California Department of Fish and Wildlife (CDFW) biologists have rescued hundreds of fish — including dozens of endangered and threatened salmon, steelhead and sturgeon — that were stranded in Sacramento Valley bypasses after recent heavy rains.
The fish — including endangered Sacramento River winter-run Chinook salmon, threatened Central Valley spring-run Chinook salmon, threatened Central Valley steelhead and a threatened green sturgeon – were trapped in Fremont and Tisdale Weirs, flood control structures off the Sacramento River, when flood waters receded after mid-March rainstorms.
Rescue efforts began in late March, concluding in mid-April. Seventeen CDFW staff participated in the rescue efforts at the weirs, using beach seines, a sturgeon hoop net, dip nets and crowder racks to capture fish trapped within each weir apron.
The bulk of the rescued fish were salmon, with biologists capturing and tagging 41 adults and 160 juveniles. Based on length-at-date, the young salmon are believed to be a mixture of spring-run and fall-run fish. Staff also rescued one oversized adult green sturgeon, a massive female white sturgeon and hundreds of other fish, including Sacramento sucker, Sacramento pikeminnow, Sacramento splittail, striped bass, smallmouth bass, bluegill and redear sunfish. All of the fish were moved back to the Sacramento River and released.
DNA tests are currently underway on a sampling of the fish rescued. Results will verify biologists’ field assessments that the adult salmon include winter-run and spring-run Chinook.
“We know these areas are prime stranding sites, so we keep them on our radar each year,” said Colin Purdy, CDFW Senior Environmental Scientist. “Rescuing state and federally listed species is a priority — particularly the adult fish, because they contribute to future generations. But all of the fish we pull out of the weir are transported back to the river for release.”
Biologists also used special tracking equipment in an effort to document the behavior and survival of the rescued fish. The green sturgeon, an adult male stranded in the Fremont Weir apron, was tagged with a surgically implanted acoustic tag on March 29 before being released into the Sacramento River. It was subsequently tracked on real-time acoustic receivers heading upstream toward its likely spawning grounds near Red Bluff. The white sturgeon, a post-spawn female, was rescued from the Tisdale Weir on March 31. It was also given an acoustic tag and was subsequently tracked heading downstream.
Four adult Chinook salmon rescued on April 8 have since been detected moving upstream by real-time acoustic receivers.
All juvenile steelhead rescued were implanted with passive integrated transponder (PIT) tags. Staff from the Pacific States Marine Fisheries oversaw their care and release as part of CDFW’s Central Valley Steelhead Monitoring Program.
CDFW has a team of scientists who monitor locations along the Sacramento River where fish tend to enter the Yolo and Sutter bypasses during high flows and become stranded once flows subside. Initial surveys of the fish stranded in water behind Fremont Weir documented four sturgeon. Only two of these were recovered during rescue efforts. CDFW is seeking information regarding possible illegal harvest or take of these two oversized sturgeon.
If you have information about this or any other fish and wildlife violation, please dial the toll-free CalTIP number, 1 888 334-CALTIP (888 334-2258), 24 hours a day, seven days a week. Anyone with a cell phone may send an anonymous tip to CDFW by texting “CALTIP”, followed by a space and the message, to 847411 (tip411).