N O A A

F I S H E R I E S

Glossary

U.S. DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

Revised Edition, June 2006

UNITED STATES DEPARTMENT OF COMMERCE

NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION

NOAA FISHERIES ISHERIES

Glossary

OCTOBER 2005

REVISED EDITION, JUNE 2006

NOAA TECHNICAL MEMORANDUM NMFS-F/SPO-69
K. Blackhart, D. G. Stanton, and A. M. Shimada

Offi ce of Science and Technology

National Marine Fisheries Service, NOAA

1315 East West Highway

Silver Spring, MD 20910

An on-line version of this glossary is available at:

http://www.st.nmfs.gov/st4/documents/F_Glossary.pdf

Cover Photo of Yellowfi n Tuna by William L. High, NMFS

This revised and updated edition has a 

correction to the Bmsy determination

 of Minimum Stock Size Threshold

on page 29.
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Contents

FROM THE

ASSISSTANT

ADMINISTRATOR

FOR FISHERIES

WILLIAM T. HOGARTH, PH.D.

NATIONAL MARINE

FISHERIES SERVICE, NOAA

SILVER SPRING, MARYLAND

NOAA’s National Marine Fisheries Service (NOAA  Fisheries Service) is dedicated to the stewardship of 

the Nation’s living marine resources and their habitat. As a 

leading voice for the economic benefi ts that can be derived 

from sustainable use and conservation of our Nation’s living 

marine resources, NOAA scientists and resource managers work 

to ensure the continued productivity and abundance of these 

resources and a bright future for the people dependent upon 

them.

To meet these goals and better serve its constituents and the 

general public, NOAA strives to develop and maintain effective 

communications and educational resources. Efforts include the 

development of outreach, educational, and reference materials 

such as this fi sheries glossary.

NOAA Fisheries Service engages in a wide range of scientifi c 

research, fi sheries management, protected species, and 

enforcement and habitat conservation programs. Each of 

these areas have a language uniquely their own, complete with 

terminology that may be unfamiliar to the general public or 

professionals working in other disciplines. 

To facilitate communication and encourage public participation 

in NOAA’s stewardship activities, this fi sheries glossary seeks 

to provide clear and understandable defi nitions for the technical 

terms likely to be encountered by our constituents and for 

interested citizens. Included are the most commonly occurring 

terms, with defi nitions derived from a variety of sources. 

JUNE 2006 1

A

Abiotic

A nonliving (physical or chemical) component of the 

environment.12

(Absolute) Abundance

The total number of a kind of fi sh in a population; this 

is rarely known, and usually estimated from the relative 

abundance.10 (see Abundance Index)

Abundance Index 

A relative measure of the weight or number of fi sh in 

a stock, a segment of the stock (e.g. the spawners), or 

an area. Often available in time series, the information 

is collected through scientifi c surveys or inferred from 

fi shery data.5

Abyssal Plain

The ocean fl oor offshore from the continental margin, 

usually very fl at with a slight slope.12

Abyssalpelagic Zone

The pelagic environment from a depth of approximately 

4,000 meters to 7,000 meters.12

Abyssal Zone

The bottom from a depth of approximately 4,000 meters 

to 7,000 meters.12

Acceptable Biological Catch (ABC)

A scientifi c calculation of the sustainable harvest 

level for a species or species group, and is used to set 

the upper limit on the range of potential annual total 

allowable catch (TAC).1,4 (see Allowable Biological 

Catch)

Accuracy

Of an estimate: an indicator of the closeness of an 

estimated value (e.g. population parameter) to the 

actual value. It should not be confused with precision, 

which relates to the confi dence limits (variability) of the 

estimate and can always be computed from the samples.5 

(see Precision)

Acoustic Survey

A systematic method of gathering information on fi sh 

availability and abundance in a water body with the 

help of sophisticated acoustic instruments, such as echo 

sounders and sonar, that generate ultrasonic sound for 

the detection of fi sh.5

Adaptive Management

1. A management process involving step-wise evolution 

of a fl exible management system in response to 

feedback information actively collected to check or test 

its performance (in biological, social, and economic 

terms). It may involve deliberate intervention to test the 

fi shery system’s response; 2. The process of improving 

management effectiveness by learning from the results 

of carefully designed decisions or experiments.5

Advisory Panel (AP)

Provides additional review and stakeholder perspective 

to a regional fi shery management council (FMC) for 

proposed actions and draft amendments to fi shery 

management plans (FMPs). The advisory panel usually 

represents a variety of interests from commercial, 

recreational, environmental, and consumer areas. 

However, panel members do not have seats on the 

council and do not vote.2 (see Scientifi c and Statistical 

Committee)

Age

The number of years of life completed, here indicated 

by an Arabic numeral, followed by a plus sign if there is 

any possibility of ambiguity (age 1, age 1+).5

Age Class

A group of individuals of the same age range in a 

population. The age 0 group are the fi sh in their fi rst 

year of life. A fi sh born in April of a given year remains 

in the age 0 group until April of the following year. The 

term usually refers to a year class in long-lived annually 

breeding species, but shorter units of time are also used, 

particularly in the tropics.5

Age Frequency or Age Structure

A breakdown of the different age groups of a kind of fi sh 

in a population or sample.2

G L O S S A R Y
2 NOAA FISHERIES GLOSSARY

Age-Length Key

One approach used to assign ages to fi sh, given length 

measurements. Used to convert catch-at-size data into 

catch-at-age data. The keys specify the probability that 

fi sh of a given size belong to one of several age groups.5

(see Length-Weight Relationship)

Allowable Biological Catch (ABC)

A term that refers to the range of estimated allowable 

catch for a species of species group. It is set each year 

by a scientifi c group. The ABC estimates are used to set 

the annual total allowable catch (TAC).4 (see Acceptable 

Biological Catch)

Allocation 

1. Distribution of the opportunity to fi sh among user 

groups or individuals. The share a user group gets 

is sometimes based on historic harvest amounts; 2. 

A quantity of catch, effort, or biomass attributed to a 

person, a vessel, and a fi shing company. The allocation 

can be absolute (e.g. a number of tons) or relative (e.g. a 

percentage of the annual allowable catch).5

Alternatives

In the context of an environmental impact statement 

for annual fi sheries management measures, alternatives 

are different suites of optimum yields and management 

actions that could be used to manage fi sheries.1

Anadromous

Fishes that migrate as juveniles from freshwater 

to saltwater and then return as adults to spawn in 

freshwater; most Pacifi c salmon are anadromous.4

Angler

A person catching fi sh or shellfi sh with no intent to sell, 

including people releasing the catch.10 (see Recreational 

Fishery)

Annual (Total) Mortality (Rate)

1. The rate of death, usually in terms of a percentage of 

fi sh dying from a population in one year, due to both 

fi shing and natural causes2

; 2. The ratio of the number 

of fi sh which die during a year divided by the number 

alive at the beginning of that year.5

Anoxic

The condition of oxygen defi ciency or absence of 

oxygen. Anoxic sediments and anoxic bottom waters 

are commonly produced where there is a defi ciency of 

oxygen due to very high organic productivity and a lack 

of oxygen replenishment to the water or sediment, as 

in the case of stagnation or stratifi cation of the water 

body.12

Aphotic

Light level modifi er of the deep epipelagic ocean 

ecosystem, and turbid regions of all other waters; areas 

never reached by natural light.12

Aquaculture

The farming of aquatic organisms including fi sh, 

mollusks, crustaceans, and aquatic plants with some 

sort of intervention in the rearing process to enhance 

production, such as regular stocking, feeding, protection 

from predators, etc. Farming also implies individual or 

corporate ownership of the stock being cultivated.5

Archipelago

A group of islands; an expanse of water with scattered 

islands.12

Area Closure

The closure to fi shing by particular gear(s) of an entire 

fi shing ground, or a part of it, for the protection of a 

section of the population (e.g. spawners, juveniles), the 

whole population, or several populations. The closure is 

usually seasonal but it could be permanent.5

Artisanal Fishery

A fi shery based on traditional or small-scale gear and 

boats.10

Assemblage

1. An association of coexisting species, in space and 

time, with similar environmental tolerance, possibly 

trophic relationships, but not totally interdependent; 

2. A collection of species inhabiting a given area, 

the interactions between the species, if any, being 

unspecifi ed.5

Assessment

A judgment made by a scientist or scientifi c body on 

the state of a resource, such as a fi sh stock (e.g. size 

of the stock, potential yield, on whether it is over- or 

underexploited), usually for the purpose of passing 

advice to a management authority.5

Assessment Level

Categories of the level of complexity of, and data 

available for each assessment: index of abundance 

(Index), yield-per-recruit analysis (Yield), analysis of 

the age structure of the catch (Age Structure), analysis 

including the relationship between recruitment and 

spawning stock size (Spawning Stock), and assessment 

that allows prediction of future (1or 2 years ahead) stock 

sizes and catches (predictive).6

Associated Species

Those species that (a) prey upon the target species, (b) 
JUNE 2006 3

are preyed on by it, (c) compete with it for food, living 

space, etc., or (d) co-occur in the same fi shing area and 

are exploited (or accidentally taken) in the same fi shery 

or fi sheries. These interactions can occur at any stage 

of the life cycle of one or other species and the range of 

species concerned can therefore be very large.5

Atoll

Earthform consisting of a ringlike perimeter reef area, 

often with a reef islet, enclosing a lagoon area.12 (see 

Lagoon, Reef)

Availability

1. The fraction of a fi sh population which lives in 

regions where it is susceptible to fi shing during a given 

fi shing season. This fraction receives recruits from or 

becomes mingled with the non-available part of the 

stock at other seasons, or in other years (any more or 

less completely isolated segment of the population is 

best treated as a separate stock); 2. The proportion of 

a stock which is susceptible to fi shing. Fish become 

“available” to fi sheries through migration, growth and 

/or change of behavior (from pelagic to demersal). If 

an available section of a stock is suffi ciently isolated 

from the rest of the stock, it could be considered a 

management unit and be managed as such; 3. Describes 

whether a certain kind of fi sh of a certain size can be 

caught by a type of gear in an area.5

B

B0 (B“zero”)

Unfi shed or virgin biomass. Rarely known. Using 

mathematical models, it is generally calculated as 

the long-term average biomass value expected in the 

absence of fi shing mortality. In production models, B0

is also known as carrying capacity. It is often used as a 

biological reference point in fi sheries management.5

BMSY

1. Long-term average biomass that would be achieved 

if fi shing at a constant fi shing mortality rate equal to 

FMSY

2,3; 2. The weight (biomass) of a group of fi sh 

necessary to produce maximum sustainable yield 

(MSY).4

Bag Limit

The number and/or size of a species that a person can 

legally take in a day or trip. This may or may not be the 

same as a possession limit.2

Bank

Submerged earthform with a crest at a depth of 20–200 

meters in oceanic waters and of 0–5 meters in nearshore 

and neritic waters.12 (see Nearshore, Neritic Zone)

Barrier Island

A sedimentary island, generally elongate and low, that 

is built by longshore transport or wave action parallel to 

the coast.12

Barrier Reef

A reef growing offshore from a land mass and separated 

from the shoreline, often by a lagoon or estuary.12 (see 

Estuary, Lagoon)

Baseline

A set of reference data sets or analyses used for 

comparative purposes; it can be based on a reference 

year or a reference set of (standard) conditions.5

Basin

Any large depression in which sediments are deposited.12

Bathyl Zone

The seafl oor between depths of 1,000 meters and 

approximately 4,000 meters.12

Bathymetry

Pertaining to the depth and relief of water basins.12

Bathypelagic Zone

The pelagic environment between depths of 1,000 

meters and 4,000 meters.12

Bayesian

A formal statistical approach in which expert knowledge 

or beliefs are analyzed together with data. Bayesian 

methods make explicit use of probability for quantifying 

uncertainty. Bayesian methods are particularly useful for 

making decision analyses.5 (see Monte Carlo)

Beach

A sloped sediment shoreline composed of sand, gravel, 

cobble, mud, or boulder-sized sediments, sometimes 

with beach rock.12

Benthic

1. Defi ning a habitat or organism found on the sea 

bottom10; 2. Of or pertaining to the seafl oor (or bottom) 

of a water body.12 (see Demersal, Pelagic)

Benthos

Organisms that live on or in the seabottom.12
4 NOAA FISHERIES GLOSSARY

Best Available Science

The term “best available science” comes from National 

Standard 2 listed in the Magnuson-Stevens Act, and 

is the informational standard mandated for decision 

making.1

Bias

A systematic difference between the expected value of a 

statistical estimate, and the quantity it estimates.5

Billfi sh

A group of tuna-like fi sh species comprising marlins, 

sailfi sh, and spearfi sh, and which are characterized by a 

snout which extends into a bill or spear.5

Bioaccumulation

The buildup over time, within animal tissues, of 

substance (e.g. heavy metals) that cannot be excreted by 

an organism.1

Bioeconomic Modeling

Mathematical formulae that simulate the interaction 

between biological behavior of fi sh stocks and human 

behavior of users of the resource as it is shaped by 

economic factors.9

Biogeography

The distribution of one or more species that is defi ned 

by abiotic factors (temperature, salinity, surface currents, 

etc.).12

Biological Assessment

An assessment conducted as part of the Endangered 

Species Act (ESA).1

Biological Diversity (Biodiversity)

1. The variety and variability among living organisms 

from all sources, including terrestrial, marine, and 

other aquatic ecosystems and the ecological complexes 

of which they are part; this includes diversity within 

species, between species, and of ecosystems. Diversity 

indices are measures of richness (the number of species 

in a system) and may refl ect ecosystem stresses (such as 

those due to high fi shing intensity); 2. Includes genetic 

diversity (within species), species diversity (within 

ecosystems), and ecosystem diversity.5 (see Species 

Diversity)

Biological Opinion

A scientifi c assessment issued by the National Marine 

Fisheries Service (NMFS) or U.S. Fish and Wildlife 

Service (USFWS), as required by the Endangered 

Species Act (ESA) for listed species. Determines the 

likelihood of an action to jeopardize the existence of a 

species listed under the ESA.1

Biological Reference Points

1. A biological benchmark against which the abundance 

of the stock or the fi shing mortality rate can be measured 

in order to determine its status. These reference points 

can be used as limits or targets, depending on their 

intended usage5; 2. Specifi c values for the variables 

that describe the state of a fi shery system which are 

used to evaluate its status. Reference points are most 

often specifi ed in terms of fi shing mortality rate and/or 

spawning stock biomass. These may indicate (a) a 

desired state of the fi shery, such as a fi shing mortality 

rate that will achieve a high level of sustainable yield, or 

(b) a state of the fi shery that should be avoided, such as 

a high fi shing mortality rate which risks a stock collapse 

and long-term loss of potential yield. The former are 

referred to as “target reference points,” and the latter are 

referred to as “limit reference points” or “thresholds.” 

Some common examples are F0.1, FMAX, and FMSY.

3

Biomass (B)

1. Or standing stock. The total weight of a group (or 

stock) of living organisms (e.g. fi sh, plankton) or of 

some defi ned fraction of it (e.g. spawners) in an area, 

at a particular time; 2. Measure of the quantity, usually 

by weight in pounds or metric tons (2,205 pounds or 1 

metric ton), of a stock at a given time.5

Biota

The plant and animal life characteristic of a specifi c 

region or biosphere, or given time period.14

Biotic

Pertaining to the living components of their 

environment.12

Blocked Quota Shares

In Alaska, quota shares in the Alaskan halibut and 

sablefi sh individual fi shing quota (IFQ) program that 

are not allowed to be subdivided when transferred. 

There are limits on the size of the blocked quota and on 

the number of blocks that an individual may own in a 

given area. This is intended to ensure the availability of 

small units of quota for purchase by new entrants.13 (see 

Unblocked Quota Shares)

Bloom

A sudden increase in the abundance of alga or 

phytoplankton resulting in a contiguous mass of highly 

concentrated phytoplankton in the water column.12

Bony Fishes

Fishes with a calcifi ed hard skeleton and belonging to 

Class Osteichthyes; includes most fi sh species except 

sharks, rays, skates, hagfi sh, and lampreys.10
JUNE 2006 5

Bootstrap

A statistical methodology used to quantify the 

uncertainty associated with estimates obtained from a 

model. The bootstrap is often based on Monte Carlo 

resampling of residuals from the initial model fi t.5

(see Monte Carlo )

Boundary Current

Large-scale water stream in the upper ocean that 

separates water masses; is driven by a combination of 

wind, temperature, geostrophic, or coriolis effects.12

Buff er Zone

The area that separates the core from areas in which 

human activities that threaten it occur.14

Bycatch 

Fish other than the primary target species that are caught 

incidental to the harvest of the primary species. Bycatch 

may be retained or discarded. Discards may occur for 

regulatory or economic reasons.13

Bycatch Reduction (Excluder) Device

A device inserted in a fi shing gear (usually trawl nets, 

close to the codend) to allow escapement, alive, of 

unwanted (nontarget and prohibited) species (e.g. 

jellyfi sh), smaller fi sh (juveniles), and threatened or 

endangered species (e.g. sea turtles, marine mammals).5

C

CAGEAN

Catch-at-age analysis. An analysis used to reconstruct 

the population history of long-lived fi sh stocks. They 

provide an estimate of the current “exploitable biomass” 

(the part of the population that can be fi shed), upon 

which the harvest rate is based.1

Capability

The ability to do something with the capacity you have; 

the capacity to be used, treated, or developed for a 

specifi c purpose.8

Capacity

1. The ability to sustain, harvest, hold, or process; 2. 

The maximum amount that can be produced per unit 

of time with existing plant and equipment, provided 

the availability of variable factors of production is not 

restricted.5

Carrying Capacity 

1. The maximum population of a species that an area 

or specifi c ecosystem can support indefi nitely without 

deterioration of the character and quality of the resource; 

2. The level of use, at a given level of management, at 

which a natural or man-made resource can sustain itself 

over a long period of time. For example, the maximum 

level of recreational use, in terms of numbers of people 

and types of activity, that can be accommodated before 

the ecological value of the area declines.5

Cash Flow Analysis

A type of fi nancial analysis that compares the timing and 

amount of cash infl ows with the timing and amount of 

cash outfl ows. A fi rm’s cash fl ow position can greatly 

affect its ability to remain in business. These effects may 

not be apparent from a cost-benefi t analysis.9

Catadromous

Fishes that spend most of their life in freshwater and 

then migrate into saltwater to spawn.10

Catch

1. To undertake any activity that results in taking fi sh out 

of its environment dead or alive. To bring fi sh on board 

a vessel dead or alive; 2. The total number (or weight) of 

fi sh caught by fi shing operations. Catch should include 

all fi sh killed by the act of fi shing, not just those landed; 

3. The component of fi sh encounter-ing fi shing gear, 

which is retained by the gear.5

Comment: The catch is usually expressed in terms of 

wet weight. It refers sometimes to the total amount 

caught, and sometimes only to the amount landed. The 

fi sh which are not landed, but returned to the sea, are 

called discards.5

Catchability

1. In general, the extent to which a stock is susceptible 

to fi shing.5 (see Vulnerability)

Comment: Catchability often increases with 

developments in fi shing technology, and so needs to be 

monitored. It depends on the habits of the fi sh as well as 

on the type and deployment of fi shing gear. It may also 

depend on the abundance of the fi sh (e.g. less abundant 

fi sh may be more catchable due to less saturation of 

gear or to concentration in schools). Specifi c climatic 

conditions may result in increased or decreased 

availability of the fi sh. This would lead to increased 

(or decreased) catchability and, thus, increased (or 

decreased) fi shing mortality rate with the same fi shing 

effort.5
6 NOAA FISHERIES GLOSSARY

Catchability Coeffi cient (q)

1. In fi sheries models, the factor (q) relates abundance 

to stock size (x = qN) and fi shing mortality to fi shing 

effort (F = qf). Following the latter, (q) is a measure of 

fi shing mortality generated on a stock by one unit of 

effort; 2. The fraction of a fi sh stock which is caught 

by a defi ned unit of the fi shing effort. When the unit 

is small enough that it catches only a small part of the 

stock —0.01 or less—it can be used as an instantaneous 

rate in computing population change.5

Catch Curve

A breakdown of different age groups of fi sh, showing 

the decrease in numbers of fi sh caught as the fi sh 

become older and less numerous or less available. Catch 

curves are often used to estimate total mortality.2

Catcher Vessel

Vessel that harvests fi sh but does not have onboard 

processing capacity.13

Catcher-Processor Vessel

Vessel that can both catch and process the catch 

onboard. Also referred to as factory trawlers or freezerlongliners.13

Catch Per Unit (of) Eff ort (CPUE)

The quantity of fi sh caught (in number or in weight) 

with one standard unit of fi shing effort; e.g. number of 

fi sh taken per 1,000 hooks per day or weight of fi sh, 

in tons, taken per hour of trawling. CPUE is often 

considered an index of fi sh biomass (or abundance). 

Sometimes referred to as catch rate. CPUE may be used 

as a measure of economic effi ciency of fi shing as well as 

an index of fi sh abundance. Also called: catch per effort, 

fi shing success, availability.5

Catch Rate

Means sometimes the amount of catch per unit time and 

sometimes the catch per unit effort.5

Ceremonial and Subsistence

A harvest category specifi c to Native American tribes 

representing fi shing rights granted by treaty.1

Cetaceans

Marine mammals of the Order Cetacea. Includes 

whales, dolphins, and porpoises.5

Charter Boat

Any vessel-for-hire engaged in recreational fi shing 

and hired for a charter fee by an individual or group of 

individuals (for the exclusive use of that individual or 

group of individuals), which results in that vessel being 

unavailable for hire to any other individual or group of 

individuals during the period of the charter.9

Closed Season

Seasonal closure. The banning of fi shing activity (in an 

area or of an entire fi shery) for a few weeks or months, 

usually to protect juveniles or spawners.5

Coastal Pelagic Species

Schooling fi sh not associated with the ocean bottom that 

migrate in coastal waters. They usually eat plankton 

and are the main food source for higher-level predators 

such as tuna, salmon, most groundfi sh, and humans. 

Examples include herring, squid, sardine, and mackerel.1

Coastal Zone Management Act (CZMA)

The main objective of the CZMA is to encourage and 

assist states in developing coastal zone management 

programs, to coordinate state activities, and to safeguard 

the regional and national interests in the coastal zone. 

It requires that any Federal activity (including fi shery 

management regulations) directly affecting the coastal 

zone of a state be consistent with that state’s approved 

coastal zone management program, since activities 

that take place beyond the territorial sea may affect the 

coastal zone.1

Code of Federal Regulations (CFR)

A codifi cation of the regulations published in the Federal 

Register by the executive departments and agencies 

of the Federal government. The CFR is divided into 

50 titles that represent broad areas subject to Federal 

regulation. Title 50 contains wildlife and fi sheries 

regulations.1 (see Proposed Rule)

Coded-wire Tag

Coded-wire tags are small pieces of stainless steel wire 

that are injected into the snouts of juvenile salmon and 

steelhead. Each tag is etched with a binary code that 

identifi es its release group.1

Codend

The end of a trawl net that retains the catch and the part 

of the net where most size-selection takes place. Codend 

mesh sizes and structure are usually regulated and may 

be preceded by a sorting grid to reduce bycatch.5 (see 

Bycatch Reduction Device)

Coeffi cient of Variation (CV) 

The standard error of a statistic, divided by its point 

estimate. The CV gives an idea of the precision of an 

estimate, independent of its magnitude.5
JUNE 2006 7

Cohort

1. In a stock, a group of fi sh generated during the same 

spawning season and born during the same time period; 

2. In cold and temperate areas, where fi sh are long-lived, 

a cohort corresponds usually to fi sh born during the 

same year (a year class). For instance, the 1987 cohort 

would refer to fi sh that are age 0 in 1987, age 1 in 1988, 

and so on. In the tropics, where fi sh tend to be shortlived, cohorts may refer to shorter time intervals (e.g. 

spring cohort, autumn cohort, monthly cohorts).5 (see 

Year Class)

Cohort Analysis

A retrospective analysis of the catches obtained from a 

given year class at each age (or length interval) over its 

life in the fi shery. Allows estimation of fi shing mortality 

and abundance at each age as well as recruitment. 

Involves the use of a simplifi ed algorithm based on an 

approximation that assumes that, in a given time period, 

all fi shing takes place instantaneously in the middle of 

the time period.5 (see Virtual Population Analysis)

Cohort Replacement Rate

The rate at which each subsequent cohort or generation 

replaces the previous one.1

Commercial Fishery

A term related to the whole process of catching and 

marketing fi sh and shellfi sh for sale. It refers to and 

includes fi sheries resources, fi shermen, and related 

businesses.2

Common Property

Form of resource ownership with a set of well-defi ned 

users capable of excluding other potential users and 

having well-understood rules regarding their rights and 

obligations with respect to other users and the resource.13

Common Property Resource

A term that indicates a resource owned by the public. 

It can be fi sh in public waters, trees on public land, or 

the air. The government regulates the use of a common 

property resource to ensure its future benefi ts.2

Community

The populations that live and interact physically and 

temporally in the same area.12

Community Development Quota (CDQ)

Program in western Alaska under which a percentage 

of the total allowable catch (TAC) of Bering 

Sea commercial fi sheries is allocated to specifi c 

communities. Communities eligible for this program 

must be located within 50 miles of the Bering Sea 

coast, or on an island within the Bering Sea; meet 

criteria established by the State of Alaska; be a village 

certifi ed by the Secretary of the Interior pursuant to the 

Alaska Native Claims Settlement Act; and consist of 

residents who conduct more than half of their current 

commercial or subsistence fi shing in the Bering Sea or 

waters surrounding the Aleutian Islands. Currently 7.5% 

of the TAC in the pollock, halibut, sablefi sh, crab, and 

groundfi sh fi sheries is allocated to the CDQ program.13

Compensatory Growth

An increase in growth rate shown by fi shes when their 

populations fall below a certain level; possibly caused 

by decreased competition between individuals for food 

or space.10

Compensatory Survival

A decrease in the rate of natural deaths that some fi shes 

may show when their populations fall below a certain 

level; possibly caused by decreased competition between 

individuals for food or space.10 (see Natural Mortality) 

Conceptual Model

A depiction or representation of the most current 

understanding of the major ecosystem features and 

processes (including biological, physical, chemical, and 

geopmorphic components) of a particular environment 

(e.g. estuaries).12

Condition Factor (K)

A mathematical measurement of the degree of 

“plumpness,” or the general health of a fi sh or group of 

fi shes.10

Confi dence Interval (CI)

The probability, based on statistics, that a number will 

be between an upper and lower limit.2

Connectivity

The movement of organisms from place to place (e.g. 

among marine reserves) through dispersal or migration.14

(see Marine Reserves)

Consumer Surplus

The welfare (or well-being) consumers derive from a 

good or service, represented by the difference between 

the maximum a consumer is willing to pay for a 

good or service and what the consumer actually pays. 

“Consumer” also applies to those gaining value from 

non-consumptive uses (e.g. observing salmon runs) and 

to nonuse benefi ts (e.g. protecting marine mammals 

from exploitation).9 (see Producer Surplus, Total 

Welfare)
8 NOAA FISHERIES GLOSSARY

Contiguous Fishery Zone (CFZ)

The 9-nautical mile (n.mi.) seaward zone, from 3 to 12 

n.mi. offshore, and adjacent to the 3-n.mi. territorial 

sea.1

Continental Margin

The edge of a continent; the zone between a continent 

and the deep-sea fl oor of the abyssal plain.12

Continental Rise

Part of the continental margin; the ocean fl oor 

from the continental slope to the abyssal plain. The 

continental rise generally has a gentle slope and smooth 

topography.12

Continental Shelf

Underwater portion (shelf) of the continent, with 

moderate inclination, extending seaward from the shore 

to the edge of the continental slope where the inclination 

increases rapidly. Sometimes conventionally considered 

as the continent margin between 0 and 200 meters 

depths.5 (see Shelf Break)

Continental Slope

Part of the continental margin; the ocean fl oor from 

the continental shelf to the continental rise or oceanic 

trench. Usually to a depth of about 200 meters. The 

continental slope typically has a relatively steep grade 

from 3 to 6 degrees.12

Contingent Valuation

A method employing a hypothetical market to elicit 

people’s preferences for a non-market good; typically 

people are questioned about what they are willing to pay 

or receive for specifi c increments or decrements in the 

provision of the good.

