Glossary
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Abdominal pelvics
Pelvic fins located on the abdomen far behind the pectoral fins; pelvic bones do not attach to pectoral girdle.
Absolute recruitment
The number of fish that grow into the catchable size range in a unit of time (usually a year).
Abundance
The number of individuals in a stock or a population.
Abundance index
Information obtained from samples or observations and used as a measure of the weight or number of fish which make up a stock.
Accessory pelvic appendage
A tapered fleshy lobe above the base of the pelvic fin.
Acclimate
The adaptation of an organism to environmental changes.
Acclimation pond
Concrete or earthen pond or a temporary structure used for rearing and imprinting juvenile fish in the water of a particular stream before their release into that stream.
Adaptation
Changes in an organism's structure or habits that allow it to adjust to its surroundings.
Adfluvial
Possessing a life history trait of migrating between lakes or rivers and streams.
Adipose fin
A small fleshy fin with no rays, located between the dorsal and caudal fins.
Adult equivalent population
The number of fish that would have returned to the mouth of a river in the absence of any prior harvest.
Affluent (Stream)
A stream or river that flows into a larger one; a Tributary.
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 5, age 5+).
Age composition
Proportion of individuals of different ages in a stock or in the catches.
Age-class
A group of individuals of a certain species that have the same age.
Alevin
The life stage of a salmonid between hatching from the egg and emergence from the stream gravels as a fry. The alevin stage is characterized by the presence of a yolk sac, which provides nutrition while the alevin develops in the protected gravel riverbed.
Alluvial
Originating from the transport and deposition of sediment by running water.
Anadromous
Fish that hatch and rear in fresh water, migrate to the ocean (salt water) to grow and mature, and migrate back to fresh water to spawn and reproduce.
Anal fin
The fin located on the ventral median line and behind the anus.
Annual Total Mortality Rate
The number of fish which die during a year (or season), divided by the initial number. Also called "actual mortality rate" or "coefficient of mortality".
Annulus
A mark or ring that forms annually on the otoliths, scales, and other bones of fish, that correspond to the annual period of slow growth that fish go through. Annuli are used by fish managers to determine age and growth of fish.
Aquaculture
The controlled cultivation and harvest of aquatic plants or animals (e.g., edible marine algae, clams, oysters, and salmon).
Artificial propagation
Any assistance provided by human technology to animal reproduction. In the context of Pacific salmonids, this assistance includes (but is not necessarily limited to) spawning and/or rearing in hatcheries, captive broodstock projects, or the use of remote site incubators.
Assessment level
Categories of the level of complexity of and data available for each assessment included in this document; 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 (one or two years ahead) stock sizes and catches (predictive). These levels are detailed in the subsection titled Kinds of Assessments.
Availability
The fraction of a fish population which lives in regions where it is susceptible to fishing during a given fishing 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.)
Barbel
A slender tactile process or fleshy projection located around the head.
Basiobranchial
The small bones behind the tongue on which the gill arches articulate.
Biodiversity
The variety and abundance of species, their genetic composition, and the natural communities, ecosystem, and landscapes in which they occur.
Biological diversity
The variety of species in a community, sometimes expressed by various quantitative measures which reflect not only the total number of species present but also the degree of domination of the system by a small number of species. Includes genetic diversity (within species), species diversity (within ecosystems) and ecosystem diversity. Diversity indices measure the richness (the number and relative numeric abundance) of species in a system, and the connections between them but are indifferent to species substitution, which may, however, reflect ecosystem stress (such as those due to high fishing intensity).
Biological reference points
Fishing mortality rates that may provide acceptable protection against growth overfishing and/or recruitment overfishing for a particular stock. They are usually calculated from equilibrium yield-per-recruit curves, spawning stock biomass-per-recruit curves and stock recruitment data. Examples are F0.1, Fmax and Fmed.
Biomass
Total weight of all individuals in a stock or a population.
Breeding unit
See Deme
Brood stock
Adult fish used to propagate the subsequent generation of hatchery fish.
Buccal
Pertaining to the cheeks or the cavity of the mouth.
Buoyancy
The tendency of a body to float or rise when submerged in a fluid.
Button-up fry
A salmonid fry that has not completely absorbed its yolk sac and has emerged from its spawning gravel.
By-catch
Species caught in a fishery targeting on other species.
Captive brood stock
Fish raised and spawned in captivity.
Carnivorous
Feeding on animal tissues.
Cartilaginous fishes
A major group of fishes including sharks and rays.
Cascade
A series of small steep drops increasing the velocity of the stream.
Catadromous
Refers to fishes that migrate from fresh water to salt water to spawn or reproduce such as the American eel.
Catch
The act of landing a fish at which point the fisher has the option of release or retention.
Catch curve
A graph of the logarithm of number of fish taken at successive ages or sizes.
Catch per unit effort
The catch of fish, in numbers or in weight, taken by a defined unit of fishing effort. Also called; catch per effort, fishing success, availability. Ex: tons of shrimp per tow, pounds of fish per hundred longline hooks.
Catchability
The fraction of a fish stock which is caught by a defined unit of the fishing 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. (For fractions taken of various portions of the stock, see "vulnerability.") Also called "catchability coefficient" or "force of fishing mortality".
Catch-At-Age
Number of individuals in each age class caught from one stock.
Catchment
The area which supplies water by surface and subsurface flow from precipitation to a given point in the drainage system.
Caudal
Pertaining to the tail.
Caudal fin
The tail fin.
Caudal peduncle
The tapering portion of a fish's body between the posterior edge of the anal fin base and the base of the caudal fin.
