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Saving Native Central Valley Salmonids

No, the fish below is not a Central Valley salmon or trout. It is a Yellowstone Cutthroat Trout from the Yellowstone River in Yellowstone National Park. This iconic species is beginning to recover from competition and predation by non-native brook, brown, rainbow, and lake trout. Yellowstone Park over the past decade has carried out an intensive eradication program of the non-native salmonids to save the iconic native cutthroat. A similar program has been underway to save the Snake River Cutthroat on the South Fork of the Snake River from Grand Teton Park in Wyoming downstream into Idaho. The eradication programs include rotenone poisoning of tributaries, gill-netting (lake trout in Yellowstone Lake), and regulations requiring angler removal (rainbow trout).

Yellowstone Cutthroat Trout caught and released in the Yellowstone River in Yellowstone National Park summer 2018

California has excellent programs to protect some of its iconic trout and salmon through strict regulations and habitat protection and enhancement.

  • Redband Rainbow Trout in the upper McCloud River
  • Golden Trout in the upper Kern River
  • Lahontan cutthroat of the Truckee drainage.
  • Coastal cutthroat (NorthCoast streams)
  • Paiute cutthroat of the eastern Sierras.
  • Winter Run Chinook salmon (endangered) spawning grounds upstream of Redding are now closed to trout angling.
  • Spring Run Chinook Salmon (threatened) spawning tribs protected
  • Wild steelhead – no harvest in mark-selected fisheries (photo below)

Wild Rainbow Trout/Steelhead caught and released in the lower Yuba River near Marysville January 2019.

One survival bottleneck that needs opening for salmon and steelhead in the Central Valley is predation by non-native fish. There is a long list of non-native and native predators from which native fish need protection. The best protection is to minimize native-nonnative habitat interactions. That can best come from adequate physical-geographical habitat and habitat water quality for natives while minimizing non-native fish habitat. Changes are necessary because of global warming and continually increasing demands on water. Stream flows are too low, water temperatures are too high, waters are clearer, and in-stream cover is low, factors that all favor non-native predators and competitors.

Because many of the non-natives are sportfish with strong angler followings, non-lethal controls best serve to reduce overall predation effects on native fishes.

  • Provide natural spring flow pulses in rivers and tributary tailwaters to help emigrating salmonids avoid predators.
  • Keep water temperatures lower in rearing habitat and migrating routes of native fish.
  • Maintain the low salinity zone, the primary rearing area for native fishes, in the Bay downstream of the Delta.

At some point population controls on non-native fish may have to be considered despite their inherent problems and low potential for success.1 Note that despite the use of 50 miles of gill nets and removal of hundreds of thousands of pounds of lake trout each year in Yellowstone Lake, lake trout remain abundant. Predator control through removal would be far more difficult in the Central Valley and Bay-Delta.

Summary and Conclusion

I remain skeptical on how effective the individual actions can be, but a comprehensive multi-action program such as that employed for the Yellowstone Cutthroat Trout has some chance of success. Such a program would come with tough choices and require considerable resources, but may need to be part of saving Central Valley salmon and steelhead. Focus should be on increasing the amount of native fish habitat and bettering spawning, rearing, and migratory habitat conditions.