The Department of Fish and Game (DFG) completed two days of successful fish rescues this week. A total of 46 sturgeon, 142 Chinook salmon, 12 steelhead and numerous striped bass were safely returned to the Sacramento River. Rescues took place at the Fremont Weir in Yolo County and Tisdale Weir in Sutter County along the Sacramento River. Several weeks of rainy weather caused the Sacramento River to overflow into the Yolo and Sutter bypasses. Once the water levels receded, fish were trapped behind two main weirs and unable to return to the river.

Twenty five of the sturgeon released are federally listed green sturgeon and the remainder are white sturgeon. Fifty-three of the salmon released are adult spring or winter run Chinook which are also federally listed. The sturgeon and adult salmon were migrating up the Sacramento River to spawn. All of the green sturgeon were implanted with acoustic tracking devices. One of the largest green sturgeon released exceeded seven feet in length and is estimated to carry more than 150,000 eggs.

DFG Senior Environmental Scientist Joe Johnson organized the rescue teams of 30 DFG biologists, wardens, technicians and natural resource volunteers (www.dfg.ca.gov/volunteer/nrvp) along with five National Marine Fisheries Service (NMFS) biologists and five UC Davis Bio-Technology Laboratory personnel. All worked on different phases of the rescue capturing and transporting fish, and placing radio telemetry devices in sturgeon.

"The rescue operation was significant," Johnson said. "We saved federally listed threaten and endangered fish. The acoustic tags inserted in each green sturgeon will enable scientists to track and tell if they survive and where they go. This was a rare opportunity."

At both locations, biologists used nets to crowd the fish into a small area and then encircle the fish with smaller seine nets. Several of the sturgeon weighed more than 200 pounds and it took three or more divers in wetsuits to wrestle the fish into hoop nets. The hoop nets were used to transfer the fish into specially designed fish cradles resembling stretchers. Sturgeon were measured, biological and genetic samples were taken, acoustic transmitters implanted and the fish were returned to the Sacramento River.

Each of the green sturgeon and some of the white sturgeon were implanted with acoustic tracking devices by Mike Thomas of the UC Davis Telemetry Laboratory. The transmitters have a 10-year life span and are expected to yield important information on the sturgeon life cycle.

"This is a unique opportunity for all of us," Thomas said. "Most important is seeing that these fish have an opportunity to spawn this year. This may be what is called a boom year for these sturgeon. It is believed by some that certain good years can sustain the population even after several bad years. Our transmitters give us the ability to follow these fish and learn more about them."

In 2006, green sturgeon were listed as threatened under the Endangered Species Act. "This was a wonder effort of agencies coming together to save these valuable green sturgeon that otherwise would not have made it to the spawning grounds," said Erin Strange, NMFS biologist. "We also had the opportunity to save listed salmon through this joint effort."

Stranding events occur on a cyclic basis when bypasses along the Sacramento River are used to spill excessive waters for flood control. This flooding event took place during the peak migration period for sturgeon. The last major flooding event that affected sturgeon took place in 2006.

For three days, DFG wardens watched over the stranded fish day and night trying to protect them. Prior to the deployment of wardens to the site, a 150 pound green sturgeon was found dead at the Fremont Weir and another had a spear shaft in it. These incidents are under investigation.