Channelized
A portion of a river channel that has been enlarged or deepened, and often has armored banks.
Chinook salmon
An anadromous salmonid of the genus Oncorhynchus and species tshawytscha. Also known as king, spring, or blackmouth salmon.
Chum salmon
An anadromous salmonid of the genus Oncorhynchus and species keta. Also known as dog salmon.
Coastal juveniles
Juvenile salmonids inhabiting the waters of the continental shelf.
Coded-wire tag
A small (0.25mm diameter x 1 mm length) wire etched with a distinctive binary code and implanted in the snout of s salmon or steelhead, which, when retrieved, allows for the identification of the origin of the fish bearing the tag.
Coho salmon
An anadromous salmonid of the genus Oncorhynchus and species kisutch. Also known as silver or hooknose salmon.
Compensatory mortality
Mortality is compensatory when the mortality rate (i.e., proportion of population affected) decreases as the population size decreases. This is in contrast to depensatory mortality, were the rate increases as the size of the population decreases.
Conditional fishing mortality rate
The fraction of an initial stock which would be caught during the year (or season) if no other causes of mortality operated. (Also called fishing mortality rate).
Conditional natural mortality rate
The fraction of an initial stock that would die from causes other than fishing during a year (or season), if there were no fishing mortality. Also called; annual natural mortality rate, seasonal natural mortality rate.
Conspecific
Individuals of the same species.
Critical size
The average size of the fish in a year-class at the time when the instantaneous rate of natural mortality equals the instantaneous rate of growth in weight for the year-class as a whole. Also called optimum size.
Critical stock
A stock of fish experiencing production levels that are so low that permanent damage to the stock is likely or has already occurred.
Ctenoid
Having a comb-like margin.
Ctenoid scales
A type of fish scale that has spines or ctenii on the posterior or exposed portion, found on bass, walleye, and other fish.
Cubic feet per second
A measurement of stream flow.
Cultured stock
A stock that depends upon spawning, incubation, hatching, or rearing in a hatchery or other artificial production facility.
Cycloid scales
Smooth, flat, round scales that have concentric lines called circuli, found on trout, herring, and other fish.
Delta
An alluvial landform, typically triangular in shape, composed of sediment at a river mouth that is shaped by river discharge, sediment load, tidal energy, land subsidence, and sea-level changes.
Deme
Reproductive or breeding unit (spawning site) comprised of individuals who are likely to breed with each other (i.e. well mixed). A single population may include more than one deme and demes may be partially isolated from one another. Their partial isolation may or may not be persistent over generations. There will always be at least as many demes as populations.
Depensatory mortality
Mortality is depensatory when its rate (i.e., proportion of population affected) increases as the size of the population decreases. This is in contrast to compensatory mortality where the mortality rate decreases as the population size decreases.
Depressed stock
A stock of fish whose production is below expected levels based on available habitat and natural variations in survival levels, but above the level where permanent damage to the stock is likely.
Descaling
A condition in which a fish has lost a certain percentage of scales.
Designatable unit
Canadian Species at Risk Act (SARA)
Discards
Portion of a catch thrown back into the water.
Distal
Away from the point of attachment or origin.
Distinct population segment
U.S. Fish and Wildlife Service Term
Dorsal
Pertaining to the back, or situated near to or on the back.
Dorsal fin
The fin located on the back of fishes, and in front of the adipose fin, if it is present.
Dorsal fin ray
Refers to one of the cartilaginous rays (stiff rods) located in the membrane of a dorsal fin.
Drainage basin
A watershed is defined by the stream that drains it. It is the surface area that collects and discharges runoff through a given point on a stream.
Ecological interaction
The sum total of impacts of one species on another species, or on other members of the same species.
Effectiveness of fishing
A general term referring to the percentage removal of fish from a stock, but not as specifically defined as either rate of exploitation or instantaneous rate of fishing.
Egg take
The number of eggs taken at hatcheries when adult salmon and steelhead are spawned.
Egg-to-smolt survival
The numerical difference between the number of fertilized eggs produced by a groups of fish and the number of smolts resulting from those eggs.
El Niño
El Niño-Southern Oscillation (ENSO). A climate event that begins as a warming episode in the tropical Pacific zone that can result in large scale intrusions of anomalously warm marine water northward along the PNW coastline.
Electrophoresis
A process whereby charged molecules (such as DNA and enzymes) are separated in an electric field.
Emarginate
Having the margin notched. As in "The tail is only very slightly emarginate in adults, but is more forked in fish that have been at sea for not more than one year."
Embeddedness
The degree to which dirt is mixed in with spawning gravel.
Embryo
The early stages of development before an organism becomes self supporting.
Emergence
The process during which fry leave their gravel spawning nest and enter the water column.
Emigration
Referring to the movement of organisms out of an area. See immigration and migrating.
Endangered Species Act
A 1973 act of congress that mandated that endangered and threatened species of fish, wildlife, and plants be protected and restored.
Enhancement
The application of biological and technical knowledge and capabilities to increase the productivity of fish stocks. It may be achieved by altering habitat attributes (e.g., habitat restoration) or by using fish culture techniques (e.g., hatcheries, production spawning channels).
Equilibrium catch
The catch (in numbers) taken from a fish stock when it is in equilibrium with fishing of a given intensity, and (apart from the effects of environmental variation) its abundance is not changing from one year to the next.
Equilibrium yield
The yield in weight taken from a fish stock when it is in equilibrium with fishing 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.
Escapement
The quantity of sexually mature adult salmon (typically measured by number or biomass) that successfully pass through a fishery to reach the spawning grounds. This amount reflects losses resulting from harvest, and does not reflect natural mortality, typically partitioned between enroute and pre-spawning mortality. Thus, escaped fish do not necessarily spawn successfully.
