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More than 200 fish rescued from Sacramento River bypass

Fishing boat

Fish biologists at NOAA Fisheries Service work hard every day doing research to save threatened and endangered fish species from extinction. It is not every day however, that they are asked to quite literally save 200 fish by hand. 

This spring, six biologists from Sacremento, Calif. branch of NOAA Fisheries Service’s Southwest Region teamed up with the California Department of Fish and Game, University of California-Davis and volunteers to rescue more than 200 fish trapped in bypass channels of the Sacramento River.

Among the rescued fish were 25 green sturgeon and numerous spring-run Chinook salmon and steelhead trout, which are all listed under the Endangered Species Act.

“We just kept netting one fish after another,” said Norm Ponferrada, one of the NOAA fishery biologists who participated in the rescue. “We knew that there were some sturgeon in the bypasses, but we had no idea there were that many fish overall. We kept going, not knowing when it would end.”

The bypass channels are normally separated from the river by levees.  However, after several weeks of unusually rainy weather, the river overflowed into the bypass channels. Once the rains stopped and the water receded to its normal level, the fish remaining in the bypasses were trapped and faced with many threats. 

“First of all, there’s not much food for them in the bypass channels,” Ponferrada said. “Also, the fact that they are confined to a small area makes them more vulnerable to poaching.”

Ponferrada also says that perhaps the biggest threat to the fish is that fact that the sturgeon were migrating upstream to spawn, and were separated from potential mates. This could reduce the breeding and survival of the species.

The fish rescuers, in wetsuits to protect against the cold, waist-deep water, used large nets to corral the fish into a smaller area. Then, they used hoop nets to capture the fish and transfer them to specially designed stretchers, upon which they were transported past the barriers and back into the river.

Given the size of the sturgeon, this was no easy task. 

Fishing boat

“The biggest one had a total length of over seven feet, had a girth of 36 inches, and weighed at least 250 pounds.  Not only were they heavy, they were very strong, too. It took several people to catch each fish in the hoop net and get them onto the stretchers,” Ponferrada said.
           
Prior to releasing the green sturgeon, University of California-Davis researchers measured the fish and took genetic samples. Then, they implanted each fish with an acoustic tag as a tracking device.  Fish biologists hope to learn more about the sturgeon movements through the information provided by these devices. 

While it was unfortunate that the fish became trapped in the first place, Ponferrada said, he and his colleagues were excited at the prospect of collecting scientific information on so many rare green sturgeon at once. 

“We’ve occasionally performed small rescue operations on juvenile salmon and steelhead that remained trapped when streams and ponds dry up, but I’ve never had to rescue sturgeon before” he said.  “This has been a rare opportunity.”

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