Control Date

Date established for defi ning the pool of potential 

participants in a given management program. Control 

dates can establish a range of years during which a 

potential participant must have been active in a fi shery 

in order to qualify for quota share.13

Control Rule

Describes a plan for pre-agreed management actions as 

a function of variables related to the status of stock in 

question. For example, a control rule can specifi c how 

fi shing mortality or yield should vary with levels of 

estimated biomass.2

Controlled Access

General term for management schemes that reduce 

or restrict the number of participants in a fi shery. (see 

Limited Entry)

Convention on the International Trade of 

Endangered Species (CITES)

A voluntary international agreement between 

governments aimed at ensuring the international trade of 

specimens of wild animals and plants does not threaten 

their survival.

Convergence Zone

The line where two oceanic water masses meet, resulting 

in the sinking of the denser one.12

Co-Occurring Stocks

Different stocks of fi sh that swim or school near one 

another, and may be caught together.1

Coral Reef

The massive deposition of calcium carbonate by coral 

polyps of colonial stony corals and other organisms 

producing large living hard structures. Coral reefs can 

range in size from a few feet to thousands of miles.12

Core Area

The central, most highly protected part of a protected 

area.14 (see Marine Reserve, Protected Area)

Cost-Benefi t Analysis

1. A comparison of the economic benefi ts and costs of 

a project, policy, or regulation; 2. A comparison of the 

economic benefi ts of using a resource to the opportunity 

cost if the resource is used. Projects or regulations are 

typically evaluated based on how they change the costbenefi t ratio.

Council

A regional fi sheries management council (FMC). 

The Fishery Conservation and Management Act of 

1976 as amended created eight regional councils 

to prepare fi shery management plans (FMPs) and 

FMP amendments for fi sheries in the U.S. Exclusive 

Economic Zone (EEZ).8

Critical Areas

Areas within a Marine Protected Area (MPA) that are 

crucial to achieving the objectives of the MPA; for 

example, spawning areas in an MPA established for 

fi sheries purposes.14 (see Marine Protected Area)

Critical Size

The average size of a fi sh in a year class at the time 

when the instantaneous rate of natural mortality equals 

the instantaneous rate of growth in weight for the yearclass as a whole. At this size, the biomass of the age 

class is maximized.5 (see Optimum Size)
JUNE 2006 9

Crustaceans

A group of freshwater and saltwater invertebrates with 

jointed legs and a hard shell of chitin. Includes shrimps, 

crabs, lobsters, and crayfi sh.2

Cultural Landscape

A cluster of beliefs, values, and norms about how places 

and things on earth are related to human behavor.14

Culturally Affi liated

To be connected to a place, region, or resource because 

it has signifi cant meaning to the culture of the individual 

and his or her group. In most cases cultural affi liation 

requires more than one generation to establish, and for 

some groups the connections have been developed over 

centuries. The Federal government uses the term in 

various environmental laws and requlations.14

Cumulative (Catch) Limit

The total allowable amount of a species or species 

group, by weight, that a vessel may take and retain, 

possess, or land during a period of time. Fishers may 

take as many landings of a species or species complex 

as they like as long as they do not exceed the cumulative 

limit that applies to the vessel or permit during the 

designated period.1

Cumulative (Catch) Limit Stacking

The association of cumulative limits with permits, 

rather than with vessels, allowing a vessel with multiple 

limited entry permits to harvest multiple cumulative 

limits. Also known as permit stacking.1

Current

A horizontal movement of water.12

Current System

Areas strongly infl uenced by large, unidirectional, 

organized, coherent fl ows of water in horizontal motion. 

These include freshwater infl ows and tidal fl ows. 

Geostrophic fl ows are currents in the deep ocean that 

fl ow along lines of constant pressure or baroclinic 

surfaces. Wind-driven currents along the shore, called 

longshore currents, fl ow parallel to the land and play a 

role in sediment transport and structuring of the habitat. 

Current systems play an especially important role by 

governing productivity, providing transport for early-life 

stages (e.g. eggs and larvae) and adults, and fl ushing 

pollutants out to sea.12 (see Primary Productivity, 

Pollution)

D

Decision Analysis

A formal analysis to aid decision-making in the face 

of uncertainty. A decision analysis usually evaluates 

the expected outcomes (e.g. average catch, constancy 

of catch, probability of rebuilding to a given biomass 

target, etc.) of alternative management controls. 

A decision analysis can also address management 

consequences under different plausible assumptions 

about the status of the stock.5

Decision Rule

Specifi cation of how pre-agreed management actions 

will respond to perceived or estimated states of nature.5

Decline

A decline is a reduction in the number of individuals, 

or a decrease of the area of distribution, the causes of 

which are either not known or not adequately controlled. 

It need not necessarily still be continuing. Natural 

fl uctuations will not normally count as part of a decline, 

but an observed decline should not be considered part 

of a natural fl uctuation unless there is evidence for this. 

A decline that is the result of harvesting that reduces 

the population to a planned level, not detrimental to the 

survival of the species, is not covered by the term.5

Dedicated Access Privileges (DAP)

Assigns an individual or other entity access to a predetermined portion of the annual catch in a particular 

fi shery. In some cases, the privilege is transferable 

and may be bought and sold, creating a market. The 

term encompasses a range of tools, including access 

privileges assigned to individuals (i.e. individual 

transferable quotas [ITQs]), and to groups or 

communities (e.g., community development quotas 

[CDQs], cooperatives, and area-based quotas).15

Deep Shelf and Terrace 

Horizontal habitat located from about 40 to 500 meters. 

Insular habitats on or above the deep shelf consisting 

of horizontal or nearly horizontal natural typographic 

features interrupting a steeper slope and often occurring 

in a series. These habitats extend seaward from the shelf 

of an island or bank.12

Deep Slope

Vertical habitat located from about 40 to 500 meters. 

Insular habitats on or above the deep slope characterized 

by a steep (often vertical) slope extending seaward from 

the shelf of an island or bank These habitats may be 

colonized by some low-light coral and bryozoans.12
10 NOAA FISHERIES GLOSSARY

Delta

A low, nearly fl at accumulation of sediment deposited at 

the mouth of a river or stream, commonly triangular or 

fan-shaped.12

Delta Method

Also known as the Taylor Series method, the Delta 

method is a statistical procedure used to quantify the 

uncertainty associated with estimates obtained from a 

model. More specifi cally, the Delta method quantifi es 

how the variance propagates from the parameters that 

are estimated directly by the statistical model (e.g. 

current spawning stock biomass, SSB), and those 

parameters that are derived from the application of 

mathematical formulations (e.g. future SSB based on 

model projections).5

Demand Function

A function that relates the quantity of a good or service 

demanded to price. It is usually an inverse relationship 

where at higher (or lower) prices, less (or more) quantity 

is consumed. Other factors which infl uence willingnessto-pay are incomes, tastes, preferences, and price of 

substitutes.9

Demersal

Living in close relation with the bottom and depending 

on it. Cods, groupers, crabs, and lobsters are demersal 

resources. The term usually refers to the living mode of 

the adult, i.e. demersal fi sh.5 (see Benthic, Pelagic)

Demography

A term referring to the study of birth rates, death 

rates, age distributions, and size of populations. It 

is a fundamental discipline within the larger fi eld of 

population biology and ecology.5 (see Population 

Biology)

Density-Dependence

The dependence of a factor infl uencing population 

dynamics (such as survival rate or reproductive success) 

on population density. The effect is usually in the 

direction that contributes to the regulative capacity of a 

stock.5

Density-Independent

External factors that infl uence all individuals of a 

population, regardless of population density, such as 

weather or climate.

Depleted Stock

A stock driven by fi shing to very low level of abundance 

compared to historical levels, with dramatically reduced 

spawning biomass and reproductive capacity. It requires 

particularly energetic rebuilding strategies and its 

recovery time will depend on the present condition, the 

level of protection, and the environmental conditions.5

Derby Fishery

A fi shery of brief duration during which fi shers race to 

take as much catch as they can before the fi shery closes.1

(see Olympic Fishing, Race-to-Fish)

Deterministic

1. A deterministic process or model does not take 

account or include any stochastic (random) variability. 

The opposite is a stochastic model; 2. A model whose 

behavior is fully specifi ed by its form and parameters, 

unlike a stochastic model.5 (see Simulation, Stochastic)

Detritus

Dead organic matter and the decomposers that live on 

it; when broken up by decomposers, detritus provides 

energy to many coastal ecosystems.12

Directed Fishery

Fishing that is directed at a certain species or group 

of species. This applies to both sport and commercial 

fi shing.2

Disappearance (Z)

A measure of the rate of decline in the numbers of 

fi sh caught as individuals become less numerous or 

available; often calculated from a catch curve.10

Discard

To release or return fi sh to the sea, dead or alive, 

whether or not such fi sh are brought fully on board a 

fi shing vessel.5

Comment: Estimates of discards can be made in a 

variety of ways, including samples from observers and 

logbook records. Fish (or parts of fi sh) can be discarded 

for a variety of reasons such as having physical damage, 

being a nontarget species for the trip, and compliance 

with management regulations like minimum size limits 

or quotas.5 (see Highgrading)

Domestic Annual Harvest (DAH)

The domestic annual fi shing capacity, modifi ed by other 

factors (such as economic factors), which will determine 

estimates of what the fl eets will harvest.1

Domestic Annual Processing (DAP)

The amount that will be domestically processed, based 

not only on physical capacity but on a demonstrated 

intent and the effects of domestic harvesting, markets, 

and other fi sheries.1
JUNE 2006 11

Downwelling

Hydroform created by convergence of surface currents 

that causes surface waters to sink, creating vertical and 

horizontal displacement of water and possibly carrying 

organisms to lower depths.12

E

Ebb Tide

A falling tide, the phase of the tide between high water 

and the succeeding low water.12

Ecological Reserve

Zoning that protects all living marine resources 

through prohibitions on fi shing and on the removal or 

disturbance of any living or nonliving resource.14 (see 

Protected Area)

Economic Effi ciency

1. A measure of the size of consumer surplus and 

producer surplus. An increase in the combined surpluses 

is an increase in economic effi ciency9

; 2. In commercial 

fi shing, the point at which the added cost of producing a 

unit of fi sh is equal to what buyers pay. Producing fewer 

fi sh would bring the cost lower than what buyers are 

paying. Producing more fi sh would raise the cost higher 

than what buyers are paying. Harvesting at the point of 

economic effi ciency produces the maximum economic 

yield (MEY).2

Economic Overfi shing

A level of fi sh harvesting that is higher than that 

of economic effi ciency; harvesting more fi sh than 

necessary to have maximum profi ts for the fi shery.2

Economic Rent

The total amount of profi t that could be earned from a 

fi shery owned by an individual after subtracting input 

costs (usually capital and labor). Individual ownership 

maximizes economic rent, but an open-entry policy 

usually results in so many fi shermen that profi ts higher 

than the opportunity cost are driven to zero.2

Economic Value

The most people are willing to pay to use a given 

quantity of a good or service; or, the smallest amount 

people are willing to accept to forego the use of a given 

quantity of a good or service.5

Ecosystem

A geographically specifi ed system of organisms, 

the environment, and the processes that control its 

dynamics. Humans are an integral part of an ecosystem.8

Ecosystem Approach to Fisheries (EAF)

An approach to fi sheries management that strives 

to balance diverse societal objectives by taking into 

account the knowledge and uncertainties about biotic, 

abiotic, and human components of ecosystems and 

their interactions and applying an integrated approach 

to fi sheries within ecologically meaningful boundaries. 

The purpose of EAF is to plan, develop, and manage 

fi sheries in a manner that addresses the multiple needs 

and desires of society, without jeopardizing the options 

for future generations to benefi t from the full range of 

goods and services provided by marine ecosystems.5

Ecosystem Approach to Management (EAM)

Management that is adaptive, is specifi ed 

geographically, takes into account ecosystem knowledge 

and uncertainties, considers multiple external infl uences, 

and strives to balance diverse social objectives.8

Ecosystem Assessment

A social process through which the fi ndings of science 

concerning the causes of ecosystem change, their 

consequences for human well-being, and management 

and policy options are brought to bear on the needs of 

decision makers.5

Ecosystem Function

An intrinsic ecosystem characteristic related to the set 

of conditions and processes whereby an ecosystem 

maintains its integrity. Ecosystem functions include 

such processes as decomposition, production, nutrient 

cycling, and fl uxes of nutrients and energy.5

Ecosystem Health

A measure of the stability and sustainability of 

ecosystem functioning or ecosystem services that 

depends on an ecosystem being active and maintaining 

its organization, autonomy, and resilience over time. 

Ecosystem health contributes to human well-being 

through sustainable ecosystem services and conditions 

for human health.5

Ecosystem-Based Management

An approach that takes major ecosystem components 

and services—both structural and functional—into 

account in managing fi sheries. It values habitat, 

embraces a multispecies perspective, and is committed 

to understanding ecosystem processes. Its goal is to 

rebuild and sustain populations, species, biological 

communities, and marine ecosystems at high levels 

of productivity and biological diversity so as not to 

jeopardize a wide range of goods and services from 
12 NOAA FISHERIES GLOSSARY

marine ecosystems while providing food, revenue, and 

recreation for humans.5

Ecosystem Properties

The size, biodiversity, stability, degree of organization, 

and internal exchanges of materials and energy among 

different pools, and other properties that characterize an 

ecosystem.5

Ecosystem Services

Ecosystem services are the benefi ts people obtain from 

ecosystems. These include provisioning services, such 

as food and water; regulating services, such as fl ood 

and disease control; cultural services, such as spiritual 

and cultural benefi ts; and supporting services, such as 

nutrient cycling, that maintain the conditions for life on 

Earth.5

Ecotourism

Tourism involving travel to areas of natural or ecological 

interest for non-consumptive purposes such as observing 

wildlife or learning about the environment.

Eff ort

The amount of time and fi shing power used to harvest 

fi sh; includes gear size, boat size, and horsepower.10 (see 

Fishing Effort)

Egg Survey

A systematic and scientifi c estimation of the abundance 

of eggs (and larvae) in an area, through sampling at the 

bottom or in the water column with appropriate devices 

(e.g. small meshed midwater trawls, plankton nets). 

Used to estimate the size of the spawning stock and the 

importance of spawning.5

Elasmobranch

Describes a group of fi sh without a hard bony skeleton, 

including sharks, skates, and rays.5

El Niño-Southern Oscillation (ENSO)

Abnormally warm ocean climate conditions, which 

in some years affect the west coast of Latin America 

(centered on Peru) often around Christmas time. The 

anomaly is accompanied by dramatic changes in coastal 

upwelling, species abundance and distribution, higher 

local rainfall and fl ooding, and massive deaths of 

fi sh and their predators (including birds). Many other 

climatic anomalies around the world (e.g. droughts, 

fl oods, forest fi res,) are attributed to consequences of El 

Niño.5 (see La Niña, Pacifi c Decadal Oscillation)

Emergency Action (EA)

A fi shery management council (FMC) may decide to 

propose an EA when a problem arises in a fi shery that 

requires regulations sooner than a fi shery management 

plan amendment can be proposed and implemented. 

Once implemented, an EA lasts for 90 days but can be 

extended by the Secretary of Commerce at the council’s 

request.

Endangered Species

A species as defi ned in the Endangered Species Act, that 

is in danger of extinction through a signifi cant portion 

of its range. A species classifi ed as threatened is likely to 

become an endangered species. 

Endangered Species Act (ESA)

The ESA is a statute which was enacted in 1973 to 

conserve species and ecosystems. Under its auspices, 

species facing possible extinction are listed as threatened 

or endangered, or as candidate species for such listings. 

When such a listing is made, recovery and conservation 

plans are drawn up to ensure the protection of the 

species and its habitat.8

Endemism

Of or relating to a native species or population 

occurring under highly restricted conditions due to the 

presence of a unique environmental factor that limits its 

distribution.14

Endorsement

A designation on a limited entry permit that authorizes 

the use of the permit for a particular gear, length of 

vessel, or in a particular segment of the fi shery.1

Environmental Assessment (EA)

As part of the National Environmental Policy Act 

(NEPA) process, an EA is a concise public document 

that provides evidence and analysis for determining 

whether to prepare an environmental impact statement 

(EIS) or a fi nding of no signifi cant impact (FONSI).1

Environmental Ethics

A cluster of beliefs, values, and norms regarding how 

humans should interact with the environment.14

Environmental Impact Statement (EIS)

As part of the National Environmental Policy Act 

(NEPA) process, an EIS is an analysis of the expected 

impacts resulting from a proposed Federal action (such 

as fi sheries management or a development plan) on 

the environment. An EIS is required for all fi shery 

management plans as well as signifi cant amendments 

to existing plans. The purpose of an EIS is to ensure 

that the proposed Federal action gives appropriate 

consideration to environmental values in order to 

prevent harm to the environment.1
JUNE 2006 13

Environmental Protection Agency (EPA)

A Federal agency charged with enforcing numerous 

environmental laws (including the Clean Water Act, the 

Clean Air Act, and the State Drinking Water Act) and 

supporting state and local governments in establishing 

and enforcing environmental laws. In addition to 

enforcement, the EPA researches causes, effects, and 

remediation of environmental problems. All fi nal 

environmental impact statements (EIS) are available 

from the EPA.

Epifauna

Benthic fauna living on the substrate but not burrowing 

into it (as on a hard seafl oor) or living on other 

organisms.12 (see Benthic)

Equilibrium Catch

The catch (in numbers) taken from a fi sh stock when it 

is in equilibrium with fi shing of a given intensity, and 

(apart from the effects of environmental variation) its 

abundance is not changing from one year to the next.6

Equilibrium Yield (EY)

The yield in weight taken from a fi sh stock when it is in 

equilibrium with fi shing of a given intensity, and (apart 

from effects of environmental variation) its biomass 

is not changing from one year to the next. Also called: 

sustainable yield, equivalent sustainable yield.6

Escapement 

The number or proportion of fi sh surviving (escaping 

from) a given fi shery at the end of the fi shing season and 

reaching the spawning grounds. The term is generally 

used for salmon management.1

Essential Fish Habitat (EFH)

Congress defi ned EFH as “those waters and substrate 

necessary to fi sh for spawning, breeding, feeding, or 

growth to maturity” (16 U.S.C. 1802(10)). The EFH 

guidelines under 50 CFR 600.10 further interpret the 

EFH defi nition as follows: Waters include aquatic areas 

and their associated physical, chemical, and biological 

properties that are used by fi sh and may include aquatic 

areas historically used by fi sh where appropriate; 

substrate includes sediment, hard bottom, structures 

underlying the waters, and associated biological 

communities; necessary means the habitat required to 

support a sustainable fi shery and the managed species’ 

contribution to a healthy ecosystem; and “spawning, 

breeding, feeding, or growth to maturity” covers a 

species’ full life cycle.7

EFH Assessment

An EFH assessment is a written assessment of the 

effects of a proposed Federal action on EFH. Federal 

agencies must provide the National Marine Fisheries 

Service (NMFS) with an EFH assessment for any 

action that may adversely affect EFH, except for 

those activities covered by a general concurrence. An 

EFH assessment must contain 1) a description of the 

proposed action; 2) an analysis of the effects, including 

cumulative effects, of the proposed action on EFH and 

managed species; 3) the Federal agency’s conclusions 

regarding the effects of the action on EFH; and 4) 

proposed mitigation, if applicable. If appropriate, the 

EFH assessment should also include the items listed at 

50 CFR 600.920(e)(4). The level of detail in an EFH 

assessment should be commensurate with the potential 

impacts to EFH.7

EFH Consultation

An EFH consultation refers to the process of satisfying 

the Federal agency consultation and response 

requirements of section 305(b)(2) and 305(b)(4)(B) of 

the Magnuson-Stevens Act, and the EFH conservation 

recommendation requirement of section 305(b)(4)(A) 

of that Act. When completed, an EFH consultation 

generally consists of: 1) notifi cation to the National 

Marine Fisheries Service (NMFS) of a Federal 

action that may adversely affect EFH; 2) an EFH 

assessment provided to NMFS; 3) EFH conservation 

recommendations provided by NMFS to the Federal 

action agency; and 4) the Federal agency’s response to 

NMFS EFH conservation recommendations.7

EFH Conservation Recommendation

EFH conservation recommendations are 

recommendations provided by the National Marine 

Fisheries Service (NMFS) to a Federal or state agency 

pursuant to section 305(b)(4)(A) of the MagnusonStevens Act regarding measures that can be taken 

by that agency to conserve EFH. EFH conservation 

recommendations may be provided as part of an EFH 

consultation with a Federal agency, or may be provided 

by NMFS to any Federal or state agency whose actions 

would adversely affect EFH (50 CFR 600.925).7

Estimated Discard Mortality

Estimates of discards can be made in a variety of ways, 

including samples from observers and logbook records.1

Estuarine

1. Relating to, or formed in an estuary (e.g. estuarine 

currents; estuarine animals); 2. Belonging to an estuary 

(river mouth), an area in which sea water is appreciably 

diluted by fresh water from rivers.5

Estuary

A coastal ecological ecosystem that is partially enclosed, 

receives freshwater input from land, and has a horizontal 
14 NOAA FISHERIES GLOSSARY

fresh-salt salinity gradient; the average salinity of 

estuarine waters is defi ned as being 30 practical salinity 

units (PSU) for at least 1 month per year.12

Euryhaline

Organisms able to tolerate a wide range of salinity.12

Eutrophication

Generally, the natural or man-induced process by which 

a body of water becomes enriched in dissolved mineral 

nutrients (particularly phosphorus and nitrogen) that 

stimulate the growth of aquatic plants and enhances 

organic production of the water body. Excessive 

enrichment may result in the depletion of dissolved 

oxygen and eventually to species mortality.5

Evolutionary Signifi cant Unit (ESU)

An ESU is a distinctive group of Pacifi c salmon, 

steelhead, or sea-run cutthroat trout that is uniquely 

adapted to a particular area or environment and cannot 

be replaced.1

Excess Capacity

In the short-term, fi shing capacity that exceeds the 

capacity required to capture and handle the allowable 

catch. In the long-term, fi shing capacity that exceeds the 

level required to ensuring the sustainability of the stock 

and the fi shery at the desired level. Fishing capacity in 

excess of what is required to reach the agreed catch or 

effort objectives materialized by agreed target reference 

points (e.g. MSY, F0.1, MEY, etc.).5

Exclusive Economic Zone (EEZ) 

The EEZ is the area that extends from the seaward 

boundaries of the coastal states (3 nautical miles (n.mi.) 

in most cases, the exceptions are Texas, Puerto Rico 

and the Gulf coast of Florida at 9 n.mi.) to 200 n.mi. off 

the U.S. coast. Within this area the United States claims 

and exercises sovereign rights and exclusive fi shery 

management authority over all fi sh and all continental 

shelf fi shery resources.8

Executive Order 12866

A presidential Executive Order that, among other things, 

requires Federal agencies to assess the economic costs 

and benefi ts of all regulatory proposals and complete 

a regulatory impact analysis (RIA) that describes the 

costs and benefi ts of the proposed rule and alternative 

approaches, and justifi es the chosen approach.1 (see 

Regulatory Flexibility Act)

Exempted Fishing Permit

A permit issued by NMFS that allows exemptions from 

some fi shery regulations for testing, public display, 

data collection, exploratory fi shing, health and safety, 

environmental cleanup, and/or hazard removal purposes. 

Previously known as an “experimental fi shing permit.”1

Existence Value

The economic value of knowing that a resource exists, 

irrespective of the ability to use the resource now or in 

the future.9 (see Heritage Value)

Exploitable Biomass

Refers to that portion of a stock’s biomass that is 

available to the fi shing gear.5

Exploitation Pattern

The distribution of fi shing mortality over the age 

composition of the fi sh population, determined by the 

type of fi shing gear, area and seasonal distribution of 

fi shing, and the growth and migration of the fi sh. The 

pattern can be changed by modifi cations to fi shing 

gear; for example, increasing mesh or hook size, or by 

changing the ratio of harvest by gears exploiting the fi sh 

(e.g. gillnet, trawl, hook and line, etc.).6

Exploitation Rate

The proportion of a population at the beginning of a 

given time period that is caught during that time period 

(usually expressed on a yearly basis). For example, 

if 720,000 fi sh were caught during the year from a 

population of 1 million fi sh alive at the beginning of the 

year, the annual exploitation rate would be 0.72.6

Ex-Vessel

Refers to activities that occur when a commercial fi shing 

boat lands or unloads a catch. For example, the price 

received by a captain (at the point of landing) for the 

catch is an ex-vessel price.5

F

F-Ratio

The ratio of fi shing mortality on the oldest age group to 

the fi shing mortality of the preceding age group. Annual 

F-ratios are estimable parameters in many virtual 

population analysis (VPA) assessments.5

Factory Trawler

A large stern trawler equipped with plant for gutting, 

fi lleting, freezing and storing fi sh, and for processing 

fi sh oil and fi shmeal. Such vessels usually have 

extensive superstructures.5
JUNE 2006 15

Fathom

1.83 meters, equivalent to 6 feet.

