In 2009, Napa RCD began the Napa River Watershed Steelhead and Salmon Monitoring Program with the goal of better understanding steelhead trout and Chinook salmon populations in the Napa River watershed. Since the program was initiated, Napa RCD has conducted annual monitoring of smolt abundance, adult returns, juvenile distribution, and genetic diversity, as funding and environmental conditions allowed.
This monitoring program is intended to provide science-based information to all stakeholders involved in steelhead and salmon management and recovery. In addition to generating data on steelhead and salmon, the monitoring program also provides information about other native fishes and tracks ecological responses to ongoing habitat restoration.
A total of five Chinook salmon spawner surveys were completed between December 11, 2019 and January 9, 2020. The surveys covered approximately 40.0 kilometers (24.9 miles) of the mainstem Napa River between Calistoga and Oak Knoll Avenue. In total, 60 salmon redds, 14 live salmon, and zero salmon carcasses were observed.
2020 represented the 12th consecutive year of steelhead and salmon out-migrant monitoring using a rotary screw trap in the Napa River. Due to exceptionally low flow conditions throughout spring, the trap was only in operation for 11 days. 1,457 fish were captured, including 11 native and 3 non-native species. Native species comprised 99.5% of the total catch and non-native fishes accounted for 0.5%.
33 Chinook parr/smolts were captured; however, the trap was not operational during the peak Chinook smolt outmigration period of May and early June. The fish may have been moving, but we just weren't able to detect it this year.
The Chinook abundance in any given year appears to be primarily dependent upon (1) natural variability in the amount and timing of rainfall, and (2) inputs of stray salmon from other river systems and/or Central Valley hatcheries that opportunistically spawn in the Napa River.
44 steelhead smolts were captured,42 of which were PIT tagged. During the past eight years (2013 - 2020) 564 steelhead smolts have been tagged. Of that total, six have been re-detected in subsequent years by the Napa River PIT tag antenna. These tagging data represent the first known confirmation of steelhead returning to the Napa River.
