Analysis of Tidal Stage Impact on Harbor Seal Haul-Out Behavior in the Snohomish River Estuary of the Salish Sea
Harbor seals fill a critical role in the balance of the Salish Sea. They occupy the middle of the food chain where Bigg’s Killer Whales use them as a source of food, and they also compete with Resident Killer Whales for salmon. Prey availability is known to be a strong indicator of seal presence, ho...
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| Format: | Text |
| Language: | English |
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Western CEDAR
2022
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| Online Access: | https://cedar.wwu.edu/ssec/2022ssec/allsessions/172 https://cedar.wwu.edu/context/ssec/article/3334/viewcontent/192_9017ec8737344880837b3988bfd17f6e.pdf |
| Summary: | Harbor seals fill a critical role in the balance of the Salish Sea. They occupy the middle of the food chain where Bigg’s Killer Whales use them as a source of food, and they also compete with Resident Killer Whales for salmon. Prey availability is known to be a strong indicator of seal presence, however, there are many more subtle environmental influences on harbor seal presence as well. This study hones in on the harbor seals of the Snohomish River Estuary and how their haul-out habits might be influenced by the unique water circulation of the area. This study analyzed data compiled by the Ocean Research College Academy at multiple log boom haul-out sites in the Snohomish River from 2015-2021. Seal counts from the Jetty Island Boat launch were included as well. Twice a week, the number of harbor seals in the water and hauled out around the boat launch by the Jetty Island ferry were counted. Weather, boat activity, air temperature, and tide height were also recorded. These data were analyzed through the lens of the tide and its movement of water by the Snohomish River estuary and tide data is from the National Oceanic and Atmospheric Administration (NOAA). It was expected that there will be an increase in seals hauled-out at flood tide as well as the very beginning of the ebbing tide due to the colder temperatures experienced during high tide. It was also expected that there will be a greater number of seals hauled-out on log booms rather than the boat launch due to space availability and a lack of human disruption. This study seeks to better understand the presence and behavior of harbor seals at the mouth of the Snohomish River. |
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