Escapement goal
A predetermined biologically derived number of salmonids that are not harvested and will be the parent spawners for a wild or hatchery stock of fish.
Euryhaline
Having a wide tolerance to salinity.
Even-year run
A population of fish that returns to its natural spawning grounds in even numbered years.
Evolutionarily Significant Unit
NMFS definition of a distinct population segment that is smallest biological unit that will be considered to be a "species" under the Endangered Species Act. A population will be is considered to be an ESU if 1) it is substantially reproductively isolated from other conspecific population units, and 2) it represents an important component in the evolutionary legacy of the species.
Exploitation pattern
The distribution of fishing mortality over the age composition of the fish population, determined by the type of fishing gear, area and seasonal distribution of fishing, and the growth and migration of the fish. The pattern can be changed by modifications to fishing gear, for example, increasing mesh or hook size, or by changing the ratio of harvest by gears exploiting the fish (e.g., gill net, trawl, hook and line, etc.).
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 fish were caught during the year from a population of 1 million fish alive at the beginning of the year, the annual exploitation rate would be 0.72.
Extinct stock
A stock of fish that is no longer present in its original range, or as a distinct stock elsewhere. Individuals of the same species may be observed in very low numbers, consistent with straying from other stocks.
Extirpation
The elimination of a species from a particular area.
Eyed egg
A fish egg containing an embryo that has developed enough so the eyes are visible through the egg membrane.
Falcate
Hooked or curved like a sickle.
Fall-run fish
Anadromous fish that return to spawn in the fall.
Fecundity
The total number of eggs produced by a female fish.
Fin ray
A soft or hard cartilaginous rod in fins.
Fingerling
Juvenile salmonids up to nine months of age and generally two to four inches in total length (also called parr). This term is typically used to refer to hatchery juveniles.
Fishery
The process of attempting to catch fish, which then may be retained or released.
Fishing effort
Quantity of effort using a given fishing gear over a given period of time. E.g.: rod-hours or trawl duration.
Fishing intensity
Effective fishing effort. Fishing effort per unit area. Effectiveness of fishing.
Fishing mortality
Death caused by fishing. Mathematical symbol: F
Fishing power
The catch which a particular gear or vessel takes from a given density of fish during a certain time interval. For example, larger vessels (horsepower) have a greater ability to catch more fish, thus the greater their fishing power. Also, improvements in a vessel or gear, such as fish finders, Loran, etc., can increase fishing power.
Fishway
A device made up of a series of stepped pools, similar to a staircase, that enables adult fish to migrate up the river past dams.
Fitness
The relative ability of an individual (or population) to survive and reproduce in a given environment. The 'fit' of an organism to its environment.
Floodplain
The part of a river valley composed of unconsolidated river deposits that periodically floods. Sediment is deposited on the floodplain during floods and through the lateral migration of the river channel across the floodplain. The 100-year floodplain refers to that area of a river valley that is inundated during a large-magnitude flood occurring, on average, once every one hundred years.
Fluvial
Migrating between main rivers and tributaries. Of or pertaining to streams or rivers.
Fontanelle
Unossified gap between cranial bones.
Forage fish
Small fish which breed prolifically and serve as food for predatory fish.
Fork length
A fish length measurement from the tip of the nose to the fork of the tail fin.
Frenum
Referring to the membrane that binds the lip to the snout or lower jaw.
Fry
A stage of development in young salmon or trout. During this stage the fry is usually less than one year old, has absorbed its yolk sac, is rearing in the stream, and is between the alevin and parr stage of development.
Game fish
A fish that is regulated by law for recreational harvest.
Gape
To open the mouth wide. In Zoological terms, it means the measurement of the widest possible opening of a mouth.
Gear limits
Restrictions placed on sport or commercial fishing gear, which are used to control the take of fish.
Gene
A specific unit of genetic material (DNA) that encodes the information for a single genetic trait.
Gene Conservation Area
Oregon Department of Fish and Wildlife Term
Gene flow
The rate of entry of non-native genes into a population, measured as the proportion of the alleles at a locus in a generation that originated from outside of the population. Can be thought of as the genetically successful stray rate into a population. See also stray rate and homing rate.
Gene pool
The total variety and proportions of alleles within a population.
Genetic diversity
the heritable variation within and between populations of species. In this context, this encompasses all the taxonomic classifications below species that are a result of environmental heterogeneity and reproductive isolation.
Genetic drift
The random fluctuation of allele frequencies in a population resulting from the sampling of gametes to produce a finite number of individuals in the next generation.
Genetic risk
The probability of an action or inaction having a negative impact on the genetic character of a population or species.
Genetic stock identification
A method that can be used to characterize populations of organisms based on the genetic profiles of individuals. The GSI process consists of a series of steps: (1) collect selected tissues from a representative sample of individuals from the population(s) under investigation; (2) develop genetic profiles for the individuals in each population by conducting starch-gel electrophoresis and histo-chemical staining using tissue extracts; (3) characterize each population by aggregating the individual genetic profiles and computing allele frequency distributions; and (4) conduct statistical tests using the allele counts characterizing each population to identify significantly different populations.
Genome
The total genetic composition of an individual. The complete genetic information possessed by an organism.
Genotype
The particular combination of genes present in the cells of an individual.
Gill rakers
A series of projections located along the front edge of the gill arch.
Gillnet
Fishing gear: netting with weights on the bottom and floats at the top used to catch fish. Gillnets can be set at different depths and are anchored to the seabed.
Gills
The fleshy, and highly vascular organs comparable to lungs used in aquatic respiration.
