cause a listed threatened species or a listed threatened ecological community to become eligible to be listed in another category representing a higher degree of endangerment, or (c) it adversely affects two or more listed threatened species (other than conservation-dependent species), or two or more listed threatened ecological communities.


Latency. Fishing capacity that is authorised for use but is 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 are not fully caught in a quota-managed fishery). It is a low-cost indicator of fishers’ views about the profitability of a fishery. High levels of latency can suggest that low expected profits in the fishery do not justify fishing.

Length-frequency distribution; modal size. The number of individuals in a catch or catch sample in each group of lengths (length intervals). The modal size is the length group into which most individuals fall. Some distributions may show several modes, reflecting fish of different ages.

Limit reference point. The level of an indicator (such as biomass or fishing mortality) beyond which the risk to the stock is regarded as unacceptably high.

Limited-entry fishery. Fishery in which the fishing effort is controlled by restricting the number of operators. Usually requires controlling the number and size of vessels, the transfer of fishing rights and the replacement of vessels (c.f. Open-access fishery).

Line fishing. Fishing methods that use fishing lines, including handlines, hand reels, powered reels, pole and line, droplines, longlines, trotlines and troll lines.

Logbook. Official record of catch-and-effort data completed by fishers. In many fisheries, a licence condition makes the return of logbooks mandatory.

Longline. Fishing gear in which short lines (branch lines, snoods or droppers) carrying hooks are attached to a longer mainline at regular intervals. Pelagic longlines are suspended horizontally at a predetermined depth with the help of surface floats. The mainlines can be 100 km long and have several thousand hooks. Droppers on demersal longlines (set at the seabed with weights) are usually more closely spaced.


M (natural mortality). Deaths of fish from all natural causes. Usually expressed as an instantaneous rate or as a percentage of fish dying in a year. See also F (fishing mortality), Mortality.

Mainline. Longline fishing gear consisting of a mainline kept near the surface or at a particular depth by means of regularly spaced floats or weights. Branch lines (snoods) with baited hooks are attached to the mainline at regular intervals.

Management strategy evaluation (MSE). A procedure whereby management strategies are tested and compared using simulations of stock and fishery dynamics.

Markov chain Monte Carlo (MCMC). As applied in stock assessment, Markov chain Monte Carlo statistical methods are a class of algorithms for sampling from probability distributions around the inputs, based on constructing a Markov chain that has the desired distribution as its equilibrium distribution. The state of the chain after a large number of steps is then used as a sample of the output distribution of the parameters explored.

Maximum economic yield (MEY). The sustainable catch level for a commercial fishery that allows net economic returns to be maximised. For most practical discount rates and fishing costs, MEY implies that the equilibrium stock of fish is larger than that associated with maximum sustainable yield (MSY). In this sense, MEY is more environmentally conservative than MSY and should, in principle, help to protect the fishery from unfavourable environmental impacts that could diminish the fish population.

Maximum sustainable yield (MSY). The maximum average annual catch that can be removed from a stock over an indefinite period under prevailing environmental conditions. MSY defined in this way makes no allowance for environmental variability, and studies have demonstrated that fishing at the level of MSY is often not sustainable.

Migration. Non-random movement of individuals of a stock from one place to another, often in groups.

Minimum size. Size below which a captured animal may not legally be retained. Usually specified by species. May be varied as a management tool.

Minor line. Term adopted by the Australian Fisheries Management Authority to refer to several line-fishing methods, including trolling, and fishing using a rod and reel, handline, or pole and line.

Modal size. See Length-frequency distribution.

Model (population). Hypothesis of how a population functions; often uses mathematical descriptions of growth, recruitment and mortality.

Mortality. Deaths from all causes (usually expressed as a rate or as the proportion of the stock dying each year).

MULTIFAN–CL. A length-based, age-structured model for assessing fishery stocks.


Nautical mile (nm). A unit of distance derived from the angular measurement of 1 minute of arc of latitude, but standardised by international agreement as 1,852 m.

Neritic. Designating, or of, the ecological zone (neritic zone) of the continental shelf, extending from low tide to a depth of around 180 m.

