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Migration
Adult Chinook salmon migrate up rivers from the ocean to spawn in their natal streams during the fall. In the Napa River, adult returns to upstream spawning areas appear to occur in November with the onset of winter rains. Chinook salmon spawn primarily in riffles and the ends of pools with appropriately sized gravel. Spawning substrates used by Chinook salmon typically range from ½ inch to 3 inches. Excessive amounts of fine sediment and sand in the bed can reduce flow through the redd and is detrimental to egg survival and development.
Source: Napa County Resource Conservation District, Stillwater Sciences - Napa River Watershed Limiting Factors Analysis
