Helping hands move fish stranded in Yolo Bypass to Sacramento River
Matt Weiser
The Sacramento Bee
04/14/2011
More than 100 sturgeon and other imperiled fish were rescued from a flood-control channel Tuesday after weeks of high water in the Sacramento River receded, leaving them stranded.
The problem occurred at the Fremont Weir, a nearly two-mile-long concrete structure, shaped like a curb, that diverts high flows in the Sacramento River into the Yolo Bypass.
The weir north of Woodland performs a brilliantly simple public-safety function: When the Sacramento River swells with winter runoff to an elevation of 33.5 feet, it spills over the weir into the Yolo Bypass, diverting floods away from the Sacramento metro area.
But the weir is also a dead end for fish drawn into the bypass at its southern end, more than 20 miles away near Rio Vista. The weir does not have a fish ladder, only a narrow slot that is too small for sturgeon and lacks adequate flow for most other fish.
When the floodwaters recede, the bypass dries out quickly, leaving thousands of fish stranded in pools and channels across a vast area.
The strandings occur almost annually, but are reaching a scale not seen in years because of the prolonged flooding of the bypass and the many fish attracted by that flow.
The bypass began flooding on March 17, and only stopped Sunday, more than three weeks later.
"We see these adult salmon and sturgeon being hurt terribly in years like this," said Tom Cannon, president of the Fishery Foundation of California, which has sought to fix the weir for at least a decade. "It's a problem everyone knows how to deal with. I don't know if people really care."
A team of more than 40 employees and volunteers organized by the state Department of Fish and Game cared enough Tuesday to rescue what fish they could find.
The rescue effort concentrated on a pool alongside the Sacramento River, which flowed swiftly by only about 100 yards from the weir, full of mud and other flood-loosened debris. After water receded from the 100-square-mile bypass, the fish were left behind in the pool, a ribbon of water about a mile long and as wide as a two-lane road.
On Tuesday, two teams holding nets across the channel advanced toward each other from each end of the pool, trapping hundreds of fish in an area the size of a two-car garage.
Numerous small fish were lifted out in hand nets, including 75 salmon and 12 steelhead, all juveniles.
Sturgeon, California's biggest inland fish, were wrestled into nets and lifted over the weir with a stretcher-like contraption.
Before setting them free, a team of experts from UC Davis measured the sturgeon, made a small incision in their bellies to determine their sex and implanted a radio tracking device. A visual tag was attached to each sturgeon's dorsal fin.
Among the 31 sturgeon rescued Tuesday, 11 were green sturgeon, listed as threatened under the federal Endangered Species Act. At least two were egg-bearing females over 200 pounds and 6 feet long, and ripe for spawning.
Each was carried in the stretcher across a wide muddy bank to the river's edge, then freed again to the current.
"It was amazing," said Erin Aquino-Carhart, an environmental scientist at Fish and Game who paired with another worker to return a green sturgeon to the river. "It's not every day you get to be hands-on with a threatened species."
The rescued large green sturgeon might be 20 or 25 years old, which means they are in the prime of their spawning years. A single female can carry 150,000 eggs, so ensuring even one fish a shot at spawning is important to the entire population, said Marty Gingras, a supervising biologist at Fish and Game.
"They have good reproductive conditions only fairly rarely," Gingras said. "So we want them to spawn whenever they're able."
Biologists in recent years have learned the bypass is a fantastic place to restore California's imperiled salmon, sturgeon and other native fish. When it floods, an explosion of insect life comes into bloom, providing a feast for fish.
Officials wrestling with California's complex water and environmental problems want to flood the bypass more often, yet the weir looms as a deadly barrier which, in just a few days, can strand thousands of endangered fish.
