Graduate Thesis Or Dissertation
 

Effects of Dissolved Oxygen, Temperature, and Dietary Carbon Sources on the Condition of Juvenile English Sole (Parophrys vetulus) from the Oregon Coast

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/dj52w7317

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  • Observations of the Oregon coast’s physical oceanography over the last few decades have revealed falling dissolved oxygen levels associated with seasonal upwelling, as well as rising water temperatures. In extreme cases, these changes have been associated with die-offs, redistribution, and decreased abundance and diversity of benthic fish and invertebrates. Many of these benthic species, including the flatfish English sole (Parophrys vetulus), are commercially harvested as adults and serve as prey for upper trophic levels. English sole utilize nearshore coastal regions and various regions within estuaries as nursery habitat during their juvenile life stage. These habitats differ with respect to temperature, dissolved oxygen, and dietary carbon sources, highlighting the complexity of nursery function and the need to assess relative quality of habitats for juvenile English sole. To this aim, I combined laboratory and field approaches to examine the effects of dissolved oxygen, temperature, and dietary carbon sources on the condition of juvenile English sole. A laboratory-controlled experiment revealed negative impacts of higher temperature and potential for an interactive effect of hypoxia and warm temperatures. However, like their adult conspecifics, juvenile English sole appear tolerant of low-oxygen environments relative to other flatfish species. Additionally, juveniles prioritized growth over lipid storage regardless of dissolved oxygen or temperature levels. Following the laboratory experiment, I compared the condition of wild-caught juvenile English sole collected from upriver and downriver habitats of the Yaquina Bay estuary. The main focus was to investigate the effects of oxygen, temperature, and dietary carbon on the energetic condition of these juveniles. I found that fish from the upriver habitat exhibited lower lipid condition, which may be attributed to warmer temperatures and weaker association with high-quality marine-sourced carbon than fish downriver. Downriver-caught fish were enriched in marine-associated biomarkers that were positively related to fish energetic condition. Though the downriver habitat appeared to provide superior nursery habitat for juveniles during the summer of 2014, this habitat’s strong coastal influence may introduce severely hypoxic waters in future upwelling seasons, highlighting the importance of preserving both habitats for optimal nursery function.
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