Month

July 2020
06
Jul

Sacramento pikeminnow and introduced striped bass in the middle Sacramento River eat a surprisingly similar diet, says a new study in San Francisco Estuary and Watershed Science.

Both species have been implicated in the decline of vulnerable native species in the river, particularly juvenile Chinook salmon, says lead author Dylan Stompe, a PhD student and researcher at the University of California at Davis. For eight months in 2017, Stompe and fellow researchers with the California State University at Chico and the California Department of Fish and Wildlife surveyed a 35 kilometer reach of the river outside Chico for the two predatory fish. They baited hooks with with sardines, worms, and chicken liver and fished from an anchored boat. When they brought a pikeminnow or striped bass on board, the researchers performed a gastric lavage, in which pulses of pressurized water are directed into the fish’s esophagus, causing...
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06
Jul

Surface water diversions in California’s Central Valley can be estimated based on readily available climate data, say researchers—a boon to efforts to track groundwater use.

Valley groundwater pumping is calculated as the total water demand minus surface water deliveries. However, today’s water model relies on individually reported diversions across the entire valley, and compiling all these data is a slow process; by the time the numbers are crunched, assessments of groundwater use are already outdated. “It can take years,” says Jordan Goodrich of University of Waikato in New Zealand. “It’s one of the biggest problems we face in tracking the Central Valley water budget.” Overdrafting groundwater can cause subsidence, permanently reducing the storage capacity of aquifers as well as jeopardizing above-ground infrastructure that delivers water and controls flooding. In the March 2020 issue of San Francisco Estuary and Watershed Science, Goodrich and colleagues at Scripps...
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06
Jul

Should the striped bass be a suspect in the decline of the Delta smelt?

Writing in the March issue of San Francisco Estuary and Watershed Science, US Fish and Wildlife Service biologists Matt Nobriga and Will Smith suggest that the smelt’s baseline might have shifted long before anyone was paying attention, and striped bass predation may have constrained its numbers before recent water diversions and food web changes added their effects. The smelt’s historic abundance is unknown; systematic surveys didn’t begin until 1959. But it’s thought to have evolved its boom-and-bust life history in response to predation pressure from native fish or birds. Was the bass, introduced in the late 19th century, one predator too many, or too effective? Nobriga notes that Delta smelt don’t respond predictably to changing flows: “From what we know...
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