Glide
A part of a river containing a smooth flow of water with an unbroken surface.
Gradient
The amount of vertical drop a stream experiences over a given distance.
Grilse
Salmon less than 22 inches (56cm) Fork Length (FL).
Groundfish
Species of fish living near the bottom such as cod, haddock, halibut and flatfish.
Growth overfishing
The rate of fishing, as indicated by an equilibrium yield-per-recruit curve, greater than which the losses in weight from total mortality exceed the gain in weight due to growth. This point is defined as Fmax.
Habitat
An area that supplies food, water, shelter, and space necessary for a particular animal's existence.
Handlining
Fishing using a line with usually one baited hook and moving it up and down in a series of short movements. Also called "jigging".
Harvest
Fish that are caught and retained in a fishery (consumptive harvest).
Harvest rate
The proportion of the available numbers of salmonids that is taken by fisheries in a specific time period.
Hatch box
A device used to incubate relatively small numbers of fish eggs. The hatch box is usually located adjacent to a stream, which supplies the box with water.
Hatchery fish
A fish that has spent some part of its life-cycle in an artificial environment and whose parents were spawned in an artificial environment.
Hatchery production
The spawning, incubation, hatching, or rearing of fish in a hatchery or other artificial production facility (e.g., spawning channels, egg incubation boxes, or pens).
Hatchery stock (population)
A stock that depends on spawning, incubation, hatching or rearing in a hatchery or other artificial propagation facility (synonymous with cultured stock).
Headwaters
The upper reaches of a stream or stream system.
Heterocercal
Said of the tail when the vertebrae curve upward into the upper lobe of the caudal fin.
Home range
The area that an animal traverses in the scope of normal activities. This is not to be confused with territory, which is the area an animal defends.
Homing
The ability of a salmon or steelhead to correctly identify and return to their natal stream, following maturation at sea.
Homing rate
Of all the fish from a population that successfully return to spawn, the homing rate is the proportion that return to spawn in the same population in which their parents spawned. See also stray rate and gene flow.
Husbandry
The scientific management and control of the hatchery environment for the production of fish or wildlife.
Hybridization
The interbreeding of fish from two or more different stocks or species.
Ichthyology
The scientific study of fishes.
Imbricated
Lying lapped over each other in regular order (like scales of a fish or shingles on a roof).
Immigration
Referring to the movement of organisms into an area. See emigration and migrating.
Imprinting
The physiological and behavioral process by which migratory fish assimilate environmental cues to aid their return to their stream of origin as adults.
Inbreeding
The mating of related individuals.
Incidental harvest
The capture and retention of species other than those a fishery is primarily opened to target/take. It can also refer to marked fish of the same species.
Incubation
The period of time from egg fertilization until hatching.
Independent tributary
A small stream flowing directly into marine waters.
Inferior mouth
The type of mouth that opens on the ventral surface (like sturgeon).
Instantaneous Rate Of Fishing Mortality
When fishing and natural mortality act concurrently, F is equal to the instantaneous total mortality rate, multiplied by the ratio of fishing deaths to all deaths. Also called rate of fishing, instantaneous rate of fishing, force of fishing mortality.
Instantaneous Rate Of Growth
The natural logarithm of the ratio of final weight to initial weight of a fish in a unit of time, usually a year. When applied collectively to all fish of a given age in a stock, the possibility of selective mortality must be considered.
Instantaneous Rate Of Mortality
The natural logarithm (with sign changed) of the survival rate. The ratio of number of deaths per unit of time to population abundance during that time, if all deceased fish were to be immediately replaced so that population does not change. Also called: coefficient of decrease.
Instantaneous Rate Of Natural Mortality
When natural and fishing mortality operate concurrently it is equal to the instantaneous total mortality rate, multiplied by the ratio of natural deaths to all deaths. Also called; force of natural mortality.
Instantaneous Rate Of Recruitment
Number of fish that grow to catchable size per short interval of time, divided by the number of catchable fish already present at that time. Usually given on a yearly basis; that is, the figure 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 fishes recruitment is not usually associated with stock size in the direct way in which mortality and growth are.
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 fishery, this increment replaces what is removed by fishing, and rate of surplus production is numerically equal to rate of fishing. Also called instantaneous rate of natural increase.
Interorbital
The space between the eyes.
Invertebrate drift
Stream and terrestrial invertebrates that float with the current.
Iteroparous
Species that reproduce repeatedly during their lifetime.
Jack salmon
A young male salmon that matures precociously (earlier than other fish in its age-class).
Jennie salmon
A young female salmon that matures precociously (earlier than other fish in its age-class).
Jugular pelvics
Pelvic fins in front of the pectoral fins.
Juvenile
Fish from one year of age until sexual maturity.
Kelt
Spent or spawned-out salmon up until the time it enters saltwater.
Kokanee
The freshwater form of the sockeye salmon. Kokanee spend their entire life history in freshwater, and in some lakes are known as silver trout.
Krill
Small abundant crustaceans that form an important part of the food chain in Antarctic waters.
Kype
The distinctive hooked jaw that male salmon develop during spawning.
Lacustrine
Referring to a lake environment.
Landings
Quantity of a species caught and landed.
Large woody debris
Logs, limbs, or root wads 4 inches or larger in diameter, delivered to river and stream channels from streamside forests (in the riparian or upslope areas) or from upstream areas. LWD provides streambed stability and habitat complexity. LWD recruitment refers to the process whereby streamside forests supply wood to the stream channel to replenish what is lost by decay or downstream transport.
Lateral line
A series of sensory pores opening to the exterior along the side of fish.
