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Trap and Haul and Reservoir Populations of Chinook Salmon

In a recent paper, Martin Perales, Jay Rowan, and Dr. Peter Moyle call attention to existing naturally breeding populations of Chinook salmon in Central Valley reservoirs.1 Though the California Department of Fish and Wildlife no longer stocks salmon in reservoirs that are capable of reproducing, residual salmon are now surviving in some reservoirs and spawning upstream, and these authors are concerned that these fish could interbreed with salmon that were transported from downstream of these reservoirs. The abstract for their paper opines: “the possibility of behavioral and genetic interactions may lead to complications of restoration efforts via trap and haul programs. The full extent of this phenomenon needs to be documented before trap and haul programs are initiated to reintroduce salmon above reservoirs.”

There are two major efforts substantially underway to trap and haul salmon past major Central Valley rim dams: the Yuba Salmon Partnership Initiative’s plan to move salmon upstream of New Bullards Bar Reservoir on the North Yuba River, and the Bureau of Reclamation’s effort to move salmon upstream of Shasta Reservoir. Both of these programs will take ten years or more to be fully implemented, if indeed they are implemented at all.

There are no Chinook in New Bullards Bar Reservoir.

There is a substantial population of fall-run Chinook in Shasta Reservoir, many of which migrate up the Upper Sacramento River to spawn. Elsewhere, CSPA has advocated that the Bureau consider the McCloud River upstream of McCloud Reservoir as a potential target location for winter-run Chinook. The concern expressed by Perales, Rowan and Dr. Moyle is one reason why that potential location might be worth a second look: the upper McCloud is not accessible to fish that swim upstream from Shasta Reservoir.

The authors also point out that study of these “adfluvial” populations of Chinook may provide insight into the possible behavior and potential success of trapping and hauling Chinook from downstream of the reservoirs. There is some opportunity for this: in ongoing FERC licensing processes, CSPA proposed studying the spawning of Chinook (as well as trout) in the Tuolumne River that move upstream from Don Pedro Reservoir.

But let’s also not get carried away with the concern, or the potential value of existing reservoir populations of Chinook. The “complications” of interbreeding with residual reservoir salmon are among dozens of potential issues and problems that must be addressed and resolved for a program to move winter-run Chinook above Shasta Reservoir to succeed. And the numbers of Chinook salmon moving upstream from Central Valley reservoirs are generally small.

Any reintroduction of salmon upstream of rim dams will require ongoing improvement and adaptation. Any good program will set up management to solve problems, based in substantial part on monitoring of what fish in the river actually do. We should prepare for and embrace the uncertainty and the challenges. We won’t know how reintroduced salmon will behave, and we won’t even know let alone solve all the problems before we start.

If we stop to study “the full extent” of every issue before we move forward, no reintroduction programs upstream of rim dams are likely to happen at all, ever.