Fecundity

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. The 

information is used to compute spawning potential.5

Federal Register (FR)

The Federal Register is the offi cial daily publication for 

rules, proposed rules, and notices of Federal agencies 

and organizations, as well as executive orders and other 

presidential documents. Fisheries regulations are not 

considered fi nal until they are published in the Federal 

Register.1 (see Rulemaking)

Fillet

A slice of meat without bones, cut out for human 

consumption.5

Financial Analysis

Cost accounting based on market prices as opposed to 

opportunity costs.9

Financial Ratio

A method of evaluating a fi rm’s fi nancial position. An 

example is the “current ratio” which is equal to current 

assets divided by current liabilities.9

Finding of No Signifi cant Impact (FONSI)

As part of the National Environment Policy Act 

(NEPA) process, a FONSI is a document that explains 

why an action that is not otherwise excluded from the 

NEPA process, and for which an environmental impact 

statement (EIS) will not be prepared, will not have a 

signifi cant effect on the human environment.1

Finfi sh

Vertebrate and cartilanginous fi shery species, not 

including crustaceans, cephalopds, or other mollusks.13

Finning

The practice of removing fi ns and discarding the carcass, 

usually pertaining to sharks.5

Fish 

Used as a collective term, includes mollusks, 

crustaceans and any aquatic animal which is harvested.5

Fish Aggregating Device (FAD) 

Artifi cial or natural fl oating objects placed on the ocean 

surface, often anchored to the bottom, to attract several 

schooling fi sh species underneath, thus increasing their 

catchability.5

Fish Meal

Protein-rich meal derived from processing whole fi sh 

(usually small pelagic fi sh, and fi shery bycatch) as well 

as residues and byproducts from fi sh processing plants 

(fi sh offal). Used mainly as agriculture feeds for poultry, 

pigs, and aquaculture feeds for carnivorous aquatic 

species.5

Fish Stock 

The living resources in the community or population 

from which catches are taken in a fi shery. Use of the 

term fi sh stock usually implies that the particular 

population is more or less isolated from other stocks 

of the same species and hence self-sustaining. In a 

particular fi shery, the fi sh stock may be one or several 

species of fi sh but here is also intended to include 

commercial invertebrates and plants.5

Fisher

A gender-neutral name for a person (male or female) 

participating in a fi shery.5

Fisheries Management

The integrated process of information gathering, 

analysis, planning, decision making, allocation of 

resources, and formulation and enforcement of fi shery 

regulations by which the fi sheries management 

authority controls the present and future behaviors of 

the interested parties in the fi shery in order to ensure the 

continued productivity of the living resources.5

Fisheries Management Authority

The body which makes the decisions on how the 

fi shery is carried out, and is responsible for all ancillary 

services, such as statistics gathering, assessment, 

monitoring, control and surveillance, consultation with 

fi shers and other users of the sea, and resource allocation 

or determining the conditions of access to the fi shery.5

Fisheries Management Organization

Institution responsible for fi sheries management, 

including the formulation of the rules that govern fi shing 

activities. The fi shery management organization, and 

its subsidiary bodies, may also be responsible for all 

ancillary services, such as the collection of information, 

its analysis, stock assessment, monitoring, control 

and surveillance, consultation with interested parties, 

application and/or determination of the rules of access to 

the fi shery, and resource allocation. Also called: fi shery 

management arrangement.5
16 NOAA FISHERIES GLOSSARY

Fishery

1. Generally, a fi shery is an activity leading to harvesting 

of fi sh. It may involve capture of wild fi sh or raising 

of fi sh through aquaculture; 2. A unit determined by an 

authority or other entity that is engaged in raising or 

harvesting fi sh. Typically, the unit is defi ned in terms of 

some or all of the following: people involved, species or 

type of fi sh, area of water or seabed, method of fi shing, 

class of boats, and purpose of the activities;5 3. The 

combination of fi sh and fi shers in a region, the latter 

fi shing for similar or the same species with similar or the 

same gear types.12

Fishery Conservation and Management Act (FCMA)

The Fishery Conservation and Management Act of 

1976 is the Federal law that created the regional fi shery 

management councils and is the Federal government’s 

basis for fi sheries management in the U.S. Exclusive 

Economic Zone (EEZ). It has been reauthorized a 

number of times and was renamed the MagnusonStevens Fishery Conservation and Management Act 

(Magnuson-Stevens Act) in honor of the late Washington 

Senator, Warren G. Magnuson, in 1980, and in 1996, 

added Alaska Senator Ted Stevens.

Fishery

The combination of fi sh and fi shers in a region, the later 

fi shing for similar or the same species with similar or the 

same gear types.12

Fishery Conservation Zone (FCZ) 

The FCZ is the area from the seaward limit of state 

waters out to 200 nautical miles. Since 1981, it is 

referred to as the U.S. Exclusive Economic Zone (EEZ).

Fishery-Dependent

Data collected directly on a fi sh or fi shery from 

commercial or sport fi shermen and seafood dealers. 

Common methods include logbooks, trip tickets, port 

sampling, fi shery observers, and phone surveys.2 (see 

Fishery-Independent)

Fishery Economic Assessment Model (FEAM)

FEAM uses historical landings data, information 

on industry cost and margin structure (vessels and 

processors), and income multipliers generated by IMpact 

analysis for PLANing (IMPLAN), a regional economic 

impact model, to produce estimates of “regionalized” 

local income impact after deducting for leakage of 

payments to nonresidents and to non-local suppliers, 

wholesalers, and manufacturers.1

Fishery-Independent

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 fi shing sector. Intended to avoid the biases inherent 

to fi shery-related data.5 (see Fishery-Dependent)

Fishery Management Council (FMC) 

A regional fi sheries management body established by the 

Magnuson-Stevens Act to manage fi shery resources in 

eight designated regions of the United States.1

Comment: “Council membership is a balance of 

commercial and recreational fi sherman, marine scientists 

and state and Federal fi sheries managers, who combine 

their knowledge to prepare fi shery management plans 

(FMPs) for stocks of fi nfi sh, shellfi sh and crustaceans. 

In developing these FMPs the councils use the most 

recent scientifi c assessments of the ecosystems involved 

with special consideration of the requirements of marine 

mammals, sea turtles and other protected resources.” 

[Magnuson-Stevens Act]

Fishery Management Plan (FMP) 

1. A document prepared under supervision of the 

appropriate fi shery management council (FMC) 

for management of stocks of fi sh judged to be in 

need of management. The plan must generally be 

formally approved. An FMP includes data, analyses, 

and management measures5; 2. A plan containing 

conservation and management measures for fi shery 

resources, and other provisions required by the 

Magnuson-Stevens Act, developed by fi shery 

management councils or the Secretary of Commerce.3

Fishery Management Unit (FMU)

A fi shery or a portion of a fi shery identifi ed in a 

fi shery management plan (FMP) relevant to the FMP’s 

management objectives. The choice of stocks or species 

in an FMU depends upon the focus of FMP objectives, 

and may be organized around biological, geographic, 

economic, technical, social, or ecological perspectives.5

Fishery Models

Simplifi ed representations of the fi sheries complex 

reality. May or may not be a mathematical 

representation.5 (see Simulation)

Fishery Policy

Measures by which a national government, regional 

or state authority, attempts to infl uence or control the 

behavior of individuals, companies, and communities 

in the fi sheries sector to achieve certain objectives. 

The measures can be of varied kinds including fi scal 

measures, (e.g. taxes, subsidies, public investments, 

etc.); trade measures (e.g. import and export duties; 
JUNE 2006 17

quotas); social measures (health and education services); 

regulations (i.e. on food quality; means and types of fi sh 

harvesting; individual transferable quotas); and others.5

Fishery Reserve

Zoning that precludes fi shing activity on some or all 

species to protect critical habitat, rebuild stocks (long 

term, but not necessarily permanent closure), provide 

insurance against overfi shing, or enhance fi shery yield.14

Fishery Resource

In general, refers to elements of a natural aquatic 

resource (e.g. strains, species, populations, stocks, 

assemblages that can be legally caught by fi shing). May 

sometimes be taken as including also the habitat of such 

resources.5

Fishery Technology

The equipment and practices for fi nding, harvesting, 

handling, processing, and distributing aquatic resources 

and their products.5

Fishing

Any activity, other than scientifi c research conducted by 

a scientifi c research vessel, that involves the catching, 

taking, or harvesting of fi sh; or any attempt to do so; or 

any activity that can reasonably be expected to result 

in the catching, taking, or harvesting of fi sh and any 

operations at sea in support of it.5

Fishing Capacity

1. The ability of a stock of inputs (capital) to produce 

output (measured as either effort or catch); 2. The 

maximum amount of fi sh over a period of time (year, 

season) that can be produced by a vessel or fl eet of 

vessels if fully utilized, given the biomass and age 

structure of the fi sh stock and the present state of the 

technology. The “fi shing fl eet” is the stock of inputs (i.e. 

physical capital and human capital). The term “fully 

utilized” is used in a precautionary context in that it 

assumes that capacity utilization is 100 percent; 3. The 

quantity of fi sh that can be taken by a fi shing unit, for 

example an individual, community, vessel, or fl eet, 

assuming that there is no limitation on the yield from 

the stock, usually expressed in terms of some measure 

of vessel size, such as gross tonnage, hold capacity, 

horsepower. Refl ects potential rather than nominal 

fi shing effort.5

Fishing Community

A community that is substantially dependent on or 

substantially engaged in the harvest or processing of 

fi shery resources to meet social and economic needs. 

Includes fi shing vessel owners, fi shing families, 

operators, crew, recreational fi shers, fi sh processors, 

gear supplies, and others in the community who depend 

on fi shing.1

Fishing Eff ort

The amount of fi shing gear of a specifi c type used on 

the fi shing grounds over a given unit of time (e.g. hours 

trawled per day, number of hooks set per day, or number 

of hauls of a beach seine per day). When two or more 

kinds of gear are used, the respective efforts must be 

adjusted to some standard type before being added. 

Sometimes referred to as effective fi shing effort.5

Comment: The effort may be nominal, refl ecting the 

simple total of effort units exerted on a stock in a given 

time period. It may also be standard or effective when 

corrected to take account of differences in fi shing 

power and effi ciency and ensure direct proportionality 

with fi shing mortality. Relates usually to a specifi c 

fi shery and gear. If more than one gear is considered, 

standardization in relation to one of them is necessary. 

For biologists, a good measure of fi shing effort should 

be proportional to fi shing mortality. For economists it 

should be proportional to the cost of fi shing.5

Fishing Gear

The equipment used for fi shing (e.g. gillnet, hand line, 

harpoon, haul seine, long line, bottom and midwater 

trawls, purse seine, rod-and-reel, pots and traps). Each 

of these gears can have multiple confi gurations.5

Fishing Intensity

1. In general, and mainly for trawling, the fi shing effort 

exerted per unit of areas (e.g. in hours of trawling per 

100 square miles). In stock assessment theory, the 

effective (or standard) fi shing effort per unit area must 

be proportional to fi shing mortality through the relation 

F = q(f/A) where (f/A) is the fi shing intensity, and q is 

the catchability coeffi cient; 2. Effective fi shing effort; 3. 

Fishing effort per unit area; 4. Effectiveness of fi shing.5

Fishing Mortality (F)

1. F stands for the fi shing mortality rate in a particular 

stock. It is roughly the proportion of the fi shable stock 

that is caught in a year5; 2. A measurement of the rate of 

removal from a population by fi shing. Fishing mortality 

can be reported as either annual or instantaneous. 

Annual mortality is the percentage of fi sh dying in one 

year. Instantaneous mortality is that percentage of fi sh 

dying at any one time.2

F0.1

The fi shing mortality rate which the increase in yield per 

recruit in weight for an increase in a unit of effort is only 
18 NOAA FISHERIES GLOSSARY

10 percent of the yield per recruit produced by the fi rst 

unit of effort on the unexploited stock (i.e. the slope of 

the yield-per-recruit curve for the F0.1 rate is only onetenth the slope of the curve at its origin).6

F10%

The fi shing mortality rate that reduces the spawning 

stock biomass per recruit (SSB/R) to 10% of the amount 

present in the absence of fi shing.3

FHIGH

Fishing mortality rate corresponding to an equilibrium 

spawning potential ratio equal to the inverse of the 90th

percentile observed survival ratio.11

FLOW

Fishing mortality rate corresponding to an equilibrium 

spawning potential ratio equal to the inverse of the 10th

percentile observed survival ratio.11

FMED

Fishing mortality rate corresponding to an equilibrium 

Spawning Potential Ratio equal to the inverse of the 

median observed survival ratio.11

f

MSY

Effective fi shing effort corresponding to FMSY.

11

FMSY

The fi shing mortality rate that, if applied constantly, 

would result in maximum sustainable yield (MSY). 

Used as a biological reference point, FMSY is the implicit 

fi shing mortality target of many regional and national 

fi shery management authorities and organizations. FMSY

can be estimated in two ways: a) from simple biomassaggregated production models; b) from age-structured 

models that include a stock-recruitment relationship.5

FMAX

1. The level of fi shing mortality (rate of removal by 

fi shing) that produces the greatest yield from the 

fi shery2; 2. A biological reference point. It is the 

fi shing mortality rate that maximizes equilibrium yield 

per recruit. FMAX is the F level often used to defi ne 

growth overfi shing. In general, FMAX is different (and 

higher) than FMSY depending on the stock-recruitment 

relationship. By defi nition, FMAX is always higher than 

F0.1.

5

Fτ (also FEXTINCTION, FCRASH) 

Fishing mortality rate corresponding to an equilibrium 

spawning potential ratio equal to the inverse of the 

survival ratio at the origin of the stock-recruitment 

relationship. A stock fi shed at or above this level for a 

prolonged period of time is expected to collapse.11

FX%

Fishing mortality rate that results in x% equilibrium 

spawning potential ratio.11

Fishing Power

1. The catch which a particular gear or vessel takes from 

a given density of fi sh during a certain time interval. 

For example, larger vessels (horsepower) have a greater 

ability to catch more fi sh, thus the greater their fi shing 

power. Also, improvements in a vessel or gear, such 

as fi sh fi nders, global positioning systems, etc., can 

increase fi shing power3; 2. Of a boat, or of a fi shing 

gear: The relative vulnerability of the stock to different 

boats or gears. Usually determined as the catch taken by 

the given apparatus, divided by the catch of a standard 

apparatus fi shing at nearly the same time and place.5 (see 

Standardization)

Comment: In such a defi nition, fi shing power is not 

measured in absolute terms and is dependent on stock 

size. For this reason, in practice, fi shing power is 

measured only in relative terms.5

Fixed Costs

Costs that do not vary with output. Fixed costs can only 

be avoided if the fi rm goes out of business.5

Fixed Gear

Fishing gear that is stationary after it is deployed (unlike 

trawl or troll gear which is moving when it is actively 

fi shing). Fixed gear includes gillnets, long lines, pots, 

traps, and any other gear that is anchored at least at one 

end.1

Fjord

An estuary with a seaward sill that is formed in a deep 

valley created by a retreating glacier.12

Food and Agriculture Organization (FAO) 

United Nations organization founded in 1945 with a 

mandate to raise levels of nutrition and standards of 

living, to improve agricultural productivity, and to better 

the condition of rural populations. FAO is active in land 

and water development, plant and animal production, 

forestry, fi sheries, economic and social policy, 

investment nutrition, food standards, and commodities 

and trade.13

Food Chain

The transfer of energy from the source in plants 

through a series of organisms with repeated eating and 

being eaten. At each transfer, a large proportion of the 

potential energy is lost as heat. The shorter the food 

chain (or the nearest the organism is from the beginning 

of the food chain), the greater the available energy 
JUNE 2006 19

which can be converted in biomass.5 (see Predator-Prey 

Relationship, Trophic Level)

Food Security

Freedom from hunger. The capability to produce an 

adequate amount of food for all consumers at affordable 

prices.5

Footrope

The rope along the bottom of a trawl net’s opening. Small

footropes can get caught or tangled in rocky reef areas, so

regulations that require small footropes protect these rocky

areas by encouraging fi shermen to fi sh elsewhere.

Forage Species

Species used as prey by a larger predator for its food. 

Includes small schooling fi shes such as anchovies, 

sardines, herrings, capelin, smelts, and menhaden, and 

invertebrates such as squid.5

Fork Length

A measurement used frequently for fi sh length when 

the tail has a fork shape. Projected straight distance 

between the tip of the snout and the fork of the tail.5

Freedom of Information Act (FOIA)

Federal statute enacted in 1996 giving members of the 

public the right to request access to Executive Branch 

records for inspection or copying.

Front

In oceanographic terms, a region of sharp gradient in 

temperature or salinity, indicating a transition between 

two current systems or water masses. Intersection 

between the thermocline (temperature discontinuity) or 

halocline (salinity discontinuity) and the surface. Fronts 

are usually associated with high biological activity, high 

abundance of highly migratory resources (e.g. tunas), 

and are actively sought as fi shing areas. Fronts can be 

monitored by satellite remote-sensing.5

Fully Exploited

Term used to qualify a stock which is probably 

neither being overexploited nor underexploited and is 

producing, on average, close to its maximum sustainable 

yield (MSY). This situation would correspond to fi shing 

at FMSY (in a classical production model relating yield to 

effort) or FMAX (in a model relating yield-per-recruit to 

fi shing mortality).5

G

Gastropods

Snails and other mollusks (e.g. abalone, Queen conch, 

and cones)that typically possess a coiled dorsal shell 

and a ventral creeping foot.12

Gear

A fi shing gear is a tool used to catch fi sh, such as hookand-line, trawl net, gillnet, pot, trap, spear, etc.5

Gear Confl ict

Confl icts between fi shing gear on fi shing grounds where 

one type of gear interferes with another type of gear. An 

example is where mobile trawling gear damages passive 

gear, such as lobster traps.5

Gear Restriction

1. A type of input control used as a management tool 

whereby the amount and/or type of fi shing gear used 

by fi shers in a particular fi shery is restricted by law5; 

2. Limits placed on the type, amount, number, or 

techniques allowed for a given type of fi shing gear.13

General Linear Model (GLM)

1. A mathematical formula (model) that relates one 

biological factor to another. Once a mathematical 

relationship is established, scientists use the model 

to predict one factor over another2; 2. A statistical 

procedure similar to an analysis of variance or a multiple 

regression that is used to estimate the magnitude of 

the effects of different factors on a variable of interest. 

GLM’s are the tool of choice for standardizing catch 

per unit effort (CPUE) data in order to obtain indices of 

abundance. In such applications, the variable of interest 

is CPUE and the factors are year and perhaps others 

such as area, gear confi guration, etc.; the standardized 

abundance index of annual abundance would then be 

given by the parameters associated with the factor, year.5

Generation Time

In the context of the National Standard Guidelines, 

generation time is a measure of the time required for 

a female to produce a reproductively-active female 

offspring for use in setting maximum allowable 

rebuilding time periods.3 (see National Standard 

Guidelines)

Genetically Modifi ed Organism

An organism in which humans by means of gene or cell 

technologies have altered the genetic material. These 

include the isolation, characterization, and modifi cation 

of genes and their introduction into living cells or 
20 NOAA FISHERIES GLOSSARY

viruses of DNA, as well as techniques for the production 

of living cells with new combinations of genetic material 

by the fusion of two or more cells.5

Geographic Information System (GIS)

A computer system for storage, analysis, and retrieval 

of information in which all data are spatially referenced 

by their geographic coordinates (latitude, longitude). 

In addition to primary data, such as climatic and soil 

characteristics, a GIS can be used to calculate derived 

values such as erosion hazard, forest yield class, or land 

suitability for specifi ed land-use types. Data are usually 

derived from maps, and derived values can be printed 

out as maps.5

Geographic Region

With regard to biogeography and species distribution, a 

region which is separated from an adjacent region by a 

barrier which is usually impenetrable to many species, 

limiting their movement or preventing establishment 

outside their natural geographic range.5 

Geothermal Vent

Submerged geoform consisting of a vent of hot, mineralrich water on the ocean fl oor, generally located on or 

near spreading oceanic ridges or on the continental 

margins of subduction trenches.12

Ghost Fishing

The accidental capture of aquatic organisms by fi shing 

gear (usually gillnets, or traps, pots, etc.) that has been 

lost or discarded into the sea and which continues to 

entangle or trap aquatic animals.5

Gillnet

With this type of gear, the fi sh are gilled, entangled or 

enmeshed in the netting. These nets can be used either 

alone or, as is more usual, in large numbers placed in 

line. According to their design, ballasting and buoyancy, 

these nets may be used to fi sh on the surface, in 

midwater or on the bottom.5

Global Positioning System (GPS)

A low cost ($1,000 to $5,000) electronic receiving 

system for fi nding three-dimensional coordinates on the 

earth using satellites.5

Gonadosomatic Index (GSI)

A ratio of the weight of a fi sh’s eggs or sperm to its 

body weight, used to determine the spawning time of a 

species of fi sh.10

Goods and Services

Any commodities or nonmaterial goods (services) such 

as assistance or accommodations that yield positive 

utility.5

Governance

1. In a particular sector (e.g. fi sheries), a continuing 

process through which governments, institutions, and 

stakeholders of the sector and of other interacting 

sectors elaborate and adopt appropriate policies, plans, 

and management strategies to ensure sustainable 

and responsible resource utilization. In the process, 

confl icting or diverse interests may be accommodated 

and cooperative action may be taken; 2. The formal 

and informal arrangements, institutions, and mores 

which determine how resources or an environment are 

utilized, how problems and opportunities are evaluated 

and analyzed, what behavior is deemed acceptable or 

forbidden, and what rules and sanctions are applied to 

affect the pattern of resource and environmental use.5

Gross Economic Benefi ts

Positive utility gained from the use of a resource prior to 

netting the costs. (see Net Economic Benefi ts)

Gross Register Ton (GRT)

A unit of internal volume of a ship, equal to 100 cubic 

feet. GRT is the total volume or capacity of a vessel.13

Groundfi sh

Collective term loosely applied to most commercially 

harvested marine fi sh other than salmonids, scombrids, 

and clupeids. Although many groundfi sh are demersal 

(e.g. yellowtail fl ounder, yellowfi n sole), other species 

are semidemersal or pelagic (e.g. pollock, cod, 

haddock).13 (see Demersal)

Growth

Usually an individual fi sh’s increase in length or weight 

with time. Also may refer to the increase in numbers of 

fi sh in a population with time.2

Growth Model

1. A mathematical formula that describes the increase 

in length or weight of an individual fi sh with time2; 2. 

A mathematical description or representation of the 

size of a living organism at its various ages. The von 

Bertalanffy growth model is commonly used in fi sh 

stock assessments.5

Growth Overfi shing

1. The situation existing when the rate of fi shing is 

above FMAX and when fi sh are harvested before their 

growth potential is fully reached3; 2. When fi shing 

pressure on smaller fi sh is too heavy to allow the fi shery 

to produce its maximum poundage. Growth overfi shing, 

by itself, does not affect the ability of a fi sh population 

to replace itself.2
JUNE 2006 21

Growth Rate (K)

1. Annual or seasonal. The increase in weight of a fi sh 

per year (or season), divided by the initial weight; 2. In 

fi sh this is often measured in terms of the parameter K 

of the von Bertalanffy curve for the mean weight as a 

function of age.5

Guyot

Submerged earthform at depths >200 meters consisting 

of a fl at-topped seamount with a cap of the carbonate 

remains of a drowned atoll.12

Gyre

Large cyclonic current that moves water in a circular 

pattern from the tropics to the polar seas.12

H

Habitat

1. The environment in which the fi sh live, including 

everything that surrounds and affects its life, e.g. water 

quality, bottom, vegetation, associated species (including food supplies); 2. The locality, site and particular 

type of local environment occupied by an organism.5

Habitat Area(s) of Particular Concern (HAPC)

Subsets of essential fi sh habitat that serve an important 

ecological function, are particularly sensitive to humaninduced environmental degradation, are particularly 

stressed by human development activities, or comprise a 

rare habitat type.2

Hadal Zone

Deepest deep bottom area or portion of submerged 

geoform at depths >7,000 meters.12

Halophytic

Salt-tolerant vegetation.12

Harvest

The total number or weight of fi sh caught and kept from 

an area over a period of time. Note that landings, catch, 

and harvest are different.2

Harvest Control Rule

Describes how harvest is intended to be controlled by 

management in relation to the state of some indicator 

of stock status. For example, a harvest control rule can 

describe the various values of fi shing mortality that will 

be aimed at for various values of the stock abundance. 

It formalizes and summarizes a management strategy. 

Constant catch and constant fi shing mortality are two 

types of simple harvest control rules.5

Harvest Guideline

A numerical harvest level that is a general objective, but 

not a quota. Attainment of a harvest guideline does not 

require a management response, but does prompt review 

of a fi shery.1

Harvest Specifi cations

The detailed regulations that make up management 

measures; for example, trawl footrope size, depth limits, 

net mesh-size, etc.1

Harvesting Capacity

The capacity of the fi shing fl eet to harvest fi sh, usually 

expressed in terms of some measure of vessel size, such 

as gross tonnage, hold capacity, horsepower.5

Head Boat

A fi shing boat that takes recreational (sport) fi shermen 

out for a fee per person. Different from a charter boat 

in that people on a head boat pay individual fees as 

opposed to renting the boat.2 (see Party Boat)

Head Rope

The length of rope or wire in a trawl to which the top 

wings and cover netting are attached.5

Health

The condition of the marine environment from the 

perspective of adverse effects caused by anthropogenic 

(human) activities, in particular habitat destruction, 

changed sedimentation rates and the mobilization of 

contaminants. Such condition refers to the contemporary 

state of the ocean, prevailing trends, and the prognosis 

for improvement or deterioration of its quality.5

Heritage Value

Site possessing historical, archaeological, architectural, 

technological, aesthetic, scientifi c, spiritual, social, 

traditional, or other special cultural signifi cance 

associated with human activity.14

Highgrading

Form of selective sorting of fi sh in which higher value, 

more marketable fi sh are retained and fi sh that could be 

legally retained, but are less marketable, are discarded.13

(see Discard)

High Seas 

All waters beyond the Exclusive Economic Zone (EEZ) 

(>200 nautical miles) of the United States and beyond 

any foreign nation’s EEZ.1
22 NOAA FISHERIES GLOSSARY

High Seas Resources

Resources distributed exclusively in the high seas, i.e. in 

waters beyond the areas of national jurisdiction (which 

can be 200 nautical miles or less) excluding species 

fi xed on the continental shelf which remain under the 

sovereign rights of the coastal states.5

Highly Migratory Species

Marine species whose life cycle includes lengthy 

migrations, usually through the exclusive economic 

zones of two or more countries as well as into 

international waters. This term usually is used to denote 

tuna and tuna-like species, sharks, swordfi sh, and 

billfi sh.5 

Hook and Line

A type of fi shing gear consisting of a hook tied to a line. 

Fish are attracted by natural bait that is placed on the 

hook, and are impaled by the hook when biting the bait. 

Artifi cial bait (lures) with hooks are often used. Hookand-line units may be used singly or in large numbers.5

Household

All the persons, kin and non-kin, who live in the 

same dwelling and share income, expenses, and daily 

subsistence tasks. A basic unit for sociocultural and 

economic analysis, a household may consist of persons 

(sometimes one but generally two or more) living 

together and jointly making provision for food or other 

essentials elements of livelihood.5

Hydrothermal Vent

A place on the seafl oor, generally associated with 

spreading centers, where warm to super-hot, mineralrich water is released; may support a diverse community 

of organisms.12

Hypersaline

Extremely salty, having much more salt than normal 

seawater.

I

Ichthyoplankton

Fish eggs and larvae belonging to the planktonic 

community.5

Incidental Catch 

Retained or discarded nontarget species caught when 

fi shing for the primary purpose of catching a different 

species.1,5

Incidental Take

The “take” of protected species (such as listed salmon, 

marine mammals, sea turtles, or sea birds) during 

fi shing. “Take” is defi ned as to harass, harm, pursue, 

hunt, shoot, wound, kill, trap, capture or collect, or to 

attempt to engage in any such conduct.1

Index of Abundance

A relative measure of the abundance of a stock; for 

example, a time series of catch per unit effort data.5

Indicators

1. A variable, pointer, or index. Its fl uctuation 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; 2. Signals of processes, inputs, outputs, 

effects, results, outcomes, impacts, etc., that enable such 

phenomena to be judged or measured. Both qualitative 

and quantitative indicators are needed for management 

learning, policy review, monitoring, and evaluation; 

3. In biology, an organism, species, or community 

whose characteristics show the presence of specifi c 

environmental conditions, good or bad.5

Indigenous Fishing

Fishing undertaken by peoples native to a land or 

region.5

Indirect Methods

Methods for stock assessment based on fi sherydependent data, such as catch and effort statistics and 

age structure of the catch.5

Individual Fishing Quota (IFQ)

A type of limited entry, an allocation to an individual (a 

person or a legal entity, e.g. a vessel owner or company) 

of a right [privilege] to harvest a certain amount of fi sh 

in a certain period of time. It is also often expressed 

as an individual share of an aggregate quota, or total 

allowable catch (TAC).5

Individual Transferable Quota (ITQ)

A type of individual fi shing quota (IFQ) allocated 

to individual fi shermen or vessel owners that can be 

transferred (sold or leased) to others.1,5

Industrial Fishery

A fi shery for species not directly used for human food, 

e.g. Atlantic menhaden fi shery.2

Infauna

Benthic fauna living in the substrate and especially in 

the soft seafl oor.12
JUNE 2006 23

Information Management 

1. A mechanism and structured set of processes, people, 

and equipment for converting data into information and 

storing and distributing information; 2. A mechanism 

for storing, generating and distributing information for 

supporting operations and management functions of an 

organization(s).5

Initial Regulatory Flexibility Analysis

An analysis required by the Regulatory Flexibility Act.1

Input Controls

Management instruments used to control the time and 

place as well as type and/or amount of fi shing with the 

view to limit yields and fi shing mortality; for example, 

restrictions on type and quantity of gear, effort, and 

capacity; closed seasons.5

Input-Output Analysis

A systematic method that both describes the fi nancial 

linkages and network of input supplies and production 

which connect industries in a regional economy 

(however defi ned), and predicts the changes in regional 

output, income, and employment. Input-output analysis 

generally focuses on economic activity and the selfsuffi ciency of an economy, unlike cost-benefi t analysis 

which focuses on changes in net national benefi ts from 

use of a productive resource.9

In-Season Adjustments

Regulatory changes that affect an ongoing fi shery.1

Inshore Waters

Waters of the shallower part of the continental shelf.5

Instantaneous Rate of Fishing Mortality (F)

When fi shing and natural mortality act concurrently, F is 

equal to the instantaneous total mortality rate, multiplied 

by the ratio of fi shing deaths to all deaths. Also called: 

rate of fi shing; instantaneous rate of fi shing.5

Instantaneous Rate of Growth (G)

The natural logarithm of the ratio of fi nal weight to 

initial weight of a fi sh in a unit of time, usually a year. 