Length frequency
An arrangement of recorded lengths which indicates the number of times each length or length interval occurs.
Lentic
Characterizing aquatic communities found in standing water.
Life history
The events that make up the life cycle of an animal including migration, spawning, incubation, and rearing. There is typically a diversity of life history patterns both within and between populations. Life history can refer to one such pattern, or collectively refer to a stylized description of the 'typical' life history of a population.
Littoral zone
The region of land bordering a body of water.
Live box
A container filled with water and often equipped with accessories such as aeration equipment that is used to hold and transport live fish.
Local population
Reproductive unit (spawning site) comprised of individuals who are likely to breed with each other (i.e. well mixed). A single population may include more than one deme and demes may be partially isolated from one another. Their partial isolation may or may not be persistent over generations. There will always be at least as many demes as populations.
Locally adapted population
A population whose members have genetically based characteristics that increase their fitness in their local environment compared individuals that lack these characteristics.
Longlining
Using long lines with a series of baited hooks to catch fish.
Long-term potential catch
The largest annual harvest in weight that could be removed from a fish 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.
Lotic
Meaning or regarding things in running water.
Macroinvertebrate
Invertebrates visible to the naked eye, such as insect larvae and crayfish.
Maintainable yield
The largest catch that can be maintained from the population, at whatever level of stock size, over an indefinite period. It will be identical to the sustainable yield for populations below the level giving the MSY, and equal to the MSY for populations at or above this level.
Management unit
A stock or group of stocks which are aggregated for the purposes of achieving a desired spawning escapement objective.
Mandibular
Pertaining to the lower jaw.
Marine subadults
Post-juvenile salmonids moving into offshore waters.
Maxillae
The upper jaw, the upper jaw bones. (Maxillaries).
Mental
Pertaining to the chin or mentum.
Mesh size
Size of the mesh of a net. Different fisheries have different minimum mesh size regulation.
Metapopulation
A population of sub-populations which are in turn comprised of local populations or demes. Note that individual sub-populations can be extirpated and consequently recolonized from other sub-populations. Stability in a metapopulation is maintained by a balance between rates of sub-population extinction and colonization. This is roughly analagous to a “classical” or “Levins” metapopulation after Richard Levins’s (1969) mathematical model describing this scenario.
Migrant
Life stage of anadromous and resident fish species which moves from one locale, habitat or system (river or ocean) to another.
Migrating
Moving from one area of residence to another.
Migration
The seasonal movement of an animal from one area to another.
Milt
The sperm of fishes.
Mitigation
An action intended to reduce the adverse impact of a specific project or development.
Mixed stock
A stock whose individuals originated from commingled native and non-native parents; or a previously native stock that has undergone substantial genetic alteration.
Mixed-stock fisheries
Any fishery that catches fish from more than one stock.
Mortality
The number of fish lost or the rate of loss.
Myomeres
The muscle segments.
Natal
Birth place.
Natal stream
Stream of birth.
Native population
See Native stock.
Native species
A species of fish indigenous to a particular region.
Native stock
An indigenous stock of fish that has not been substantially impacted by genetic interactions with non-native stocks or by other factors, and is still present in all or part of its original range. In limited cases, a native population may also exist outside of its original range (e.g. in a captive broodstock program).
Natural fish
A fish that has spent essentially all of its life-cycle in the wild and whose parents spawned in the wild. Synonymous with wild fish and with natural origin recruit (NOR).
Natural mortality
Mortality due to natural causes. Mathematical symbol: M.
Natural origin recruit
See Natural fish.
Natural population
See Native stock.
Natural return rate
The number of native, naturally produced fish spawning in on generation divided by the total number of naturally spawning fish (hatchery plus naturally -produced fish) in the previous generation.
Natural spawners
See Natural fish.
Naturally spawning populations
Populations of fish that have completed their entire life cycle in the natural environment without human intervention.
Net Increase (or decrease)
New body substance elaborated in a stock, less the loss from all forms of mortality.
Net pen
A fish-rearing enclosure used in lakes and marine areas.
Nominal catch
The sum of the catches that are landed (expressed as live weight or equivalents). Nominal catches do not include unreported discards.
Non-native stock (population)
A stock (population) that has become established outside of its original range.
Non-target population
Any natural populations that is not intended to be integrated with a particular artificial propagation program.
Odd-year run
A population of fish that returns to its natural spawning grounds in odd numbered years, such as the pink salmon.
Off-channel area
Any relatively calm portion of a stream outside of the main flow.
Opercle
Refers to the largest bone in the operculum.
Operculum
The gill cover.
Optimum yield
The yield from a fishery which provides the greatest overall benefit to the nation with particular reference to food production and recreational opportunities; it is based on MSY as modified by economic, social or ecological factors. Precision and Accuracy Precision is the closeness to each other of repeated measurements of the same quantity or object, while accuracy is closeness of a measured or computed value to its true value.
Otolith
Structure of the inner ear of fish, made of calcium carbonate. Also called "ear bone" or "ear stone". Otoliths are used to determine the age of fish: annual rings can be observed and counted. Daily increments are visible as well on larval otoliths.
Outmigration
The migration of fish down the river system to the ocean.
Outplanting
Hatchery reared fish released into streams for rearing and maturing away from the hatchery sites.
Overfishing
Matching a species in such quantity that it reduces the stock biomass and future catches below desirable levels.
Pacific Decadal Oscillation
A pattern of climate and ocean condition regimes occurring in the north Pacific Ocean (associated with the Aleutian low pressure system) that results in shifts in sea surface temperatures and plankton abundance on a decades long time scale.
