Ageing and backcalculated length at age are based on counts andmeasurements ofannual rings on scales or otoliths (a calcareous "earstone" found inthe internal ear of fishes). The typically anadromous life history of steelhead and their abilityto undergo multiplespawning migrations complicate the matter of reporting the age offish of this species. Numerous authors have developed notation styles for this purpose. Original citations shouldbe consulted for in-depth descriptions (e.g., Shapovalov and Taft1954). Freshwater age isgenerally separated from saltwater age by either a slash (/) orperiod (.); for example, a fishwhich smolted after 2 years in fresh water and was caught after 3years in the ocean could berepresented 2/3 or 2.3.
Cole Rivers Hatchery
An Oregon Department of Fish and Wildlife fish hatchery on theupper Rogue River,northeast of Medford, constructed by the U.S. Army Corps of Engineersin connection withLost Creek Dam. Hatchery operations began in 1979. This hatcherywas named for ColeRivers, a long-time fish biologist for the State of Oregon, whospent much of his career on theRogue River and is cited several times in this document.
The U.S. Endangered Species Act.
Evolutionarily Significant Unit; a "distinct" population ofPacific salmon, and hence aspecies, under the Endangered Species Act.
Electrophoresis refers to the movement of charged particles inan electric field. It hasproven to be a very useful analytical tool for biochemical charactersbecause molecules can beseparated on the basis of differences in size or net charge. Proteinelectrophoresis, whichmeasures differences in the amino acid composition of proteins fromdifferent individuals, hasbeen used for over two decades to study natural populations,including all species ofanadromous Pacific salmonids. Because the amino acid sequence ofproteins is coded for byDNA, data provided by protein electrophoresis provide insight intolevels of genetic variabilitywithin populations and the extent of genetic differentiation betweenthem. Utter et al. (1987)provide a review of the technique using examples from Pacific salmon,and the laboratorymanual of Aebersold et al. (1987) provides detailed descriptions ofanalytical procedures. Genetic techniques that focus directly on variation in DNA alsoroutinely use electrophoresis toseparate fragments formed by cutting DNA with special enzymes(restriction endonucleases).
Other genetic terms used in this document include allele(an alternate form of a gene);allozymes (alternate forms of an enzyme produced by differentalleles and often detected byprotein electrophoresis); chromosome (a thread-like structurecontaining many genes);dendrogram (a branching diagram, sometimes resembling a tree,that provides one way ofvisualizing similarities between different groups or samples);gene (the basic unit of hereditypassed from parent to offspring); gene locus (pl. loci;the site on a chromosome where a geneis found); genetic distance (a quantitative measure of geneticdifferences between a pair ofsamples); introgression (introduction of genes from onepopulation or species into another);and karyotype (the number, size, and morphology of thechromosome complement).
A life history trait of steelhead exhibited in the Rogue,Klamath, Mad, and Eel Riversof southern Oregon and northern California. Followingsmoltification, half-pounders spendonly 2-4 months in the ocean, then return to fresh water. Theyoverwinter in fresh water andemigrate to salt water again the following spring. This is oftentermed a false spawningmigration, as few half-pounders are sexually mature.
Salmon hatcheries use artificial procedures to spawn adults andraise the resultingprogeny in fresh water for release into the natural environment,either directly from thehatchery or by transfer into another area. In some cases, fertilizedeggs are outplanted(usually in "hatch-boxes"), but it is more common to releasefry (young juveniles) or smolts(juveniles that are physiologically prepared to undergo the migrationinto salt water).
The broodstock of some hatcheries is based on the adults thatreturn to the hatcheryeach year; others rely on fish or eggs from other hatcheries, orcapture adults in the wild eachyear.
The phenotype is the appearance of an organism resulting fromthe interaction of thegenotype and the environment.
A card (alternatively called a tag or stamp) used by steelheadand salmon anglers torecord catch information; it is returned to management agency afterthe fishing season.
Most salmonids deposit their eggs in nests called redds,which are dug in thestreambed substrate by the female. Most redds occur in predictableareas and are easilyidentified by an experienced observer by their shape, size, and color(lighter than surroundingareas because silt has been cleaned away).
Spawning surveys utilize counts of redds and fishcarcasses to estimate spawnerescapement and identify habitat being used by spawning fish. Annualsurveys can be used tocompare the relative magnitude of spawning activity between years.
River Kilometer (RKm)
Distance, in kilometers, from the mouth of the indicated river. Usually used to identifythe location of a physical feature, such as a confluence, dam, orwaterfall.
The anadromous form of the species Oncorhynchusmykiss. Anadromous fish spendtheir early life history in fresh water, then migrate to salt water,where they may spend up toseveral years before returning to fresh water to spawn. Rainbowtrout is the nonanadromousform of Oncorhynchus mykiss.