When applied collectively to all fi sh of a given age in 

a stock, the possibility of selective mortality must be 

considered. 5

Instantaneous Rate of Mortality (Z) 

When fi shing and natural mortality act concurrently, 

the natural logarithm of the survival rate (with sign 

changed) for deaths due to either natural causes 

(instantaneous rate of natural mortality, M) or due to 

fi shing mortality (instantaneous rate of fi shing mortality, 

F). The instantaneous rate of total mortality, Z, is the 

sum of these two rates: Z = F + M, also called the 

coeffi cient of decrease.5

Comment: Usually given on a yearly basis; the 

fi gure just described is divided by the fraction of a 

year represented by the “short interval” in question. 

This concept is used principally when the size of the 

vulnerable stock is not changing or is changing only 

slowly, since among fi shes recruitment is not usually 

associated with stock size in the direct way in which 

mortality and growth are.5 

Instantaneous Rate of Recruitment

Number of fi sh that grow to catchable size per short 

interval of time, divided by the number of catchable fi sh 

already present at that time. Usually given on a yearly 

basis; that is, the fi gure just described is divided by the 

fraction of a year represented by the “short interval” in 

question. This concept is used principally when the size 

of the vulnerable stock is not changing or is changing 

only slowly, since among fi shes recruitment is not 

usually associated with stock size in the direct way in 

which mortality and growth are.6

Instantaneous Rate of Surplus Production

Equal to rate of growth plus rate of recruitment less 

rate of natural mortality—all in terms of weight and on 

an instantaneous basis. In a “balanced” or equilibrium 

fi shery, this increment replaces what is removed by 

fi shing, and rate of surplus production is numerically 

equal to rate of fi shing. Also called instantaneous rate of 

natural increase.5 

Integrated Analysis

Refers to stock assessment methodologies that attempt 

to integrate multiple sources of data into a single 

estimation framework. For example, an integrated 

assessment can attempt to fi t the following observations 

based on model predictions: total landings by fl eet, size 

samples of landings, discard estimates, size samples 

of discards, standardized catch per unit effort by fl eet, 

fi shery-independent surveys, and tagging records on 

movement, growth, and recoveries.5

Integrated Management

An approach by which the many competing 

environmental and socioeconomic issues are considered 

together, with the aim of achieving the optimal solution 

from the viewpoint of the whole community and the 

whole ecosystem.14

Interstate Marine Fisheries Commissions

Non-regulatory agencies that serve multiple states 

(Pacifi c States: Alaska, California, Idaho, Oregon, and 

Washington; Atlantic States: Maine, New Hampshire, 
24 NOAA FISHERIES GLOSSARY

Massachusetts, Rhode Island, Connecticut, New York, 

New Jersey, Pennsylvania, Delaware, Maryland, 

Virginia, North Carolina, South Carolina, Georgia, and 

Florida; Gulf States: Texas, Louisiana, Mississippi, 

Alabama, and Florida) and as a mechanism for Federal 

funding of regional fi shery projects. Interstate marine 

fi sheries commissions provide a communication 

exchange between individual fi shery management 

councils and information in the form of data services for 

various fi sheries.1

Intertidal Zone

The area on a seacoast between the highest and lowest 

tide.12 (see Littoral Zone)

Intrinsic Growth Rate (r)

A value that quantifi es 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.5

Intrinsic Rate of Increase (z)

The change in the amount of harvestable stock, 

estimated by recruitment increases plus growth minus 

natural mortality.10

Introduced Species 

With respect to a particular ecosystem, any species, 

including its seeds, eggs, spores, or other biological 

material capable of propagating that species, that is 

not native to that ecosystem. Introduced species often 

compete with and cause problems for native species. 

Introduced species are also called exotic, nonnative, and 

alien species.4 (see Invasive Species, Native Species)

Invasive species

An introduced species that out-competes native species 

for space and resources.4 (see Introduced Species, Native 

Species)

Invertebrate 

Animals without a backbone. In fi shery management 

terms, refers to shellfi sh, including lobsters, clams, 

shrimps, oysters, crabs, and sea urchins.12

Island

Emergent land mass larger than 1 square kilometer in 

area, completely surrounded by water. Also refers to 

aquatic habitats that are associated with land masses 

completely surrounded by water or elevated ridges 

extending from the seafl oor covered with shallow water 

(banks) which may support unconsolidated sediments 

(shoals), rocks, or shallow reefs rising above the surface 

of the water.12

Isobath

A line on a map connecting points of equal bathymetry, 

i.e. equal depth, in the ocean or another water body.12

J

Jigging

A method of fi shing using lures on a vertical line that 

snag fi sh when they pass near. The line is moved up 

and down (jigged) by hand or mechanically. Extremely 

effi cient for fi shing oceanic squids at night.5

Juvenile

A young fi sh or animal that has not reached sexual 

maturity.5

K

Krill

From the Norwegian word meaning “young fi sh” 

and is now commonly used as the common term for 

euphausids, a family of crustaceans found throughout 

the world oceans. There are 85 species of krill, some of 

which are exploited commercially. The Antarctic krill 

is Euphausia superba. Other species include Euphausia 

pacifi ca, Euphausia nana, Thysanoessa inermis, 

Meganyctiphanes norvegica, Nyctiphanes australis.

5

L

Lagoon

Coastal water body entirely or almost entirely enclosed 

by a landmass with minimal connection to the sea; a 

shallow, sheltered body of water separated from the 

open sea by coral reefs, sand bars, or barrier islands.12

La Niña

Climate anomaly opposite to El Niño with unusually 

cold ocean temperatures in the Equitorial Pacifi c, 

leading to warmer winter temperatures in the 
JUNE 2006 25

southeastern United States and cooler temperatures 

in the Pacifi c Northwest. La Niña events occur after 

some, but not all El Niño events. (see El Niño-Southern 

Oscillation)

Landings

1. The number or poundage of fi sh unloaded by 

commercial fi shermen or brought to shore by 

recreational fi shermen for personal use. Landings are 

reported at the locations at which fi sh are brought to 

shore2; 2. The part of the catch that is selected and kept 

during the sorting procedures on board vessels and 

successively discharged at dockside.5

Landings Data

Information on the amount of fi sh caught and landed per 

year.10

Large Fluctuations

Large fl uctuations occur in a number of species where 

the population size or area of distribution varies widely, 

rapidly, and frequently, with a variation greater than one 

order of magnitude.5

Large Marine Ecosystem (LME)

A geographic area of an ocean that has distinct 

bathymetry, hydrography, productivity, and trophically 

dependent populations.5

Latent Species

A species of fi sh that has the potential to support a 

directed fi shery.10

Least Squares

A statistical criterion for the estimation of the goodness 

of fi t in correlation analysis. Least squares methods aim 

to minimize the sum of squared differences between 

the observations and the predictions from a model. 

For example, virtual population analysis (VPA) tuning 

often involves fi nding the estimates of abundance 

and mortality rates that minimize the sum of squared 

differences between standardized catch per unit effort 

(CPUE) and predicted abundance from the VPA.5 (see 

Regression Analysis, Residual)

Length at First Maturity

Length at which 50 percent of the individuals of a 

given sex (normally females) are considered to be 

reproductively mature.5

Length Frequency

A length frequency distribution is an arrangement of 

recorded lengths (in a total catch, a stock, or a sample) 

which indicates the number of individuals encountered 

in each length interval.5

Length-Frequency Distribution

The number of individuals of a catch or catch sample in 

each length interval. The modal size is the length group 

with the higher number of individuals. Distributions may 

be uni- or bimodal but are more generally multimodal, 

refl ecting multiple age-groups.5

Length Requirement

Specifi es that permits may not be registered for use with 

vessels more than 5 feet longer (in overall length) than 

the length endorsed on the permit.1

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.2 (see Age-Length Key)

Level of Exploitation

This can mean the amount of catch or level of fi shing 

mortality, or is sometimes used without any precise 

quantity in mind.5

License

Also known as permit. A license or permit is a document 

giving the producer the right to operate in a fi shery 

according to the terms established by the regulating 

authority.5

License Limitation

Legally restricting the number of commercial fi shermen 

licensed to fi sh. Often a management agency uses this as 

a means of limited entry.5 (see Limited Entry)

Life Cycle

Successive series of changes through which an organism 

passes in the course of its development.5

Lifespan

The maximum expected age, on average, for a species, 

cohort, stock, or a population in the absence of fi shing 

or human-induced mortality. Lifespan is inversely 

proportional to natural mortality. Often referred to as 

Tmax in stock assessment models. Different and smaller 

than the absolute maximum age.5

Limit Capacity

The maximum amount of fi sh that can be produced on a 

sustainable basis by a fully utilized fl eet. Thus, the limit 

capacity corresponds to maximum sustainable yield 

(MSY).5

Limit Reference Points

Benchmarks used to indicate when harvests should 

be constrained substantially so that the stock remains 

within safe biological limits. The probability of 
26 NOAA FISHERIES GLOSSARY

exceeding limits should be low. In the National Standard 

Guidelines, limits are referred to as thresholds. In much 

of the international literature (e.g. United Nations Food 

and Agricultural Organization, FAO) thresholds are 

used as buffer points that signal when a limit is being 

approached.3 (see National Standard Guidelines)

Limited Entry

A program that changes a common property resource 

like fi sh into private property for individual fi shermen. 

License limitation and individual transferable quotas 

(ITQ) are two forms of limited entry.2

Limited Entry Fishery

Fishery where the number of operators (and size of 

boats) is restricted through license limitation or quota 

systems, to control the amount of fi shing effort. It 

frequently involves controls on the number and size of 

vessels, and conditions relating to the transfer of fi shing 

rights or the replacement of vessels.5

Littoral Zone

The zone on the coast where land mets sea. Often called 

the intertidal zone but is more comprehensive, including 

the supratidal and infratidal zones.12 (see Intertidal 

Zone)

Local Depletion

Local depletion occurs when localized catches take more 

fi sh than can be replaced either locally or through fi sh 

migrating into the catch area. Local depletion can occur 

apart form the status of the overall stock, and can be 

greater than decreases in the entire stock.1

Location

Location defi nes a geographically or ecologically 

distinct area in which a single event (e.g. pollution) 

will soon affect all individuals of the taxon present. A 

location usually, but not always, contains all or part of 

a subpopulation of the taxon, and is typically a small 

proportion of the taxon’s total distribution.5

Logbook

A detailed, usually offi cial, record of a vessel’s fi shing 

activity registered systematically on board the fi shing 

vessel, usually including information on catch and 

its species composition, the corresponding fi shing 

effort and location. Completion of logbooks may be a 

compulsory requirement for a fi shing license.5

Longline

Fishing method using a horizontal mainline to which 

weights and baited hooks are attached at regular 

intervals. The horizonal mainline is connected to the 

surface by fl oats. The mainline can extend from several 

hundred yards to several miles and may contain several 

hundred to several thousand baited hooks.13

Longliner

Vessel specifi cally designed to catch fi sh using the 

longline fi shing method.13

Long-Term Potential Catch (Yield)

The largest annual harvest, in weight, that can be 

removed from a fi sh stock year after year, under existing 

environmental conditions. This can be estimated in 

various ways, from maximum values from production 

models to average observed catches over a suitable 

period of years.6 (see Maximum Sustainable Yield)

M 

Macrofauna

Large animals (for example fi sh).12

Magnuson-Stevens Fishery Conservation and 

Management Act (Magnuson-Stevens Act)

Federal legislation responsible for establishing 

the fi shery management councils (FMCs) and the 

mandatory and discretionary guidelines for Federal 

fi shery management plans (FMPs). This legislation was 

originally enacted in 1976 as the Fishery Management 

and Conservation Act; its name was changed to the 

Magnuson Fishery Conservation and Management Act 

in 1980, and in 1996 it was renamed the MagnusonStevens Fishery Conservation and Management Act.13

Maintainable Yield

The largest catch that can be maintained from the 

population, at whatever level of stock size, over an 

indefi nite period. It will be identical to the sustainable 

yield for populations below the level giving the 

maximum sustainable yield (MSY), and equal to the 

MSY for populations at or above this level.6

Management

The art of taking actions that affect a resource and its 

exploitation with a view to achieve certain objectives, 

such as maximizing the production of that resource. 

Management includes, for example, fi shery regulations 

such as catch quotas or closed seasons. Managers are 

those who practice management.5

Management Authority

The legal entity that has been assigned by a state or 

states with a mandate to perform certain specifi ed 
JUNE 2006 27

management functions in relation to a fi shery, or an area 

(e.g. a coastal zone). Generally used to refer to a state 

authority, the term may also refer to an international 

management organization.5

Management Objective

A formally established, more or less quantitative target 

that is actively sought and provides a direction for 

management action.

Comment: The United Nations Food and Agricultural 

Organization (FAO) Code of Conduct for Responsible 

Fisheries provides that: “Fisheries management should 

promote the maintenance of the quality, diversity and 

availability of fi shery resources in suffi cient quantities 

for present and future generations in the context of 

food security, poverty alleviation and sustainable 

development. Management measures should not only 

ensure the conservation of the target species but also of 

species belonging to the same ecosystem or associated 

with or dependent upon the target species.” FAO (1995, 

Article 6.2). 

It also provides that management “maintains or restore 

stocks at levels capable of producing maximum 

sustainable yield, as qualifi ed by relevant environmental 

and economic factors.” FAO (1995, Article 7.2). 5

Management Reference Points

Conventional (agreed values) of indicators of the 

desirable or undesirable state of a fi shery resource of 

the fi shery itself. Reference points could be biological 

(e.g. expressed in spawning biomass or fi shing mortality 

levels), technical (fi shing effort or capacity levels) or 

economic (employment or revenues levels). They are 

usually calculated from models in which they may 

represent critical values.5

Management Strategy

The strategy adopted by the management authority to 

reach established management goals. In addition to the 

objectives, it includes choices regarding all or some of 

the following: access rights and allocation of resources 

to stakeholders, controls on inputs (e.g. fi shing capacity, 

gear regulations), outputs (e.g. quotas, minimum size at 

landing), and fi shing operations (e.g. calendar, closed 

areas, and seasons).5

Comment: The management strategy may also 

include control laws establishing formally the course 

of management action in relation to stock or fi shery 

indicators. A precautionary management strategy 

takes uncertainty into account in order to reduce the 

probability of negative outcomes.5

Marginal Yield

The increase in yield obtained by an increase in fi shing 

effort (or fi shing mortality) by one unit. In mathematical 

terms, it is given by the slope of the tangent to the 

relationship between effort and yield (or between fi shing 

mortality and yield-per-recruit).5

Mariculture

1. Marine fi sh farming (aquaculture). Raising of marine 

animals and plants in the ocean; 2. The raising of marine 

fi nfi sh or shellfi sh under some controls. Ponds, pens, 

tanks, or other containers may be used, and feed is often 

used. A hatchery is also mariculture but the fi sh are 

released before harvest size is reached.5

Marine

Waters that receive no freshwater input from the land 

and are substantially of full oceanic salinity (>30 

practical salinity units (PSU) throughout the year).12

Marine Mammals

Warmblooded animals that live in marine waters and 

breathe air directly. These include porpoises, dolphins, 

whales, seals, and sea lions.2

Marine Mammal Protection Act (MMPA)

The MMPA prohibits the harvest or harassment of 

marine mammals, although permits for incidental take 

of marine mammals while commercial fi shing may be 

issued subject to regulation.1 (see Incidental Take).

Marine Pollution

The introduction by man, directly or indirectly, of 

substances or energy into the marine environment 

(including estuaries) resulting in such deleterious 

effects as harm to living resources, hazards to human 

health, hindrance to marine activities including fi shing, 

impairment of quality for use of seawater, and reduction 

of amenities.5

Marine Protected Area (MPA)

Geographic area with discrete boundaries that has 

been designated to enhance the conservation of marine 

resources. This includes MPA-wide restrictions on some 

activities such as oil and gas mining and the use of zones 

such as fi shery and ecological reserves to provide higher 

levels of protection.14 (see Marine Reserve, Protected 

Area)

Marine Recreational Fisheries Statistical Survey (MRFFS)

An annual national survey conducted by the National 

Marine Fisheries Service (NMFS), in cooperation with 

the coastal states, to estimate the number, catch, and 

effort of recreational fi shermen. It serves as a basis for 

many parts of fi sheries management plans (FMPs).2
28 NOAA FISHERIES GLOSSARY

Marine Reserve

A geographically defi ned space in the marine 

environment where special restrictions are applied to 

protect some aspect of the marine ecosystem including 

plants, animals, and natural habitats.2 (see Marine 

Protected Area, Protected Area)

Mark-Recapture

The tagging and releasing of fi sh to be recaptured later 

in their life cycles. These studies are used to elucidate 

fi sh movement, migration, mortality, and growth to 

estimate population size.2

Mature Individuals

The number of individuals known, estimated, or inferred 

to be capable of reproduction.5

Maturity

Refers to the ability, on average, of fi sh of a given age or 

size to reproduce. Maturity information, in the form of 

percent mature by age or size, is often used to compute 

spawning potential.5

Maximum Economic Yield (MEY)

This is the total amount of profi t that could be earned 

from a fi shery if an individual owned it. An open-entry 

policy usually results in participation by so many 

fi shermen that profi ts higher than opportunity cost 

(economic rent) are driven to zero.2 (see Economic Rent)

Maximum Expected Stationary Yield (MESY)

Maximum statistical expectation of long-term yield, 

considering uncertainties in parameter values and natural 

(process) variability.11

Maximum Expected Log Stationary Yield (MELSY)

Maximum statistical expectation of the logarithm of 

long-term yield, considering uncertainties in parameter 

values and natural (process) variability.11

Maximum Fishing Mortality Threshold (MFMT, Fthreshold)

One of the status determination criteria (SDC) for 

determining if overfi shing is occurring. It will usually 

be equivalent to the fi shing mortality (F) corresponding 

to the maximum sustainable yield (MSY) control rule. 

If current fi shing mortality rates are above Fthreshold, 

overfi shing is occurring.3

Maximum Likelihood

A statistical criterion for the estimation of parameters in 

models. Maximum likelihood methods aim to maximize 

the likelihood (or probability) of having collected the 

observed data, given predictions from a model. For 

example, virtual population analysis (VPA) tuning 

often involves fi nding the estimates of abundance and 

mortality rates that maximize the likelihood for the 

observed standardized catch per unit effort (CPUE). 

Under some conditions, the methods of maximum 

likelihood and least squares give similar results.5 (see 

Least Squares)

Maximum Spawning Potential (MSP) 

This type of reference point is used in some fi shery 

management plans to defi ne overfi shing. The MSP is 

the spawning stock biomass per recruit (SSB/R) when 

fi shing mortality is zero. The degree to which fi shing 

reduces the SSB/R is expressed as a percentage of the 

MSP (i.e. %MSP). A stock is considered overfi shed 

when the fi shery reduces the %MSP below the level 

specifi ed in the overfi shing defi nition. The values of 

%MSP used to defi ne overfi shing can be derived from 

stock-recruitment data or chosen by analogy using 

available information on the level required to sustain the 

stock.3

Maximum Sustainable Yield (MSY)

The largest average catch or yield that can continuously 

be taken from a stock under existing environmental 

conditions. For species with fl uctuating recruitment, 

the maximum might be obtained by taking fewer fi sh 

in some years than in others. Also called: maximum 

equilibrium catch; maximum sustained yield; sustainable 

catch.6

Maximum Willingness to Pay

The maximum price a person is willing to pay for a good 

or service.

Maximum Yield-per-Recruit

Maximum expected lifetime yield per fi sh recruited in 

the stock.5 (see Yield-per-Recruit)

Mean Generation Time

The average time it takes for a sexually mature female 

fi sh to be replaced by an offspring with the same 

reproductive capacity; used in setting maximum 

allowable rebuilding time periods in rebuilding plans.

Megafauna

Larger animals (e.g. whales).12

Meristics

A series of measurements on a fi sh, such as scale counts, 

spine counts, or fi n-ray counts, which are used to 

separate different populations or species of fi sh.10 (see 

Morphometrics)

Mesh Size

The size of holes in a fi shing net. Minimum mesh sizes 

are often prescribed by regulations in order to avoid the 
JUNE 2006 29

capture of the young of valuable species before they 

have reached their optimal size for capture.5

Mesopelagic Zone

The pelagic environment from a depth of approximately 

100–200 meters to 1,000 meters.12

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).14

Metric Ton (t, mt)

1,000 kilograms, equivalent to 2,204.6 pounds.

Mid-Ocean Ridge

The continuous chain of volcanic submarine mountains 

and elongated rises on the ocean fl oor, extending around 

the earth where basalt periodically erupts, forming new 

ocean crust; similar to continental rift zones; includes 

the Mid-Atlantic Ridge and East Pacifi c Rise.12

Midwater

Any part of the water column between the surface and 

the seafl oor. Fish living at the surface or on the seafl oor 

do not live in midwater.5

Migration

1. Systematic (as opposed to random) movement 

of individuals of a stock from one place to another, 

often related to season. A knowledge of the migration 

patterns helps in targeting high concentrations of fi sh 

and managing shared stocks; 2. The movements of fi sh 

from feeding ground to spawning ground and back 

again, from nursery ground to feeding ground, and from 

spawning ground to nursery ground.5

Minimum Mesh Size

The smallest size of mesh permitted in nets and traps; 

this allows smaller individuals than a defi ned mesh size 

to escape unharmed.5

Minimum Size

The smallest individual size allowed in landings or 

markets. Established by fi shery management councils 

(FMCs) and enforced through control at landing sites 

or markets, it is intended to minimize the catch of small 

(undersized) fi sh or juveniles giving them a better 

chance to grow before being vulnerable to fi shing. Based 

on yield per recruit considerations and models, it aims at 

avoiding or correcting growth overfi shing.5

Minimum Stock Size Threshold (MSST, Bthreshold)

Another of the status determination criteria (SDC). 

The greater of (a) 1

2

 BMSY, or (b) the minimum stock 

size at which rebuilding to BMSY will occur within 10 

years while fi shing at the maximum fi shing mortality 

threshold (MFMT). MSST should be measured in terms 

of spawning biomass or other appropriate measures 

of productive capacity. If current stock size is below 

Bthreshold, the stock is overfi shed.4

Mixed Layer

The upper water layer in a two-layer system that is 

mixed by the wind or by convection in circulation from 

top to bottom of the layer, extending from the water 

surface to the density-stability discontinuity.12 (see 

Pycnocline, Stratifi cation, Thermocline)

Mixed-Stock Exception

In “mixed-stock complexes,” many species of fi sh 

swim together and are caught together. This becomes 

a problem when some of these stocks are healthy and 

some are overfi shed, because even a sustainable harvest 

of the healthy stocks can harm the depleted stock. 

In order to avoid having to shut down all fi sheries to 

protect one particular overfi shed stock, the National 

Standard Guidelines allow a “mixed-stock” exception 

to the “overfi shed” defi nition. This would allow higher 

catches of some overfi shed species than ordinarily 

allowed in order to avoid severe hardship to fi shing 

communities.1 (see National Standard Guidelines)

Model

In fi sheries science, a description of something that 

cannot be observed. Often a set of equations and data 

used to make estimates.2

Modeling

The construction of physical, conceptual, or 

mathematical simulations of the real world. Models 

help to show relationships between processes (physical, 

economic, or social) and may be used to predict the 

effects of changes in the components of a system.5

Mollusk

Invertebrates with a soft, unsegmented body, a muscular 

foot, and, with some exceptions, a calcareous shell. 

Includes the oyster, clam, mussel, snail, conch, scallop, 

squid, and octopus.12

Monitoring

1. To observe and record changes; 2. The collection 

of information for the purpose of assessment of the 

progress and success of a plan. Monitoring is used for 

the purpose of assessing performance of a management 
30 NOAA FISHERIES GLOSSARY

plan or compliance scheme and revising them, or to 

gather experience for future plans.5

Monte Carlo 

Monte Carlo simulation is a statistical approach whereby 

the inputs that are used for a calculation are resampled 

many times assuming that the inputs follow known 

statistical distributions. The Monte Carlo method is 

used in many applications such as Bayesian analyses, 

parametric bootstraps, and stochastic projections.5 (see 

Bayesian, Bootstrap)

Moratorium

A mandatory cessation of fi shing activities on a species 

(e.g. the blue whale), in an area (e.g. a sanctuary), with 

a particular gear (e.g. large scale driftnets), and for a 

specifi ed period of time (temporary, defi nitive, seasonal, 

or related to reopening criteria).5

Morphometrics

The physical features of a fi sh (coloration for example); 

differences may be used to identify separate fi sh 

populations.10 (see Meristics)

Mortality

Measures the rate of death of fi sh. Mortality occurs at 

all life stages of the population and tends to decrease 

with age. Death can be due to several factors such as 

pollution, starvation, and disease but the main source of 

death is predation (in unexploited stocks) and fi shing (in 

exploited ones).5

Mortality Rate

The rate at which the numbers in a population decrease 

with time due to various causes. Mortality rates 

are critical parameters in determining the effects of 

harvesting strategies on stocks, yields, revenues, etc. 

The proportion of the total stock (in numbers) dying 

each year is called the “annual mortality rate.”5

Mudfl at

A muddy bottom that is exposed at low tide.12

Multiple-Use Marine Protected Area 

An approach, often employed over much larger areas, 

that allows for integrated management of complete 

marine ecosystems, usually through a zoning process.14

Multispecies Fishery

Fishery in which more than one species is caught at the 

same time. Because of the imperfect selectivity of most 

fi shing gears, most fi sheries are “multispecies.” The 

term is often used to refer to fi sheries where more than 

one species is intentially sought and retained.13

Multiplier

A number used to multiply a dollar amount to get an 

estimate of economic impact. It is a way of identifying 

impacts beyond the original expenditure. It can also be 

used with respect to income and employment.2

N

National Academy of Sciences (NAS) 

Private nonprofi t, self-perpetuating society of scientists. 