Palatines
Paired bones in the roof of the mouth, lateral to vomer; may bear teeth.
Papilla
A small fleshy projection.
Papillose
Covered with papilla.
Parameter
A "constant" or numerical description of some property of a population (which may be real or imaginary). Cf. statistic.
Parietals
Pared bones on posterior roof of skull, lateral to supraoccipital.
Parr
The developmental life stage of salmon and trout between alevin and smolt, when the young have developed parr marks and are actively feeding in fresh water.
Parr marks
Distinctive vertical bars on the sides of young salmonids.
Passive Integrated Transponder tags
Passive Integrated Transponder tags are used for identifying individual salmon for monitoring and research purposes. This miniaturized tag consists of an integrated microchip that is programmed to include specific fish information. The tag is inserted into the body cavity of the fish and decoded at selected monitoring sites.
Peak flows
Extremely high winter-time flows which can cause excessive streambed scour and damage or destroy salmon eggs incubating in the gravel. Peak flows can become more severe as a result of an increase in impervious surfaces and a reduction of hydrologic maturity, both of which increase the rate of water delivery to stream channels.
Pectoral fins
The anterior(front) paired fins, attached to pectoral (shoulder) girdle.
Pelagic
Of or in the open ocean or open water.
Pelvic fins
Posterior paired fins, located in the abdominal position or towards the rear.
Peritoneum
Membrane lining the body cavity.
Pharyngeal teeth
Teeth located behind the gills and before the esophagus, and anchored in bone.
Phenotype
The detectable outward manifestation of a psecific genetic trait or genotype.
Phytoplankton
Microscopic floating plants, mainly algae, that live suspended in bodies of water and that drift about because they cannot move by themselves or because they are too small or too weak to swim effectively against a current.
Pieces
Individual items, as in the expression "two dollars a piece." Individual fish.
Pink salmon
An anadromous salmonid of the genus Oncorhynchus and species gorbuscha. Also known as humpy or humpback salmon.
Placoid scale
Small plate-like scales that have a rough exterior edge found on sharks and related species.
Plankton
Minute floating forms of microscopic plants and animals in water which cannot get about to any extent under their own power. They form the important beginnings of food chains for larger animals.
Pond
A body of water smaller than a lake, often artificially formed.
Pool
A relatively deep, still section in a stream.
Population
Group of interbreeding salmon that is sufficiently isolated from other populations so that there will be persistent adaptations to the local habitat.
Population Viability Analysis
A statistical analysis that provides an estimate of the probability that a population will become extinct over a specific time frame.
Post-smolt
Life stage of salmon from the time it departs from the river as a smolt until the end of its first winter at sea.
Precautionary approach
Set of agreed cost-effective measures and actions, including future courses of action, which 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.
Precocious
Fish that have matured quickly, or faster than the remaining fish of its age-class.
Predation
Hunting and killing another animal for food.
Premaxilla
The paired bones forming the front of the upper jaw.
Preopercle
The large membrane bone lying in front of and parallel to the opercle.
Preorbital
The membrane bone lying in front of and below the eye.
Pre-spawning mortality
Generally refers to non-fishery mortality of adult salmon and steelhead between the time the fish enter the Columbia River and the completion of spawning.
Pre-terminal fishing (management) area
Marine waters where specific stocks (or groups of stocks) are mixed with fish returning to other regions.
Production
The total elaboration of new body tissue in a stock in a unit of time, irrespective of whether or not it survives to the end of that time. Also called net production, total production yield.
Productivity
A measure of a biological system's ability to supply organisms with energy and resources to feed, grow, and survive.
Pteryhoids
Bones of the roof of the mouth lying behind and articulating with the palatines.
Purse Seine
Fishing gear: large net used to encircle fish from a boat called a "seiner" and equipped with a wire rope on the bottom to draw the net together. A small boat, called "skiff," participates in maneuvering the net.
Pyloric
Pertaining to that part of the stomach from which the intestine leads.
Pyloric caecum
A projection in the form of a blind sac attached to the intestine near the posterior end of the stomach.
Quota
Portion of the total allowable catch that a unit such as vessel class, country, etc. is permitted to take from a stock in a given period of time.
Radio-telemetry
Automatic measurement and transmission of data from remote sources via radio to a receiving station for recording and analysis.
Ramus
A branch; a projecting part.
Rate of exploitation
The fraction, by number, of the fish 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. Also called; *fishing coefficient .
Rate of removal
An inexactly-defined term that can mean either rate of exploitation or rate of fishing--depending on the context .
Rate of utilization
Similar to rate of exploitation, except that only the fish landed are considered. The distinction between catch and landings is important when considerable quantities of fish are discarded at sea.
Ray
One of the supports of a fin.
Rear
To feed and grow in a natural or artificial environment.
Rearing
Refers to the amount of time that juvenile fish spend feeding in nursery areas of rivers, lakes, streams and estuaries before migration.
Re-colonization
The reestablishment of a salmonid stock in a habitat that the species previously occupied.
Recovery project
Artificial production projects primarily designed to aid in the recovery, conservation or reintroduction of particular natural population(s).
Recruitment
Addition of new fish to a defined life history stage by growth from among smaller size categories. Often used in context of management, where the stage is the point where individuals become vulnerable to fishing gear.
Redd
A nest of fish eggs consisting of gravel, typically formed by digging motion performed by an adult female salmon.
Relative abundance
An estimate of actual or absolute abundance; usually stated as some kind of index; for example, as bottom trawl survey stratified mean catch per tow.
Remote site incubator
A lightweight, dark colored plastic barrel incubator that employs plastic substrate (hatching medium), and can be sized to accommodate 5,000 to 125,000 eggs per incubator. They are used mainly for incubating chum salmon eggs.
