In early October, East Bay Municipal Utility District sent surges of water from the Camanche Reservoir down the Mokelumne River to coax Chinook salmon from the inner bay or the Delta into the river.
The surges, or pulse flows, have been considered successful as nearly four times the salmon are in the river as this time last year.
“It’s definitely up,” said Jose Setka, supervising fisheries and wildlife biologist for EBMUD. “We counted roughly 1,600 past Woodbridge as of Nov. 8.”
Setka said the pulse flows are just one way they are trying to beef up the river’s salmon population.
“Last year was such a bad year, we emptied out the toolbox,” he said.
The salmon population in the Mokelumne River has steadily dwindled in recent years. In 2005, there were an estimated 16,000 salmon in the river.
Besides the pulse flows, EBMUD is working with Nimbus fish hatchery to find Mokelumne salmon and bring their fertilized eggs back to the Mokelumne River hatchery.
Since eggs of unknown origin aren’t allowed to be transferred from one hatchery to another, precautions must be taken to ensure the right eggs are being taken.
Setka said juvenile fish are fitted with a computerized wire tag that identifies where they come from. When the time comes for them to spawn, the fertilized eggs are removed and taken to the appropriate hatchery.
While the pulse flows have helped create a more successful salmon run, Setka said more work needs to be done to make the season ideal.
“Meeting the hatchery’s mitigation goal of 3.4 million fish produced would be ideal,” Setka said. He added that seeing 4,200 salmon run down the river would make the season excellent.
Last year, there were an estimated 400 Chinook salmon in the Mokelumne River. EBMUD won’t give its final estimate until the end of the season in midto late-December. The estimates are done electronically and manually.
He said EBMUD will rely on carcass surveys to finish off their estimates.
Since Woodbridge Dam has been lowered, the cameras at the fish ladders are turned off and they are now unable to track them that way.
The high-stage fish ladder is useful when the lake is high, but when it is low there are no cameras available for the low-stage fish ladders. There used to be one several years ago, but it was damaged and has not yet been replaced. Setka said he and his associates have been seeing a lot of salmon that are two years old. He said it is a good indicator of next year’s run. However, he did not say when people could expect to be able to fish for salmon in the Mokelumne.
While encouraged by the increased numbers in the Mokelumne due to the pulse flows, one local fishing advocate is not going to get too excited until the final tallies come in.
“We’ve been plagued with several years of abysmal runs,” said Bill Jennings, executive director for the California Sportfishing Protection Alliance. “It doesn’t solve the overall problem.”
Jennings said the pulse flows were helpful because releasing slugs of quality water down the river will trigger migrations up it.
“Surprise — you release water and fish come,” he said. “Generally speaking, you provide ample water of sufficient quality and you have fish; something water agencies too frequently fail to acknowledge.”
He believes having a pulse flow was better than not having one, but is still troubled by dwindling salmon numbers and how the population is at risk of not being self-sustaining. He attributes the shrinking population in the region to Camanche Reservoir and Pardee Dam, which were constructed on spawning grounds.
“It’s been a general trend downward since Pardee and Camanche were built,” he said. “You are talking about a remnant of magnificent fisheries that existed before EBMUD started sucking this watershed dry.”