The NAS was granted a charter by Congress in 1863 that 

requires it to advise the Federal government on scientifi c 

and technical matters.13

National Environmental Policy Act (NEPA)

Passes by Congress in 1969, NEPA requires Federal 

agencies to consider the environment when making 

decisions regarding their programs. Section 102(2)(C) 

requires Federal agencies to prepare an environmental 

impact statement (EIS) before taking major Federal 

actions that may signifi cantly affect the quality 

of the human environment. The EIS includes the 

environmental impact of the proposed action, any 

adverse environmental effects which cannot be avoided 

should the proposed action be implemented, alternatives 

to the proposed action, the relationship between local 

short-term uses of the environment and long-term 

productivity, and any irreversible commitments of 

resources which would be involved in the proposed 

action should it be implemented.1

National Marine Fisheries Service (NMFS)

Federal agency within the National Oceanic and 

Atmospheric Administration (NOAA) and responsible 

for overseeing fi sheries science and regulation of the 

fi sheries.13

National Oceanic and Atmospheric Administration 

(NOAA)

A bureau within the Department of Commerce 

responsible for atmospheric, ocean, and coastal sciences 

and Federal management.13

National Research Council (NRC)

Operating arm of the National Academy of Sciences 

(NAS).13

National Standards

The Magnuson-Stevens Act requires that a fi shery 

management plan and its regulations meet ten national 

standards.2 
JUNE 2006 31

National Standard 1 

Requires that “conservation and management measures 

shall prevent overfi shing while achieving, on a 

continuing basis, the optimum yield from each fi shery 

for the U.S. industry;” where “optimum yield” is defi ned 

in terms of the amount of fi sh which will provide the 

greatest overall benefi t to the Nation.

National Standard 2 

Requires that “conservation and management measures 

shall be based upon the best scientifi c information 

available.”

National Standard 3 

“To the extent practicable, an individual stock of fi sh 

shall be managed as a unit throughout its range, and 

interrelated stocks of fi sh shall be managed as a unit or 

in close coordination.”

National Standard 4 

Requires that “conservation and management measures 

shall not discriminate between residents of different 

states. If it becomes necessary to allocate or assign 

fi shing privileges among various U.S. fi shermen, 

such allocation shall be (a) fair and equitable to all 

such fi shermen; (b) reasonably calculated to promote 

conservation; and (c) carried out in such manner that 

no particular individual, corporation, or other entity 

acquires an excessive share of such privileges.”

National Standard 5 

Requires that “conservation and management measures 

shall, where practicable, consider effi ciency in the 

utilization of fi shery resources; except that no such 

measure shall have economic allocation as its sole 

purpose.”

National Standard 6

“Conservation and management measures shall take 

into account and allow for variations among, and 

contingencies in, fi sheries, fi shery resources, and 

catches.”

National Standard 7 

Requires that “conservation and management measures 

shall, where practicable, minimize costs and avoid 

unnecessary duplication.”

National Standard 8 

States that “conservation and management measures 

shall, consistent with the conservation requirements of 

this Act (including the prevention of overfi shing and 

rebuilding of overfi shed stocks) take into account the 

importance of fi shery resources to fi shing communities 

in order to (a) provide for the sustained participation 

of such communities, and (b) to the extent practicable, 

minimize adverse economic impacts on such 

communities.”

National Standard 9

Requires that “conservation and management measures 

shall, to the extent practicable, (a) minimize bycatch; 

and (b) to the extent bycatch cannot be avoided, 

minimize the mortality of such bycatch.” The National 

Marine Fisheries Service (NMFS) has defi ned the term 

“to the extent practicable” to include a consideration of 

the effects of reducing bycatch and bycatch mortality on 

the overall benefi t to the Nation.

National Standard 10 

Requires that “conservation and management measures 

shall, to the extent practicable, promote the safety of 

human life at sea.”

National Standard Guidelines

Advisory guidelines issued by the National Marine 

Fisheries Service (NMFS) to provide comprehensive 

guidance for the development of fi shery management 

plans and amendments that comply with the National 

Standards of the Magnuson-Stevens Act. These 

guidelines are found in Title 50, Code of Federal 

Regulations, Part 600.1

Native Species

A local species that has not been introduced.12 (see 

Introduced Species, Invasive Species)

Natural Mortality (M)

1. Deaths of fi sh from all causes except fi shing (e.g. 

ageing, predation, cannibalism, disease, and perhaps 

increasingly pollution). It is often expressed as a rate 

that indicates the percentage of fi sh dying in a year; e.g. 

a natural mortality rate of 0.2 implies that approximately 

20 percent of the population will die in a year from 

causes other than fi shing; 2. The loss in numbers in a 

year class from one age group to the subsequent one, 

due to natural death.5

Comment: These many causes of death are usually 

lumped together for convenience, because they are 

diffi cult to separate quantitatively. Sometimes natural 

mortality is confounded with losses of fi sh from the 

stock due to emigration. M has proven very diffi cult 

to estimate directly, and is often assumed based on the 

general life history. M values is also often assumed to 

remain constant through time and by age, a very unlikely 

assumption.5
32 NOAA FISHERIES GLOSSARY

Nautical Mile

International unit of distance equal to 1,852 meters or 

6,067 feet.

Nearshore

Shallow waters at a small distance from the shore.5

Nearshore Marine System

Those waters in the region between the coastal land 

margin and the 30-meter depth contour and where the 

salinity is substantially marine (>30 practical salinity 

units (PSU) throughout the year.)12

Nekton

Pelagic organisms that are free-swimming and so whose 

movements are independent of the tides, currents, and 

waves. Such animals include fi shes, whales, squids, 

crabs, and shrimps. The distribution of nekton is limited 

by temperature and nutrient supply and decreases with 

decreasing depth.4 (see Benthic, Pelagic, Plankton)

Neritic (Coastal) Zone

The pelagic marine environment above and on the 

continental shelf, landward of the shelf-slope break and 

having a depth of 30 to 200 meters.12

Neritic System

Those waters between the 30-meter depth contour and 

the continental shelf break, nominally at about 200 

meters depth, and where the salinity is substantially 

marine (>30 practical salinity units (PSU) throughout 

the year). Although relatively farther from land than 

coastal systems, these regions can receive signifi cant 

runoff infl uence from land and the water column is 

in close contact with the bottom relative to oceanic 

systems.12

Net Economic Benefi ts

Positive utility gained from the use of a resource, less 

the opportunity costs. (see Gross Economic Benefi ts)

Net Present Value

The value of an enterprise at the present time, after 

applying the process of discounting its costs and 

benefi ts.5

Network Marine Protected Areas

A group of reserves designed to meet objectives that 

single reserves cannot achieve on their own. Networks 

of reserves are linked by dispersal of marine organisms 

and by ocean currents.14

Nominal Catch

The sum of the catches that are landed (expressed as live 

weight or equivalents). Nominal catches do not include 

unreported discards.6

Nominal Eff ort

Nominal effort pertains to measures of fi shing effort or 

vessel carrying capacity that have not been standardized. 

When catchability changes, e.g. through changes in 

gear technology, trends in nominal effort can give a 

misleading picture of trends in exploitation.5

Non-Consumptive Use

Individuals may use (i.e. observe), yet not consume, 

certain living ocean resources, like whale watching, 

sight-seeing, or scuba diving. Additionally, individuals 

might value the mere existence of living ocean resources 

without actually observing them.9

Non-Governmental Organization (NGO)

Any organization that is not a part of Federal, state, 

territorial, or municipal government. In fi sheries, 

usually refers to nonprofi t organizations involved in 

environmental issues and activities.5

Non-Monetary Benefi ts

Benefi ts that are not, or cannot be, directly measured in 

terms of monetary units. These include the satisfaction 

realized from enjoying a certain way of life or style of 

work, such as fi shing in a rural coastal community.5

Non-Point Sources

Sources of sediment, nutrients, or contaminants that 

originate from many locations.12

Non-Target Species

Species not specifi cally targeted as a component of 

the catch; may be incidentally captured as part of the 

targeted catch.

Non-Users

Individuals who obtain value from a resource, but do not 

use the resource.9

Normative

Analysis leading to a recommendation or prescription 

that is based on value judgments or that refl ects society’s 

preferences.5

Norms

The understood rules for appropriate behavior. This is 

broader than social organization and includes nonsocial 

behavior.5

Notice Actions

Actions that a fi shery management council can take 
JUNE 2006 33

without passing an amendment to implement the 

regulation because the reasons for the action were 

prespecifi ed in the fi shery management plan (i.e. closing 

a fi shing season if fi shing mortality exceeds a set limit).

Notice of Violation and Assessment (NOVA)

Tickets and penalties issued by National Oceanic and 

Atmospheric Administration Offi ce of General Counsel 

to fi shermen in violation of fi shing regulations. (see 

Summary Settlement)

Numbers-at-Age

The numbers of fi sh in each age class of a stock, in a 

particular year.5

Nursery

That part of a fi sh’s or animal’s habitat where the young 

develop and grow.

O

Objective

Expresses the object of an action or what is intended 

to be achieved. Any objective will include explicit 

statements against which progress can be measured, and 

identify which things are truly important and the way 

they interrelate; quantifi ed objectives are referred to as 

targets.5

Observer

A certifi ed person on board fi shing vessels who collects 

scientifi c and technical information on the fi shing 

operations and the catch. Observer programs can be 

used for monitoring fi shing operations (e.g. areas fi shed, 

fi shing effort deployed, gear characteristics, catches and 

species caught, discards, collecting tag returns, etc.). 

Observers may or may not have legal coercion powers 

and, their data may or may not be used for nonscientifi c 

purposes (e.g. enforcement) depending on the situation.5

Oceanic

Related to open ocean waters beyond the edge of the 

continental shelf and the neritic zone.5 (see Neritic)

Oceanic System

Those waters of the open ocean, in areas beyond the 

shelf break in depths generally greater than 200 meters, 

extending to maximum ocean depths. These waters 

are removed from primary continental infl uences, and 

the seafl oor interacts little or not at all with the water 

column.12 (see Pelagic)

Off shore Waters

Waters located well beyond the shores (beyond the edge 

of the nearshore or inshore waters). Part of the oceanic 

environment.5

Olympic Fishing

A popular term to denote the “race-to-fi sh” phenomenon 

which is characterized by an increasing number of 

highly effi cient vessels fi shing at an increasing pace, 

with season length becoming shorter and shorter.5 (see 

Derby Fishery, Race-to-Fish) 

Open Access 

Condition in which access to a fi shery is not restricted 

(i.e. no license limitation, quotas, or other measures that 

would limit the amount of fi sh that an individual fi sher 

can harvest).13

Open Access Resource

A good or service over which no property rights are 

recognized.5

Opportunity Costs

1. Defi ned as the benefi t foregone by using a resource 

for one purpose instead of its next best alternative. 

Typically applied to capital and labor inputs to refl ect 

their real costs to society as against their costs to a 

private entrepreneur which may be lower or higher 

because of subsidies, taxes, and various kinds of market 

distortions; 2. An amount a fi sherman could earn for his 

time and investment in another business or occupation; 

3. The benefi ts forgone by undertaking one activity 

instead of another.5

Optimum Age

The average age of the fi sh in a year-class at which 

the instantaneous rate of natural mortality equals the 

instantaneous rate of growth in weight for the year-class 

as a whole. At this age, the biomass of the age class is 

maximum.5

Optimum (Fishing) Capacity

The desired stock of inputs that will produce a desired 

level of outputs (e.g. a set of target fi shing mortality 

rates for the species being harvested) and will best 

achieve the objectives of a fi shery management plan 

(e.g. minimizing costs). Current or transient optimal 

capacity (related to current fl eet and stock conditions) 

may differ from long run optimal capacity (refl ecting 

management long-term objectives) particularly if the 

fi shery resource is currently depleted and the management strategy is to rebuild this depleted resource.5
34 NOAA FISHERIES GLOSSARY

Optimum Size

The average size of the fi sh in a year-class at the time 

when the instantaneous rate of natural mortality equals 

the instantaneous rate of growth in weight for the yearclass as a whole. At this size, the biomass of the ageclass is maximum.5

Optimum Sustainable Population (OSP)

Defi ned by the Marine Mammal Protection Act (MMPA) 

as, “with respect to any population stock, the number of 

animals which will result in the maximum productivity 

of the population or the species, keeping in mind 

the carrying capacity of the habitat and health of the 

ecosystem of which they form a constituent element.” 

(see Carrying Capacity, Potential Biological Removal)

Optimum Yield (OY)

1. The harvest level for a species that achieves the 

greatest overall benefi ts, including economic, social, 

and biological considerations. Optimum yield (OY) is 

different from maximum sustainable yield (MSY) in 

that MSY considers only the biology of the species. 

The term includes both commercial and sport yields5; 

2. The amount of fi sh that will provide the greatest 

overall benefi t to the Nation, particularly with respect 

to food production and recreational opportunities and 

taking into account the protection of marine ecosystems. 

MSY constitutes a “ceiling” for OY. OY may be lower 

than MSY, depending on relevant economic, social, or 

ecological factors. In the case of an overfi shed fi shery, 

OY should provide for the rebuilding of the stock to 

BMSY.

3

Organic Material

Once-living material (typically with high carbon 

content), mostly of plant origin.12

Otolith

The ear bone of a fi sh. Otoliths have rings on them like 

the rings on a tree stump, and are used to fi nd the age of 

the fi sh and its growth rate.5

Output Controls

Management instruments aimed at directly limiting fi sh 

catch or landings through total allowable catch (TAC) or 

quotas.5

Overcapacity

A level of fi shing pressure that threatens to reduce a 

stock or complex below the abundance necessary to 

support maximum sustainable yield (MSY) and allow an 

economically sustainable fi shing industry.1

Overcapitalization

Where the amount of harvesting capacity in a fi shery 

exceeds the amount needed to harvest the desired 

amount of fi sh at least cost.5

Over-Exploitation

Rate of exploitation where the resource stock is drawn 

below the size that, on average, would support the longterm maximum sustainable yield (MSY) of the fi shery.5

Overexploited

When stock abundance is too low. The term is used 

when biomass has been estimated to be below a limit 

biological reference point that is used as the threshold 

that defi nes “overfi shed conditions.”5

Overfi shed

1. An overfi shed stock or stock complex “whose size is 

suffi ciently small that a change in management practices 

is required to achieve an appropriate level and rate of 

rebuilding.” A stock or stock complex is considered 

overfi shed when its population size falls below the 

minimum stock size threshold (MSST). A rebuilding 

plan is required for stocks that are deemed overfi shed2; 

2. A stock is considered “overfi shed” when exploited 

beyond an explicit limit beyond which its abundance 

is considered ‘too low’ to ensure safe reproduction. In 

many fi sheries fora the term is used when biomass has 

been estimated to be below a limit biological reference 

point that is used as the signpost defi ning an “overfi shed 

condition.” This signpost is often taken as being FMSY, 

but the usage of the term may not always be consistent.5

(see Minimum Stock Size Threshold)

Comment: The stock may remain overfi shed (i.e. with a 

biomass well below the agreed limit) for some time even 

though fi shing pressure might be reduced or suppressed.5

Overfi shing

1. According to the National Standard Guidelines, 

“overfi shing occurs whenever a stock or stock complex 

is subjected to a rate or level of fi shing mortality that 

jeopardizes the capacity of a stock or stock complex 

to produce maximum sustainable yield (MSY) on 

a continuing basis.” Overfi shing is occurring if the 

maximum fi shing mortality threshold (MFMT) is 

exceeded for 1 year or more3; 2. In general, the action 

of exerting fi shing pressure (fi shing intensity) beyond 

the agreed optimum level. A reduction of fi shing 

pressure would, in the medium term, lead to an increase 

in the total catch.5 (see National Standard Guidelines, 

Maximum Fishing Mortality Threshold, Maximum 

Sustainable Yield)
JUNE 2006 35

Comment: For long-lived species, overfi shing (i.e. using 

excessive effort) starts well before the stock becomes 

overfi shed. The use of the term “overfi shing” may not 

always be consistent.5

Overfi shing Limit (OFL)

Point at which fi shing seriously compromised a fi shery’s 

continued, sustained productivity. Overfi shing limits 

may be set based on standardized biological criteria 

established for a particular fi shery. Overfi shing limits 

may also incorporate economic and social considerations 

relevant to a particular fi shery.13

P

PMAX

The probability of rebuilding a fi sh stock by TMAX; 

a higher PMAX probability is associated with a lower 

fi shing mortality rate.

Pacifi c Decadal Oscillation (PDO)

A long-term pattern of Pacifi c Ocean climate variability, 

with events lasting 20 to 30 years and oscillating 

between warm and cool regimes. Unlike the El NiñoSouthern Oscillation (ENSO), the North Pacifi c 

and North America are most strongly affected, with 

secondary signatures seen in the tropics. The PDO has 

been linked to major changes in northeastern Pacifi c 

marine ecosystems—during warm events, coastal 

productivity is enhanced in Alaska and inhibited off the 

U.S. west coast; the opposite pattern is seen during cool 

events. (see El Niño-Southern Oscillation)

Pacifi c Coast Fisheries Information Network (PacFIN)

PacFIN provides commercial fi shery information for 

Washington, Oregon, and California. Maintained by the 

Pacifi c States Marine Fisheries Commission (PSMFC).1

Pacifi c States Marine Fisheries Commission (PSFMC)

The PSMFC is a non-regulatory agency that serves 

Alaska, California, Idaho, Oregon, and Washington. 

PSMFC (headquartered in Portland) provides a 

communication exchange between the Pacifi c Fishery 

Management Council and the North Pacifi c Fishery 

Management Council, and a mechanism for Federal 

funding of regional fi shery projects. The PSMFC 

provides information in the form of data services for 

various fi sheries.1

 

Paralytic Shellfi sh Poisoning (PSP)

Condition in humans caused by the ingestion of bivalve 

mollusks that have accumulated dangerous levels of 

neurotoxins from plankton.13 (see Red Tide)

Parameter

A “constant” or numerical description of some property 

of a population (which may be real or imaginary).5

Partial Recruitment

1. The degree to which a year class has joined the 

fi shable stock. When a year class is young, only some of 

its fi sh are big enough to be caught, so it is partly but not 

fully recruited5; 2. Patterns of relative vulnerability of 

fi sh of different sizes or ages due to the combined effects 

of selectivity and availability.6

Party Boat

Any vessel-for-hire engaged in recreational fi shing and 

hired (or leased, in whole or part) per a per-capita fee on 

a fi rst-come, fi rst-served basis.9 (see Head Boat) 

Pelagic

Inhabiting the water column as opposed to being 

associated with the sea fl oor; generally occurring 

anywhere from the surface to 1,000 meters.1 (see 

Benthic, Demersal, Oceanic)

Pelagic Fish

Fish that live in the open ocean at or near the water’s 

surface and usually migrate long distances. Examples 

include swordfi sh, tunas, and many species of billfi sh 

and shark.12

Permit Stacking

The registration of more than one limited entry permit 

for a single vessel, where a vessel is allowed additional 

catch for each additional permit registered for use with 

the vessel.1

Photic Zone

The surface layer where there is suffi cient light for 

photosynthesis to occur.12

Phytoplankton

Small, usually microscopic plants drifting in the upper 

layers of the ocean, consuming nutrients and light 

energy to produce biomass. In particularly nutrient-rich 

conditions (including eutrophication) phytoplankton 

blooms may occur and can be toxic.5 (see Primary 

Production, Red Tide, Zooplankton)

Pinniped

Of or belonging to the Pinnipedia, a suborder of 

carnivorous aquatic mammals that includes the seals, 

walruses, and similar animals having fi nlike fl ippers 

used for locomotion.4
36 NOAA FISHERIES GLOSSARY

Plankton

Floating organisms whose movements are more or less 

dependent on currents. While some zooplankton exhibit 

active swimming movements that aid in maintaining 

vertical position, plankton as a whole are unable to move 

against appreciable currents.5 (see Zooplankton)

Poaching

Catching fi sh for which no quota is held. Illegally 

harvesting fi sh.13

Point Source

A source of sediment, nutrients, or contaminants into a 

water body that comes from one discharge location.12

Policy

A fi sheries policy is the defi nite course or method 

of action, selected from among alternatives, by a 

government or its mandated fi sheries authority, in light 

of given conditions including legal and constitutional 

constraints, to guide and determine present and 

future development and management actions towards 

satisfaction of agreed objectives.5

Policymaker

A person with power to infl uence or determine policies 

and practices at an international, national, regional, or 

local level.5

Pollution

1. The introduction by man, directly or indirectly, of 

substances or energy into the marine environment, 

including estuaries, which results or is likely to result 

in such deleterious effects as harm to living resources 

and marine life; hazards to human health; hindrance to 

marine activities, including fi shing and other legitimate 

uses of the sea; impairment of quality of sea water; and 

reduction of amenities; 2. Presence of substances and 

heat in environmental media (air, water, land) whose 

nature, location, or quantity produces undesirable 

environmental effects; 3. Activity that generates 

pollutants.5

Pop-Up Tag

A tag that detaches itself from an animal after a 

predetermined period of time has elapsed since 

tagging. After detachment, the tag sends a signal via 

satellite, providing its position and downloading any 

other available information (if the pop-up tag is also 

an archival one). This technology does not rely on the 

recapturing/reporting of tagged individuals to recover 

the information.5

Population

The number of individuals of a particular species that 

live within a defi ned area.4 (see Stock)

Population Dynamics

The study of fi sh populations and how fi shing mortality, 

growth, recruitment, and natural mortality affect them.2

Population Model

A component of a stock assessment model, made 

up of formulations that describe how the population 

changes from one time period to the next. The types of 

population models vary depending on the species life 

history and on data availability. Population models can 

roughly be classifi ed as age/size structured or biomassbased, deterministic or stochastic, density-dependent 

or density-independent, spatially structured or spatially 

aggregated, equilibrium or nonequilibrium.5 (see Model, 

Simulation)

Possession Limit

The number and/or size of a species that a person can 

legally have at any one time. Applies to commercial and 

recreational fi shermen. A possession limit generally does 

not apply to the wholesale market level and beyond.2

Post Larvae

Fish that have changed from the larval form to the very 

fi rst stages of juvenile or adult form.5

Potential Biological Removal (PBR)

The maximum number of individuals, not including 

natural mortalities, that may be removed from a marine 

mammal stock while allowing that stock to reach or 

maintain its optimum sustainable population.1 (see 

Optimum Sustainable Population)

Pots

Traps, designed to catch fi sh or crustaceans, in the form 

of cages or baskets of various materials (wood, wicker, 

metal rods, wire netting, etc.) and having one or more 

openings or entrances. Usually set on the bottom, with 

or without bait, singly or in rows, connected by ropes 

(buoy-lines) to buoys on the surface showing their 

position.5

Practical Salinity Unit (PSU)

A unit of measurement of salinity similar to parts per 

thousand (ppt).12

Precautionary Approach (PA)

Set of measures taken to implement the Precautionary 

Principle. A set of agreed cost-effective measures 

and actions, including future courses of action, which 
JUNE 2006 37

ensures prudent foresight, reduces or avoids risk to 

the resource, the environment, and the people, to the 

extent possible, taking explicitly into account existing 

uncertainties and the potential consequences of “being 

wrong.”5

Precision

Is the closeness to each other of repeated measurements 

of the same quantity or object, while accuracy is the 

closeness of a measured or computed value to its true 

value.6 (see Accuracy)

Predation

Relationship between two species of animals in which 

one (the predator) actively hunts and lives off the meat 

and other body parts of the other (the prey).5

Predator-Prey Relationship

The interaction between a species (predator) that eats 

another species (prey). The stages of each species’ 

life cycle and the degree of interaction are important 

factors.5 (see Food Chain, Trophic Level)

Preferred Alternative

The alternative that is identifi ed as preferred by the 

authors of an environmental impact statement or 

environmental assessment. It is identifi ed to indicate 

which alternative is likely to be selected, thereby helping 

the public focus its comments.1

Pre-Recruits

Fish that have not yet reached the recruitment stage (in 

age or size) to a fi shery.5

Primary Production

Assimilation (gross) or accumulation (net) of energy 

and nutrients by green plants and by organisms that use 

inorganic compounds as food.5 (see Phytoplankton)

Primary Productivity

A measurement of plant production that is the start of 

the food chain. Much primary productivity in marine or 

aquatic systems is made up of phytoplankton, which are 

one-celled algae that fl oat freely in the water.2

Principal Species

Species important to the viability of the fi shery, both 

target and nontarget.5

Private Costs and Benefi ts

Costs and benefi ts directly felt by individual economic 

agents or groups as seen from their perspective 

(externalities imposed on others are ignored). Costs and 

benefi ts are valued at the prices actually paid or received 

by the group, even if these prices are highly distorted. 

Sometimes termed “fi nancial” costs and benefi ts. 

Compare social costs and benefi ts.5

Processing

The preparation or packaging of fi sh to render it suitable 

for human consumption, retail sale, industrial uses, or 

long-term storage, including but not limited to cooking, 

canning, smoking, salting, drying, fi lleting, freezing, or 

rendering into meal or oil, but not heading and gutting 

unless additional preparation is done.1

Producer Surplus

Producer surplus is defi ned as the difference between 

what producers actually receive when selling a product 

and the amount they would be willing to accept for a 

unit of the good. (see Consumer Surplus, Total Welfare)

Production

1. The total output especially of a commodity or an 

industry; 2. The total living matter (biomass) produced 

by a stock through growth and recruitment in a given 

unit of time (e.g. daily, annual production). The “net 

production” is the net amount of living matter added 

to the stock during the time period, after deduction 

of biomass losses through mortality; 3. The total 

elaboration of new body substance in a stock in a unit of 

time, irrespective of whether or not it survives to the end 

of that time.5 

Production Expansion Factor (PEF)

The total number of Pacifi c salmon released from a west 

coast hatchery divided by the total number of tagged fi sh 

released. Used to elucidate hatchery contribution and 

fi sh survival rates.1

Production Model

1. The highest theoretical equilibrium yield that can 

be continuously taken (on average) from a stock under 

existing (average) environmental conditions without 

affecting signifi cantly the reproduction process. Also 

referred to sometimes as potential yield; 2. Maximum 

sustainable yield (MSY) or sustainable yield (SY). The 

largest average catch or yield that can continuously 

be taken from a stock under existing environmental 

conditions. For species with fl uctuating recruitment, 

the maximum might be obtained by taking fewer fi sh 

in some years than in others.5 (see Carrying Capacity,

Maximum Equilibrium Catch, Maximum Sustainable 

Yield, Schaefer Model, Sustainable Yield)

Productivity

Relates to the birth, growth and death rates of a stock. A 

highly productive stock is characterized by high birth, 
38 NOAA FISHERIES GLOSSARY

growth, and mortality rates, and as a consequence, a 

high turnover and production to biomass ratios (P/B). 

Such stocks can usually sustain higher exploitation 

rates and, if depleted, could recover more rapidly than 

comparatively less productive stocks.5

Profi t

The total revenue obtained from using a productive 

resource minus all opportunity costs of production 

(opportunity costs of entrepreneurs’ skills, labor, capital, 

and ownership of natural resources).9

Programmatic Environmental Impact Statement (PEIS)

An environmental impact statement (EIS) that applies to 

an entire program or management regime, rather than a 

specifi c action.1

Prohibited Species

Any species of fi sh that a vessel is not specifi cally 

allocated or authorized to retain, including fi sh caught or 

received in excess of any allocation or authorization.5

Projection

A computation of how the stock and fi shery will 

behave in the future. Projections are made to address 

“what-if” questions of relevance to management. 

