Spring-run Chinook. (Bureau of Reclamation)

FRESNO, Calif. (CN) – Surviving an exhaustive maze of manmade barriers and hungry predators, a hardy group of salmon have beat the odds and returned to spawn in one of California’s most-heavily dammed rivers.

The U.S. Bureau of Reclamation says for the first time in over 65 years, threatened spring-run Chinook adult salmon have returned to the San Joaquin River near Fresno to complete their life cycle. The return of the hatchery-reared fish marks a huge milestone for a billion-dollar undertaking to revive an ancient population of salmon that disappeared in the 1940s with the opening of Friant Dam.

Officials announced that at least five adult spring-run Chinook born in fish hatcheries and released into the wild several years ago, have made the 370-mile trek from the Pacific Ocean back to the San Joaquin River.

Don Portz, who oversees the fish restoration program for the bureau, says the salmon that have been caught in nets prove that the joint-effort by the feds and state is going in the right direction.

“This is monumental for the program,” Portz said in a statement. “It’s a clear indication of the possibility for these fish to make it out of the system as juveniles and then return as adults in order to spawn.”

For thousands of years California’s second largest river teemed with salmon, providing food for Native American tribes and then settlers during the 1800s. But as the Gold Rush died down, Californians headed south and found the Central Valley ripe for farming.

In their lust for water, farmers and government agencies ended up damming the river dry in some parts by the 1940s. Water was divvyed up and delivered in canals to farmers for crops like almonds and cotton, but the native salmon species and their spawning habitat vanished. Today, parts of the river go dry during certain times of the year and other sections have manmade barriers that prevent salmon from reaching their spawning beds.

Thanks to a nearly two-decade-long lawsuit fought by the National Resources Defense Council, things are changing on the San Joaquin. A settlement reached in 2006 with the federal government set goals of restoring native fish populations to “good condition” without overtly damaging water suppliers’ take of the river; the state and federal government plan to spend over a billion dollars to restore flows, wetlands and fish to the river.

The five Chinook captured this month returned from the ocean on their own, but had to be transported by researchers in a 500 gallon tank to bypass manmade barriers. The biologists confirmed that the fish were from a California hatchery because they were missing a small rear fin.

The five adult salmon and any others that may return will hold in the cool water below Friant Dam for the summer, before hopefully spawning in the fall.

“Now, that’s worth a toast!,” tweeted Kate Poole about the salmon’s return, senior director at the NRDC.

The long-term goal is to update the barriers to allow fish to swim upstream in the future without being transported, Portz said. Restoration efforts are meant to help spring and fall-run Chinook, Pacific lamprey and white sturgeon.