Salmon
East Bay Municipal Utility District file photo

November 20, 2024 - The East Bay Municipal Utility District (EBMUD) reports the 2024-25 fall run of Chinook salmon currently underway on the Mokelumne River has set a new record for the second year in a row. More than 30,000 fish have been counted to date with hundreds more arriving daily from the Pacific Ocean to spawn. This is the largest salmon return on the Mokelumne since record keeping began in 1940, surpassing the record-setting 2023-24 total count of 28,698 Chinook with several weeks still left to go in this spawning season.

“I’m proud of EBMUD’s decades-long dedication to sustaining the health of the Mokelumne River habitat and investing in fish hatchery operations,” said EBMUD Board President Lesa McIntosh. “This historic salmon run is a testament to our science-driven management, cooperative relationships with neighbors on the river, and our collaboration with local, state and federal partners to enhance spawning grounds, operate our hatchery effectively, and protect vital natural resources.”

The Mokelumne River is the primary drinking water source for over 1.4 million EBMUD customers in Alameda and Contra Costa counties. The not-for-profit public agency is dedicated to balancing customers’ water needs with environmental protection and river stewardship.

EBMUD manages river flows, enhances habitat, and funds the Mokelumne River Hatchery, which is operated in partnership with the California Department of Fish and Wildlife (CDFW). The Mokelumne contributes only about 3 percent of the freshwater flow into the Sacramento-San Joaquin Delta, yet its salmon population makes up as much as 50 percent of the commercial catch off the California coast.

Salmon returns are counted every year during the spawning season, which typically runs from September to January. These Chinook return to their home waters in the Mokelumne to reproduce and die after spending two to five years maturing in the Pacific Ocean. The pattern is a significant stage in the salmon life cycle and a strong indicator of the habitat's ecological health and the population's survival rate. On October 16, 2024, EBMUD biologists recorded the passage of 3,824 migrating fish, the largest one-day salmon count in more than 30 years. Passage is measured as salmon pass through a fish ladder at a small irrigation impoundment owned by Woodbridge Irrigation District.

The statewide closure of California’s 2023 and 2024 commercial and recreational salmon fishing seasons to protect the Central Valley fall-run Chinook population has certainly had a positive impact on the number of fish coming back to freshwater. The commercial and recreational salmon fishing fleet, which funds the production of ocean enhancement fish at the hatchery, forewent both seasons and contributed to this year’s success on the Mokelumne. But similar returns have not been realized elsewhere in the Central Valley. In fact, the Mokelumne hatchery is supporting the Coleman National Fish Hatchery by providing approximately 3 million eggs this spawning season.

The science-driven hatchery management program by EBMUD and CDFW includes operations that support ocean fisheries and natural spawning in the river. Long-term strategies and actions that affect the fishery 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, and with recent funding provided by the California Department of Water Resources under the Healthy Rivers and Landscapes Program Early Implementation actions.
• Flow management, including fall 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 to improve survival to the ocean; and management of the fish ladder leading into the hatchery to support both hatchery and natural spawners.

“We are excited to have another robust salmon return that allows us to support all our hatchery goals, including mitigation, enhancement and climate resilience, as well as meet our in-river spawning targets with enough fish to fill the habitat,” said EBMUD Manager of Fisheries and Wildlife Michelle Workman. “We continue to face the challenge of climate variability with record air temperatures in July and October affecting our cold-water availability strategies. Our investments in chillers for the hatchery enable us to support the Chinook population even when environmental conditions work against us. This year we are fortunate to have enough returning fish to also support Coleman National Fish Hatchery with eggs to help sustain the fishery on the Sacramento River and the broader Central Valley.”

The  has a proud history of providing high-quality drinking water for 1.4 million customers in Alameda and Contra Costa counties. EBMUD’s wastewater system serves 740,000 customers and helps protect the ecosystem of San Francisco Bay. EBMUD is a not-for-profit public agency established in 1923.
Source: EBMUD