Short-term (1–4 years) projections are typically used 

in support of decision-making on quotas. Longer term 

projections become much more uncertain in terms of 

absolute quantities, because predicted recruitment tends 

to dominate the results and recruitment itself is very 

diffi cult to predict. For this reason, long-term projections 

are more useful to evaluate overall management 

strategies than for making detailed decisions.5

Property

Is a benefi t (or income) stream associated with a 

property right.5

Property Rights

1. A legal right or interest in respect to a specifi c 

property. A type of resource ownership by an individual 

(individual right) or a group (communal right); 2. A 

claim to the benefi t stream that some higher authority, 

usually government, will agree to protect through 

the assignment of duty to others who may covet, or 

somehow interfere with, the benefi t stream.5

Proposed Alternatives

Alternatives proposed by a fi shery management council 

(FMC) for a proposed management action (such as 

annual management specifi cations). The alternatives 

are presented to the public for comment, and are voted 

upon at a subsequent council meeting. The options 

always include a “status quo” alternative; for example, 

maintaining the current seasons allowable biological 

catches (ABCs) and optimum yields (OYs).1

Proposed Rule

The regulation that implements a fi shery management 

plan (FMP) and is incorporated in the Code of Federal 

Regulations (CFR) when approved. The public can 

comment on the proposed rule as well as the FMP. (see 

Code of Federal Regulations, Rulemaking)

Protected Area

1. An area set aside for the preservation and protection 

of highly important natural and cultural features 

and for the regulation of the scientifi c, educational, 

and recreational use. Such areas include national 

parks, Nature reserves, wildlife sanctuaries, natural 

monuments, archaeological reserves, forest reserves, 

and marine reserves; 2. A geographically defi ned area 

which is designed and managed to achieve specifi c 

conservation objectives.5 (see Marine Protected Area, 

Marine Reserve)

Protected Species

Refers to any species which is protected by either the 

Endangered Species Act (ESA) or the Marine Mammal 

Protection Act (MMPA), and which is under the 

jurisdiction of the National Marine Fisheries Service 

(NMFS). This includes all threatened, endangered, and 

candidate species, as well as all cetaceans and pinnipeds, 

excluding walruses.8

Pulse Fishing

Harvesting a stock of fi sh, then moving on to other 

stocks or waiting until the original stock recovers.10

Probability

The statistical likelihood that something will occur.

Producer Surplus

The welfare a producer derives from selling a good, 

represented by the difference between the revenue the 

seller gets for a good and the minimum amount they 

would accept to produce it.

Pure Public Good

A good that can be used by anyone and for which one 

person’s use does not diminish the good’s value for 

others.5

Purse Seine

Nets characterized by the use of a purse line at the 

bottom of the net. The purse line enables the net to be 

closed like a purse and thus retain all the fi sh caught. 

The purse seines, which may be very large, are operated 

by one or two boats. The most usual case is a purse seine 
JUNE 2006 39

operated by a single boat, with or without an auxiliary 

skiff.5

Pycnocline

1. The transitional zone in the water column between 

layers of two densities; 2. Pycnocline or sharp density 

gradients; this parcel includes the air-water interface. 

Pycnoclines are generally formed by salinity or 

temperature differences between the upper and lower 

water layers and create effective barriers to transport 

across layers.12 (see Mixed Layer, Stratifi cation, 

Thermocline)

Q

q (“que”)

(see Catchability Coeffi cient)

Quota

A specifi ed numerical harvest objective, the attainment 

(or expected attainment) of which causes closure of the 

fi shery for that species or species group.1

Quota Shares

A share of the total allowable catch (TAC) allocated 

to an operating unit such as a vessel, a company or an 

individual fi sherman (individual fi shing quota, IFQ) 

depending on the system of allocation. Quotas may or 

may not be transferable, inheritable, and tradable. While 

generally used to allocate total allowable catch, quotas 

could be used also to allocate fi shing effort or biomass.5

R

Race-to-Fish

A pattern of fi shing characterized by an increasing 

number of highly effi cient vessels fi shing at an 

increasing pace, with season length becoming shorter 

and shorter.5 (see Derby Fishery, Olympic Fishing)

Rate of Fishing

(see Instantaneous Rate of Fishing Mortality)

Rate of Exploitation

The fraction, by number, of the fi sh in a population at 

a given time, which is caught and killed by man during 

the year immediately following. The term may also be 

applied to separate parts of the stock distinguished by 

size, sex, etc.5

Rate of Natural Increase

(see Instantaneous Rate of Surplus Production)

Rate of Removal

An inexactly defi ned term that can mean either rate of 

exploitation or rate of fi shing, depending on the context.5

Rebuilding

1. Implementing management measures that increase 

a fi sh stock to its target size1; 2. For a depleted stock, 

or population, taking action to allow it to grow back 

to a predefi ned target level. Stock rebuilding at least 

back to the level (BMSY) at which a stock could produce 

maximum sustainable yield (MSY).5

Rebuilding Analysis

An analysis that uses biological information to describe 

the probability that a stock will rebuild within a given 

time frame under a particular management regime.1

Rebuilding Plan

1. A document that describes policy measures that will 

be used to rebuild a fi sh stock that has been declared 

overfi shed1; 2. A plan that must be designed to recover 

stocks to the BMSY level within 10 years when they are 

overfi shed (i.e. when biomass [B] < minimum stock 

size threshold [MSST]).4 (see Minimum Stock Size 

Threshold) 

Recreational Fishery

Harvesting fi sh for personal use, sport, and challenge 

(e.g. as opposed to profi t or research). Recreational 

fi shing does not include sale, barter, or trade of all or 

part of the catch.5

Recreational Fishery Information Network (RecFin)

A database managed by the Pacifi c States Marine 

Fisheries Commission (PSMFC) that provides 

recreational fi shery information for Washington, Oregon, 

and California.1

Recruit

1. A young fi sh entering the exploitable stage of its life 

cycle; 2. A member of “the youngest age group which is 

considered to belong to the exploitable stock.”5

Recruitment (R)

1. The amount of fi sh added to the exploitable stock 

each year due to growth and/or migration into the fi shing 

area. For example, the number of fi sh that grow to 

become vulnerable to the fi shing gear in one year would 

be the recruitment to the fi shable population that year; 2. 
40 NOAA FISHERIES GLOSSARY

This term is also used in referring to the number of fi sh 

from a year class reaching a certain age. For example, all 

fi sh reaching their second year would be age 2 recruits.6

Recruitment Curve

A graph of the progeny from an adult year-class at the 

time they reach a specifi ed age (for example, the age 

at which half of the brood has become vulnerable to 

fi shing), plotted against the abundance of the stock that 

produced them.5

Recruitment Overfi shing

A situation in which the rate of fi shing is (or has been) 

such that annual recruitment to the exploitable stock 

has become signifi cantly reduced. The situation is 

characterized by a greatly reduced spawning stock, 

a decreasing proportion of older fi sh in the catch, 

and generally very low recruitment year after year. If 

prolonged, recruitment overfi shing can lead to stock 

collapse, particularly under unfavorable environmental 

conditions.5

Recruitment per Spawning Stock Biomass (R/SSB)

The number of fi shery recruits (usually age 1 or 2) 

produced from a given weight of spawners, usually 

expressed as numbers of recruits per kilogram of mature 

fi sh in the stock. This ratio can be computed for each 

year class and is often used as an index of pre-recruit 

survival, since a high R/SSB ratio in one year indicates 

above-average numbers resulting from a given spawning 

biomass for a particular year class, and vice versa.3

Recruits

The numbers of young fi sh that survive (from birth) to a 

specifi c age or grow to a specifi c size. The specifi c age 

or size at which recruitment is measured may correspond 

to when the young fi sh become vulnerable to capture in 

a fi shery or when the number of fi sh in a cohort can be 

reliably estimated by a stock assessment.5

Red Tide

Proliferation of marine plankton that is toxic and often 

fatal to fi sh. This natural phenomenon is stimulated by 

phosphorus and other nutrients that are discharged into 

waterways by human beings. The color of the tide can 

be red, yellow, green, or brown.5 (see Phytoplankton)

Reef

A large ridge or mound-like structure within a body 

of water that is build by calcareous organisms such as 

coral, red algae, and bivalves.12 (see Atoll)

Reef Fish 

Fish that live mostly on or around reefs. Reef fi sh 

include snappers, groupers, grunts, porgies, and others.

Reference Level

A particular level of an indicator (e.g. level of 

fi shing effort, fi shing mortality, or stock size) used 

as a benchmark for assessment and management 

performance.5

Reference Point

1. A reference point indicates a particular state of a 

fi shery indicator corresponding to a situation considered 

as desirable (target reference point) or undesirable and 

requiring immediate action (limit reference point and 

threshold reference point); 2. An estimated value derived 

from an agreed scientifi c procedure and/or model, 

which corresponds to a specifi c state of the resource 

and of the fi shery, and that can be used as a guide 

for fi sheries management. Reference points may be 

general (applicable to many stocks) or stock-specifi c5; 

3. Values of parameters (e.g. BMSY, FMSY, F0.1) that are 

useful benchmarks for guiding management decisions. 

Biological reference points are typically limits that 

should not be exceeded with signifi cant probability (e.g. 

MSST) or targets for management (e.g. OY).3

Refuges

A part of the range of a stock that is not accessible to 

fi shing. If the species in question is not too diffusive, the 

existence of such refuges may enable it to persist under 

a higher level of fi shing mortality than it otherwise 

would.5

Regime Shift

A (medium- or long-term) shift in environmental 

conditions that impacts the productivity of a stock.5

Regression Analysis

A statistical method to estimate any trends that might 

exist among important factors; an example in fi sheries 

management is the link between catch and other factors 

like fi shing effort and natural mortality.10 (see Least 

Squares, Residuals)

Regulative Capacity

A population’s tendency to revert towards some typical 

average level of abundance rather than to increase or 

decline indefi nitely or to drift aimlessly. The regulative 

mechanisms by which this can be achieved include, 

for example, inverse dependence of survival rate 

(and/or reproductive success) on population density, a 

phenomenon often used synonymously with densitydependence and sometimes called homeostasis.5

Regulatory Amendment

An option available to fi shery management councils for 

making regulatory changes to a fi shery management 
JUNE 2006 41

plan; different from a full amendment but still requires 

some opportunity for public input.10

Regulatory Flexibility Act (RFA)

Enacted in 1980 to reduce the burden of regulatory 

and record-keeping requirements on small businesses 

organizations. The RFA requires that fi shery 

management plans undergo a regulatory fl exibility 

analysis. (see Executive Order 12866)

Regulatory Flexibility Analysis

Conducted for each fi shery management plan (FMP) to 

study the costs and benefi ts that the plan may have on an 

individual small business or organization (e.g. a single 

fi shing vessel). The Regulatory Flexibility Act (RFA) 

mandates this analysis and allows it to be combined with 

the draft regulatory impact review (RIR). (see Executive 

Order 12866)

Regulatory Impact Review (RIR)

A regulatory impact review (RIR) is required by the 

National Marine Fisheries Service (NMFS) for all 

regulatory actions of public interest. It is the basis for 

determining whether any proposed regulations are a 

“signifi cant regulatory action” under certain criteria 

provided in Executive Order 12866 and whether the 

proposed regulations will have a “signifi cant economic 

impact on a substantial number of small entities” in 

compliance with the Regulatory Flexibility Act (RFA).

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 stratifi ed mean catch 

per tow.6

Reliability

The extent to which a resource, if managed properly, can 

be depended on to provide a reasonably constant yield. 

An unreliable resource is one that may fail suddenly 

due to causes not obviously related to fi shing.5 (see 

Robustness)

Removals

All of the fi sh “removed” from a stock by fi shing, 

including the catch and any fi sh killed but not caught.5

Renewable Natural Resource

Natural resources that, after exploitation, can return 

to their previous stock levels by natural processes of 

growth or replenishment. Conditionally renewable 

resources are those whose exploitation eventually 

reaches a level beyond which regeneration will become 

impossible. Such is the case with the clear-cutting of 

tropical forests.5

Rent

1. In a sole ownership fi shery, the difference between 

the total revenues obtained from the fi shery resource 

and the total costs of production, i.e. capital and labor 

valued at their opportunity costs. The total costs of 

production include a reasonable profi t and the rent is 

often considered as a “surplus” profi t, over and above 

what would be considered a ‘normal’ rate of return. For 

this reason, the decision as to who gets the rent (e.g. 

society, the management authority, or the fi shermen) 

remains a key policy issue; 2. Any payment to an owner 

of a productive resource that is an amount in excess of 

the payment needed to keep the resource in its current 

use. Applied to fi sheries, the amount of pure profi t that 

can be gained from a fi shery resource by using no more 

fi shing effort than needed to harvest the resource. Under 

open access, the resource would yield no economic rent, 

whereas a sole owner would seek to maximize economic 

rent.5

Replacement Yield

The amount of yield in weight that can be removed from 

a population of fi sh without leading to biomass increase 

or decline. When the population net productivity is high 

(e.g. at medium levels of, close to maximum sustainable 

yield, MSY), the replacement yield will also be high. 

Conversely, when the productivity is low (e.g. when 

the population is underexploited or overexploited), 

the replacement yield will be low. In either case, if the 

actual yield taken is equal to the replacement yield, then 

the biomass will not change from one year to the next.5

Residual

In statistical models, a residual is the difference between 

an observed quantity and the prediction given by the 

model.5 (see Least Squares, Regression Analysis)

Resilience

Capacity of a natural system (fi sheries community or 

ecosystem) to recover from heavy disturbance such as 

intensive fi shing.5

Resource Rent

In the fi sheries context, the value to fi shers of the fi sh 

in the water before they are caught. It is usually a large 

component of the economic rent.5

Resource Valuation

Calculation or estimation of the economic value of a 

natural resource.5

Resources

1. A natural source of wealth and revenue. Biological 

resources include genetic resources, organisms or parts 

thereof, populations, or any other biotic component 
42 NOAA FISHERIES GLOSSARY

of ecosystems with actual or potential use of value 

for humanity. Fishery resources are those resources of 

value to fi sheries; 2. Anything that has value; living and 

nonliving components of nature such as fi sh, oil, water, 

and air.5

Responses

Human actions, including policies, strategies, and 

interventions, to address specifi c issues, needs, 

opportunities, or problems. In the context of ecosystem 

management, responses may be of legal, technical, 

institutional, economic, and behavioral nature and 

may operate at local or micro, regional, national, or 

international level and at various time scales.5

Responsible Fisheries

The concept of responsible fi sheries encompasses the 

sustainable utilization of fi shery resources in harmony 

with the environment; the use of capture and aquaculture 

practices which are not harmful to ecosystems, 

resources, and their quality; the incorporation of added 

value to such products through transformation processes 

meeting the required sanitary standards; the conduct of 

commercial practices so as to provide consumers access 

to good quality products.5

Retention

In stock assessment, the probability of a fi sh 

encountering fi shing gear (hook, webbing, mesh, trap) 

and being retained by it after coming in contact with 

it. Often expressed as a function of size or age.5 (see 

Retention Curve)

Retention Curve

Relationship between the size (age) of a fi sh and 

its probability to be retained by the gear (a hook, a 

webbing, a mesh, a trap) after encountering it.5

Reversibility

The extent to which a change in a stock or ecosystem 

induced by exploitation will reverse itself when the 

causative factor is removed. Extinction of a species is an 

example of an irreversible change.5

Riparian

Living on or near the bank of a river or lake.13

Riparian Habitat

Areas adjacent to rivers and other water bodies that have 

a high density and large variety of plants and animal 

species relative to nearby uplands.5

Risk

1. In general, the possibility of something undesirable 

happening, of harm or loss. A danger or a hazard. 

A factor, thing, element, or course involving some 

uncertain danger; 2. In decision-theory, the degree or 

probability of a loss; expected loss; average forecasted 

loss. This terminology is used when enough information 

is available to formulate probabilities; 3. The probability 

of adverse effects caused under specifi ed circumstances 

by an agent in an organism, a population, or an 

ecological system5

Risk Assessment

A process of evaluation including the identifi cation 

of the attendant uncertainties, of the likelihood and 

severity of an adverse effect(s)/event(s) occurring to 

man or the environment following exposure under 

defi ned conditions to a risk source(s). A risk assessment 

comprises hazard identifi cation, hazard characterization, 

exposure assessment, and risk characterization.5

Risk Management

The process of weighing policy alternatives in the light 

of the result of a risk assessment and other relevant 

evaluation and, if required, selecting and implementing 

appropriate control options (which should, where 

appropriate, include monitoring or surveillance).5

River Plume

Turbid freshwater fl owing from land and generally in the 

distal part of a river (mouth) outside the bounds of an 

estuary or river channel.12

Robustness

The capacity of a population to persist in the presence of 

fi shing. This depends on the existence of compensatory 

mechanisms.5 (see Reliability)

Round Weight

The weight of the whole fi sh before processing or 

removal of any part.5

Run

Seasonal migration undertaken by fi sh, usually as part 

of their life history; for example, spawning run of 

salmon, upstream migration of shad. Fishers may refer 

to increased catches as a “run” of fi sh, a usage often 

independent of their migratory behavior.5

Runoff 

Portion of rainfall, melted snow, or irrigation water 

that fl ows across the ground’s surface and is eventually 

returned to streams. Runoff can pick up pollutants from 

air or land and carry them to receiving waters.5
JUNE 2006 43

Resource Management Plan (RMP)

A plan that covers impacts to listed species from 

activities of state and local governments, under section 

4(d) of the Endangered Species Act (ESA).1

Rulemaking

The process of developing Federal regulations which 

occurs in several steps, including publishing proposed 

rules in the Federal Register, accepting comments on 

the proposed rule, and publishing the fi nal rule. An 

“advanced notice of proposed rulemaking” is published 

when dealing with especially important or controversial 

rules.1 (see Code of Federal Regulations, Proposed 

Rule)

S

Salinity

The total mass of salts dissolved in seawater per 

unit mass of water; generally expressed in parts per 

thousands (ppt).12

Salt Marsh

A macrohabitat comprised of emergent rooted 

macrophytes in a soft sedimentary substrate tolerant of 

long periods of partial submersion along the shores of 

estuaries and sheltered coasts.12

Salt Wedge

A layer of denser, saltier seawater that intrudes into 

coastal waters in the form of a wedge along the seabed 

and fl ows landward along the bottom in estuaries. The 

lighter freshwater from riverine sources overrides the 

denser saltwater.12

Saltonstall-Kennedy Act (SK Funds)

The Saltonstall-Kennedy Act allocates 30% of the 

collected duties for imported fi shery products to 

technological, biological, marketing, and other research 

and services in order to promote the free fl ow of 

domestically produced fi shery products and to develop 

markets for domestic fi shery products.1

Sample

A proportion or a segment of a fi sh stock that is removed 

for study, and is assumed to be representative of the 

whole. The greater the effort, in terms of both numbers 

and magnitude of the samples, the greater the confi dence 

that the information obtained is a true refl ection of the 

status of a stock (level of abundance in terms of numbers 

or weight, age composition, etc.).6

Sampling Design

The sampling design of a scientifi c survey refers to the 

statistical techniques and methods adopted for selecting 

a sample and obtaining estimates of the survey variables 

from the selected sample.5

Sashimi

Japanese term for sliced fi sh (especially tuna) and 

shellfi sh (scallop, abalone, lobster, squid, octopus) 

served raw as a delicacy.5

Satellite Imagery

Remote sensing imagery gathered by earth-orbiting 

satellites (e.g. Landsat). Images are in specifi c 

wavebands (visible, infrared, etc.), which may be 

combined for purposes of interpretation.5

Comment: Images look like photographs but are not 

obtained by photographic methods, hence the terms 

“images or imagery.” Data from satellite imagery can 

be interpreted visually or analyzed by computers in 

digitized form; they can also be entered directly into 

geographic information systems (GIS).5

Scattergram

A visual (not statistical) method; graphically shows the 

relationship between two factors (such as fi sh age and 

fi sh size).

Scenario

A plausible and often simplifi ed description of how 

the future may develop based on a coherent and 

internally consistent set of assumptions about key 

driving forces (e.g., rate of technology change, prices) 

and relationships. Scenarios are neither predictions nor 

projections and sometimes may be based on a “narrative 

storyline.” Scenarios may be derived from projections 

but are often based on additional information from other 

sources.5

Schaefer Model

The basic form of production model in which the 

relation between yield and effort takes the form of a 

symmetric parabola. In the Schaefer Model, BMSY is 

at one-half of the carrying capacity.5 (see Carrying 

Capacity, Production Model)

School

Aggregation of fi sh that move together as a group. It is 

usually considered that schooling reduces the impact 

of predation. Schools can be themselves aggregated in 

concentrations.5

Scientifi c Cruise

The period of time during which a scientifi c research 
44 NOAA FISHERIES GLOSSARY

vessel is operated in furtherance of a scientifi c research 

project, beginning when the vessel leaves port to 

undertake the project and ending when the vessel 

completes the project as provided for in the applicable 

scientifi c research plan.5

Scientifi c Fishery (Resource) Survey 

Sampling, collecting, observing, or surveying the fi sh or 

fi shery resources, on board scientifi c research vessels, 

to increase scientifi c knowledge of the fi shery resources 

or their environment, or to test a hypothesis as part of 

a planned, directed investigation or study conducted 

according to methodologies generally accepted as 

appropriate for scientifi c research.5

Comment: A scientifi c survey may involve fi shing, but 

is usually exempted from fi shing regulations. It may 

address one or more issues involving taxonomy, biology, 

physiology, behavior, disease, aging, growth, mortality, 

migration, recruitment, distribution, abundance, ecology, 

stock structure, bycatch, and catch estimation of fi nfi sh 

and shellfi sh (invertebrate) species considered to be a 

component of the fi shery resources. It does not include 

the collection and retention of fi sh outside the scope of 

the applicable research plan. The capture and landing of 

quantities of fi sh or invertebrates for commercial testing 

of fi shing gear, product development, market research, 

and/or public display may not be considered scientifi c 

research activities and require permission under 

exempted fi shing procedures. The activity of foreign 

fi shery research vessels in an exclusive economic zone 

(EEZ) will usually be considered as scientifi c research if 

they are carried out in full cooperation with the coastal 

state.5

Scientifi c (Fisheries) Research Vessel 

A vessel owned or chartered by, and controlled by, a 

government agency, a university (or other educational 

institution accredited by a recognized national or 

international accreditation body), an international treaty 

organization, or a scientifi c institution. The vessel must 

have scientifi c research as its exclusive mission during 

the scientifi c cruise in question and its operations must 

be conducted in accordance with a scientifi c research 

plan.5

Scientifi c and Statistical Committee (SSC)

An advisory committee of a regional fi shery 

management council (FMC) composed of scientists, 

economists, and other technical experts. The MagnusonStevens Act requires that each council maintain an 

SSC to assist in gathering and analyzing statistical, 

biological, ecological, economic, social, and other 

scientifi c information that is relevant to the management 

of council fi sheries.1 (see Advisory Panel)

Seagrass

Rooted, grasslike fl owering plants, such as eelgrass, that 

are adapted to live at sea, submersed, and can tolerate a 

saline environment.12

Seamount

A large isolated elevation rising more than 1,000 meters 

above the sea fl oor, and characteristically of conical 

form.5 (Notable examples include Shimada Seamount in 

the Eastern Equatorial North Pacifi c and Bear Seamount 

in the New England Seamount Chain.)

Seasonal Closure

Closed season. The banning of fi shing activity (in an 

area or of an entire fi shery) for a few weeks or months, 

to protect juveniles or spawners.5

Secretary of Commerce

The Secretary has responsibility for reviewing, 

approving, and implementing fi shery management plans 

(FMPs).

Secretarial Fishery Management Plan

A plan developed by the Secretary of Commerce in 

response to an emergency, a council’s failure to act, or 

for highly migratory species.2

Sedentary Species

Organisms which, at the harvest stage, either are 

immobile on or under the seafl oor or are unable to move 

except in constant physical contact with the seafl oor or 

the subsoil.5

Seine Net

Nets that are usually set from a boat, and can be 

operated either from the shore (beach seines) or from 

the boat itself (e.g. purse seines). The manner of capture 

is to surround an area of water with a very long net, 

with or without a bag at the center. The net is usually 

operated by two ropes fi xed to its ends, used both for 

hauling it in and for herding the fi sh.5 (see Purse Seine)

Selective Gear

A gear allowing fi shers to capture few (if any) species 

other than the target species.5

Selectivity

1. Ability to target and capture fi sh by size and species 

during harvesting operations, allowing bycatch of 

juvenile fi sh and nontarget species to escape unharmed; 

2. In stock assessment, conventionally expressed as a 

relationship between retention and size (or age) with no 

reference to survival after escapement.5
JUNE 2006 45

Sensitivity Analysis

In stock assessment modeling, the process of testing 

the sensitivity of model results in relation to errors and 

uncertainties in the input parameters. For example, 

a virtual population analysis (VPA) might be used 

to determine the fi shing mortality rates over several 

years. The results might be conditioned on an assumed 

annual natural mortality rate (M) of 0.2. The sensitivity 

of this assumption might be examined by redoing the 

VPA based upon a different M, perhaps M=0.15 to 

0.3. From the sensitivity analysis one can determine 

the importance of particular parameters to the overall 

scientifi c advice.5

Separability

1. Separability is the assumption, made in some agestructured stock assessment models (used to track 

changes in fi shing mortality by fi sh age and by fi shing 

year) that the fi shing mortality matrix can be partitioned 

into two components: An age-specifi c component that 

does not vary over time (i.e. a constant exploitation 

pattern), and an annual multiplier that scales the agespecifi c pattern up or down; 2. Independence among 

resources and in economics; an ability to substitute 

environmental inputs in order to produce outputs. 

Therefore, these resources may be managed or utilized 

separately due to the lack of strong linkages to other 

large marine ecosystem (LME) components.5

Sequential Population Analysis

Generic name for methods of back-calculating stock 

sizes, recruitment levels, and fi shing mortality for 

different ages/years using catch-at-age data. A statistical 

criterion may be used in addition to fi t indices of 

abundance.5

Sessile

Attached to the substrate.5

Set Gillnet

A gillnet fi xed to the bottom, or at a certain distance 

above it, by means of anchors or ballast suffi ciently 

heavy to neutralize the buoyancy of the fl oats.5

Set Longline

Longlines consist of a main line, sometimes of 

considerable length, to which snoods with baited or 

unbaited hooks are fi xed at regular intervals. The main 

line is set either horizontally on or near the bottom or 

less commonly near the surface.5

Sexual Dimorphism

Pertains to systematic differences between males and 

females. Several species of tunas and billfi shes show 

sexual dimorphism in growth or mortality.5

Shadow Price

In economic analysis, this is any distortion of a free 

market price that is made in order to refl ect the real 

scarcity value of foods or services, including labor. An 

example of a shadow price is the elimination of the 

effect of taxes or subsidies.5

Shared Stock

Stocks of fi sh that migrate across the exclusive 

economic zone (EEZ) boundary of adjacent or opposite 

coastal states.5

Shelf Break

Region where the continental shelf and continental slope 

meet; i.e. where the more gently sloping region of the 

seabed adjacent to a landmass rather abruptly slopes 

steeply down towards the ocean depths; commonly 

around depths of 200 meters.5

Shelf Edge

A narrow zone at the outer margin of a shelf along 

which there is a marked increase of slope.5

Shellfi sh

Shellfi sh include both mollusks, such as clams, and 

crustaceans, such as lobsters.5

Shoal

School of fi sh, but usually at the surface or in shallow 

water.5

Shoaling Fish

Species of relatively small (usually pelagic) fi sh that 

congregate in large schools, such as anchoveta and 

sardines.5

Sink

Habitats in which birth rates are lower than dealth rates 

and emigration is lower than immigration, as applied 

to equilibrium populations. A more general defi nition 

is that a sink is a compartment that is a net importer of 

individuals.14 (see Source)

Simulation

In fi sheries, the use of a body of numerical techniques 

and specifi ed inputs to reproduce by calculations 

the functioning of a stock or fi shery.5

 (see Model, 

Population Model)

Comment: Simulations may be deterministic (assuming 

no variability) or stochastic (to explore the range of 

variability in the results). Sensitivity analyses and 

projections of the status of the fi shery system into the 

future are forms of simulation. There are several ways 

of accounting for uncertainty in simulations, such as 
46 NOAA FISHERIES GLOSSARY

bootstrapping, Bayesian methods, and Monte Carlo 

simulations.5 (see Bayesian, Deterministic, Monte Carlo, 

Sensitivity Analysis, Stochastic) 

Single-Species Fishery 

A type of fi shery in which fi shers target only one species 

of fi sh, although it is usually impossible not to catch 

others incidentally. 

