LeMoine, M., 2021. Salmon Habitat Vulnerability Assessment for the Skagit River Estuary Thermal Landscape . Skagit River System Cooperative, La Conner, WA. pp. 22.

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Ecological responses to climate change have been observed across many aquatic ecosystems, yet in
estuaries much of the focus has been on physical responses such as sea level rise, sediment movement
and circulation of fresh and marine waters. Numerous fishes use the highly productive estuaries as
nurseries for their juveniles. Currently, few studies have evaluated vulnerability of fish species that
inhabit estuarine systems to future climate. The Skagit River estuary in Washington State is important
for juvenile Chinook salmon rearing and restoration of estuary habitats are critical to the recovery of
Skagit River Chinook. I evaluated the influence of climate drivers (e.g., air temperatures, river discharge,
pacific decadal oscillations) and local sites conditions (e.g., size and vegetation cover) on water
temperatures of tidally influenced channels in the Skagit River delta. Indeed, air temperature, river
discharge and vegetation were associated with water temperatures in tidal channels, however, water
temperatures were not associated with density of juvenile Chinook salmon in the Skagit River estuary at
this time. Low dissolved oxygen concentration tended to be associated with low juvenile Chinook
salmon densities in tidal channels. Evaluation of future scenarios suggests the available juvenile Chinook
salmon habitat will decrease as climate drivers increase water temperatures, yet restoration and flow
management might lessen this effect. Overall, our evaluation is a first step, and I suggest improving the
temperature monitoring network in the Skagit River estuary to improve our understanding on the Skagit
River estuary thermal landscape.

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