Glossary
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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.