Jordan Colby, a researcher with UC Davis, measures baby salmon in a flooded rice field © REUTERS/Nathan Frandino
By Daniel Trotta and Nathan Frandino
In an experiment a decade in the making, biologists and California conservationists are releasing hatchery salmon onto flooded Northern California rice fields, seeking to replenish endangered fish species while benefiting the farmers’ business model.
While environmentalists are often pitted against agribusiness in California’s water wars, conservation scientists and rice farmers are working together, trying to reclaim the great flood plains of the Sacramento River for salmon habitat.
Their task is daunting. California’s wetlands have all but disappeared, converted into farms and cities in one of the great engineering feats, or environmental crimes, of the 20th century.
Now, for the cost and inconvenience of flooding their fields, rice farmers are earning goodwill and betting that a healthy salmon population will avoid new regulations to protect wildlife and keep adequate water flowing.
In recent years, biologists discovered that as rice straw decomposes in flooded fields, it creates a broth rich in fish food—they call it “zoop soup.”
“The zooplankton are so big and they’re so juicy, it’s like filet mignon,” said Andrew Rypel, a professor of fish ecology at the University of California Davis and lead investigator on the project.
After fattening up on their zooplankton, the salmon return to the river, swim downstream and beneath the Golden Gate Bridge on their way to sea, returning years later to spawn the next generation.
The university’s researchers have joined the California Rice Commission, the conservation group California Trout and the U.S. Department of Agriculture on the project, seeking to reverse the trend toward dwindling fish populations as a result of human re-engineering of the state’s waterways and, in recent years, extreme drought exacerbated by climate change.
Before industrialization, the northern end of California’s Central Valley was a miles-wide flood plain straddling the Sacramento River—a natural feeding ground for fish. That land is ideal for farming rice, and about 500,000 acres are under cultivation today. Though the natural state will never be restored, the flood plain can reconnect to the river.
Though the experiment has placed salmon on small parcels before, this winter marks the first time it has been tried on a large scale on a working rice farm. Conservation scientists hope to replicate the model on more farms in years to come.
The salmon project is using 389 acres on a pair of rice farms at the Sutter Bypass near Robbins, about 30 miles northwest of Sacramento. One farm is intentionally flooded with water and planted with hatchery fish, enabling the biologists to study their progress and tag some with microchips to track their movements.
A second farm is being prepared just in case the Sacramento overflows this year, delivering naturally spawned salmon.
The project was inspired by changes that turned flooded rice farms into habitats for migrating ducks, geese, and other waterfowl within the Pacific Flyway, a north-south corridor linking North and South America.
California rice farmers traditionally burned leftover rice straw after the autumn harvest until a 1991 state law banned the practice, largely in response to human complaints about smoke. When farmers started using water to break down rice straw, the smoke cleared, and the birds started coming back.
Though no longer pristine wetlands, 90 percent of which have been lost in California, the rice fields enticed enough migratory birds to darken the sky, their honks once again bombinating across the valley.
“We don’t want to just sit silently while extinctions happen,” Rypel said.