California salmon being pushed to the edge of extinction

Nearly half of California’s salmon species will be extinct in 50 years if current trends continue, a new study has found.

The fish face myriad threats. Climate change will warm the cold-water streams on which spawning fish rely, while dams block passage to headwaters. Ocean acidification will disrupt marine food webs, while hatchery-raised fish threaten to interbreed with wild fish, weakening future populations.

If nothing is done to reverse current trends, about 45 percent of the state’s salmon, steelhead and trout are likely to be extinct in 50 years, and 74 percent will be extinct in 100 years, the study says.

The snapshot study, completed by the University of California, Davis’s Center for Watershed Sciences and the conservation group California Trout, was completed at the tail end of the state’s historic five-year drought, which pushed more species than a decade ago onto a list of critical concern – meaning they are likely to face extinction in 50 years.

“Drought really took its toll on fish populations statewide and, almost across the board, abundance is down as a result of low stream flows and high stream temperatures,” Patrick Samuel, a report co-author and conservation program coordinator at Cal Trout, told SeafoodSource.

California’s fish have survived millennia of droughts, floods and other disasters, and will recover if given the chance. 

“But they need our help, and some innovative thinking and creative partnerships with various groups to help them return to abundance,” Samuel said.

However, current trends paint a dire picture, if unchanged.

Climate change will reduce the amount and timing of cold-water stream flows. Rising air and water temperatures will make streams too warm for salmon in the summer and fall, and lower amounts snowfall will lessen flows of cold snowmelt during the summer. 

Ocean acidification – caused by rising concentrations of carbon dioxide in the ocean – isn’t a severe problem yet, but still threatens to disrupt the life cycles of marine species, including some that juvenile salmon prey on.

California last lost a salmonid species, the bull trout, four decades ago. Though 31 species of salmon, steelhead and trout remain, their decline has been long and steady, according to Peter Moyle, the associate director of the Center for Watershed Sciences and the report’s lead author.

Moyle has studied California fish for 47 years, and in 1976 published the book that served as a baseline for the new report. Additionally, it was actually one of Moyle’s graduate students who caught that last bull trout on the McCloud River in 1975.

“The long-term decline in our salmonids is well-documented,” Moyle told SeafoodSource.

In centuries past, enormous salmon runs supported commercial fisheries from San Francisco to the Oregon border, along with numerous canneries supplying seafood for gold miners and export. Native American tribes in Northern California depended on salmon, and their cultures revolved around the abundance of the fish in rivers like the Klamath, Trinity, Eel, Sacramento and San Joaquin. Every year, millions of Chinook spawned up some of those rivers, as did smaller numbers of coho, pink and chum salmon.

Today, better access to historical spawning and rearing habitat, plus better routes downstream, to the ocean, would help salmon recover.

Though removing some dams would help salmon, other dams are used to release cold water during summer months when stream flows are low. Shasta Dam, for instance, drove the demise of winter-run Chinook on the Sacramento River, but temperature-controlled releases of cold water keep the struggling population alive.

“Where they no longer serve their purpose for water storage, flood protection, power generation, or don’t make economic sense anymore, or the environmental degradation outweighs potential benefits, dams should be removed to allow our species access to important historical habitat,” Samuel said.

Hatchery-raised fish also threaten wild salmon runs, mainly because they compete with, prey on, and mate with wild fish and the hybrid offspring are weaker than their wild counterparts, Samuel said. He added that it is possible to sustainably raise fish in hatcheries – in Alaska, for instance, hatchery fish are located away from wild fish. While the wild fish migrate upstream, the hatchery fish return to net pens in the bay or river mouth, where fishermen target them.

To restore California’s salmon in especially heavily altered habitats like California’s Central Valley, many partners are needed – including the farmers who use much of the water the salmon depend on, Samuel said.

“We are not going back to some pristine state in many of these altered habitats,” Samuel said. “Humans are a key and integral part of these ecosystems, and we seek to work with diverse partners to find creative solutions to agricultural operations to benefit people and fish.”