Salmon Life History in an Altered Landscape: Reconstructing Juvenile Migration Using Chemical and Structural Analysis


Samuel L. Bourret. (2013). Salmon Life History in an Altered Landscape: Reconstructing Juvenile Migration Using Chemical and Structural Analysis. Theses and Dissertations Collection, University of Idaho Library Digital Collections.

Salmon Life History in an Altered Landscape: Reconstructing Juvenile Migration Using Chemical and Structural Analysis
Samuel L. Bourret
Chinook salmon
Fish and Wildlife Sciences
The understanding of movement is critical for the conservation of culturally and economically important migratory species. Migration, the act of moving periodically from one region to another, is taxonomically widespread throughout the animal kingdom (Webster et al. 2002) such that animals may exhibit migratory behavior owing to resource availability and/or reproductive opportunities. The “decision” to migrate can be viewed as a tradeoff between the survival and energetic costs of movement and the benefits gained in a new habitat (Lack 1954). These benefits include release from density dependent competition, increased growth potential in more productive habitats, and decreased risk of predation (Anholt 1995, Gross 1987). Chinook salmon is one of several species that exhibit migratory behavior, whereby individuals are born in freshwater streams and rivers, move to the ocean to mature, and return to freshwater to spawn and die (i.e., anadromy). Unfortunately, several migrant populations have been severely impacted by human activities (Berger 2004). For example, the construction of hydroelectric impoundments in the Pacific Northwest, US, has blocked access to spawning and rearing habitat of Chinook salmon (NRC 1996) and thus resulted in decreased viability of these migrant populations. Variability in migration timing within and among populations can have fitness implications (Drent et al. 2003). An individual change in fitness can lead to a deviation in a particular life history strategy and contribute to the expression of an array of life histories, especially since environmental conditions are constantly changing (Stearns 1976). Life histories evolve in response to variation in fitness and underlying genetic differences among individuals, which drives natural selection. Chinook salmon exhibit high variability in migration timing within and among populations across their range. Knowledge of animal movement has been constrained due to difficulties in tracking individuals over long distances for entire life cycles (Rubenstein and Hobson 2004). This lack of empirical data is an impediment to a greater understanding of dispersal and migration processes (Colbert et al. 2001, Webster et al. 2002). Recent technological advances in the use of natural tracers such as otolith microchemistry are now making it easier to determine the movement behavior of individuals (Webster et al. 2002). Otolith microchemistry represents a technique for studying early Chinook salmon movement and habitat use that would be difficult to asses using traditional marking and tagging technologies (Kalish 1990, Thorrold et al. 1997, Campana 1999, Kennedy et al. 2000, Kennedy et al. 2002, Wells et al 2003). Otoliths are mineral structures located within the semicircular canals of the fish’s inner ear, in which increments of calcium carbonate, as aragonite, are accreted daily as thin concentric rings (Kennedy et al. 2000, Kennedy et al. 2002). This daily deposition of calcified material reflects the distinct geochemical signature of the aqueous environment, and because otoliths are inert, this signature remains stable after deposition (Neilson and Geen 1982, Campana and Neilson 1985). The geochemical signature of the water is influenced by variation in the age and composition of the underlying bedrock geology. Using geochemical isotopic and elemental signatures from Chinook salmon otoliths I investigated the migratory patterns within the Willamette Basin. Specifically, my objectives were to quantify the representation of juvenile freshwater life history strategies in the Upper Willamette spring Chinook salmon population, and to develop a methodological test between scale and otolith juvenile life history interpretations, which was used to test the accuracy of scale assignment. I also reconstructed the juvenile rearing and migratory patterns of a sample of natural origin adult Chinook salmon that returned to the Middle Fork Willamette Basin.
Thesis (M.S., Fish and Wildlife Sciences)--University of Idaho, April 2013
Major Professor:
Brian P. Kennedy, Christopher C. Caudill

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