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Contribution of three life history types to smolt production in a Chinook salmon (Oncorhynchus tshawytscha) population

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The most productive juvenile life history in the Pahsimeroi River Chinook salmon (Oncorhynchus tshawytscha; Idaho, USA) population (in terms of smolt production) is being eliminated. Length at emigration and survival from spawning areas to Lower Granite Dam within each of three juvenile phenotypes (age-0 smolts, fall parr, age-1 smolts) were influenced by initial cohort abundance. The proportion of age-1 emigrants reaching Lower Granite Dam was dome-shaped with respect to initial cohort abundance. As initial abundance increased, higher proportions of juveniles adopted the age-1 smolt phenotype or emigrated as fall parr. The age-0 smolt phenotype had the highest relative survival, and the fall parr phenotype, the lowest. The contributions of each emigrant type to cohort smolt production varied with circumstances; hence, the full expression of phenotypic diversity is important to the study population. However, there were no records of tagged age-0 smolts surviving to return from the Pacific Ocean. Given the potential productivity of this life history, management and recovery efforts should be directed at the age-0 smolt phenotype.

Le cycle biologique juvénile le plus productif (en ce qui a trait à la production de saumoneaux) de la population de saumons chinook (Oncorhynchus tshawytscha) de la rivière Pahsimeroi, Idaho, É.-U., est en train d’être éliminé. La longueur à l’émigration et la survie depuis les sites de fraie jusqu’au barrage Lower Granite chez chacun des trois phénotypes juvéniles (saumoneaux d’âge 0, tacons d’automne et saumoneaux d’âge 1) sont influencées par l’abondance initiale de la cohorte. La proportion d’émigrants d’âge 1 qui atteint le barrage Lower Granite se répartit en dôme par rapport à l’abondance initiale de la cohorte. À mesure que l’abondance initiale augmente, des proportions plus élevées de jeunes adoptent le phénotype de saumoneau d’âge 1 ou émigrent comme tacons d’automne. Le phénotype d’âge 0 possède la survie relative la plus élevée et le phénotype de tacon d’automne la plus basse. Les contributions de chaque type d’émigrant à la production de saumoneaux de la cohorte varient selon les circonstances; l’expression de l’entière diversité phénotypique est donc importante dans l’étude de la population. Cependant, il n’existe aucune information concernant des saumoneaux d’âge 0 marqués ayant survécu jusqu’à leur retour du Pacifique. Étant donné la productivité potentielle de ce type de cycle biologique, on devrait concentrer des efforts de gestion et de conservation sur le phénotype de saumoneau d’âge 0.

Document Type: Research Article

Publication date: October 1, 2009

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  • Published continuously since 1901 (under various titles), this monthly journal is the primary publishing vehicle for the multidisciplinary field of aquatic sciences. It publishes perspectives (syntheses, critiques, and re-evaluations), discussions (comments and replies), articles, and rapid communications, relating to current research on cells, organisms, populations, ecosystems, or processes that affect aquatic systems. The journal seeks to amplify, modify, question, or redirect accumulated knowledge in the field of fisheries and aquatic science. Occasional supplements are dedicated to single topics or to proceedings of international symposia.
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