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    Feeding ecology of juvenile sockeye salmon in Afognak Lake, Alaska

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    Author
    Richardson, Natura
    Chair
    Beaudreau, Anne
    Committee
    Wipfli, Mark
    Finkle, Heather
    Metadata
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    URI
    http://hdl.handle.net/11122/6641
    Abstract
    Much attention has been given to juvenile Sockeye Salmon (Oncorhynchus nerka) ecology with particular focus on pelagic food webs in deep nursery lakes. In contrast, this study took place at Afognak Lake, Alaska, to better understand juvenile Sockeye Salmon foraging ecology, potential consumer interactions, and metabolic opportunities and constraints in a shallow nursery lake. I collected fish every two weeks from Afognak Lake from May through August, 2013. I described ontogenetic and temporal variation in the diets of juvenile Sockeye Salmon and a potential competitor, adult Threespine Stickleback (Gasterosteus aculeatus). Notably, this study revealed that adult aquatic insects are an important prey item for lake rearing juveniles. Threespine Stickleback diets showed some overlap with diets of juvenile Sockeye Salmon; however, significant differences in diet composition suggest that Sockeye Salmon and Threespine Stickleback partition prey and habitat resources. I then used my field-derived temperature, demographic, and diet data as inputs to a bioenergetics model to estimate summer consumption rate and growth efficiency of juvenile Sockeye Salmon from Afognak Lake across a range of foraging scenarios. Consumption rate was greater and mean growth efficiency was lower for all littoral-use scenarios relative to pelagic-use scenarios. Further, daily consumption was lowest and mean growth efficiency was highest for model scenarios in which insects were a dominant component of the diet relative to scenarios in which zooplankton were the dominant prey. My findings highlight the importance of benthic-pelagic coupling in Sockeye Salmon nursery lakes and the potential for juveniles to navigate trade-offs between energy acquisition and thermal conditions across lake habitats.
    Description
    Thesis (M.S.) University of Alaska Fairbanks, 2016
    Table of Contents
    General Introduction -- Chapter 1: Feeding ecology of juvenile Sockeye Salmon and a potential competitor, Threespine Stickleback, in a shallow Alaskan lake -- Chapter 2: Bioenergetic tradeoffs among foraging environments for lake rearing juvenile sockeye salmon -- General Conclusions -- Benthic and pelagic production pathways in Afognak Lake -- Potential for competition between Threespine Stickleback and Sockeye Salmon -- Heterogeneity in lake foraging habitat for Sockeye Salmon.
    Date
    2016-05
    Type
    Thesis
    Collections
    Fisheries

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