Measures save young salmon after failure of Oroville Dam spillway

A million fingerling salmon, rescued from almost certain death after the Oroville Dam spillway fell apart last month, began their remarkable journey to the ocean Monday by being launched unceremoniously out of tanker trucks into the Feather River.

The flapping, flopping chinook were poured through pipes into the water at a Yuba City boat ramp, where their trek downstream to the ocean, through a gantlet of predators and environmental perils, started amid cheers from biologists and schoolchildren on a field trip.

The lucky fish are among 2 million spring-run chinook moved from the state-run Feather River Fish Hatchery last month after a gaping hole opened in the main spillway at Oroville Dam and erosion on the emergency spillway sent plumes of suffocating silt into their rearing pens.

Five million salmon in all were moved to 600-foot-long concrete tanks at a hatchery annex downstream, and, surprisingly, almost all survived. The release Monday was the first of several planned over the next month at the hatchery annex, which was built to hold only 2 million fish.

“I would call this an unqualified success, especially under these emergency conditions,” said Andrew Hughan, spokesman for the California Department of Fish and Wildlife, as thousands of the tiny fish were sucked through a giant hose out of the annex tanks and into the tanker trucks. “Protection of salmon is critically important because, first of all, they are a historic fish ... and also they are a key part of a $1.4 billion fishing industry.”

Photo: Chris Kaufman, Special To The Chronicle Adam Anton, with the California Department of Fish and Wildlife,...

All of the salmon were removed from the hatchery last month after water cascading off the busted concrete spillway opened a yawning crater in the earth.

The damage on the main spillway of the nation’s tallest dam was first detected Feb. 7, forcing operators to reduce the flow. Within days of the initial spillway failure, the Lake Oroville water rose and began pouring over an emergency spillway that had never been used. The hill eroded quickly, causing the state to warn of a catastrophic collapse and temporarily evacuate nearly 200,000 people downstream.

The fish were removed as mud-filled water flowed downstream, but 1 million federally threatened steelhead trout could not be moved, Hughan said. An emergency settling basin system was set up using water from a fire hydrant, saving most of the steelhead, but 300,000 of them died.

“It’s unfortunate, but we budget for loss,” Hughan said. “Still, that’s 700,000 fish that we wouldn’t have had.”

Monday’s salmon release came three days after water began flowing down the mangled spillway for the first time since Feb. 27. The flow, scheduled to continue throughout the week, is an attempt to make room for the rain forecast this week. Engineers also want to see if the sheared-off chute and the carved-out hillside around it can handle more pummeling as flows into Lake Oroville increase during the spring snowmelt.

Dam managers expect to open the floodgates two more times this spring, but fishery managers believe the danger to the fish has passed. That’s because most of the dirt around the spillway appears to have washed away, leaving mostly bare rock.

Photo: Chris Kaufman, Special To The Chronicle Adam Anton, with the Department of Fish and Wildlife, weighs salmon...

Chinook, otherwise known as king salmon, are historically most abundant in the Sacramento River and its tributaries, making up 90 percent of the salmon caught in California. They pass through San Francisco Bay and roam the Pacific Ocean as far as Alaska before returning to spawn an average of three to four years later. Their imprint cues and sense of smell are so strong that the fish often find their way back to almost the exact spot in the river where they were born.

The release Monday of spring-run chinook is important because the fish are listed as threatened under the federal Endangered Species Act. There are three distinct runs of salmon — winter, spring and fall — based on the time of year they swim back upriver and lay eggs.

The Feather River Hatchery is the only facility that raises Central Valley spring-run chinook.

“These spring-run salmon are special fish,” Hughan said. “If we didn’t do this, there wouldn’t be any fish.”

All of the fish being released in the Feather River have coded wire tags injected into their snouts so biologists can determine how many make it to adulthood. Typically only 2 to 3 percent of the 35 million hatchery-raised salmon that are released into California rivers and the ocean every year survive.

Salmon survival is a huge issue for the state and federal governments, which are obligated to make sure the pink delicacy still exists in the future. The hatcheries were created in an attempt to help the salmon after dam construction, irrigation and pollution contributed to an enormous decline in the fish’s population over the past century.

Tony Lombardi, left, Omar Jimenez and Joe Amoroso, with the Department of Fish and Wildlife, move fish from the raceway into a fish truck at the Feather River Hatchery Thermalito Annex in Oroville, Calif. on Monday, March 20, 2017. less Tony Lombardi, left, Omar Jimenez and Joe Amoroso, with the Department of Fish and Wildlife, move fish from the raceway into a fish truck at the Feather River Hatchery Thermalito Annex in Oroville, Calif. on ... more Photo: Chris Kaufman, Special To The Chronicle Photo: Chris Kaufman, Special To The Chronicle Image 1 of / 8 Caption Close Measures save young salmon after failure of Oroville Dam spillway 1 / 8 Back to Gallery

Even with the hatcheries, the Sacramento River population hit rock bottom in 2008 and 2009, when so few salmon came back to spawn that commercial fishing was banned off the coasts of California and Oregon.

The state has been experimenting with different ways to release salmon — in the rivers, delta or ocean — in an attempt to optimize survival rates. But the work hasn’t helped salmon populations this year, according to Amanda Cranford, a natural resources specialist for the National Marine Fisheries Service.

The lack of chinook in the ocean now is likely to result in severe restrictions on salmon fishing along the California coast this year.

“It’s been a pretty dismal year so far, likely because of the drought,” Cranford said, citing estimates by the Pacific Fishery Management Council. “We have to give these fish an opportunity to rebound.”

A group of third- and fourth-graders from Yuba Environmental Science Charter Academy who were watching the release Monday were clearly rooting for the salmon’s recovery.

“They are hopping like little frogs,” shouted a gleeful Marly Terry, 8, whose class was there to release 25 fish of their own. “It’s so cool. Now they are out in the river to make homes and babies.”

Peter Fimrite is a San Francisco Chronicle staff writer. Email: pfimrite@sfchronicle.com Twitter: @pfimrite