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

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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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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Bob Fujimura spent his entire career with the California Department of Fish and Wildlife.

Bob Fujimura spent his entire career with the California Department of Fish and Wildlife. From 1987 until his retirement in late 2018, Fujimura served in a variety of roles at the department—but he is likely best known for heading up its long-term monitoring of native fishes in the Bay and Delta. Beginning in the mid-2000s, he oversaw annual smelt surveys with far-reaching implications for management and conservation, including the Spring Kodiak Trawl, which determines the relative abundance and distribution of...
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Rainer Hoenicke is optimistic about the changes he saw in his five years as the Delta Stewardship Council’s Science Director.

“People are coming to the table and realizing we need to be anticipating and forecasting how to adapt,” he says. Prior to joining the Science Program, Hoenicke served for nearly a decade as deputy and executive director of the San Francisco Estuary Institute, where he managed two Boards of Directors and reorganized the Institute’s program areas. “I felt challenged to do something different,” he says of the move, “since the Delta is much more controversial territory.” In Hoenicke’s eyes, the...
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A new system for treating agricultural drainage water in the Delta could also help rebuild subsided islands.

The approach—known as a Chemically Enhanced Treatment Wetland—combines chemical treatment with natural wetland processes; researchers tested it on Twitchell Island, which features corn and rice crops, as well as wetlands. They dosed agricultural ditch water with dissolved organic material (DOM), then treated it with a coagulant to precipitate the DOM, forming flocculant. The resulting water then passed though treatment wetlands, where the flocculant settled and blended with plant detritus in the sediment. The study, reported in the September 2019 San...
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Manmade features in the Delta, including riprap-armored banks, water diversion pipes, pilings, and woody debris, may be sending juvenile native fishes into the jaws of finned invaders.

“We know from a decade of doing survival studies that migrating juvenile salmon are dropping out of the system pretty much everywhere in the Delta,” says UC Santa Cruz fisheries biologist Brendan Lehman. “Physical habitat features are potentially aggregating predators and prey in ways detrimental to salmon smolts and steelhead.” The scientists report in the December 2019 San Francisco Estuary and Watershed Science that artificial light and submerged aquatic vegetation pose the most severe and widespread risks to native fishes....
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Levels of pyrethroid insecticides spike sharply in the North Delta’s Cache Slough during winter rainstorms, rendering the water so toxic that it decimates laboratory populations of a half-inch crustacean called Hyalella azteca.

However, according to a study reported in the September 2019 San Francisco Estuary and Watershed Science, Hyalella collected in the wild from Cache Slough are resistant to pyrethroids. Genetic analysis revealed that, collectively, Hyalella in the slough have four mutations for pyrethroid resistance. They also have a fifth mutation for resistance to organophosphates and likely carbamates, two additional major classes of pesticides that are applied extensively on agricultural and urban lands. “Hyalella are special,” explains co-author Helen Poynton, a molecular...
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Researchers hope new computer models will help clarify the effects of entrainment on the population of endangered Delta smelt.

Entrainment at the South Delta pumps of the State Water Project and the Central Valley Project has been a concern for years, but disentangling its impact on the dwindling smelt population from those of other environmental and water management factors isn’t easy, and operational differences between the SWP and CVP facilities complicate analysis. Now, US Fish and Wildlife Service statistician Will Smith has developed computer models for entrainment effects on different smelt life stages, part of a larger Delta Smelt...
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While the acreage of wetland restoration projects is growing throughout the Delta, scientists are still working to understand how best to help these areas become fully functioning, complex habitat as quickly and successfully as possible.

A study published in September’s San Francisco Estuary and Watershed Science shed light on some essential questions about what triggers seed generation in wetland habitat. “Wetland restoration practices can be enhanced by a solid understanding of basic plant life history and species ecology,” says co-author Taylor Sloey of Yale-NUS College in Singapore. The researchers looked at three questions: what seeds are present in the seed bank (the viable seeds that accumulate naturally in the soil), and how exposure to cold...
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An emergency barrier installed to protect the state’s water supply from saltwater intrusion during the recent record-setting drought had little effect on the ecosystem.

