Dan Bacher
The Stockton Record
CLEMENTS − A record high number of over 23,000 fall-run Chinook salmon have returned to the Mokelumne River, a tributary of the San Joaquin River, while the second lowest number of Sacramento River fall Chinook have come back to Coleman National Fish Hatchery on Battle Creek this year.
The fish are returning from the ocean during a year when all salmon fishing was closed in California’s rivers and ocean waters due to the projected low ocean abundance of Sacramento and Klamath River fall-run Chinook salmon.
The previous record for the Mokelumne River Fish Hatchery was 19,962 salmon for the 2017 fall run ending in January 2018.
The East Bay Municipal Utility District (EBMUD) reported the 2023-24 fall run of Chinook salmon on the Mokelumne River is now “the most successful return in more than 80 years.” A total of 23,681 fish had been reported as of Nov. 20, according to Michelle Workman, EBMUD Manager of Fisheries and Wildlife.
The Mokelumne contributes only about 3% of the freshwater flow into the Sacramento-San Joaquin Delta, yet its salmon population makes up as much as 50% of the commercial catch off the coast of California in years when the season is open, according to data from the Pacific Fishery Management Council (PFMC).
On Oct. 29, EBMUD biologists tallied the largest one-day salmon count in 30 years of 1,941 fish.
Workman said the hatchery is working towards its 10 million egg-take goal to produce approximately 9 million smolts (juvenile salmon), including the required 3.4 million mitigation fish, 3 million enhancement fish, and 2.5 million drought recovery fish.
The mitigation fish are funded by EBMUD, the enhancement fish are funded through the ocean commercial and CPFV (Commercial Passenger Fishing Vessel) salmon stamp and the drought recovery fish are funded by the CDFW.
The majority of the enhancement fish will be trucked to release sites including Fort Baker, Richmond, Marin Rod & Gun Club, Tiburon, Half Moon Bay, Santa Cruz and Monterey in 2024. The mitigation fish will be released at Sherman Island.
Last year, a total of 6.4 million salmon smolts were produced at the Mokelumne River Fish Hatchery.
“We are proud of the collaboration between EBMUD and the California Department of Fish and Wildlife and we attribute much of our success to our partnership,” said Workman. “This large run translates into meeting the hatchery goals and also being able to fill all of the restored habitat that we spent millions of dollars creating over the past 30 years.”
Long-term strategies cited by the agency that led to the big run this year on the Mokelumne include:
Habitat enhancement to improve natural river spawning and rearing, in partnership with both the U.S. Fish and Wildlife Service’s Anadromous Fish Restoration Program and the CDFW.
Flow management, including pulse flows from EBMUD’s Camanche Reservoir into the river to attract returning fish; coordination with the U.S. Bureau of Reclamation to close the Delta Cross Channel to reduce straying; and management of the Camanche cold water pool to support spawning, incubation, and rearing.
Hatchery management, including investments in chillers and ultraviolet filters to improve egg survival; collaboration on the release of juvenile fish; and management of the fish ladder leading into the hatchery.
The statewide closure of California’s 2023 commercial and recreational salmon fishing season to protect the Central Valley fall-run Chinook population.
The agency said when the season is complete and full data is available, experts will determine which strategies contributed most to the success on the Mokelumne, given that some rivers are experiencing low returns, as has the Mokelumne in previous years.
“The Mokelumne faces many challenges,” said Workman. “It is a small river that can be overwhelmed by flows from larger Central Valley rivers when attracting salmon back from the ocean. But through collaborations with our agency partners, we have found winning strategies.”
“This year’s large run allows us to meet our hatchery goals as well as improve natural production numbers in the river by maximizing the use of the available spawning habitat we worked so hard to build. Decades of work to improve the natural habitat are paying off,” concluded Workman.
It is important to point out that in calculating the ocean salmon abundance estimates that are used by the Pacific Fishery Management Council (PFMC) to craft the ocean and river fisheries each year, the Mokelumne River is not included because it is a tributary of the San Joaquin, not the Sacramento River.
The ocean abundance modeling uses the salmon spawning escapements on the Sacramento River and its tributaries, along with the Klamath River and its tributaries, to develop the ocean and river salmon fishing seasons every year.
In contrast with the Mokelumne, the fish counts for the main stem of the Sacramento River are looking dismal. On Battle Creek, the Coleman National Fish Hatchery has seen only 5,200 adult kings and 245 jacks to date.
This is the second lowest total of all time, according to J.D. Richey in an action alert for the Nor-Cal Guides and Sportsmen’s Association (NCGASA) requesting the transfer of 10 to 15 million eggs from other fish hatcheries to Coleman to meet their minimum goal.
In addition, biologists have found only 116 carcasses and 109 redds on the main stem of the Sacramento River this fall.
After the action alert was shared widely on social media, the CDFW responded by allowing a transfer of 5 million Chinooks from the Mokelumne River Fish Hatchery to the Coleman National Fish Hatchery (NFH) in order to meet their minimum goal.
“This week we are thankful for the Mokelumne River Hatchery and the California Department of Fish and Wildlife,” the hatchery staff reported on Facebook. “We are cooperating with the CA DFW to increase the number of salmon raised at Coleman NFH this year after a low return to Battle Creek. Over the next few weeks we are transferring up to 5 million Chinook salmon eggs from Mokelumne River Hatchery to Coleman NFH.”
However, NCGASA Executive Director James Stone criticized the hatchery’s plan to truck the juvenile salmon (smolts) originating from the 5 million egg transfer, noting that the U.S. Fish and Wildlife Service trucking Coleman smolts “leads to a 98% stray rate and collapses of the stock 3 years later.”
“The 5 million fish raised and transferred won’t contribute back to Sacramento main stem salmon,” said Stone. “This is where the Chinook salmon population collapse is happening. Trucking Coleman fish in the 2014/2015 years led to the lowest return to Coleman and the Sacramento main stem in the history of the river — why can’t we learn from our mistakes?”
