Gold Ridge Resource Conservation District

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How Much Water Do Coho Salmon Need?

Researchers Find Surprising Answer

For California’s endangered Coho salmon, just a trickle of water may mean survival in the small rivers and streams where the fish spend their first year, researchers found.

The Sonoma County Water Agency Mirabel inflatable dam and fish ladder on the Russian River in Sonoma County, California. A new study of Russian River tributaries found that even small amounts of streamflow can help endangered Coho salmon stay alive.Florence Low / California Department of Water Resources

In California’s small coastal streams, where hundreds of thousands of Coho salmon once returned each year to spawn, most wild populations now barely cling to survival. Habitat loss and intensive water use have pushed them to the brink; now climate change and increasing competition for water resources could send them over the edge.

However, recent research offers some encouraging findings – that juveniles of Coho salmon, an endangered species in California, can survive in creeks where just a trickle of water remains flowing. Since Coho spend their entire first year in fresh water before heading for the sea, it’s critical that their creeks don’t dry out in the summer.

Scientist Mariska Obedzinski and three collaborators – Sarah Nossaman Pierce, a California Sea Grant Extension specialist; Gregg Horton, a principal environmental specialist at the Sonoma County Water Agency; and Matthew Deitch, an assistant professor of watershed management at the University of Florida – found that less than 1 gallon per second of flow in small streams is all it takes in some creeks to keep pools interconnected.

Continue here.

Source:  Alastair Bland, Water Deeply, July 9, 2018.

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