SALMON REVIVAL
Drought’s over: Fish returning strong after barge assists, water releases
EAST OF LODI >> Salmon populations in a Central Valley river are on track for record highs after years of suffering through drought, thanks to some clever human intervention.
The new fish-friendly efforts by the state and an East Bay water district may shed light on how to increase California’s struggling salmon runs. Salmon suffered in the drought from 2011 to 2015 due to shriveled river flows, higher water temperatures and disrupted food supplies.
But salmon hatched in the drought three years ago are returning this fall to the Mokelumne River — the water supply for the East Bay Municipal Utility District — in big numbers.
“The salmon are doing great on the Mokelumne River fall run, while it’s a mixed bag at the hatcheries
“The fish are jumping and doing somersaults to get into the hatchery this fall. You see hundreds churning the water.” — Tracie Morales, an EBMUD spokeswoman
on other rivers,” said Peter Tira, a spokesman for the California Department of Fish and Wildlife. “They are doing some innovative things at the hatchery, and it seems to be paying off.”
East Bay water officials said they believe a combination of new measures are producing more fish for the Mokelumne River’s fall salmon run, which supplies an estimated 10 to 15
percent of the California salmon caught in the ocean.
“The fish are jumping and doing somersaults to get into the hatchery this fall. You see hundreds churning the water,” Tracie Morales, an EBMUD spokeswoman, said of the hatchery at Camanche Reservoir
The healthier the salmon runs, the less chance environmental regulators will order EBMUD to give up more drinking water to protect fish — a common fear among California water suppliers.
More than 15,200 adult salmon have swum into the Upper Mokelumne River since early October, on pace to break an all-time record of 18,000 returning adults in 2011, the water district reported. The run may last weeks longer.
To help baby salmon, the water district and its partners have transported many hatchery fish by barge to San Francisco Bay in three of the last four years. This intervention gets the young fish past the predators, confusing flows and fish-chomping water pumps in the Sacramento-San Joaquin River Delta, the major confluence of California rivers.
“The big challenge for these young fish is getting past the Delta,” said Jose Setka, EBMUD’s manager of fisheries and wildlife. “They get a ride on a barge with circulating water. The results of the tests are very encouraging.”
Some state hatcheries shipped fish by barge past the Delta during the drought, but none are doing it this year, Tira said.
In the past few years, EBMUD has released more extra water from its dams into the Mokelumne in early fall in pulse flows to attract returning salmon to their home river rather than straying to rivers elsewhere.
Cold water from the Mokelumne signals the salmon to come home to spawn before dying as 3-year-old fish. Mokelumne River fish also have benefited from a state water operations change that helps fish from other rivers as well.
The state Department of Water Resources this fall has closed the Delta Cross Channel Gates — a barrier near Walnut Grove — more frequently to steer migrating salmon home instead of getting lost in the Delta. The gates were closed on all weekdays in early fall, opening on weekends to accommodate boaters.
EBMUD and state fishery officials also have worked together to attach coded wire tags to many young fish to track survival rates and the effectiveness of measures to help them.
Changing fish chow also may have helped them survive. In the week before young hatchery fish are released to swim to the ocean, East Bay water and the state switched them to saltier food to prepare them for life in seawater rather than freshwater.
“Making the adjustment to the ocean is very stressful for the fish,” Setka said. “Increasing the salt content in their food kick-starts this process and makes the transition easier.”
And when it trucks some hatchery fish to the Delta, EBMUD has changed up the fish release days to avoid being so predictable that predator fish know when to camp out to gobble up the tasty baby fish.
The salmon relief measures have been planned by the water district in collaboration with the state Department of Fish and Wildlife, which operates the Mokelumne River hatchery, federal regulators and other groups and organizations.
The head of the Golden Gate Salmon Association praised EBMUD and the state operators of the Mokelumne River hatchery for innovation to help salmon.
“The Mokelumne hatchery is leading the way in the 21st century salmon hatchery techniques with higher survival than other salmon hatcheries in the Central Valley,” said John McManus, the association’s executive director.
While the success of the Mokelumne River hatchery is partly due to its location closer to the ocean than other hatcheries, McManus said, “some of it has to do with the progressive hatchery practices, and alertness to lessons learned.”
EBMUD, like many water agencies, was required to build a hatchery to offset the environmental damage caused by its dams flooding or cutting off access to miles of productive spawning gravels in the Sierra foothills.