By John R. Moring, Ronald L. Youker, Robert M. Hooton
Fisheries Research, Volume 4, Issues 3-4, December 1986, Pages 343-354, ISSN 0165-7836, DOI: 10.1016/0165-7836(86)90013-5.

The movements of distinctive potamodromous populations of cutthroat trout (Salmo clarki clarki) were studied in the Willamette River watershed, Oregon, U.S.A., from 1976 to 1979. This sub-species is often anadromous in coastal streams, but the upstream passage of trout was historically blocked at the lower end of the Willamette Valley. Although there are now passage facilities, coastal cutthroat trout remain either potamodromous or non-migratory. Almost 3600 cutthroat trout were collected, 2855 scale samples were taken, and 2087 fish were tagged and released. Movements were inferred from recoveries of tagged fish and estimates of ages derived from readings of scales. Downstream movements were indicated by a shift in year-class appearance from small to large streams. These downstream movements may commence a year earlier in the life-cycle compared to anadromous stocks of Oregon coastal streams. Most tag recaptures came from areas near release locations; 15% of the tags were recaptured. Instances of extensive movement were recorded in the large rivers of the watershed, apparently as a consequence of spawning movements. Large rivers of the Willamette watershed tend to reflect the mixture of several life-history patterns evident among trout of the drainage.

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