Honors College Thesis
 

Fish assemblages and sizes against distance from ocean and other factors in Yaquina Bay estuarine seagrass beds

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https://ir.library.oregonstate.edu/concern/honors_college_theses/5h73q534t

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  • Estuaries are highly valuable ecosystems due to their role as nursery habitats for commercially and recreationally important species. Yet, several anthropogenic stressors such as dredging, development, shipping traffic, and a changing climate imperil estuarine habitats, particularly seagrass beds, which provide foraging grounds and refuge for many marine species. The Yaquina Estuary in Newport, Oregon has faced these anthropogenic stressors and has experienced significant decadal shifts in the communities that utilize seagrass habitat. To understand the current status of seagrass fish communities in the Yaquina Estuary, from June to August 2024, we sampled fishes and crustaceans using box minnow traps placed in five seagrass habitats within the estuary. We identified each individual to determine species composition, measured the body length of each individual, and collected salinity, temperature, and distance from ocean data to see if those environmental variables explained species data. We then determined which species were most abundant across the sampling period and examined their body sizes against the chosen environmental variables. The fish species of highest abundance were juvenile English Sole (Parophrys vetulus), Saddleback Gunnel (Pholis ornata), juvenile Pacific Staghorn sculpin (Leptocottus armatus), and various juvenile rockfishes (Sebastes spp.). We found no relationship between fish community assemblages or proportions and any of the tested factors, while expectations believed that salinity, temperature, or distance from the ocean would have some influence. For results on the relationship between body sizes and environmental factors, juvenile Dungeness Crab and juvenile rockfishes were larger at higher salinities while juvenile English Sole and Saddleback Gunnel were larger at lower salinities, mostly matching the results of previous studies. Juvenile English Sole and juvenile Dungeness Crab were larger further from the ocean while juvenile Pacific Staghorn Sculpin were larger closer to the ocean, which does not match the results of most prior studies. Saddleback Gunnel and juvenile Pacific Staghorn Sculpin were larger at colder temperatures, which does not match the results of most prior studies. This study provides baseline information on the influence of several abiotic factors on the community assemblages and body size of estuarine species in Yaquina Bay. Further research is needed to better understand community assemblages and fish size and growth trends within non-seagrass estuarine habitats to best document how Yaquina Bay has responded to disturbances in recent years and inform future conservation actions.
  • Keywords: estuary, body size, Yaquina Estuary, distance from ocean, community assemblage, salinity, temperature
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