Net economic returns (NER). A fishery’s NER over a particular period are equal to fishing revenue less fishing costs. Fishing costs include the usual accounting costs of fuel, labour, and repairs and maintenance, as well as various economic costs such as the opportunity cost of owner labour and capital (c.f. Opportunity cost). The concept of NER is very closely related to economic efficiency, a necessary condition for NER to be maximised.

Non-detriment finding. Relating to a species listed in an appendix of the Convention on International Trade in Endangered Species (CITES), a conclusion by a scientific authority that the export of specimens of the species will not negatively affect the survival of that species in the wild. A non-detriment finding is required before an export or import permit, or a certificate for an introduction from the sea may be granted for a specimen of an Appendix-I species, and before an export permit or a certificate for an introduction from the sea may be granted for a specimen of an Appendix-II species.

Non-target species. Species that is unintentionally taken by a fishery or not routinely assessed for fisheries management. See also Bycatch, Byproduct.

Not overfished. See Overfished.


Oceanic. Open-ocean waters beyond the edge of the continental shelf.

Offshore Constitutional Settlement (OCS). The 1982 package of uniform national, state and territory laws that forms the basis for Australian governments at those levels to enter into agreements for specified fisheries to be managed by a government or group of governments. A fishery might be managed by the Australian Government, one or more state or territory governments, or any combination of the two acting through a joint authority. Fisheries for which OCS arrangements are not in place may be managed under joint control or continue under current management arrangements.

Open-access fishery. Fishery in which there is no limit on the number of operators or vessels allowed to operate in the fishery (c.f. Limited-entry fishery). Such a fishery is liable to suffer the ‘tragedy of the commons’, where a ‘race to fish’ generally leaves a fish stock below its maximum sustainable yield and unable to support an economically sustainable fishery. Under open access, a fishery operates with a harvest and effort that result in total revenue-equalling costs, with no economic profits being generated. The fishing effort employed at this point exceeds the level that would achieve maximum economic yield.

Operating model. Simulation of stock dynamics (and the impact of fishing) used in management strategy evaluation.

Opportunity cost. The compensation a resource forgoes by being employed in its present use and not in the next best alternative. For example, the opportunity cost incurred by the skipper of a fishing vessel is the amount they would have received by applying their skill and knowledge in the next best alternative occupation. The opportunity cost of owning a fishing vessel might be the interest that could be earned if the vessel were sold and the capital invested elsewhere. Although these costs are not usually reflected in a firm’s financial accounts, they are very important.

Otoliths. Bone-like structures formed in the inner ear of fish. The rings or layers can be counted to determine age.

Otter trawl. Demersal trawl operated by a single vessel in which the net is held open horizontally by angle-towed otter boards (large rectangular ‘boards’ of timber or steel), and vertically by a combination of floats on the headrope and weights on the ground line. Attached between the head and ground ropes and the towing warps, the otter boards are spread apart by the hydrodynamic forces acting on them when the net is towed.

Output controls. Management measures that place restraints on what is caught, including total allowable catch, quota, size limits and species limits.

Overfished. A fish stock with a biomass below the biomass limit reference point or below its specified indicator limit reference point. ‘Not overfished’ implies that the stock is not below the threshold; it is now used in place of the status classifications ‘fully fished’ or ‘underfished’ that were used in earlier editions of the Fishery status reports.

Overfishing, subject to. A stock that is experiencing too much fishing, and the removal rate from the stock is unsustainable. Also:

  • Fishing mortality (F) exceeds the limit reference point (FLIM). When stock levels are at or above BMSY, FMSY will be the default level for FLIM.
  • Fishing mortality in excess of FLIM will not be defined as overfishing if a formal ‘fish-down’ or similar strategy is in place for a stock and the stock remains above the target level (BTARG).
  • When the stock is less than BMSY but greater than BLIM, FLIM will decrease in proportion to the level of biomass relative to BMSY.
  • At these stock levels, fishing mortality in excess of the target reference point (FTARG) but less than FLIM may also be defined as overfishing, depending on the harvest strategy in place and/or recent trends in biomass levels.
  • Any fishing mortality will be defined as overfishing if the stock level is below BLIM, unless fishing mortality is below the level that will allow the stock to recover within a period of 10 years plus one mean generation time, or three times the mean generation time, whichever is less.


