Are young salmon bigger, healthier in Yolo Bypass?
Researchers have issued a dire warning for California’s native trout and salmon: Three-quarters of them will be extinct in the next 100 years unless urgent action is taken.
This bleak assessment came Tuesday from biologists at the UC Davis Center for Watershed Sciences and from California Trout, a nonprofit advocacy group. In a new report, the groups said nearly 75 percent of California’s 31 salmon, trout and steelhead will be extinct by 2117 unless critical habitat is protected and restored.
The report follows up on the groups’ 2008 assessment that established a baseline level of health for each type of native fish. The researchers said that almost all of the fish are worse off than they were a decade ago. California’s record-breaking drought that officially ended this winter wreaked havoc on many of the already-struggling fish, which depend on cold water.
The researchers warned that warming waters from climate change only will exacerbate problems that already exist. Dams, for example, often block fish migrating to cold-water spawning grounds. Humans have transformed many of California’s river channels and estuaries into what are basically large, engineered drainage ditches – used for shipping, water supply and flood control. These waterways bear little resemblance to natural river systems that shrink and swell with the seasons, creating flood-plain habitat rich in food and sheltered areas critical to young fish.
To save the species, the report stated, regulators need to focus on the protection of rivers least altered by humans, such as the Smith and Eel rivers on the North Coast. Researchers said other needed efforts include protecting rivers’ cold headwaters, creating better groundwater management, removing problem dams or building fish passageways around them, and using altered landscapes such as flooded rice fields to mimic natural floodplains.
The good news is that many of those changes already are happening, said Curtis Knight, Cal Trout’s executive director.
He pointed to ongoing efforts to get fish around a dam blocking Battle Creek, a key cold-water tributary of the Sacramento River, and the pending removal of four huge hydroelectric dams on the Klamath River. There also are promising partnerships among Sacramento Valley rice farmers, state water managers and biologists to create habitat in and around the engineered Yolo Bypass floodplain west of Sacramento.
“We recognize that we’re not going back to 1826 California,” Knight said. “It’s an altered environment. That doesn’t mean we can’t have wild fish, too.”