Scientists are finding it increasingly difficult to predict how ecosystems will respond to sudden and rapid changes such as extreme droughts, wildfires, and flooding.

Scientists are finding it increasingly difficult to predict how ecosystems will respond to sudden and rapid changes such as extreme droughts, wildfires, and flooding.

Writing in the June 2021 issue of San Francisco Estuary & Watershed Science, a group led by environmental economist Richard Norgaard note that due to the increasing pace of ecological change associated with a warming world, models derived using past data are less able to provide reliable predictions, particularly as extreme events create conditions outside historic reference points. This has global implications for environmental management, but the authors—many of whom have served on the Delta Independent Science Board—center their focus on...
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When it comes to managing Delta salinity, a new research paper suggests we treat public policy like a science experiment.

As anthropogenic factors like salt accumulation through irrigation and freshwater storage combine with drought and sea-level rise, the Delta is headed for a saltier future. The June 2021 paper, published in San Francisco Estuary and Watershed Science, integrates biological and physical sciences to draw a comprehensive picture of Delta salinity and changing freshwater inflow. Changing salinity patterns could have a profound impact on the region’s ecology, affecting how and when fish like the Delta smelt or Coho salmon spawn, and which aquatic plants...
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Smelt cam photo

Monitoring Delta smelt with an underwater camera could be safer and more effective than with a traditional trawl.

Standard smelt surveys rely on the use of boat-driven nets, which trap fish by funneling them from the wide mouth of the net to the closed end (known as the cod end). To check their catch, researchers must pull the net and its contents from the water. But this additional handling can harm and even kill the same fish that wildlife agencies are trying to save with the support of robust, long-running monitoring efforts. There may be a better way:...
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photograph of beautiful tree overhangin a river

Modern water management practices damp down natural river patterns and produce streamside forests that “live fast and die young.”

Such practices also hasten the destruction of an important and dwindling habitat. Melissa Rohde of the State University of New York College of Environmental Science and Forestry (SUNY-ESF) and colleagues analyzed five years of high-resolution satellite and water resource data showing vegetation greenness along California rivers. Trees growing alongside the 30 percent of state rivers with natural flows decreased in greenness from the wet spring through the dry summer months, the scientists report in the Proceedings of the National Academy...
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Leading with Science: DWR’s Ted Sommer To Retire

A few months before his retirement in October 2021, Ariel Rubissow Okamoto asked Ted Sommer, lead scientist for the California Department of Water Resources, to reflect on his accomplishments and hopes for the future. Sommer is a leading researcher on native fishes, and has published more than 60 research articles in peer-reviewed scientific publications since 2001. Sommer began his long career at DWR in 1991 under Dr. Randy Brown. Early on he founded the Feather River fish monitoring program, but his...
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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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The robust monitoring programs established to track now-rare Delta smelt could benefit other native fishes, too.

Decades ago, resource managers first learned of declining Delta smelt numbers not through surveys targeting the once-abundant native fish, but rather as a byproduct of long-term monitoring programs for non-native striped bass. Now, the authors of a new study published in the March 2021 issue of San Francisco Estuary and Watershed Science advocate for the use of bycatch data from the recently established Enhanced Delta Smelt Monitoring (EDSM) program to better understand juvenile Chinook salmon distribution. “The scope of [this...
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New insights into Delta smelt swimming behavior could help locate the increasingly elusive fish and prevent losses at the pumps.

Scientists know that smelt use tidal ebbs and flows to migrate landward to spawn, but the degree to which external cues influence behavior remains unclear. In a new study published in the March 2021 issue of San Francisco Estuary and Watershed Science, researchers used computer modeling to predict smelt distribution based on hypothesized swimming behaviors. Six increasingly complex behaviors were tested. For example, the “passive” category assumes that smelt do not swim at all, simply drifting with currents and tides....
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Water turbidity in the Sacramento-San Joaquin Delta can be used as a reliable indicator of smelt entrainment rates in the fish screens of the export pumps at the southern edge of the Estuary.

In a new study published in the March 2021 issue of San Francisco Estuary and Watershed Science, researchers Lenny Grimaldo, William Smith, and Matthew Nobriga used advanced statistical approaches to understand what factors best predict Delta smelt entrainment at the pumps. The paper builds upon research that Grimaldo conducted in the 2000s, which provided the basis for regulations established in the 2008 Delta smelt Biological Opinion. “This study reinforces previous work that adult Delta smelt salvage is largely explained by...
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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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Science-in-Short ~ Podcast

Drift, Drop or Floc? Tailing Sediment as it Moves Through Marsh Margins This June two USGS scientists will be trying to get as close as they can to the edge of the South Bay’s Whale’s Tail Marsh to lay out their tools: tiles, filter paper, current profilers, and other sediment accretion measuring instruments. Estuary Reporter Ariel Rubissow Okamoto interviews reseachers Jessie Lacy and Karen Thorne about what they’re looking for at the marsh edge, and how it may help us...
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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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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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Scientists Nail Climate Links to Extreme Events

While a supermajority of Americans finally believe we are warming the world, a 2020 Yale Climate Opinion survey shows that most people still aren’t very worried about it. “Climate change is abstract to them,” says UCLA climate scientist Daniel Swain. “They don’t connect it to their personal lives.” But Californians do. Reeling from a decade of record-shattering drought, heat waves, and wildfires, people in the Golden State overwhelmingly tell Public Policy Institute of California pollsters that the effects of global...
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Sub-Standard Snow

At a glance, the recent winter storms and inches of snow in the Sierra seem like a reassuring sign: more snow means more snow melt, which means more water moving through our freshwater systems during dry summer months. But it turns out that there are different types of snow with differing levels of moisture locked up inside — and the latest Sierra snowfall appears to be holding less water than usual. This means the Bay’s streams and estuaries could have...
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Sediment Paparazzi

As the Estuary faces drowning marshes due to rising seas, people want to see action – acres saved, walls built, marsh mice whisked to safety after crawling to the tip of the tallest gumplant. In terms of action, “sediment monitoring” doesn’t come immediately to mind. Monitoring is something you do after all the action is over, isn’t it? And as for “sediment,” well what’s all the fuss over some dirt and mud? In fact, there is quite a fuss. The...
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North America’s largest and most ancient freshwater fish species, white sturgeon, hang out in some kinds of Estuary waterways more than others, scientists find.

 Researchers with the U.S. Geological Survey found that adult and sub-adult white sturgeon occupy deep open-water channels and shallow open-water shoals in equal measure, but don’t use shallow wetland channels. As a group, white sturgeon are characterized as amphidromous, meaning they regularly migrate between freshwater and the sea, in both directions, but not for the purpose of breeding. According to the study, which appears in the December 2020 issue of San Francisco Estuary and Watershed Science, adults in the local...
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