Biologists this week helped 54,000 Northern California salmon become San Joaquin River inhabitants — launching the river's largest experiment to rejuvenate a long-dead salmon run.
As part of the nearly 5-year-old San Joaquin restoration project, half of the juvenile fish will be released today for a long, dangerous swim to the Pacific Ocean. The other half will be released Friday.
The fish are tagged so survivors can be identified in a few years on the return trip to the San Joaquin for spawning.
"This is a big step for the project," said biologist John Netto of the U.S. Fish and Wildlife Service. "We're coordinating the right window of opportunity to get the fish down the river."
The San Joaquin's first large-scale reintroduction of spring-run salmon faces hurdles — the driest season in decades, a long truck trip from Friant Dam to the confluence with the Merced River and potentially lethal warm water.
The salmon restoration is part of a 2006 agreement that ended a long-running environmental lawsuit. Environmentalists sought to reconnect a 60-mile section of dried-out river with the ocean six decades after Friant Dam was built.
This year, the restoration project stopped water releases many weeks ago due to the extreme dry season. But even with a flow of water, fish could not get through the river on their own yet. Downstream dam bypass projects and other river fixes have been delayed.
Federal leaders decided to push forward with the salmon release when they received the necessary permits to begin the process.
Biologists also wanted to take advantage of water releases now being made on tributaries, such as the Stanislaus River. The releases will help young salmon move toward the ocean.
Netto said he could only offer a wide estimate of how many survivors might return in a few years — 50 to 800.
"Because of the dry year, I think it might be closer to the lower end of the range," he said.
Several days ago, the young salmon were transported from the Feather River Fish Hatchery in Oroville, officials said. The fish have been kept in net pens in the cool water near Friant Dam, northeast of Fresno.
The fish are "imprinting" the scent of the San Joaquin's water as a natural homing mechanism for their possible return from the ocean as adults.
Because of above-average April temperatures, the fish will be moved at night from the Friant Dam area to the confluence with the Merced River, where the San Joaquin refills with a steady flow of water.
The fish can't tolerate afternoon water temperatures of 75 degrees or higher, biologists said. The fish will be kept overnight in a net pen at the Merced River confluence so they can acclimate to the water in that location.
"We're also letting them recover from the trip over to this spot," said Netto. "This can be very stressful on young fish."
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