New research indicates that survival of juvenile Chinook salmon in the Sacramento River system can be significantly boosted by achieving key thresholds for river flow.

New research indicates that survival of juvenile Chinook salmon in the Sacramento River system can be significantly boosted by achieving key thresholds for river flow.

The findings, published in the journal Ecosphere, add important context to the general scientific understanding that more water in the river improves fish survival. Previous studies, the authors explain in their paper, have demonstrated that more juvenile salmon migrating toward the sea complete their journey when the Sacramento River system contains more water. Just how much water has been the source of much controversy among user groups. “These studies have not explored the potential nonlinearities between flow and survival, giving...
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Electrofishing is a powerful but underutilized tool for monitoring Delta fish, particularly species favoring “structured” habitats that are difficult to sample using more common methods like trawls and seines.

By analyzing fish catch data from past surveys, researchers Ryan McKenzie, of the US Fish and Wildlife Service, and Brian Mahardja, of the US Bureau of Reclamation, determined that electrofishing resulted in better detection rates for many native and non-native species than net-based surveys. Although electrofishing is currently restricted to freshwater areas of the Estuary and is more selective of larger fish and those with swim bladders, McKenzie and Mahardja recommend that resource managers employ the technique more widely to...
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sunset delta climate map

MEGA-PEARLS Part 4-Climate, Bay-Delta Science Conference, April 2021

A Stream of Science Takeaways. ESTUARY News sent reporters to the biennial Bay-Delta Science Conference in September. This special edition of Pearls shares more than 20 takeaways.
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pesticide resistance delta map

MEGA-PEARLS Part 3-HABs & More, Bay-Delta Science Conference, April 2021

A Stream of Science Takeaways. ESTUARY News sent reporters to the biennial Bay-Delta Science Conference in September. This special edition of Pearls shares more than 20 takeaways.
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photo of salmon injection USFWS

MEGA-PEARLS Part 2-Fish-Birds, Bay-Delta Science Conference, April 2021

A Stream of Science Takeaways. ESTUARY News sent reporters to the biennial Bay-Delta Science Conference in September. This special edition of Pearls shares more than 20 takeaways.
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Above: Lewis holding white sturgeon in Delta. Photo: Jim Ervin

MEGA-PEARLS-Part 1-Diversity, April 2021

A Stream of Science Takeaways. ESTUARY News sent reporters to the biennial Bay-Delta Science Conference in September. This special edition of Pearls shares more than 20 takeaways.
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Delta Study Predicts Stronger Floods and Less Water Supply

Though most don’t realize it, practically all Californians are linked to the Bay-Delta region via its triple function as a source of drinking water for some 27 million Californians, a critical water provider for the Golden State’s hefty agricultural industry, and a rich and unique ecosystem. But for those who live in the legal Delta zone – some 630,000 people – the braided weave of the Sacramento and San Joaquin Rivers and their maze of associated wetlands and levees provides...
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Dutch Slough Laboratory

For a hawk’s-eye view of one of the Estuary’s most ambitious restoration efforts, visit the Dutch Slough Tidal Marsh Habitat Restoration Project’s YouTube channel. Drone-shot footage shows what the Department of Water Resources has been doing on 1,200 acres of former wetland, converted to pasture and subsided up to 15 feet, in the West Delta between Big Break and Jersey Island. After moving millions of cubic yards of soil to elevate the marsh plain, a team of engineers, scientists, and...
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As agencies wrangle over how best to protect the Delta’s dwindling native fish species, researchers want to see more consideration to the needs of the estuary’s birds.

 “If we want to restore the ecology of the Delta, we can’t just be looking in the water,” says Kristen E. Dybala of Point Blue Conservation Science. In a paper published in San Francisco Estuary and Watershed Science, Dybala and two co-authors make the case that “birds and their habitat needs are often not addressed in science syntheses, conservation planning, and large-scale restoration initiatives in the Delta.” While some birds use the same sloughs and channels that support such high-profile...
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Filling significant recently identified gaps in monitoring spring-run Chinook is critical to protecting these threatened Central Valley salmon.

“There’s no way we can manage them for recovery if we don’t understand the biological processes that govern their dynamics through time and space,” says UC Santa Cruz/NOAA salmon expert Flora Cordoleani, lead author of a study reported in the December 2020 issue of San Francisco Estuary and Watershed Science. Cordoleani and colleagues identified the monitoring gaps while building a model of the spring-run Chinook life cycle. The model accounts for three self-sustaining populations of these at-risk fish, assessing survival...
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Current estimates of young salmon lost to the south Delta pumps are based on a smattering of studies from the 1970s and should be updated, according to a new analysis.

