Tag

salmon

As organizations and agencies scramble to preserve the Central Valley’s dwindling Chinook salmon runs, a group of scientists believes they may be overlooking a key factor in the decades-long decline of the fish: disease.

In a paper published in September’s issue of San Francisco Estuary and Watershed Science, a research team proposes that diseases—caused by viruses, bacteria and other microbes—could be suppressing juvenile salmon survival in a river system that once hosted millions of adult spawners each year. According to tracking studies, nearly all juvenile Chinook born from natural spawning die before they reach the Golden Gate Bridge; habitat enhancement efforts have failed to mitigate this mortality rate. Short-term studies of Central Valley salmon...
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Current estimates of young salmon lost to the south Delta pumps are based on a smattering of studies from the 1970s and should be updated, according to a new analysis.

“They don’t represent current operations,” says Ukiah-based consultant Andrew Jahn, lead author of the analysis reported in the September 2020 issue of San Francisco Estuary and Watershed Science. Current operations at the State Water Project (SWP) and the Central Valley Project (CVP) can reverse flows in the Old and Middle rivers, diverting salmon on their way to the ocean towards the projects. Existing salmon loss estimates also fail to account for a likely Old River hotspot for predators, drawn to the...
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A unique adaptive behavioral trait that may once have helped winter-run Chinook salmon thrive in the Sacramento River system could now be working against the fish as they face extinction.

The trait – which cues fish when to spawn based on water temperature – isn’t syncing up with current conditions in the Sacramento River below Shasta Dam. A paper published in the June issue of San Francisco Estuary and Watershed Science, reports that cooler springtime river temperatures seem to prompt earlier winter-run spawning while warmer temperatures push back the peak spawning period by a week or two. Under historic conditions, when winter-run Chinook spawned in high-elevation streams now inaccessible to...
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More than half the water diverted from Central Valley rivers is used to irrigate cattle-feed crops, implicating beef and dairy as top drivers of recent fish declines.

Recent findings, published in Nature Sustainability in March, strengthen the environmental arguments for going vegan while rewriting the familiar narrative that almonds and other high-value tree crops are the top hogs of Central Valley water resources. The study’s authors, led by Brian Richter of Virginia-based Sustainable Waters, focused on the arid West and found that irrigated crops like alfalfa and hay, more than any others, are drying out rivers. The reduced flows are pushing dozens of fish species toward extinction....
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The San Francisco Bay-Delta is named in the federal Clean Water Act as one of 28 “estuaries of national significance." For over 20 years, the San Francisco Estuary Partnership has worked together with local communities and federal and state agencies to improve the health of California’s most urbanized estuary.

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