Graduate Thesis Or Dissertation
 

Modeling the habitat occupancy and abundance of salmonid ectoparasite Salmincola californiensis in Willamette Valley reservoirs

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/kk91ft73j

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  • The freshwater copepod Salmincola californiensis is an ectoparasite of Pacific salmonids (Oncorhynchus spp.) Threatened and endangered salmonids that rear in the reservoirs have been reported to experience higher rates of infection by S. californiensis than would be experienced by their stream-reared counterparts. These high levels of infection can lead to decreased fish fitness and survival that might ultimately hinder salmon recovery efforts. To date, the relationship between reservoir environmental conditions and infection rates is poorly understood. This research aimed to evaluate sampling methods designed to catch the infectious lifestage of the copepods and to develop predictive models of the distribution and abundance of S. californiensis in relation to pertinent environmental factors (e.g., temperature, water clarity, reservoir plankton profiles, and season) in three Willamette Project reservoirs. During five months in 2020, we used light traps to collect nearly 700 zooplankton samples from various sites and depths in Cougar, Lookout Point, and Fall Creek reservoirs, Oregon, USA. These samples were searched for S. californiensis, and this information was paired with concurrently measured environmental data to create occupancy and abundance models. Our models showed a strong influence by water temperature on copepodid habitat occupancy and abundance of the free-swimming stage of S. califoniensis, with maximum occupancy and abundance occurring at 15.2 °C. Mean site occupancy probability in August was 0.75 for all reservoirs and mean August abundance was 92.5 copepodids per site in Cougar reservoir, 62.1 copepodids per site in Fall Creek, and 1.9 copepodids per site in Lookout Point. The efficacy of our sampling method was influenced by ambient light at depth, water temperature, and number of juvenile sculpin (Cottus spp.) nearby. Trap efficacy ranged from 34% when ambient light was low to 89% when ambient light was high. Information gained from this work will be useful for guiding management decisions made by biologists and dam operators regarding salmonid populations in the region.
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  • This work was funded in part by the United States Army Corps of Engineers.
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  • Pending Publication
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  • 2023-01-08 to 2023-08-09

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