During the recent drought, temperature conditions below Shasta Dam were catastrophically bad – leading to the loss of a large percentage of juvenile fall and winter run salmon. That problem and the low survival of the remaining juvenile salmon as they out migrated down the Sacramento River, played a major part in the current season closure. The past winter was reasonably wet, and the 2022-2023 winter was very wet. GSSA and our allies have been meeting with the Bureau of Reclamation regularly to push for a better approach to temperature management at Shasta Dam. In fact, we even filed oppositions to the Draft Shasta Temperature Management Plan as reported in early June.
It looks like our work, pressure and precipitation will pay off for salmon this fall. Temperature conditions below Shasta Dam will be far better this fall. The Bureau of Reclamation recently completed a Final Temperature Management Plan for Shasta Dam for this year. That plan projects that temperature dependent mortality will be 0.4% for Sacramento River winter-run – with similar high survival for fall-run. The estimate prepared by National Marine Fisheries Service (NMFS) is higher. NMFS estimated 2% Sacramento River winter-run juvenile losses from temperature. If these estimates prove to be correct, this fall should provide good conditions for Sacramento River runs to start rebuilding.
The Bureau is also working to develop a new way to estimate Sacramento River fall-run temperature survival. Sacramento River fall-run suffer along with the Endangered Species Act listed winter-run when temperature conditions are bad. However, the fact that fall-run spawns after the winter-run can make predicting fall-run temperature mortality a bit of a challenge. Fall temperatures are less predictable, and rainfall in the fall can change the situation for fall-run. GSSA continues to push the agencies to develop improved tools to help them better protect fall-run salmon.