Reproduce
To produce offspring.
Research survey
Survey at sea, on a research vessel, allowing scientists to obtain information on the abundance and distribution of various species and/or collect oceanographic data. Ex: bottom trawl survey, plankton survey, hydroacoustic survey, etc.
Riffle
A shallow gravel area of a stream that is characterized by increased velocities and gradients, and is the predominate stream area used by salmon for spawning.
Riparian
Referring to the transition area between aquatic and terrestrial ecosystems. The riparian zone includes the channel migration zone and the vegetation directly adjacent. to the water body, that influence channel habitat through alteration of microclimate or input of LWD.
River mile
A statute mile measured along the center line of a river. River mile measurements start at the stream mouth (RM 0.0).
Riverine
Referring to the entire river network, including tributaries, side channels, sloughs, intermittent streams, etc.
Riverine sockeye
Small populations of sockeye salmon that spawn and rear in some rivers systems that have no available lake for rearing.
Roe
The eggs of fishes.
Run
A group of fish of the same species that migrate together up a stream to spawn, usually associated with the seasons, e.g., fall, spring, summer, and winter runs. Members of a run [may] interbreed, and may be genetically distinguishable from other individuals of the same species.
Run reconstruction
A post season accounting of all salmon escaping and harvested from individual stocks or management areas.
Salmonid
Fish of the family Salmonidae, including salmon and steelhead.
Sample A
proportion or a segment of a fish stock which 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 confidence that the information obtained is a true reflection of the status of a stock (level of abundance in terms of numbers or weight, age composition, etc.)
Sampling design
The sampling design of a scientific survey refers to the statistical techniques and methods adopted for selecting a sample and obtaining estimates of the survey variables from the selected sample
Sand
Small substrate particles, generally referring to particles less than 2 mm in diameter. Sand is larger than silt and smaller than cobble or rubble.
Scute
An extendal bony plate, usually keeled.
Seasonal Total Mortality Rate
See Annual Total Mortality Rate.
Sediment
The organic material that is transported and deposited by wind and water.
Selective fishery
A fishery that allows the release of non-targeted fish stocks/runs, including unmarked fish of the same species.
Self-sustaining population
A population of salmonids that exists in sufficient numbers to replace itself through time without supplementation with hatchery fish. It does not necessarily produce surplus fish for harvest.
Semelparous
Species that reproduce only once during their lifetime.
Silt
Substrate particles smaller than sand and larger than clay.
Smolt
Refers to the salmonid or trout developmental life stage between parr and adult, when the juvenile is at least one year old and has adapted to the marine environment.
Smoltification
Refers to the physiological changes anadromous salmonids and trout undergo in freshwater while migrating toward saltwater that allow them to live in the ocean.
Sockeye salmon
An anadromous salmonid of the genus Oncorhynchus and species nerka. Also known as red or blueback salmon. (See Kokanee).
Spawn
The act of reproduction of fishes. The mixing of the sperm of a male fish and the eggs of a female fish.
Spawner
Sexually mature individual.
Spawning stock
Mature part of a stock responsible for the reproduction. Strictly speaking, the part of an overall stock having reached sexual maturity and able to spawn. Often conventionally defined as the number of biomass of all individuals beyond the "age at first maturity" of size at first maturity (i.e. beyond the age or size class in which 50% of the individuals are mature.
Spawning stock biomass
The total weight of all sexually mature fish in the population. This quantity depends on year class abundance, the exploitation pattern, the rate of growth, fishing and natural mortality rates, the onset of sexual maturity and environmental conditions.
Spawning stock biomass-per-recruit
The expected lifetime contribution to the spawning stock biomass for a recruit of a specific age (e.g., per age 2 individual). For a given exploitation pattern, rate of growth, and natural mortality, an expected equilibrium value of SSB/R can be calculated for each level of F. A useful reference point is the level of SSB/R that would be realized if there were no fishing. This is a maximum value for SSB/R, and can be compared to levels of SSB/R generated under different rates of fishing. For example, the maximum SSB/R for Georges Bank haddock is approximately 9 kg for a recruit at age 1.
Species
A taxon of the rank of species; in the hierarchy of biological classification the category below genus; the basic unit of biological classification; the lowest principal category of zoological classification.
Spine
A single, median supporting element of a fin, usually stiff. Distinguished from a ray in that it is single, median, never branched or jointed.
Standard length
The straight distance between the tip of the snout and the base of the caudal fin rays.
Standardization
The procedure of maintaining methods and equipment as constant as possible.
Status of exploitation
An appraisal of exploitation is given for each stock discussed in the Species Synopsis section using the terms unknown, protected, not exploited, underexploited, moderately exploited, fully exploited, and over-exploited. These terms describe the effect of current fishing effort on each stock, and is based on current data and the knowledge of the stocks over time.
Stock
[Individuals that share] a particular migration pattern, specific spawning grounds, and subject to a distinct fishery. A fish 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 which are old enough to reproduce. [This level of classification typically subsumes race, metapopulation, subpopulation, and demes. Used in the context of management.]
Stock A
Part of a fish population usually with a particular migration pattern, specific spawning grounds, and subject to a distinct fishery. A fish stock may be treated as a total or 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 which are old enough to reproduce. This level of classification typically subsumes race, metapopulation, subpopulation, and demes. Used in the context of management.
Stock assessment
The process of collecting and analyzing biological and statistical information to determine the changes in the abundance of fishery stocks in response to fishing, and, to the extent possible, to predict future trends of stock abundance. Stock assessments are based on resource surveys; knowldege 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 probably future condition of a fishery.
