FRESNO, Calif. (CN) – A staggering number of Chinook salmon are returning to a California river that hasn’t sustained salmon for decades due to agricultural and urban demands, giving biologists hope that threatened fish are finally spawning in their native grounds without human help.
Officials working on a restoration program announced Tuesday that they have counted a record number of spring-run Chinook salmon fish nests (redds) so far this fall on a stretch of the San Joaquin River near Fresno. Program staff has discovered over 160 redds with several weeks to go, toppling the total of 40 recorded in 2018.
Not only have the number of redds increased, biologists say many of them appear to have been fashioned by fish that weren’t hatchery raised or part of the billion-dollar program – meaning salmon were able to swim from the Pacific Ocean and through dams on their own.
“The volume of returns is a complete surprise,” said Pat Ferguson in a statement, a program fish biologist with the California Department of Fish & Wildlife.
Biologists say the quadrupled number of redds is exciting considering they have only released 37 adult female salmon this year to breed in the river below Friant Dam. There are other signs that natural or “volitionally passed” salmon have returned to the river: Biologists have found untagged spring-run carcasses in recent weeks.
“The majority of the fish that we’re seeing in the river spawning right now don’t appear to have tags,” said Lori Smith, a program fish biologist with the US Fish & Wildlife Service.
Smith said it is possible that the salmon lost their tags during their 370-mile journey back to the river, but genetic testing will ultimately confirm if they were hatchery bred or not.
Tuesday’s announcement is the second major milestone for the restoration program this year, as in April spring-run Chinook adults returned to the river for the first time in 65 years. The hatchery salmon returned from the ocean on their own in the spring but had to be transported by researchers to bypass a series of dams and diversion canals.
Biologists believe an abnormally wet rainy season may have helped some of the fish return to their ancient spawning grounds on their own.
“We appear to be seeing spring-run Chinook able to make it up into the restoration area on their own to spawn,” said Donald Portz, program manager. “It’s likely springtime high flows provided an opportunity for fish to get over obstacles that would normally limit their ability to migrate,” he said.
Salmon and other species disappeared from California’s second largest river in the 1940s following the opening of Friant Dam. Today, parts of the river often go dry during certain times of the year and other sections have manmade barriers that prevent salmon from reaching their spawning beds.
Because of a nearly two-decade-long lawsuit fought by the Natural Resources Defense Council, things are changing on the heavily altered San Joaquin. A settlement with the federal government reached in 2006 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 $1 billion to restore flows, wetlands and fish to the river.
Doug Obegi, lawyer with the council, said the increased redds are encouraging and a “sign that the river is ready for fish” in high-water years like 2018-19.
“It’s great to see salmon returning after so many decades, and it’s a reminder that when we add water to our rivers, they will return,” Obegi said in a phone interview. “It’s a little bit like the ‘Field of Dreams;’ if you build it, they will come.”
Obegi added the next major steps for the program are finishing a bypass that will allow salmon to swim upstream in low water years and improved fish screens near smaller dams and water intakes.
“We were starting from probably one of the most degraded states and yet it’s showing that in just a few years of work, we are seeing the river come back to life,” Obegi said.