Pair trawling. Trawling by two vessels steaming in parallel with the net towed between them. Very large nets can be held open and towed in this way. The net may be hauled aboard the two vessels alternately for processing of the catch.

Parameter. Characteristic feature or measure of some aspect of a stock, usually expressed as a numerical value (for example, see M [natural mortality]).

Parental biomass. Weight of the adult (reproductively mature) population of a species. See also SB (spawning biomass).

Pelagic. Inhabiting surface waters rather than the sea floor. Usually applied to free-swimming species such as tunas and sharks (c.f. Demersal).

Pole-and-line fishing (poling). Fishing method in which fishers attract schools of fish to the vessel with live or dead bait, get them into a feeding frenzy with more bait and water sprayed onto the sea surface to simulate the behaviour of small baitfish, and then use poles with short, fixed lines and lures to ‘pole’ the fish aboard. Also called ‘pole-and-live-bait fishing’.

Population structure. Composition of a population in terms of size, stock (genetic or regional), age class, sex and so on.

Precautionary approach. Approach to resource management in which, where there are threats of serious irreversible environmental damage, a lack of full scientific certainty is not used as a reason for postponing measures to prevent environmental degradation. In the application of the precautionary approach, uncertainties should be evaluated and taken into account in a risk assessment, and decisions should be designed to minimise the risk of serious or irreversible damage to the environment.

Productivity (biological). An indication of the birth, growth and death rates of a stock. A highly productive stock is characterised by high birth, growth and mortality rates, and can sustain high harvesting rates.

Productivity (economic). The ability of firms or an industry to convert inputs (for example, labour, capital, fuel) into output. Economic productivity is often measured using productivity indices, which show whether more or less output is being produced over time with a unit of input. The index is calculated by comparing changes in total output (fish) with changes in total inputs such as fuel, labour and capital.

Profit, economic. The difference between total revenue and explicit costs and opportunity costs (See Opportunity cost). Explicit costs include wages, fuel, repairs, maintenance and depreciation of physical capital (for example, vessels). Economic profit differs from accounting profit in that it includes opportunity cost.

Protected species. As per the meaning used in the Environment Protection and Biodiversity Conservation Act 1999.

Purse seining. Harvesting of surface-schooling pelagic fish by surrounding the school with a net. A line that passes through rings on the bottom of the net can be tightened to close the net so that the fish cannot escape (c.f. Danish-seining).


Quad gear. Four fishing nets towed simultaneously by a vessel, with the opening of each net being controlled by otter boards.

Quota. Amount of catch allocated to a fishery (total allowable catch), or to an individual fisher or company (individual transferable quota).

Quota species. Species for which catch quotas have been allocated.


Real prices; real terms. Real prices are historical prices that have been adjusted to reflect changes in the purchasing power of money (most commonly measured by the consumer price index). Such prices may also be expressed as being in real terms. Commonly, a year is indicated alongside a real price to show the year’s prices to which historical prices have been adjusted. Prices quoted in real terms allow meaningful comparison over time because any fluctuations exclude the effect of inflation.

Rebuilding strategy. Strategy designed to rebuild a stock when a measure of its status (for example, its biomass) is below the biomass limit reference point (that is, the stock is assessed as overfished). Stock rebuilding strategies should include elements that define rebuilding targets, rebuilding time horizons and control rules related to the rate of progress.

Recovery plan. Management process to rebuild a stock when a measure of its status (for example, its biomass) is outside a defined limit (that is, the stock is assessed as overfished). Recovery plans should include elements that define stock-specific management objectives, harvesting strategies specified by control rules, and recovery periods.

Recruit. Usually, a fish that has just become susceptible to the fishery. Sometimes used in relation to population components (for example, a recruit to the spawning stock).

Recruitment. The amount of fish added to the exploitable stock each year due to growth and/or migration into the fishing area. Also used to refer to the number of fish from a year-class reaching a certain age.

Recruitment overfishing. Excessive fishing effort or catch that reduces recruitment to the extent that the stock biomass falls below the predefined limit reference point.