In spring 2015 the California Department of Water Resources dropped 150,000 tons of rock into False River in the Central Delta to halt encroaching tides that had little freshwater to hold them back. A few months later, it was clear the barrier worked, as salinity rose on one side and fell on the other. But what were the effects on local plants and animals? Through six overlapping yet distinct projects funded by the state Delta Science Program and NASA, and...
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Flows and Ecosystem Function Dominate Delta Plan Amendment

With the Delta lagging behind the Bay on four of the State of the Estuary Report’s five indicators, the last long-range plan for restoring its ecological health abandoned, and the threats from climate change becoming ever more alarming, the need for a new regulatory vision for the region may never have been greater. A pending amendment to the Delta Plan, shared by Ron Melcer at the State of the Estuary Conference as part of a policy update session, is meant...
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Drones Pilot Vegetation Mapping

By Michael Hunter Adamson In the world of conservation, as attested to by multiple speakers at a late summer UC Davis event, drones, or UAVs (unmanned aerial vehicles) may be the vehicle of choice for mapping the future of invasive plant management in the Delta. The California Department of Water Resources began using UAVs in earnest after the Oroville dam failure in the winter of 2017, when drones offered visuals no one could get near on the ground. The Blacklock...
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Invasive clams and freshwater exports from the Delta have created dramatic and unsustainable changes in the San Francisco Estuary’s foodweb over the past 50 years.

 A study by UC Davis researchers found a 97% decline in phytoplankton, the microscopic foundation of the food chain. “Understanding the causes for the decline in the pelagic [water column] community is essential so that efficient solutions can be implemented,” says Bruce Hammock, a research scientist at the UC Davis School of Veterinary Medicine’s Aquatic Health Program. The invasive clams (Potamocorbula amurensis), originally from Asia, have been over-consuming phytoplankton and zooplankton for more than 30 years, and have long been...
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Brinkmanship for Frail Smelt

By Joe Eaton Delta smelt had a bad year in 2017. Although scientists are still analyzing the data, the message seems to be that strong freshwater flows alone are not sufficient to allow the population to increase. The resulting sense of urgency has led fish biologists to consider how cultured smelt, raised in hatcheries, could be used to supplement the wild population. “We’ve considered the cultured smelt as a lifeboat,” says California Department of Water Resources biologist Ted Sommer. “Now...
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Sandhill crane

Wildlife and Way of Life in the North Delta?

Californians ask a lot of the Sacramento-San Joaquin River Delta, where the state’s longest rivers meet and deliver snowmelt from the mountains. Water suppliers want to reconfigure the Delta’s plumbing via the ever-contentious Water Fix project, which Governor Gavin Newsom just sent back to the drawing board. State wildlife officials want to boost restoration in the region, and the 2019 Delta Conservation Framework outlines their latest plan. And people in the Delta want to live and farm there as they...
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Joaquin Esquivel is impatient with the narrative that has dominated California water policy for decades, especially when it comes to the Delta and the eternal tug-of-war between farms, cities and the environment.

“For so long in the water space you’ve had these false dichotomies where you are being told you have to choose one or the other,” says Esquivel, who Governor Gavin Newsom appointed Chair of the State Water Resources Control Board in February. “These narratives can fuel themselves, they take root in communities, but they don’t really do much to get to the heart of the policy question.” A native of the Coachella Valley, Esquivel served on the State Board for...
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Susan Tatayon wants to bridge the emerging communication gap between Delta science and policy.

While Tatayon, who was installed as Chair of the Delta Stewardship Council in January, sees good communication efforts on the part of council scientists and staff, not everyone on the receiving end gets their drift. “What I’m learning from some council members and others is that they don’t understand the connection between the science being done and the policies they want to make.” Tatayon assumes her new position after a career that includes stints at The Nature Conservancy, the U.S....
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Kris Tjernell thinks there could hardly be more a more exciting time to be leading conservation and water management programs in the country’s most populous and perhaps most water-stressed state.

“I see opportunities for big change,” says Tjernell, who was appointed California Department of Water Resources’ deputy director last May. At the time the DWR was adopting a new approach toward land and water management—especially the inclusion of floodplain restoration in many of its flood control projects. “We are demanding a lot out of the landscape of the Delta, and we are demanding a lot out of the Central Valley and beyond,” Tjernell says, describing a system of resource allocation...
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Louise Conrad sees the Delta Stewardship Council’s science program, which she now leads, as poised to shift into a new gear – from breaking down the science landscape and building a new foundation for Delta science to actually doing it.

 “With the update of the Delta science plan done, we can now can sink our teeth into some topical issues our scientists can be passionate about, such as aquatic invasive vegetation, microcystis and climate change, for example,” says the former Department of Water Resources (DWR) fish biologist. Conrad grew up in Philadelphia and developed an interest in conservation on summer road trips to western national parks in their family’s Dodge Ram. “My mom sewed us individual seat covers with pockets...
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Choppy Waters for Flow Rules

By Cariad Hayes Thronson The winter kicked off with the State Water Resources Control Board’s December vote to adopt increased flow objectives for the southern Delta. The vote provoked an immediate volley of lawsuits, both from water users and from environmental organizations. The water users claim that the required flows would be an unconstitutional waste, while the environmental groups argue the plan doesn’t go far enough to restore endangered fish populations. Overshadowing the discussions are the vigorous efforts by the...
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