“They don’t represent current operations,” says Ukiah-based consultant Andrew Jahn, lead author of the analysis reported in the September 2020 issue of San Francisco Estuary and Watershed Science. Current operations at the State Water Project (SWP) and the Central Valley Project (CVP) can reverse flows in the Old and Middle rivers, diverting salmon on their way to the ocean towards the projects. Existing salmon loss estimates also fail to account for a likely Old River hotspot for predators, drawn to the...
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Science in Short ~ Podcast

David Ayers: How Fish Interact with Wetlands Topography  In this podcast, Estuary News reporter Alastair Bland and UC Davis PhD student and fish researcher David Ayers discuss the Sacramento-San Joaquin Delta, its fish, its marshlands, its flows, and its future. Ayers explains the focus of his research, which seeks to reveal how underwater topography in the wetlands fringing the estuary affects interactions between predators and small fish. While restoration projects often focus on adding more water to this ecosystem and...
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Londons Roam and Feast on the Bay circa 1910

Jack London usually sailed west whenever he left the Oakland Municipal Wharf, but on December 18, 1913, he headed east — because he could. Although the canal connecting the Oakland Estuary to San Leandro Bay had been completed in 1902, it wasn’t until the U.S. Army Corps of Engineers widened and deepened the canal in 1913 that it became navigable. Aboard the Roamer, a 30-foot yawl London bought used in 1910, Jack and his wife, Charmian, approached the Park Street...
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The Delta’s Blooming Problem

Bright-green blotches of algae have been popping up all over the Delta since early summer, from Discovery Bay to the Stockton waterfront, befouling the air and poisoning the water with toxins that can sicken or even kill humans and animals. Veteran Delta watchers believe that this year’s harmful algal blooms may be the worst ever, and worry that some features of Governor Gavin Newsom’s recently released Water Resilience Portfolio for California will aggravate the problem. “We don’t have enough data...
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wetland landscape photo

Better scientific preparation could help Delta water and environmental managers respond to droughts more effectively.

That’s one key takeaway from a review of environmental management and the use of science during the 2012-2016 drought commissioned by the Delta Science Program and published in the June 2020 issue of San Francisco Estuary and Watershed Science. “There are lots of mysteries about how to manage water to benefit species, agriculture, upstream and downstream users. I think science is going to be the best solution,” says lead author John Durand of UC Davis’ Center for Watershed Science. Durand...
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More than half the water diverted from Central Valley rivers is used to irrigate cattle-feed crops, implicating beef and dairy as top drivers of recent fish declines.

Recent findings, published in Nature Sustainability in March, strengthen the environmental arguments for going vegan while rewriting the familiar narrative that almonds and other high-value tree crops are the top hogs of Central Valley water resources. The study’s authors, led by Brian Richter of Virginia-based Sustainable Waters, focused on the arid West and found that irrigated crops like alfalfa and hay, more than any others, are drying out rivers. The reduced flows are pushing dozens of fish species toward extinction....
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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...
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Sinking Islands Capture Carbon Credits

By Emily Underwood As sea levels rise and land in the Delta sinks, agencies and landowners are recognizing that levees alone will not protect critical fresh water supplies and infrastructure. Encouraged by a recently vetted new method for calculating carbon offsets from wetlands, a flurry of new climate adaptation projects on publicly owned islands strewn along the central Delta corridor aim to defend against sea-level rise, restore habitat, and reduce greenhouse gas emissions. Until recently, the prospect of selling carbon...
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Carbon Goes Deep

By Aleta George Many Yolo County farmers and ranchers are keenly aware of climate shifts and actively involved in GHG reduction strategies. Scott and Karen Stone run Yolo Land & Cattle, a 7,500-acre ranch that lies partly in the Blue Ridge Berryessa Natural Area. The Stones have planted riparian areas and hedgerows for carbon sequestration, use solar water pumps to reduce GHGs, and manage a 400-acre conservation easement for Swainson’s hawk on their irrigated pastureland. In the Capay Valley, Fully...
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Kinky Fish Spines Linked to Selenium

By Joe Eaton Scientists with the U.S. Geological Survey and the National Oceanic and Atmospheric Administration are using new tools to track selenium, with the Sacramento splittail, a California-endemic fish, as an indicator species. Robin Stewart, lead author of a new paper on splittail and selenium, is one of the region’s most seasoned current experts on bioaccumulation of metals in estuarine species. In some sampled splittail, selenium levels exceeded the proposed EPA protective criteria for fish ovaries. Liver levels, not...
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