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Hatchery upriver bright (URB) fall Chinook salmon are straying into the White Salmon River (Figure 1). ESA-listed tule fall Chinook population in the White Salmon River spawns earlier (Sept � Oct) than URBs (late Oct � Nov). Tule redds at risk to superimposition which may displace eggs and reduce egg-to-fry survival.

A surprisingly high incidence of tule redds monitored were superimposed by URBs in 2022 and 2023.  Counts of redds superimposed from aerial surveys can be especially valuable for high-density spawning areas. Efficient processing of aerial imagery requires high performance computing environment. â€� Aerial drone surveys can provide high-resolution georeferenced imagery of a more expansive area of spawning grounds.

Next steps: Compare count estimates of redds superimposed from ground surveys with aerial surveys.  Estimate aerial observer error among four independent observers.  Prepare for 2024 aerial surveys using a Skydio X10 drone with onboard AI for obstacle avoidance.