Reference point. Specified level of an indicator (for example, fishing mortality, biomass) used as a benchmark for assessment.

Ricker curve/function. Mathematical function that describes the relationship between stock size and recruitment.


SB (spawning biomass). Total weight of all adult (reproductively mature) fish in a population. Also called ‘spawning stock biomass’.

SBMEY; SMEY. Spawning or ‘adult’ equilibrium biomass at maximum economic yield.

SBMSY; SMSY. Spawning or ‘adult’ equilibrium biomass at maximum sustainable yield.

Seasonal closure. Closure of a fishing ground for a defined period; used as a management tool, often to protect one component of the stock.

Seines. Seine nets are usually long, flat nets like a fence that are used to encircle a school of fish, with the vessel driving around the fish in a circle. Purse-seine and Danish-seine nets are used in a range of fisheries.

Shelf break. Region where the continental shelf and continental slope meet—that is, where the seabed slopes steeply towards the ocean depths.

Shot (shot by shot). Pertaining to each separate deployment of a fishing gear by a fishing vessel.

Size frequency. See Length-frequency distribution.

Size at maturity. Length or weight of fish when they reach reproductive maturity.

Slope (mid-slope; upper slope). Part of the continental slope—the more steeply dipping sea floor beyond the edge of the continental shelf.

Snood. Short lengths of line that attach baited hooks to longlines (pelagic or demersal). See also Longline.

Spawner per recruit (spawner–recruit). An index that gives the number of spawners of a particular age divided by the initial number of recruits.

Spawning potential ratio (SPR). The average fecundity of a recruit over its lifetime when the stock is fished divided by the average fecundity of a recruit over its lifetime when the stock is unfished.

Species group. Group of similar species that are often difficult to differentiate without detailed examination.

Standard length. The length of a fish measured from the tip of the snout to the posterior end of the last vertebra or to the posterior end of the mid-lateral portion of the hypural plate.

Standardised data. Data that have been adjusted to be directly comparable to a unit that is defined as the ‘standard’ one. For example, catch-per-unit-effort data are often used as an indicator of fish abundance.

Statutory fishing rights (SFRs). Rights to participate in a limited-entry fishery. An SFR can take many forms, including the right to access a fishery or area of a fishery, the right to take a particular quantity of a particular type of fish, or the right to use a particular type or quantity of fishing equipment.

Steepness (h). Conventionally defined as the proportion of unfished recruitment (R0) that would be expected to be produced if the spawning biomass were reduced to 20% of unfished spawning biomass (S0). Stocks with high steepness produce many more births than deaths, on average, when the spawning stock is reduced to low levels by fishing. A greater number of individuals can be sustainably taken by fishing from a stock with high steepness than from a comparable stock with lower steepness. The steepness of a stock is typically both very difficult to estimate and highly influential on stock assessment model outputs such as maximum sustainable yield and spawning stock biomass. It is therefore a major source of uncertainty in most comprehensive stock assessments.

Stock. Functionally discrete population that is largely distinct from other populations of the same species and can be regarded as a separate entity for management or assessment purposes.

Stock recruitment. See Recruit.

Stock–recruitment relationship. Relationship between the size of the parental biomass and the number of recruits it generates. Determination of this relationship is difficult, and involves studying the population’s size–age composition, and growth and mortality rates.

Straddling stock. Migratory species that spends part of its life cycle in two or more jurisdictions, especially one that migrates between Exclusive Economic Zones and the high seas.

Subtropical waters. Waters adjacent to, but not within, the tropics; in the Australian region, the waters south of the Tropic of Capricorn (about 23°26'S).

Surplus production. Inherent productivity of a fish stock that can be harvested sustainably. Based on the theory that, at large stock size, rates of reproduction and stock increase are slowed by self-regulating mechanisms, and that the stock increases faster after removals as it attempts to rebuild. In theory, fishing can be moderated to take advantage of the more productive rates of stock increase, provided it does not exceed the stock’s capacity to recover.

Surplus production model. Mathematical representation of the way a stock of fish responds to the removal of individuals (for example, by fishing).

