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Gushing downpours finally arrived in California last month, when December rains brought some relief to a landscape parched after three years of severe drought.
But the rain came too late for thousands of Chinook salmon that spawned this summer and fall in the northern Central Valley. The Sacramento River, running lower than usual under the scorching sun, warmed into the low 60s — a temperature range that can be lethal to fertilized
Chinook, the largest species of Pacific salmon, need cool waters to reproduce.
Chinook eggs. Millions were destroyed, and almost an entire year-class of both fall-run Chinook, the core of the state’s salmon fishing industry, and winter-run Chinook, an endangered species whose eggs incubate in the summer, was lost.
The disaster comes on the heels of a similar event the previous autumn. It is also reminiscent of ongoing troubles on northern California’s Klamath River, where diversion of water for agriculture has at times left thousands of adult Chinook — the largest species of Pacific salmon — struggling to survive in water too shallow and warm to spawn in.
Now, scientists — who are observing increasing human demand for water, genetic decline of hatchery-reared salmon, and climate change models predicting intensified droughts — are concerned that the Chinook salmon will be unable to tolerate future river conditions and will all but vanish from California’s landscape.
Jumping Salmon image via Shutterstock.
Read more at Yale Environment360.
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