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Essay On Chinook Salmon

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DISCUSSION
Strength and limitations of the method
Ten juveniles were caged in different locations across three years and their length and weight recorded every week. The premise of this approach was that the muscle 13C would provide information about the source of carbon fueling the juvenile Chinook salmon muscle growth if they remained in each site long enough to reflect local food sources rather than hatchery fish feed products. As Chinook salmon are anadromous fish, the carbon isotope ratios of juvenile muscle tissues are influenced by maternal sources enriched in marine-based isotopes ratios relative to most freshwater energy sources (Doucett et al. 1999). Differences in salmonid allochthony among locations and years may have resulted from differences in age of the fish used in the experiment. These differences in
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Using this approach, we estimated percent contribution of terrestrial organic carbon sources in juvenile Chinook salmon and interpreted the dynamics of its use spatially and temporally in the Merced River. Our research indicated that the contribution of the terrestrial vegetation to juvenile Chinook salmon growth was highly variable across locations and years. In the river-marsh-estuary San Francisco complex, Cloern et al. (2002) concluded that carbon stable isotopes could not be used as biomarkers for tracing the origins of organic matter, due to high variability in isotope ratios within-plant groups and high dissimilarity between isotopic signatures of primary producers and their organic-matter pools in the seston and sediments. Research in aquatic ecosystems using stable isotopes has shown that there can be significant between and even within-year variation in the isotopic signatures of primary production sources (Post
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