Sustainable yield. Catch that can be removed over an indefinite period without reducing the biomass of the stock. This could be either a constant yield from year to year, or a yield that fluctuates in response to changes in abundance.


Tagging. Marking or attaching a tag to an animal so that it can be identified when recaptured; used to study fish growth, movement, migration, and stock structure and size.

Target fishing (targeting). Fishing selectively for particular species or sizes of fish.

Target reference point. The desired state of the stock or fishery (for example, MEY or BTARG).

Target species. See Key commercial species.

Taxonomic group. A group of organisms with similar physical, chemical and/or structural composition.

Territorial sea baseline. The baseline from which all the zones (for example, Exclusive Economic Zone) of Australia’s maritime jurisdiction are measured. The baseline is defined as the level of lowest astronomical tide along the coast. Straight baselines may be drawn along deeply indented coastlines or to encompass islands fringing the coast. The baseline may also be drawn straight across the entrances to bays and estuaries, rather than following the coast inshore.

Threat abatement plan. Plan formalised under endangered species legislation to counter the effects of a listed key threatening process.

Threatened species. As per the meaning used in the Environment Protection and Biodiversity Conservation Act 1999.

Tori line. Line with streamers, towed as a scaring device over the area behind a vessel where sinking, baited hooks are within range of diving seabirds; attached to a tori pole (boom) at the vessel’s stern.

Total allowable catch (TAC). For a fishery, a catch limit set as an output control on fishing (see also Output controls). Where resource-sharing arrangements are in place between commercial and recreational fishers, the term total allowable commercial catch (TACC) will apply. The term ‘global’ is applied to TACs that cover fishing mortality from all fleets, including Commonwealth, state and territory fleets.

Total allowable catch (TAC), actual. The agreed TAC for a species with amendments applied, such as carryover or debits from the previous year.

Total allowable catch (TAC), agreed. The TAC for individual quota species as determined by the Australian Fisheries Management Authority Commission.

Total allowable commercial catch (TACC). See Total allowable catch (TAC).

Total allowable effort. An upper limit on the amount of effort that can be applied in a fishery.

Total length. The length of a fish from the tip of the snout to the tip of the longer lobe of the caudal fin, usually measured with the lobes compressed along the midline. It is a straight-line measure, not measured over the curve of the body.

Trap fishing. Fishing by means of traps, often designed to catch a particular species (for example, rock lobster pots).

Trawl fishing. Fishing method in which a large, bag-like net is drawn along behind a vessel to target either demersal or pelagic fish species. There are many variations.

Trigger catch limit. When catches reach this limit, management actions are triggered.

Trigger points. Pre-specified quantities (for example, total catch, spawning biomass) that indicate the need for a management response.

Trolling. Fishing method in which lines with baits or lures are dragged by a vessel at 2–10 knots. Used widely to catch fish such as Spanish mackerel, yellowtail kingfish and several tuna species.

Trotline. A dropline of hooks suspended from a mainline.

Turtle excluder device. A device fitted to a net or a modification made to a net that allows turtles to escape immediately after being captured in the net.


Uncertain. Status of a fish stock for which there is inadequate or inappropriate information to make a reliable assessment of whether the stock is overfished or not overfished, or subject to overfishing or not subject to overfishing.


Vessel-level efficiency. Vessel-level efficiency requires that revenues be maximised and catching costs be minimised for a given quantity of catch. The choice of management regime will have a substantial bearing on whether vessel-level efficiency is achieved, because it largely defines the incentive structure within which fishers operate.

Vessel monitoring system. Electronic device that transmits the identity and location of a vessel.

Virgin biomass. Biomass of a stock that has not been fished (also called the ‘unfished’ or ‘unexploited’ biomass).

Vulnerable species. Species that will become endangered within 25 years unless mitigating action is taken. The Environment Protection and Biodiversity Conservation Act 1999 dictates that a native species is eligible to be included in the vulnerable category at a particular time if, at that time, (a) it is not critically endangered or endangered, and (b) it is facing a high risk of extinction in the wild in the medium-term future, as determined in accordance with the prescribed criteria. See also Endangered species.

Last reviewed: 4 November 2019
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