The first indicators of winter-run salmon spawning survival in the Sacramento River in 2021 indicate poor production, as expected.1 The drought and Reclamation’s operations in 2021 have provided production levels on par with 2014 and 2015, the last two critical drought years.
Red Bluff screw-trap collections since August 1, 2021 have been very low (Figure 1). The spawning delay in 2021 due to high spring water temperatures and low flows may be delaying downstream movement. However, outmigration patterns are similar to 2014 and 2015 (Figures 2 and 3). Even 2020, a dry year with poor production, had numbers five times higher than 2021 to date (Figure 4). Historical wet years with good production like 2006 had collection numbers ten times higher (Figure 5). There is a slim chance that the spawning delays and low flows of 2021 will provide screw-trap collection patterns similar to 2018, a dry year with a later collection peak (Figure 6).
Regardless of the low fry production, the young winter-run salmon must still make it 300 miles to the ocean this fall and winter, a phenomenal hurdle under the best of circumstances. Low fall flows will make the journey difficult. The class of 2021 will get no help from storage releases. Like almost every other user of California water in the beginning of water year 2022, outmigrating winter-run salmon are wholly dependent on future rain to provide the water they need.
Figure 1. Late summer 2021 catch of salmon fry at Red Bluff traps with water temperature, streamflow, and water turbidity.
Figure 2. The 2014 catch of salmon fry at Red Bluff traps with water temperature, streamflow, and water turbidity.
Figure 3. The 2015 catch of salmon fry at Red Bluff traps with water temperature, streamflow, and water turbidity.
Figure 4. The 2020 catch of salmon fry at Red Bluff traps with water temperature, streamflow, and water turbidity.
Figure 5. The 2006 catch of salmon fry at Red Bluff traps with water temperature, streamflow, and water turbidity.
Figure 6. The 2018 catch of salmon fry at Red Bluff traps with water temperature, streamflow, and water turbidity.