State and federal fisheries experts arrived at Butte Creek yesterday, expecting to capture and transport 75-80 spring run Chinook salmon stranded in Butte Creek. They captured and relocated 123. The salmon, which are listed as threatened under the Endangered Species Act, had stopped their migratory journey through the lower reach of the river because of rising water temperatures.

The Department of Fish and Game (DFG) and the National Oceanic and Atmospheric Administration (NOAA) combined efforts to rescue the fish. Staff netted the salmon, implanted radio transmitters in 22 of them and moved them upstream to cooler water, so they can continue their spawning migration.

“Due to the extremely low number of returning fish this year to Butte Creek, every fish is important,” said Joe Johnson, DFG Fisheries Supervisor. “We didn't expect to find 123 fish, but we were prepared. We tagged all of them and place radio transmitters in two groups of fish in two areas. We want to find out how many of these stranded salmon will survive to spawn, and what the results are for this type of rescue.”

Snorkel surveys conducted at the end of June only recorded 300 salmon in this area, instead of an expected 3,000 to 5,000. A variety of factors may have delayed or altered the normal migration timing and pattern, including a late spring and cold high flows out of the Yuba River.

The water in the Butte Creek pool where the fish were stranded is significantly warmer than the rest of the river, creating a “thermal block” that causes the migrating salmon to dive to the bottom in search of cooler waters. As long as the water remains warm, the fish will not move forward. This particular spot on the river has been a “trouble spot” for spring run salmon in previous years.

DFG fisheries staff and NOAA biologists solved the problem by setting seine nets to capture the stranded salmon. Biologists then used dip nets to capture fish out of the larger seine net and place them in a net pen. Each fish, some of whom weighed up to 30 lbs., was carefully moved from the net pen in dip nets by a line of workers to transfer the fish up a steep bank. The fish were then loaded into a hatchery truck and transported up river for release, thus moving them around the warm water thermal block.

This year, for the second time, DFG, NOAA and staff from the University of California, Davis implanted a percentage of the rescued salmon with radio tracking devices, while the rest were tagged with a small external colored tags. The trackers will enable biologists to monitor how rescued fish behave after being rescued and if they contribute to the overall salmon population.

Butte Creek's spring run Chinook salmon have been listed as a threatened species since 1999. More than $35 million has been spent by state, federal and private parties on restoration and recovery efforts on the watershed. Over the past decade, changes in habitat and water management have helped the population rebound somewhat, but Central Valley salmon populations can still vary significantly from year to year. Over the past ten years, the run has averaged 6,000 fish, but today, surveys indicate a much lower salmon return.

The Department of Fish and Game (DFG) completed the release of 16.5 million young Sacramento Fall-Run Chinook salmon in northern California on June 15. The majority of the young salmon, called smolts, were placed into acclimation pens in San Pablo Bay prior to release, while others were released in rivers that flow to the bay. Smolts that survive to adulthood will return in two to four years to spawn in Central Valley rivers, boosting the recovery of the species in California waters.

“We hope this year’s above-average water flow and the use of a variety of release sites will improve the overall survival of the smolts and increase the return of adult salmon to their home rivers,” said Neil Manji, DFG Fisheries Branch Chief.

On June 8, the last major release of 650,000 Sacramento Fall-Run Chinook smolts took place near Mare Island Straits adjacent to San Pablo Bay. They were trucked from Nimbus Hatchery in Rancho Cordova to the site, confined in net pens to acclimate and towed out into the bay and released on the outgoing tide. The acclimation pens are operated by the nonprofit Fishery Foundation of California (FFC).

Since the collapse of the Sacramento Fall-Run Chinook salmon stocks in 2007, DFG has stepped up acclimation efforts and selected new release sites to help improve survival rates. This year, new sites for release included the mouth of the American River (to boost returns to the American River) and Eddos Harbor on the San Joaquin River near the Antioch Bridge (to boost returns to Mokelumne and Merced rivers).

“The releases went well,” said Biologist Kari Burr, FFC Acclimation Project Manager. “Once adults return and information is collected, biologists will be able to fine-tune release locations for the coming years.”

At release sites in the San Pablo Bay and Eddos Harbor, acclimation pens provided safe haven for the 3- to 5-inch-long salmon when they were released from pitch-dark transport tanks into bay and river waters. The pens allow the smolts to adjust to their new surroundings inside the safety of the net pens.

The release sites were selected in order to minimize in-river losses due to predation, pollution and other causes, and to help minimize the number of salmon that return to a different river than the one where they were raised.

The salmon smolts were raised at and trucked in from four DFG-operated Central Valley hatcheries. Please see related May 10, 2010 news release, DFG to Release Three Million Salmon Smolts Near Mouth of American River.

Contact
Harry Morse, DFG Office of Communications, (916) 322-8962
Neil Manji, Fisheries Branch Chief, (916) 327-8840

http://www.dfg.ca.gov/news/news10/2010062102-Massive-Salmon-Release.html