Monitoring the Distribution of Spawning Chinook Salmon to Provide Feedback on Restoration Efforts on the Trinity River, CA

We monitor the spawning distribution of Chinook Salmon in the Trinity River for response to management actions on two spatiotemporal scales. The Trinity River Restoration Program aims to address juvenile rearing habitat bottlenecks and increase the Trinity River’s ability to naturally produce salmon through actions that alter the River’s morphology. Morphology plays a key role in the suitability of salmon spawning habitat and changes at the rehabilitation site scale occur rapidly through construction or channel response to significant flow events. The localized use of spawning habitats likewise responds quickly to these morphological changes.  The broader spatiotemporal distribution of spawning is influenced by the spatial distribution of spawning habitat, distribution of habitats for subsequent life stages, and proximity to Trinity River Hatchery where straying significantly skews distribution. Salmon born proximate to rearing areas of sufficient quantity and quality are more likely to contribute to the distribution of fish returning to construct redds than those experiencing unfavorable rearing conditions. As management actions and river response improve rearing conditions throughout the Trinity River, spawning distribution of natural origin salmon should increase in relation to the influence exerted by straying hatchery fish and be detectable over a temporal scale that spans multiple salmon generations.