Single-Species Model

A model describing the dynamics of a species that does 

not explicitly incorporate the effects of interactions with 

other species.5

Size Distribution

A breakdown of the number of fi sh of various sizes in a 

sample or catch, most often shown on a chart; the sizes 

can be in length or weight.10

Size Limit

A minimum or maximum limit on the size of fi sh that 

may be legally be caught.5

Size Samples

Refers to samples taken from the catch (from the 

landings) in order to determine the size distribution 

of the catches. This information is important for stock 

assessments (particularly for age/size-structured 

methods) and management advice.5

Size-at-Age

Length or weight at a particular age.5

Size-at-First-Maturity

Length or weight of the fi sh when it attains maturity 

as defi ned by: 1) the minimal size at which maturity is 

reached; 2) the size at which 50 percent of the fi sh of 

that size is mature.5

Slope

The slope seaward from the shelf edge to the beginning 

of a continental rise or the point where there is a general 

reduction in slope.5

Slot Limit

1. A limit on size of fi sh that may be kept—allows a 

harvester to keep fi sh under a minimum size and over a 

maximum size, but not those in between the minimum 

and maximum; 2. Size limits that allow a harvester 

to keep only fi sh that fall between a minimum and 

maximum size.10

Small-Scale Producers

Producers operating at a small scale, used to distinguish 

from industrialized producers. In truth, the line 

separating small and large-scale producers is arbitrary. 

What is considered small scale in one country or region 

may be considered large scale in another.5

Smolt

An adolescent salmon which has metamorphosed and 

which is found on its way downstream toward the sea.5

Social Capital

The social resources (networks, memberships of groups, 

relationships of trust, access to wider institutions 

of society) upon which people draw in pursuit of 

livelihoods.5

Social Costs

Costs associated with the disruption of communities, 

households, and related social structures resulting in the 

loss of human potential.5

Social Costs and Benefi ts

Costs and benefi ts as seen from the perspective of 

society as a whole. These differ from private costs and 

benefi ts in being more inclusive (all costs and benefi ts 

borne by some member of society are taken into 

account) and in being valued at social opportunity cost 

rather than market prices, where these differ. Sometimes 

termed “economic” costs and benefi ts. Compare private 

costs and benefi ts.5

Social Discount Rate

The rate used in estimating the present value to society 

of an enterprise. It is sometimes held that, to refl ect 

social values, the social discount rate should be lower 

than the discount rate used in the private sector.5

Social Factors

In addition to factors related to economics such as 

benefi ts, capital, and labor, considerations such as social 

structure and social organization, people’s knowledge 

and views (norms and values) about their work and how 

this relates to the resource. Also referred to as: cultural 

factors.5

Social Impacts

The changes in people, families, and communities 

resulting from a fi shery management decision.10

Social Impact Assessment

An evaluation of the likely outcomes and impacts of 

a specifi c policy or regulation on a designated target 

group or groups, as well as likely ripple effects to other 

groups.5

Social Rate of Time Preference

The rate used for discounting future benefi ts and costs 
JUNE 2006 47

based on the way that society values present, as opposed 

to future, consumption; typically one component of the 

social discount rate.

Socio-Economic

Pertaining to the combination or interaction of social 

and economic factors and involves topics such as 

distributional issues, labor market structure, social and 

opportunity costs, community dynamics, and decisionmaking processes.5

Socio-Economic Benefi ts

Benefi ts to humans gained through utilization of 

resources, including both economic and social benefi ts.5

Sonar

An apparatus that uses sound waves to detect objects 

underwater by measuring or classifying the echoes 

received from them. An echo sounder is a sonar that 

transmits vertically. In practice, a sonar is an apparatus 

other than an echo sounder, i.e. a sonar transmits 

horizontally.5

Source

Patches in which birth rates are higher than death rates 

and emigration rates are higher than immigration rates, 

as applied to equilibrium populations. A more general 

defi nition is a compartment that, over a large period of 

time (e.g. several generations), shows no net change 

in population size, but nonetheless is a net exporter of 

individuals.14 (see Sink)

Spatial (Area) Closures

Permanent or seasonal ban of fi shing activities in an 

area.5

Spatial Heterogeneity

The non-homogeneous nature of habitats or spatial 

distributions of organisms, often ignored in simple 

models.5

Spawner-Recruit Relationship

The concept that the number of young fi sh (recruits) 

entering a population is related to the number of parent 

fi sh (spawners).2 (see Recruitment)

Spawning

Release of ova, fertilized or to be fertilized.5

Spawning Biomass

The total weight of all sexually mature fi sh in the 

population.

Spawning Output per Recruit (SPR)

Amount of per capita spawning biomass (or other 

appropriate measure of reproductive output) obtained 

from a given value of fi shing mortality, conditional 

values of partial recruitment, growth, maturity (and/or 

fecundity), and natural mortality.11

Spawning Potential Ratio (SPR)

The number of eggs that could be produced by an 

average recruit in a fi shed stock divided by the number 

of eggs that could be produced by an average recruit 

in an unfi shed stock. SPR can also be expressed as the 

spawning stock biomass per recruit (SSBR) of a fi shed 

stock divided by the SSBR of the stock before it was 

fi shed.2

Comment: SPR’s require information on natural 

mortality, growth, spawning potential at age, and the 

relative vulnerability by age to fi shing. If possible, 

spawning potential per recruit is measured in fecundityper-recruit, but often spawning stock biomass per recruit 

(SSB/R, see below) is an appropriate substitute. SPR 

and SSB/R are simple extensions to yield-per-recruit in 

that there are two ways in which recruits can be used: 

they can be caught, in which case they are part of the 

yield (yield-per-recruit), or they can survive, in which 

case they are part of the SPR, SSB/R. SPR is expressed 

as a ratio of a fi shed condition to an unfi shed condition, 

thus the ratio varies from 0 to 1. Additionally, empirical 

studies have shown that for some populations SPR’s in 

the order of 20% to 30% may run the risk of recruitment 

declines, thus there is a basis of comparison between 

populations. Therefore, FX%SPR fi shing mortality rates 

are sometimes used as biological reference points. 

(Note: SPR is sometimes used to mean “spawners per 

recruit,” but this usage should be avoided and replaced 

by SSB/R). 5

Spawning Stock

1. Mature part of a stock responsible for reproduction; 

2. Strictly speaking, the part of an overall stock having 

reached sexual maturity and able to spawn. Often 

conventionally defi ned as the number or biomass of all 

individuals beyond “age at fi rst maturity” or “size at fi rst 

maturity”; that is, beyond the age or size class in which 

50 percent of the individuals are mature.5

Spawning Stock Biomass (SSB)

1. The total weight of all fi sh (both males and females) 

in the population that contribute to reproduction. Often 

conventionally defi ned as the biomass of all individuals 

beyond “age at fi rst maturity” or “size at fi rst maturity,” 

i.e. beyond the age or size class in which 50 percent of 

the individuals are mature; 2. The total biomass of fi sh 

of reproductive age during the breeding season of a 

stock.5
48 NOAA FISHERIES GLOSSARY

Comment: Most often used as a proxy for measuring 

egg production, the SSB depends on the abundance of 

the various age classes composing the stock and their 

past exploitation pattern, rate of growth, fi shing and 

natural mortality rates, onset of sexual maturity, and 

environmental conditions.5

Spawning Stock Biomass per Recruit (SSB/R or SBR)

The expected lifetime contribution to the spawning 

stock biomass for the average recruit, SSB/R is 

calculated assuming that fi shing mortality is constant 

over the life span of a year class. The calculated value 

is also dependent on the exploitation pattern and rates 

of growth and natural mortality, all of which are also 

assumed to be constant.3

Spawning Substrate

The type of bottom habitat required by a fi sh species for 

spawning.5

Species

Group of animals or plants having common 

characteristics, able to breed together to produce fertile 

(capable of reproducing) offspring, and maintaining 

their “separateness” from other groups.5

Species Assemblage

Group of species co-occurring in a given area and likely 

to be caught together in a given gear.5 (see Species 

Group)

Species Diversity

The variety of species in a community, which can be 

expressed quantitatively in ways which refl ect both the 

total number of species present and the extent to which 

the system is dominated by a small number of species.5

(see Biological Diversity)

Species Group

Group of species considered together, often because they 

are diffi cult to differentiate without detailed examination 

(very similar species) or because data for the separate 

species are not available (e.g. in fi shery statistics or 

commercial categories).5 (see Species Assemblage)

Species Richness

Species richness/abundance is the distribution of the 

number of species and the number of individuals of each 

species in a community.5

Spill-Over Eff ects

Sometimes referred to as externalities, an unintended 

effect (positive or negative, benefi t or cost) imposed on 

others and not borne by the party responsible for the 

effect.5

Stability

This term is applied very loosely to ecosystems or 

communities, but it usually means their tendency to 

retain their essential characteristics in the shorter or 

longer term. It sometimes refers to the more particular 

capacity of systems to return to their original state 

following a disturbance.5

Stakeholder

1. A large group of individuals and groups of individuals 

(including governmental and non-governmental 

institutions, traditional communities, universities, 

research institutions, development agencies and banks, 

donors, etc.) with an interest or claim (whether stated or 

implied) that has the potential of being impacted by or 

having an impact on a given project and its objectives. 

Stakeholder groups that have a direct or indirect “stake” 

can be at the household, community, local, regional, 

national, or international level; 2. An actor having 

a stake or interest in a physical resource, ecosystem 

service, institution, or social system, or someone who is 

or may be affected by a public policy.5

Standard

A criterion (or indicator, or reference point) that 

has been formally established and is enforced by an 

authority.5

Standardization (Calibration)

The procedure of maintaining methods and equipment 

as constant as possible. Without standardization one 

cannot determine whether measurements of yearly 

differences in relative abundance are caused by actual 

fl uctuations in stock abundance or by differences 

in the measurement procedure used. The lack of 

standardization is one reason why surveys using 

different commercial fi shing vessels in different years 

do not produce comparable information. For example, if 

two vessels of different horsepower are used in separate 

years, the results cannot be compared unless vessel 

mensuration experiments are performed. This would 

involve a comparison of the two vessels’ catches to 

determine the infl uence of their fi shing power on the size 

of the catch, and a determination of a correction factor.6

Standardized

Refers to quantities that have been adjusted to be 

directly comparable to a unit that is defi ned as the 

“standard” one. Nominal catch per unit effort (CPUE) 

is standardized to remove the effect of factors that are 

known not to be related to abundance.5

Comment: This means that the effects of factors such as 

vessel size or spatial availability, which clearly affect 

CPUE, are removed, e.g. by adjusting all observations 
JUNE 2006 49

to the “standard vessel” in the “standard area.” A variety 

of techniques are available for standardization such as 

generial linear models (GLMs).5 

Standard Length (SL)

The length of a fi sh as measured from the tip of the 

snout to the hidden base of the tail fi n rays.2

Standing Stock

1. The total weight of a group (or stock) of living 

organisms (e.g. fi sh, plankton) or of some defi ned 

fraction of it (e.g. spawners), in an area, at a particular 

time. Example: the spawning biomass of the cod stock 

on the Georges Bank in 1999; 2. The weight of a fi sh 

stock, or of some defi ned portion of it.5 (see Abundance)

State of Stocks 

An appreciation of the situation of a stock, usually 

expressed as: protected, underexploited, intensively 

exploited, fully exploited, overexploited, depleted, 

extinct, or commercially extinct.5

Stated Preference Methods

General category of valuation methods that includes 

contingent choice and contingent valuation techniques. 

Individuals are asked to makes choices concerning 

their willingness to pay (or accept compensation) for, 

rank, or make choices among alternative provisions of 

environmental goods.

States of Nature

A description of a condition and dynamics of the 

resource and the fi shery, including parameters such as 

stock abundance, age structure, fi shing mortality, the 

economic condition of the industry and the state of the 

environment.5

Stationary

Things that do not change over time. In fi shery science, 

refers usually to a parameter or life history characteristic that does not change over time. The concept is 

closely related to that of equilibrium, although it is 

possible to have one without the other. For example, 

yield-per-recruit can be stationary (constant) if the 

fi shing and natural mortality, exploitation pattern, and 

growth remain stationary, but the overall yield can vary 

over time if the number of recruits varies.5

Statistic

The estimate of a parameter, which is obtained by 

observation, and which in general is subject to sampling 

error.5

Statistical Model

A component of an estimation model, that defi nes the 

criteria for how the observations are fi tted. Statistical 

models include least squares, maximum likelihood, 

Bayesian, and ad hoc procedures.5 (see Least Squares, 

Bayesian)

Status Determination Criteria (SDC)

Objective and measurable criteria used to determine 

if a stock is being overfi shed or is in an overfi shed 

state according to National Standard Guidelines.3 (see 

National Standard Guidelines)

Status of Exploitation

An appraisal of exploitation is given for each stock 

using the terms unknown, protected, not exploited, 

underexploited, moderately exploited, fully exploited, 

and overexploited. These terms describe the effect of 

current fi shing effort on each stock, and are based on 

current data and the knowledge of the stocks over time.6

Status Quo

Can mean the general current state of affairs in a 

fi shery.5

Steady State

A population in a steady state may fl uctuate about a 

mean but does not increase or decline in a systematic 

way with time.5

Stern Trawler

A fi shing vessel designed for trawling, in which the nets 

are hauled over the stern, up a ramp, or over a roller or 

the bulwark, with the aid of a derrick or gantry.5

Stochastic

1. Where system components are affected by random 

variability. For example, when fi shery stock projections 

are elaborated, future recruitments are projected with 

a stochastic component (i.e. the values introduced in 

the projection randomly vary from year to year); 2. A 

stochastic model is a model whose behavior is not fully 

specifi ed by its form and parameters, but which contains 

an allowance for unexplained effects represented by 

random variables.5 (see Deterministic)

Stock

A part of a fi sh population usually with a particular 

migration pattern, specifi c spawning grounds, and 

subject to a distinct fi shery. A fi sh stock may be treated 

as a total or a spawning stock. Total stock refers to both 

juveniles and adults, either in numbers or by weight, 

while spawning stock refers to the numbers or weight of 

individuals that are old enough to reproduce.6

Comment: In theory, a unit stock is composed of all 

the individual fi sh in an area that are part of the same 
50 NOAA FISHERIES GLOSSARY

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.5

Stock Assessment

The process of collecting and analyzing biological and 

statistical information to determine the changes in the 

abundance of fi shery stocks in response to fi shing, and, 

to the extent possible, to predict future trends of stock 

abundance. Stock assessments are based on resource 

surveys; knowledge of the habitat requirements, 

life history, and behavior of the species; the use of 

environmental indices to determine impacts on stocks; 

and catch statistics. Stock assessments are used as a 

basis to assess and specify the present and probable 

future condition of a fi shery.5

Stock Assessment and Fishery Evaluation Report (SAFE)

A report that provides a summary of the most recent 

biological condition of a stock of fi sh and the economic 

and social condition of the recreational fi shermen, 

commercial fi shermen, and seafood processors who use 

the fi sh. The report provides information to the fi shery 

management councils (FMCs) for determining harvest 

levels.5

Stock Structure

1. The spatial organization of a species in terms of the 

genetic structure of the species across geographic space 

(e.g., a species of large pelagic fi sh (tunas) may be 

composed of three separate stocks in the North Atlantic, 

South Atlantic, and Pacifi c Ocean); 2. The structure of a 

particular stock, in terms of its size or age composition 

or in terms of its species composition (for a multispecies 

stock).5

Stock-Recruitment Relationship (SRR)

The relationship between the level of parental biomass 

(e.g. spawning stock size) and subsequent recruitment 

level. Determination of this relationship is useful to 

analyze the sustainability of alternative harvesting 

regimes and the level of fi shing beyond which stock 

collapse is likely. The relation is usually blurred by 

environmental variability and diffi cult to determine with 

any accuracy.5

Comment: Such a relationship always exists in principle, 

in that the existence of a parent stock is a prerequisite for 

the generation of recruitment. However, in many cases 

there exist regulatory mechanisms such that the number 

of recruits is not strongly related to the parent stock size 

over the range of stock sizes observed: this situation 

is sometimes described as the absence of a stockrecruitment relationship, but is more logically described 

as a special case of a stock-recruitment relationship. 

Some stock assessment methods incorporate the 

estimation of such a relationship directly into the model, 

either explicitly (e.g. some age-structured assessments) 

or implicitly (most stock production models).5 

Stocking

The practice of putting artifi cially reared young fi sh 

into a sea, lake, or river. These are subsequently caught, 

preferably at a larger size.5

Straddling Stock

1. A stock which occurs both within the exclusive 

economic zone (EEZ) and in an area beyond and 

adjacent to the EEZ; 2. Fish stocks that migrate between 

national EEZs and the high seas.5

Strategy

A statement involving the projections of actions, 

including the direction of means, to achieve an 

objective.5

Stratifi cation

The separation of the water column into layers, with the 

densest at the bottom and the lease dense at the surface, 

typically caused by temperature and/or salinity. A 

stratifi ed water column is said to be stable.12 (see Mixed 

Layer, Pycnocline, Thermocline)

Stratifi ed Mean (Average) Catch Per Tow

From research vessel surveys, for separate species of 

fi sh, each average catch per tow, determined from a 

series of tows, in each geographic stratum of a region 

is multiplied by that area (square nautical miles) of 

the stratum in which the tows are made. All of the 

individual products are added together and the total 

is divided by the sum of the entire area of the region. 

The fi nal result is stratifi ed mean catch per tow; this is 

used as an index of relative abundance. For example, 

a scientist wishes to calculate the stratifi ed mean catch 

per tow of cod in a region (perhaps Georges Bank) that 

measures 100 square nautical miles. The region has 

been divided into 5 strata on the basis of depth. In each 

stratum, 5 tows are made and the average catch of cod is 

calculated.6

Submarine Canyon

Submerged earthform consisting of an incised largescale submarine feature on a high angle slope normally 

associated with the continental shelf.12
JUNE 2006 51

Submerged Bank

Large, relatively fl at shoal or other expansive submerged 

feature that is markedly shallower than the surrounding 

ocean bottom (e.g. Georges Bank with water depths 

between 30 to 50 meters).12

Subpopulations

Subpopulations are defi ned as geographically or 

otherwise distinct groups in the population between 

which there is little exchange.5

Subsidence

The sudden sinking or gradual downward settling of the 

Earth’s surface with little or no horizontal motion.12

Subsidy

A direct or indirect payment, economic concession, 

or privilege granted by a government to private fi rms, 

households, or other governmental units in order to 

promote a public objective.5

Subsistence Fishery

A fi shery where the fi sh caught are shared and consumed 

directly by the families and kin of the fi shers rather than 

being sold at the next larger market.5

Substitutions

In data processing, refers to the practice of substituting 

missing information (e.g. the catch composition of 

country A vessels) with an available one (e.g. the catch 

composition of country B vessels), assuming some 

degree of similarity (e.g. same fi shing area, gear, and 

practice). Substitutions are often needed to obtain 

estimates of the total catch-at-size for a species with 

incomplete datasets.5

Substrate

Seafl oor or other solid surface to which animals or 

plants attach, or on which they move.5

Subtidal

Permanently below the level of low tide, an underwater 

environment.12

Summary Settlement

A ticket with a discounted fi ne that is issued to a 

fi sherman prior to the issuance of a notice of violation 

and assessment (NOVA), offered only in cases where the 

violation is not contested. Allows violators to quickly 

resolve their case without incurring the expense of the 

legal process. Any property that was seized is forfeited 

by paying the penalty.10 (see Notice of Violation and 

Assessment) 

Super Seiner

A large purse seiner, usually more than 70 meters long 

and equipped with considerable freezing and storage 

facilities, capable of undertaking extended transoceanic 

voyages for harvesting fi sh.5

Supply Function

The relationship between the quantity of good or service 

supplied and price.

Supply Gluts

A situation in which the market is supplied with an 

unusually large amount of product, which strains the 

capacity of primary buyers, processors, and wholesalers 

and causes prices to drop to very low levels.5

Support

Any operation by a vessel assisting fi shing by foreign 

or national vessels, including supplying water, fuel, 

provisions, fi sh processing equipment, or other supplies 

to a fi shing vessel.5

Supporting Ecosystem Services

Supporting ecosystem services are those services (e.g. 

primary production, oxygen production, soil formation) 

that are necessary for the production of all other 

ecosystem services (e.g. food, employment, recreation, 

erosion control, etc.).5

Supporting Services

Ecosystem services those are necessary for the 

production of all other ecosystem services. Some 

examples include biomass production, production of 

atmospheric oxygen, soil formation and retention, 

nutrient cycling, water cycling, and provisioning of 

habitat.5

Supratidal

Above the level of high tide; a terrestrial environment 

that is infl uenced by proximity to the sea, including 

infl uency by sea spray, sea breezes, and aeolian 

processes, and geological and biological “spillover” 

such as dune development.12

Surface (Mixed) Layer

The upper layer of water that is mixed by wind, waves, 

and currents.12

Surface Runoff 

The fl ow across the land of water that accumulates 

on the land surface when the rainfall rate exceeds the 

infi ltration capacity of the soil.12
52 NOAA FISHERIES GLOSSARY

Surface Water

All water naturally open to the atmosphere, including 

rivers, lakes, reservoirs, streams, impoundments, seas, 

estuaries, and so on. The term also covers springs, wells 

or other collectors of water that are directly infl uenced 

by surface waters.5

Surimi

Protein paste derived from processing raw fi sh, primarily 

Alaska (walleye) pollock and Pacifi c whiting (hake). 

Surimi can be combined with fl avoring agents and other 

substances and extruded to create marketable foodstuffs 

(e.g. imitation crab meat).13

Surplus Production

1. The amount of biomass produced by the stock 

(through growth and recruitment) over and above that 

which is required to maintain the total stock biomass 

at a constant level between consecutive time periods; 

2. Production of new biomass by a fi shable stock, plus 

recruits added to it, less what is removed by natural 

mortality. This is usually estimated as the catch in a 

given year plus the increase in stock size (or less the 

decrease). Also called: natural increase, sustainable 

yield, and equilibrium catch.5

Surplus Production Model

Mathematical representation of the way a stock of fi sh 

responds to the removal of its individuals (for example 

by fi shing). In fi sheries, usually represented by a 

relationship between yield and/or catch per unit effort 

(CPUE) and fi shing effort or mortality.5

Survey Design

The overall survey design refers to the defi nitions and 

the established methods and procedures concerning all 

phases needed for conducting the survey: the sample 

design, the selection and training of personnel, the 

logistics involved in the management of the fi eld force, 

the distribution and receipt of survey questionnaires and 

forms, and the procedures for data collection, processing 

and analysis.5

Survival Rate

Number of fi sh alive after a specifi ed time interval, 

divided by the initial number. Usually on a yearly 

basis.5

Survival Ratio

1. Ratio of recruits to spawners (or parental biomass) in 

a stock-recruitment analysis. Changes in survival ratios 

indicate that the productivity of a stock is changing; 

2. Number of fi sh alive after a specifi ed time interval, 

divided by the initial number. Usually calculated on a 

yearly basis.5

Sustainability

1. Ability to persist in the long-term. Often used 

as “short hand” for sustainable development; 2. 

Characteristic of resources that are managed so that 

the natural capital stock is non-declining through time, 

while production opportunities are maintained for the 

future.5

Sustainability Indicators

A variable, a pointer, an index of a complex 

phenomenon. Its fl uctuations reveal the variations 

in components of the ecosystem, the resource, or 

the sector. The position and trend of the indicator in 

relation to the criteria indicate the present state and 

dynamics of the system. Ideally, composite indicators 

are needed, the position and trajectory of which, within 

a system of reference of related criteria, would allow 

simple holistic assessment of sustainability. One can 

distinguish indicators of state of the system, pressure 

(or stress, driving forces) on the system, and response 

(refl ecting action taken to mitigate, reduce, eliminate, or 

compensate for the stress).5

Sustainable Catch (Yield)

The number (weight) of fi sh in a stock that can be taken 

by fi shing without reducing the stock biomass from year 

to year, assuming that environmental conditions remain 

the same.6

Sustainable Development

1. Management and conservation of the natural 

resource base, and the orientation of technological and 

institutional change in such a manner as to ensure the 

attainment of continued satisfaction of human needs 

for present and future generations. Such sustainable 

development conserves land and water, plant and animal 

genetic resources, is environmentally non-degrading, 

technologically appropriate, economically viable, and 

socially acceptable; 2. Development that meets the needs 

of the present generation without compromising the 

ability of future generations to meet their own needs.5 

Sustainable Fishing

Fishing activities that do not cause or lead to undesirable 

changes in the biological and economic productivity, 

biological diversity, or ecosystem structure and 

functioning from one human generation to the next.5

Comment: Fishing is sustainable when it can be 

conducted over the long-term at an acceptable level of 

biological and economic productivity without leading 

to ecological changes that foreclose options for future 

generations.5
JUNE 2006 53

Sustainable Fisheries Act (SFA)

The SFA is a statute enacted in 1996 which amended 

the Magnuson-Stevens Act. Among its provisions were 

mandatory ovefi shing elimination and stock rebuilding, 

the establishment of a program to protect essential fi sh 

habitat, and the establishment of a new national standard 

for bycatch reduction.8

Sustainable Use

The use of components of biological diversity in a way 

and at a rate that does not lead to the long-term decline 

of biological diversity, thereby maintaining its potential 

to meet the needs and aspirations of present and future 

generations.5

Sustainable Yield

1. Equilibrium yield; 2. The amount of biomass or 

the number of units that can be harvested currently 

in a fi shery without compromising the ability of the 

population/ecosystem to regenerate itself.5

Sustained Use

Continuing use without severe or permanent 

deterioration in the resources.5

Systems Analysis

The analysis and modeling of interrelated processes and 

operations with a view to designing a more effi cient use 

of resources.5

T

Tagging

Marking an individual or group of individuals (e.g. by 

clipping a fi n, injecting a die, inserting a tag) in order 

to identify it when recaptured. Tagging allows the 

study of growth, mortality, and migration as well as the 

estimation of the stock size.5

Target Fishing

Fishing for the primary purpose of catching a particular 

species or species group.1 (see Target Species)

Target Fishing Capacity

The maximum amount of fi sh over a period of time 

(year, season) that can be produced by a fi shing fl eet 

if fully utilized while satisfying fi shery management 

objectives designed to ensure sustainable fi sheries:

YT = Y (ET, S) in which YT is target yield or catch; 

ET is target effort generated by a fully-utilized fl eet; 

and S is stock size (biomass). The “fi shing fl eet” is 

meant to be the stock of inputs (i.e. physical capital and 

human capital). The term “fully-utilized” is used in a 

precautionary context in that it is assumed that capacity 

utilization is 100%. The maximum catch that capital 

stocks could remove can be determined by observing 

the fi shery under study during a period with few 

restrictions.5

Target Reference Point (TRP)

1. Benchmarks used to guide management objectives 

for achieving a desirable outcome (e.g. optimum yield, 

OY). Target reference points should not be exceeded 

on average3; 2. Corresponds to a state of a fi shery or 

a resource that is considered desirable. Management 

action, whether during a fi shery development or a 

stock rebuilding process, should aim at bringing the 

fi shery system to this level and maintaining it there. In 

most cases a TRP will be expressed in a desired level 

of output for the fi shery (e.g. in terms of catch) or of 

fi shing effort or capacity, and will be refl ected as an 

explicit management objective for the fi shery.5

Target Species

Those species primarily sought by the fi shermen in a 

particular fi shery. The subject of directed fi shing effort 

in a fi shery. There may be primary as well as secondary 

target species.5

Target Strength

The ratio of received signal to transmitted signal from 

an object as at 1 meter from the transmitter, expressed in 

decibels.

