California's Salmon Barely Survived the 20th Century, (But Will They Vanish Before the Next One?) 

Though fishing industry observers fear for the worst, some fisheries advocates can see a path forward.

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Still, he worries things will get worse for salmon before they get better.

"It could take another extinction or two before the state of California gets serious about protecting its resources," he said.

Historic Highs to Current Lows

The Central Valley river system marks the southern limit of the Chinook's range. In most ecological scenarios, a species will thrive in the middle reaches of its range and exist more tenuously on the outskirts and edges. But by chance, California — though similar in climate and latitude to Spain and Turkey — is more than suitable for a species that also thrives in the soggy Northwest and icy sub-Arctic.

That's because of the remarkable mountains that line the eastern and northern boundaries of the Central Valley. Snow lingers most of the year on the highest slopes of the Sierra Nevada, as well as Mount Lassen and Mount Shasta — the southernmost of the Cascades. Historically, this snow, when it melted, created cold-water river conditions that were just about perfect for salmon.

The best estimates suggest that one to two million adult Chinook entered the Sacramento and San Joaquin rivers every year to spawn — some of the largest runs in the species' entire range. The rivers of the North Coast probably supported that many more. Coho salmon and steelhead were plentiful, too.

In a 1998 paper, U.C. Davis biologist Ronald Yoshiyama reported that native Californians may once have caught, using relatively simple gear, more than 8.5 million pounds of Chinook each year in the Central Valley's rivers alone — apparently without seriously denting the stocks. By comparison, the typical statewide annual catch by fishermen today, of both commercial and sport, using high-powered boats and state-of-the-art fishing gear, usually run between half a million and 2 million pounds.

In 1846, Captain John Fremont reported seeing salmon "generally between three and four feet in length" in the Sacramento River. In that same year, Edwin Bryant, an early Californian, reported seeing salmon in the Sacramento that were five feet long — what might have been an exaggeration but could just as well have been 100-pound Chinook.

Almost as soon as the Gold Rush began, salmon populations began their downhill slide. Just about every industry and economy introduced to Northern California played its part in eliminating the river habitat required by the fish, both for adult spawning and for the early months of their offspring's lives. Hydraulic gold mining unleashed mountainsides' worth of sediment that buried spawning gravels and ruined many streams almost beyond recovery. The dam-building boom of the 1930s and 1940s had the longest lasting impacts. Knowing in advance what those barriers would do to salmon, the agencies that built them also constructed several large fish hatcheries.

But this intended mitigation program has worked only marginally well. Even though they release tens of millions of baby Chinook into the Central Valley's rivers each year, the state's hatcheries cannot match the damage that has been done to the fish's natural habitat. Much research even suggests that hatcheries make things worse by overwhelming naturally born salmon with genetically inferior fish, denied the gene-polishing pressures of natural selection. When the different gene pools mix, the whole population suffers. 

Commercial fishery data reflects the 20th century decline of salmon. From 1966 to 1980, fishermen caught an average of 555,000 Chinook per year (and sometimes several hundred thousand Coho, which are now endangered and relatively rare due to North Coast stream destruction).

By the 1990s, the fishery was a shadow of its historic glory, and in the 2000s it hit new lows. Commercial fishermen caught 54,000 fish per year on average from 2007 to 2018. This period included two years — 2008 and 2009 — when the season was entirely shut down due to record-low fish returns. That collapse came three years after Delta water exports hit record-high levels — more than 6-million acre-feet each year, four times the diversions of the 1960s.

Fish Versus Farms?

While biologists generally agree that poor marine conditions — subdued upwelling and less phytoplankton production — contributed to the late-2000s salmon crash, they also generally agree that excessive water diversions played their part. Some water is removed from the system before it starts its journey into the Central Valley. San Franciscans use water that once flowed through the Delta but is now impounded in Hetch Hetchy reservoir and piped to the Bay Area. East Bay MUD similarly takes its water from the Sierra foothills. Both reduce total Delta flows. 

Within the Delta itself, the pumps are a major stressor on the system. They move huge amounts of water, and in doing so suck small fish to their deaths or leave them lost in backwaters and sloughs where they're eaten by bass and catfish.

The Los Angeles area receives about a quarter of the water pumped from the Delta, while a tiny slice of the pie goes to the South Bay. Most of the rest is consumed by San Joaquin Valley farmland. Here, lucrative orchards and vineyards have proliferated since the 1990s as farmers shift away from annual crops like cotton, cantaloupes, and alfalfa. 

Nuts and grapes generate big money for farmers. However, unlike annual crops, trees and grapevines cannot be fallowed during dry times without great cost to the farmer. Instead, they require irrigation almost constantly, even during periods when water for irrigation is scarce. For this reason, this agricultural shift has placed heavy strain on water supplies.


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