Stock origin
The genetic history of a stock.
Stray
An individual that breeds in a population other than that of its parents.
Stray rate
The proportion of a population that consists of strays.
Straying
A natural phenomena of adult spawners not returning to their natal stream, but entering and spawning in some other stream.
Subabdominal pelvic fin
Said of pelvic fins when placed forward on abdomen but not attached internally to pectoral girdle.
Subadult
A developmental life stage when fish exhibit most but not all traits of an adult fish.
Sub-Population
A well-defined set of interacting individuals that compose a proportion of a larger, interbreeding metapopulation.
Subspecies
A population of a species occupying a particular geographic area, or less commonly, a distinct habitat, capable of interbreeding with other populations of the same species.
Substrate
The material which comprises a stream bottom.
Subtidal zone
Shallow-water areas below mean low water.
Subyearling
A developmental life stage of fish that are less than one year old.
Success (of fishing)
Catch per unit of effort.
Supplementation
The use of artificial propagation to maintain or increase natural production while maintaining the long-term fitness of the target population, and keeping the ecological and genetic impacts to non-target populations within specified biological limits.
Supramaxilla
A small bone attached to the posterior end of the maxilla, dorsally.
Surplus production
Production of new weight by a fishable 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, equilibrium catch.
Survival rate
Number of fish alive after a specified time interval, divided by the initial number. Usually on a yearly basis.
Swim-up fry
A salmonid fry that is swimming in the water column in search for food.
Targeted fishery
A harvest strategy designed to catch a specific group of fish.
Terminal fisheries
A fishery in a river or near the mouth of a river where returning salmon pass through or congregate near to an prior to spawning, and where stocks are relatively unmixed. [occurring close to point where local populations separate]
Terminal fishing (management) area
Marine waters near the ultimate freshwater destination of specific salmonid stocks (or groups of stocks) where they have separated from fish returning to other regions.
Terminal mouth
Said of the location of the mouth when it opens at the end of the head, as in trout.
Territory
The area that an animal defends, usually during breeding season, against intruders of its own species.
Thoracic pelvics
Said of the pelvic fins when attached immediately below the pectorals and connected internally with the pectoral girdle.
Trawl
Fishing gear: cone-shaped net towed in the water by a boat called a "trawler". Bottom trawls are towed along the ocean floor to catch species such as groundfish. Mid-water trawls are towed within the water column.
Trend
The directional change over time in a series of data.
Tributary
A smaller stream which flows into a larger stream.
Tule
Fall chinook stock native to the Columbia River tributaries.
Undulating
To move in waves. Referring to the movement of a female fish's tail in a waving motion used to move gravel for the construction of a redd.
Unknown stock
A stock for which there is insufficient information to identify stock origin or stock status with confidence.
Upwelling
The movement of nutrient rich waters from the bottom of the ocean to the surface.
Usable stock
The number or weight of all fish in a stock that lie within the range of sizes customarily considered usable (or designated so by law). Also called standing crop.
Utilized stock (population)
The part, by number, of the fish alive at a given time, which will be caught in future.
Ventral fins
See pelvic fins.
Vermiculations
Irregular lines or impressions like worm tracks.
Viable population
A population that maintains its vigor and its potential for evolutionary change.
Viable salmonid population
NOAA Fisheries Term defined as "an independent population of any Pacific salmonid that has negligible risk of extinction due to threats from demographic variation (random or directional), local environmental variation, and genetic diversity changes (random or directional) over a 100-year time frame."
Virtual population
Utilized stock.
Virtual population analysis
An analysis of the catches from a given year class over its life in the fishery. If 10 fish from the 1968 year class were caught each year for 10 successive years from 1970 to 1979 (age 2 to age 11), then 100 fish would have been caught from the 1968 year class during its life in the fishery. Since 10 fish were caught during 1979, then 10 fish must have been alive at the beginning of that year. At the beginning of 1978, there must have been at least 20 fish alive because 10 were caught in 1978 and 10 more were caught in 1979. By working backward year by year, one can be virtually certain that at least 100 fish were alive at the beginning of 1970. A virtual population analysis goes a step further and calculates the number of fish that must have been alive if some fish also died from causes other than fishing.
Vomer
The most anterior bone of the roof of the mouth; may bear teeth.
Warmwater fish
A broad classification on non-salmonid fish that generally have at least one spiny ray, have pelvic and pectoral fins located behind the gills, and are usually suited for water that consistently exceeds 70 degrees F.
Weak stock
Listed in the Integrated System Plan's list of stocks of high or highest concern; listed in the American Fisheries Society report as at high or moderate risk of extinction; or stocks the National Marine Fisheries Service has listed. "Weak stock" is an evolving concept; the Council does not purport to establish a fixed definition. Nor does the Council imply that any particular change in management is required because of this definition.
Weight-at-age
Average weight of individuals in each age class of a particular stock.
Weir
Usually a barrier constructed to catch upstream migrating adult fish.
Wild population
Fish that have maintained successful natural reproduction with little or no supplementation from hatcheries.
Wild salmon
Salmon produced by natural spawning in fish habitat from parents that were spawned and reared in fish habitat.
Within-stock diversity
The overall genetic variability among individuals of a single population or stock.
Yearling
Yield
Another word for catch.
Yield-per-recruit
The expected lifetime yield-per-fish of a specific age (e.g., per age 2 individual). For a given exploitation pattern, rate of growth, and natural mortality, an expected equilibrium value of Y/R can be calculated for each level of F.
Yolk
The food part of an egg.
Zooplankton
Small aquatic animals that are suspended or swimming in water.