Technological Interaction

An interaction between fi sheries resulting from the 

impact of one fi shery using a particular technology (e.g. 

trawl gear) on another fi shery, usually using a different 

technology (e.g. pots), but exploiting the same resources 

as target or bycatch. Because of their importance, the 

cross-impact of various fl eets targeting overlapping 

species groups must be assessed. Major source of 

failure in total allowable catches (TACs) and quotas 

management strategies for multispecies and multigear 

fi sheries.5

Temperate Waters

Waters in the region of higher (cooler; more pole-ward) 

latitudes than tropical latitudes; literally those between 

the Tropic of Cancer and the Arctic Circle in the 

northern hemisphere, and the Tropic of Capricorn and 

the Antarctic Circle in the southern hemisphere.5

Tenure

Socially-defi ned agreements held by individuals or 

groups (either recognized by law or customary norms) 
54 NOAA FISHERIES GLOSSARY

on the rights of access and the rules for use of either 

a land area or associated resources such as individual 

trees, plant species, water, or animals.5

Terminal F

In a stock assessment (e.g. a virtual population analysis), 

refers to fi shing mortality values in the last year for 

which data are available.5

Terrace

A relatively fl at horizontal or gently inclined surface, 

sometimes long and narrow, which is bounded by a 

steeper ascending slope on one side and by a steeper 

descending slope on the opposite side.5

Territorial Sea

Extends 12 nautical miles offshore of the United States. 

States exercise authority over marine fi sheries in waters 

from the coastline to 3 nautical miles offshore, and out 

to 9 nautical miles for Texas, Puerto Rico, and the Gulf 

coast of Florida.1

Thermocline

Region below the surface layer of the sea or lake, where 

the temperature gradient increases abruptly (i.e. where 

temperature decreases rapidly with increasing depth). A 

thermocline may reach the surface and become a front. 

It is usually an ecological barrier, and its oscillations 

have signifi cant consequences on stock distribution 

and ocean productivity.5 (see Mixed Layer, Pycnocline, 

Stratifi cation)

Threshold Reference Point (ThRP)

Indicates that the state of a fi shery and/or a resource is 

approaching a target reference point (TRP) or a limit 

reference point (LRP), and that a certain type of action 

(usually agreed beforehand) needs to be taken. Fairly 

similar to a LRP in their utility, the ThRP specifi c 

purpose is to provide an early warning, reducing 

further the risk that the LRP or TRP are inadvertently 

passed due to uncertainty in the available information 

or inherent inertia of the management and industry 

systems. Adding precaution to the management setup, 

they might be necessary only for resources or situations 

involving particularly high risk.5

Thresholds

1. Levels of environmental indicators beyond which a 

system undergoes signifi cant changes; points at which 

stimuli provoke signifi cant response; 2. A point or 

level at which new properties emerge in an ecological, 

economic, or other system, invalidating predictions 

based on mathematical relationships that apply at lower 

levels. For example, species diversity of a landscape 

may decline steadily with increasing habitat degradation 

to a certain point, and then fall sharply after a critical 

threshold of degradation is reached. Human behavior, 

especially at group levels, sometimes exhibits threshold 

effects. Thresholds at which irreversible changes occur 

are especially of concern to decision-makers.5

Tidal Current

An alternating, horizontal movement of water associated 

with the rise and fall of the tide, these movements 

being caused by gravitational forces due to the relative 

motions of Moon, Sun, and Earth.12

Tidal Flat

Level, muddy surface bordering an estuary, alternately 

submerged and exposed to the air by changing tidal 

levels.5

Tidal Marsh

Low, fl at marshland traversed by channels and tidal 

hollows and subject to tidal inundation. Normally, the 

only vegetation present are salt-tolerant bushes and 

grasses.5

Tidal Range

The difference in water level between successive high 

and low tides.12

Tidal Wetlands

A coastal area that experiences periodic inundation as a 

result of daily tides.12

Top-Down Management

A process of management in which management 

information and decisions are centralized and resource 

users are kept outside the decision-making process.5

TMAX

The maximum time period to rebuild an overfi shed 

stock, according to National Standard Guidelines. 

Depends on biological, environmental, and legal/policy 

factors.1 (see National Standard Guidelines)

TMIN

The minimum time period to rebuild an overfi shed stock, 

according to National Standard Guidelines. Technically, 

this is the minimum amount of time in which a fi sh 

stock will have a 50% chance of rebuilding if no fi shing 

occurs (depends on biological and environmental 

factors).1 (see National Standard Guidelines)

Total Allowable Catch (TAC)

The annual recommended or specifi ed regulated catch 

for a species or species group. The regional fi shery 

management council sets the TAC from the range of 

acceptable biological catch (ABC).2
JUNE 2006 55

Total Catch 

Total catch (optimum yield, OY). The landed catch plus 

discard mortality.1

Total Economic Value Framework

A framework that incorporates all components of 

economic value, including use value (consumptive and 

non-consumptive use) and non-use value (option, quasioption, and existence values).

Total Length (TL)

The length of a fi sh defi ned as the straight-line distance 

from the tip of the snout to the tip of the tail (caudal fi n) 

while the fi sh is lying on its side, normally extended.5

Total Maximum Daily Load

The amount of pollutant that a water body can receive 

and still meet water quality standards. Set by the 

Environmental Protection Agency.1

Total Mortality (Z)

1. A measurement of the rate of removal of fi sh from 

a population by both fi shing and natural causes. 

Total mortality can be reported as either annual or 

instantaneous. Annual mortality is the percentage of 

fi sh dying in 1 year. Instantaneous mortality is that 

percentage of fi sh dying at any one time2; 2. The sum of 

natural (M) and fi shing (F) mortality rates.5

Total Welfare

The sum of consumer surplus and producer surplus.9

(see Consumer Surplus, Producer Surplus)

Tradable Permits

An economic policy instrument under which rights 

to discharge pollution or exploit resources can be 

exchanged through either a free or a controlled -permitmarket. Examples include individual transferable quotas 

(ITQs) in fi sheries, tradable depletion rights to mineral 

concessions and marketable discharge permits for 

waterborne effl uents.5

Trade Analysis

Economic analysis of the trade of goods and services 

between countries.9

Trade-Off 

A balancing of factors all of which are not attainable at 

the same time (e.g. maximum economic yield, MEY, and 

maximum sustainable yield, MSY). A giving up of one 

thing in return for another.5

Comment: Sustainability can be evaluated by the sum 

of the various social, economic, and natural resources 

where the degree of use, exchange, and trading among 

resources will vary according to the values given 

to each. The understanding of social dynamics and 

resource-use systems and the evaluation of related tradeoffs, in terms of equity, productivity, resilience, and 

environmental stability, are useful to envision alternative 

development scenarios.5

Tradeoff s

Compromises among resource uses that are required 

because some bundles of entitlements defy divisibility/

separability.5

Traditional Rights

Rights of indigenous or traditional people which (to 

present) have not been considered in a national and 

international context or have not (yet) been recorded, 

and which are based on the legal system of the 

individual cultures.5

Tragedy of the Commons

The overuse of a resource resulting from a lack of 

assigned and enforceable property rights.

Transaction Costs

1. In the context of a market exchange of goods and 

services, transaction costs include the costs of time, 

effort, and other resources necessary to search out, 

negotiate, and consummate an exchange. In a resource 

management context, transaction costs include the 

costs of describing the principal elements of a fi shery 

(resource, producers, processors, markets), and 

designing, implementing, monitoring, and enforcing 

regulation; 2. Collection of costs involved with 

gathering information on, and otherwise delineating, 

a resource; establishing contracts (formal or informal) 

that defi ne the entitlement; monitoring and enforcing the 

entitlement.5

Transboundary Stocks

Stocks of fi sh that migrate across international 

boundaries or, in the case of the United States, across 

the boundaries between states or fi shery management 

council (FMC) areas of control.5

Transferred Species

Transplanted species. Any species intentionally or 

accidentally transported and released by humans into an 

environment inside its present range. Also referred to as 

a “Transfer.”5

Transgenic

Organisms whose genetic makeup includes a gene or 

genes from another genus or species.5
56 NOAA FISHERIES GLOSSARY

Transshipment

Transfer of product from one ship to another at sea for 

further transport.13

Transitional

Relates usually to the more or less abrupt passage 

(or evolution) from one state, stage, subject, or place 

to another. In fi shery science, refers to what happens 

between two equilibrium states corresponding to two 

different fi shing regimes (i.e. the non-equilibrium 

trajectory between two states).5

Comment: Transitional situations may be extremely 

important in terms of comparing performance of 

different management options. For example, equilibrium 

yield analyses might indicate that a given regulation will 

increase equilibrium yield by, say, twofold. However, 

the transition between the two levels of yield will 

actually involve a short-term loss in yield, and hence 

may meet with stakeholders’ resistance.5

Translocation

Movement of native or introduced (exotic) species 

to waters or habitats outside their natural or previous 

distribution.5

Transnational Fisheries

Fisheries in which the same resource stock(s) crosses 

the exclusive economic zones (EEZs) of two or more 

countries.5

Transparency

The openness of governance processes and decisionmaking to stakeholders and the public.

Transshipment

1. Act of transferring the catch from one fi shing vessel 

to either another fi shing vessel or to a vessel used solely 

for the carriage of cargo; 2. Off loading and on loading 

or otherwise transferring fi sh or fi sh products and/or 

transporting fi sh or products made from fi sh.5

Trap Fishing

Fishing by means of devices able to trap fi sh in a 

confi ned environment (traps, pots) often designed and 

baited to catch a particular species—crab pot, lobster 

pot, tuna trap, fyke nets.5

Trawl Net

Towed net consisting of a cone-shaped body closed by 

a bag or codend and extended at the opening by wings. 

It can be towed by one or two boats and, according to 

the type, used on the bottom or in midwater (pelagic). 

In certain cases, as in trawling for shrimp or fl atfi sh, the 

trawler can be specially rigged with outriggers to tow up 

to four trawls at the same time (double rigging).5

Trawling

Fishing technique in which a net is dragged behind the 

vessel and retrieved when full of fi sh. This technique is 

used extensively in the harvest of pollock, cod, and other 

fl atfi sh in North Pacifi c and New England fi sheries. It 

includes botto- and midwater fi shing activities.13

Trench

A long, narrow, characteristically very deep and 

asymmetrical depression of the sea fl oor, with relatively 

steep sides.5

Trip Limits 

A quota that each fi sher or vessel is allowed to catch per 

trip out to sea. Trip limits are the commercial equivalent 

of a recreational bag limit. 

Troller

A vessel used for catching pelagic fi sh by towing a 

number of lines fi tted with lures.5

Trolling

A surface and subsurface fi shing method in which lines 

with baits or lures are dragged by a vessel at a speed of 

2–10 knots. Trolling is used to catch tuna and tuna-like 

fi sh.5

Trophic Group

Group of organisms eating resources from a similar level 

in the energy cycle.5

Trophic Level

1. Classifi cation of natural communities or organisms 

according to their place in the food chain. Green 

plants (producers) can be roughly distinguished from 

herbivores (consumers) and carnivores (secondary 

Syn: Trophic group consumers); 2. Group of organisms 

eating resources from a similar level in the energy cycle; 

3. Position in food chain determined by the number 

of energy-transfer steps to that level. Plant producers 

constitute the lowest level, followed by herbivores and 

a series of carnivores at the higher levels.5 (see Food 

Chain, Predator-Prey Relationship)

TTARGET

The target year set by policy for a fi sh stock to be 

completely rebuilt.1 

Tuning

Improving the fi t between observed and calculated data 

using a mathematical (stock assessment) model.5
JUNE 2006 57

Turtle Excluder Device (TED)

A gear modifi cation used on shrimp trawls that enables 

incidentally caught sea turtles to escape from the nets.

Two-pie System

Form of quota allocation in which both harvesters and 

processors are allocated shares of quota. The harvester 

and processor allocations would be transferable within 

but not between each category.13

Typographic Features

The relief features of the Earth’s surface, above and 

below sea level; the set of landforms in a region.12

Turbidity

The condition resulting from the presence of suspended 

particles in the water column which attenuate or reduce 

light penetration.12

U

Unblocked Quota

Quota shares in the Alaskan halibut and sablefi sh 

individual fi shing quota (IFQ) programs that are allowed 

to be subdivided when transferred. There are limits 

on the total number of unblocked quota shares that an 

individual may own.13 (see Blocked Quota)

Uncertainty

1. In general, the incompleteness of knowledge about the 

states and processes in nature5; 2. In statistics and risk 

analysis, refers to the estimated amount (or percentage) 

by which an observed or calculated value may differ 

from the true value; 3. Lack of perfect knowledge of 

many factors that affect stock assessments, estimation of 

biological reference points, and management.5

Comment: Sources of uncertainty include measurement 

error (in observed quantities), process error (or natural 

population variability (e.g. in recruitment), model error 

(misspecifi cation of assumed values or population model 

structure), estimation error (in population parameters 

or reference points, due to any of the preceding types 

of errors), and implementation error (or the inability to 

implement management controls for whatever reason).5

UNCLOS

United Nations Convention on the Law of the Sea. 

Adopted in 1982. Entered into force in 1994.5

Underfi shed

Characteristic of a stock that may sustain catches higher 

than current ones.5

Undersized

Fish (caught) at a size smaller than the minimum size 

limit established by regulation.5

Underutilized Species

A species of fi sh that has potential for large additional 

harvest.5

Undeveloped Fishery

A fi shery in its very early stage of development, with 

very low levels of fi shing effort, producing much lower 

quantities of fi sh than its potential maximum yield.5

Unit Stock

A population of fi sh grouped together for assessment 

purposes, which may or may not include all the fi sh in a 

stock.5 (see Stock)

Unregulated Fishery

A fi shery in which producers (and any other participants) 

are not subjected to any regulations.5

Upland

An area that is higher relative to the surrounding areas, 

but not mountainous.12

Upwelling

Upward movement of cool and nutrient-rich subsurface 

waters towards the surface often leading to exceptionally 

rich areas. There exist various types of upwelling. For 

fi sheries, the most important type is the wind-induced 

coastal upwelling where the upward movement is a 

consequence of wind stress (along shore) and Eckman 

transport (offshore).5

Usable Stock

The number or weight of all fi sh in a stock that lie 

within the range of sizes customarily considered usable 

(or designated so by law). Also called: standing crop.5

Use Rights

Rights for the use of resources that can be defi ned by 

local custom, mutual agreements, or prescribed by other 

entities holding access rights. These rights may restrict 

the use of particular resources to specifi c levels of 

consumption or particular harvesting techniques.5

User

The term includes a commercial, recreational, and 

indigenous fi sher; fi sh watcher (scuba diver); and 
58 NOAA FISHERIES GLOSSARY

a member of the community. What constitutes a 

“signifi cant user interest” must be decided on in a caseby-case basis.5

User Group

A group of individuals that utilize a resource in a 

specifi c manner such as inshore lobster fi shermen.5 (see 

Stakeholder)

User-Pays Principle (UPP)

The UPP states that the price of a natural resource 

should refl ect the full range of costs involved in using 

it, including the costs of the external effects associated 

with exploiting, transforming, and using the resource, 

together with the cost of the future uses forgone. It 

follows that the price for the use of a resource should 

be the full long-run marginal social cost of using 

it, including the external costs associated with its 

development and any resultant pollution prevention and 

control activities.5

Utility

1. The level of welfare that a person gets from 

consuming a good or undertaking an activity; 2. In 

economics, the measure of the degree of satisfaction or 

happiness of a person.5

Utilized Stock

The part, by number, of the fi sh alive at a given time, 

which will be caught in future.5

V

Valuation

The process of expressing a value for a particular good 

or service in a certain context (e.g. of decision-making) 

usually in terms of something that can be counted, often 

money, but also through methods and measures from 

other disciplines (sociology, ecology, and so on).5

Value

1. Market and nonmarket values, gross and net values, 

and net benefi ts to consumers or goods and services; 2. 

The contribution of an action or object to user-specifi ed 

goals, objectives, or conditions.5

Value Added

The dollar value of a fi rm’s output (i.e. harvest) minus 

the dollar value of the inputs it purchases from other 

fi rms.9

Values

Ideals, customs, and beliefs of a given society.5

Variable

Anything changeable. A quantity that varies or may 

vary. Part of a mathematical expression that may assume 

any value.5

Variable Costs

Costs that vary with the level of output.9

Vertical Integration

A fi shery (or industry) is vertically integrated when 

fi rms in the fi shery engage in multiple levels of the 

supply chain. For example, a fi rm that operates and 

manages fi shing vessels, processing plants, and a 

wholesale distribution operation is considered vertically 

integrated.5

Vessel Catch Limits

A limit on the quantity each individual vessel can land 

per trip or short period of time (e.g. day, week).5

Vessel Class

Commercial fi shing vessels are classifi ed according 

to their gross registered tons (GRT) of displacement. 

Vessels displacing less than 5 GRT are not routinely 

monitored, and are referred to as undertonnage.6 

Vessel Monitoring System (VMS)

A satellite communications system used to monitor 

fi shing activities—for example, to ensure that vessels 

stay out of prohibited areas. The system is based on 

electronic devices (transceivers), which are installed on 

board vessels. These devices automatically send data to 

a shore-based “satellite” monitoring system.1

Vessel Operator

The master or other individual aboard and in charge of 

that vessel.5

Vessel Owner

Any person who owns a vessel in whole or in part; 

any charter of the vessel, whether bare boat, time, 

or voyage; any person who acts in the capacity of 

a charterer, including, but not limited to, parties to 

a management agreement, operating agreement, or 

any similar agreement that bestows control over the 

destination, function, or operation of the vessel; or any 

agent designated as such by a person described in this 

defi nition.5
JUNE 2006 59

Virgin Biomass (B0)

The average biomass of a stock that has yet not 

been fi shed (in an equilibrium sense). Biomass of 

an unexploited (or quasi unexploited) stock. Rarely 

measured. Most often inferred from stock modeling. 

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). It is usually assumed that, 

in absence of better data, B = 0.30 B0 is a limit below 

which a stock should not be driven.

Comment: Virgin Biomass corresponds to a stock’s 

theoretical carrying capacity.5

Virgin Stock

A stock of fi sh with no commercial or recreational 

harvest. A virgin stock changes only in relation to 

environmental factors and its own growth, recruitment, 

and natural mortality.2

Virtual Population Analysis (VPA)

A retrospective analysis of the catches from a given year 

class which provides estimates of fi shing mortality and 

stock size at each age over its life in the fi shery. This 

technique is used extensively in fi shery assessments.3

(see Cohort Analysis)

Viscosity

1. The property of resistance to fl ow in a fl uid or semi 

fl uid. By analogy, in fi sheries: the property of resistance 

of elements of a stock to move and mix together. As a 

consequence of stock “viscosity,” mixing of individuals 

is neither complete nor instantaneous and the transfer of 

the local impact of fi shing to the entire stock (through 

directional or turbulent mixing) is a function of the 

stock ́s “viscosity.” If there is zero mixing, the viscosity 

is infi nite. Because of lack of data on mixing rates, 

the term “viscosity” is often used only in a qualitative 

fashion.5

Vital Rates

Rates (such as natural mortality, fecundity, and growth 

rates) affecting the dynamics of a stock.5

Vulnerability

A term equivalent to catchability (q) but usually applied 

to separate parts of a stock, for example those of a 

particular size, or those living in a particular part of the 

range.5

W

Waste

Physical waste is product that is caught but does not 

have market value. It is a byproduct of the production 

process that is not utilized.

Water Column

The vertical column of seawater that extends from the 

surface to the bottom.12

Water Mass

A body of water that can be identifi ed by its temperature 

and salinity.12

Water Pollution

Presence in water of harmful and objectionable 

material—obtained from sewers, industrial wastes, and 

rainwater runoff—in suffi cient concentrations to make it 

unfi t for use.

Water Quality

The chemical, physical, and biological characteristics of 

water in respect to its suitability for a particular purpose.

Water Quality Criteria

Specifi c levels of water quality desired for identifi ed 

uses, including drinking, recreation, farming, fi sh 

production, propagation of other aquatic life, and 

agricultural and industrial processes.

Water Resources

Water usable as inputs for economic production and 

livelihoods. A distinction is made between renewable 

and nonrenewable water resources. Nonrenewable 

water resources are not replenished at all or for a very 

long time by nature. This includes the so-called fossil 

waters. Renewable water resources are rechargeable due 

to the hydrological cycle unless they are overexploited, 

comprising groundwater aquifers and surface water like 

rivers and lakes.

Watershed

The areas which supplies water by surface and 

subsurface fl ow from rain to a given point in the 

drainage system.

Weight-at-Age

The average individual weight of the fi sh in each age 

class of a particular stock.
60 NOAA FISHERIES GLOSSARY

Welfare

The prosperity or, more broadly, the well being of a 

person or group.

Wetland

Partially or permanently fl ooded, soft bottom fl at that is 

vegetated by vascular plants.12

Y

Year Class

Fish in a stock born in the same year. For example, 

the 1987 year class of cod includes all cod born in 

1987. This year class would be age 1 in 1988, age 2 

in 1989, and so on. Occasionally, a stock produces a 

very small or very large year class that can be pivotal 

in determining stock abundance in later years.3 (see 

Cohort)

Yield

1. The yield curve is the relationship between the 

expected yield and the level of fi shing mortality or 

(sometimes) fi shing effort; 2. Catch in weight. Catch 

and yield are often used interchangeably. Amount of 

production per unit area over a given time. A measure of 

agricultural production.5

Yield per Recruit (Y/R or YPR)

1. A model that estimates yield in terms of weight, 

but more often as a percentage of the maximum yield, 

for various combinations of natural mortality, fi shing 

mortality, and time exposed to the fi shery2; 2. The 

average expected yield in weight from a single recruit. 

Y/R is calculated assuming that fi shing mortality is 

constant over the life span of a year class. The calculated 

value is also dependent on the exploitation pattern, rate 

of growth, and natural mortality rate, all of which are 

assumed to be constant.3

Yield-per-Recruit Analysis

Analysis of how growth, natural mortality, and fi shing 

interact to determine the best size of animals at which 

to start fi shing them, and the most appropriate level of 

fi shing mortality. The yield-per-recruit models do not 

consider the possibility of changes in recruitment (and 

reproductive capacity) due to change in stock size. They 

also do not deal with environmental impacts.5

Z

Zero Opportunity Costs

Where the next best income alternative yields zero 

additional earnings.5

Zero Mortality Rate Goal (ZMRG)

A goal stated in the Marine Mammal Protection 

Act (MMPA) that the “incidental kill or incidental 

serious injury of marine mammals permitted in the 

course of commercial fi shing operations be reduced to 

insignifi cant levels approaching a zero mortality and 

serious injury rate.”1

Zoning

A process in which a protected area is divided into 

discrete zones and particular human uses of each zone is 

permitted, often with conditions such as gear limitations 

in fi shing and waste discharge prohibitions in tourism.14

Zooplankton

Non-photosynthetic, heterotrophic planktonic 

organsisms, including protists, small animals, and 

larvae, which exist within the water column.12 (see 

Phytoplankton)

Numbered 

Terms

602 Guidelines

Rules for fi shery management plans (FMPs); require 

an FMP to defi ne overfi shing, to specify measures to 

prevent overfi shing, and to establish a program for 

rebuilding a stock if overfi shing already exists.10
JUNE 2006 61

Source 

Materials

1

Pacifi c Fisheries Management Council. 2005. 

Commonly Used Acronyms and Defi nitions.

http://www.pcouncil.org/acronyms.html

2

Understanding Fisheries Management: A Manuel 

for understanding the Federal Fisheries Management 

Process, Including Analysis of the 1996 Sustainable 

Fisheries Act (2nd Edition). 2000. R. K. Wallace and 

K. M. Fletcher. Publication MASGP 00-005 of the 

Mississippi-Alabama Sea Grant Consortium.

 http://nsgl.gso.uri.edu/masgc/masgch00001.pdf

3

Northeast Fisheries Science Center. 2005. The 40th 

Northeast Regional Stock Assessment Workshop Draft 

Assessment Report. 

http://www.nefsc.noaa.gov/nefsc/saw/

4

Northwest Fisheries Science Center. Glossary.

http://www.nwfsc.noaa.gov/resources/lingo.cfm

5

United Nations Food and Agricultural Organization. 

Fisheries Glossary.

http://www.fao.org/fi /glossary/default.asp

6

Northeast Fisheries Science Center. Defi nition of 

Fisheries Technical Terms.

http://www.nefsc.noaa.gov/techniques/tech_

terms.html

7

National Marine Fisheries Service. Offi ce of Habitat. 

http://www.nmfs.noaa.gov/habitat/index.html

8

National Marine Fisheries Service. 2004. Fisheries 

Strategic Plan for Fisheries Research. U.S. Dep. 

Commer., NOAA Tech. Memo. NMFS F/SPO-61, 148 p.

http://www.nmfs.noaa.gov/om2/glossary.html

9

Data Needs for Economic Analysis of Fishery 

Management Regulations. 1999. A. W. Kitts and S. R. 

Steinbeck. NOAA Technical Memorandum NMFS-NE119.

http://www.nefsc.noaa.gov/nefsc/publications/

tm/tm119/tm119gloss.htm

10Fisheries Management for Fishermen: A Manual 

for Helping Fishermen Understand the Federal 

Management Process. 1994. R. K. Wallace, W. Hosking, 

and S. T. Szedlmayer. Publication 94-012 of the 

Mississippi-Alabama Sea Grant Consortium. 

11Technical Guidance on the Use of Precautionary 

Approaches to Implementing National Standard 

1 of the Magnuson-Stevens Fishery Conservation 

and Management Act. 1998. V. R. Restrepo, G. G. 

Thompson, P. M. Mace, W. L. Gabriel, L. L. Low, A. D. 

MacCall, R. D. Methot, J. E. Powers, B. L. Taylor, P. R. 

Wade, and J. F. Witzig. NOAA Technical Memorandum 

NMFS-F/SPO-31.

12A Framework for a Coastal/Marine Ecological 

Classifi cation Standard. 2004. C. J. Madden and D. H. 

Grossman. NatureServe, Arlington, VA. Prepared for 

the National Oceanic and Atmospheric Administration 

under Contract EA-133C-03-SE-0275.

13Sharing the Fish: Toward a National Policy on 

Individual Fishing Quotas. Glossary. 1999. Committee 

to Review Individual Fishing Quotas. Ocean Studies 

Board, Commission on Geosciences, Environment, and 

Resources. National Research Council. Washington, 

D.C.

14Marine Protected Areas: Tools for Sustaining 

Ocean Ecosystems. Glossary. 2001. Committee on 

the Evaluation, Design, and Monitoring of Marine 

Reserves and Protected Areas in the United States. 

Ocean Studies Board, Commission on Geosciences, 

Environment, and Resources. National Research 

Council. Washington, D.C.

15An Ocean Blueprint for the 21st Century, Final Report. 

2004. U.S. Commission on Ocean Policy. Washington, 

D.C.
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