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Glossary of Terms

Photo by Luke Kelly

DID YOU KNOW?

  • A wild steelhead is a wild fish whose ancestors adapted over biological time to that river. This fish has no hatchery background, rather it the progeny of only wild fish.
  • Hatchery fish, on the other hand, may be from an out-of-basin source or may be from a wild brood stock hatchery.
  • When planted in another river, out-of-basin hatchery steelhead are genetically inferior to the wild fish as they are adapted to a different set of physical and biological properties.

Commonly-used steelhead words and phrases 

Photo by Luke Kelly

Photos on this page by Luke Kelly

Biological Opinion: A written statement, often in a special report, issued by NOAA on fisheries and other issues related to listed species under the Endangered Species Act.

Co-managers: Federal, state, county, local, and tribal agencies and governments that cooperatively manage salmonids in the Pacific Northwest.

Compensation: Traditional fish population models predict higher rates of growth and productivity at lower population levels due to reduced interspecific competition.

Critical stock: A stock of fish experiencing production levels that is so low that permanent damage to the stock is likely or has already occurred.

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.

Depensation: The opposite of compensation occurs when populations are at low levels and growth and productivity is reduced due to competition with the other species, predation, low productive success, impaired aggregation, conditioning of the environment, efficiency of food locations and impaired aggregation. Depensation can lead to extinction of a species under any of the above actions.

Distribution: The spatial arrangement of a species or a meta population within its range. At the stock level this means, for the riverine environment, the tributaries, and mainstream areas traditionally utilized for reproduction and rearing of young fish.

Diversity: The amount of different traits expressed by a species, the amount of genetic variation within a stock of fish, and the variety within ecosystems such as species. In this paper we speak to life history diversity, genetic diversity, and biodiversity as important mechanisms that provide resilience to the survival and productivity of salmonids.

Endangered species: Any species of plant or animal defined through the Endangered Species Act as being in danger of extinction, throughout all or a significant portion of its range and published in the Federal Register.

Escapement: The portion of a fish population that survives natural and fishing mortality to reach its natural spawning grounds.

Escapement goal: The number of fish, as defined as a parameter of a fish reproduction model (MSH model), that is necessary to return and spawn to maintain maximum sustainable yield.

Equilibrium point: The upper level of recruitment that, above that level, will not produce more recruits in the next generation.

Evolutionary Significant Unit (ESU): A distinct population or metapoplation of Pacific salmon or steelhead, and hence a species under the Endangered Species Act.

Functional depletion: A species or stock that has been reduced to a low abundance and low level of productivity. This stock will naturally become extinct in time or be subject to extinction through depensatory mortality.

Mixed Stock Fishery: A harvest management technique where different species, strains, or races of stocks, or wild and hatchery fish, are harvested together. Caution must be exercised to properly manage the smaller or weaker stock to prevent depletion and possible extinction.

Maximum Sustainable Harvest (MSH): The largest average catch that can continuously be taken from a stock during existing environmental conditions. For species with a fluctuating environment and recruitment, the maximum will vary and may be obtained by taking fewer fish in some years than others. Also called Maximum Sustainable Yield (MSY).

Natural Equilibrium: A maximum population abundance that will not increase (in the next generation). Such a stock and its production of eggs, fry, and juveniles is generally considered to be at its carrying capacity.

Rainbow Trout: The resident form of O. mykiss that may live in any part of a river or its tributaries. It may disperse locally and may spawn with the anadromous form of O. mykiss, but is generally considered non-migratory.

Recruits: The total number of fish of a specific stock and year class (s) available at a particular stage of their life history, generally as adults. An example would be the number of adults that become available to a fishery at a specific time and area.

Smolt: The salmon or steelhead development state between parr and adult when the juvenile is adapting to the salt content of the marine environment.

Steelhead: The anadromous form of O. mykiss. This form spends its early life history (generally 1 to 3 years) in freshwater, then migrates to sea where it will spend several years (generally 2 or 3) before returning to its natal river to spawn.

Threatened: The whole population, or a metapopulation of fish defined as an ESU, in danger of becoming endangered.

Wild Fish Release (WFR) and Wild Steelhead Release (WSR): In the context of salmon and steelhead, WFR and WSR are intended to indicate the release of wild fish/steelhead for conservation purposes. This definition would contrast with Catch and Release Fisheries (CnR) that are designed to save fish for improved fishing opportunity.

Wild Steelhead vs Native Steelhead: A wild steelhead is a wild fish whose ancestors adapted over biological time to that river. This fish has no hatchery background, rather it the progeny of only wild fish. Hatchery fish, on the other hand, may be from an out-of-basin source or may be from a wild brood stock hatchery. Neither of these two examples should be classified as a wild fish as they are genetically and reproductively inferior.

The out-of-basin hatchery steelhead (the two common types are Chambers Creek and Skamania River) adapted to another river through biological time. When planted in another river, they are genetically inferior to the wild fish as they are adapted to a different set of physical and biological properties. Because they have also been artificially spawned for many generations they have also lost genetic diversity. These hatchery fish have lost most of their reproductive fitness and studies have shown they produce only 2% to about 30% as compared to wild fish.

Wild brood stock hatchery fish also quickly loose reproductive fitness. Recent studies in Oregon show they may lose 35% in their first hatchery generation and 70% in the second. This is due to fast genetic (river diversity is one trait lost) divergence from the wild stocks.