Asked to suggest an appropriate future for four Delta islands owned by the Metropolitan Water District, it’s difficult not to want the moon.

subisdence on 4 delta islands map

Asked to suggest an appropriate future for four Delta islands owned by the Metropolitan Water District, it’s difficult not to want the moon.

Why not richer rice fields, more wetlands, better boat launches, extended trails, even eco-tourism? ? A new survey for the Delta Islands Adaptation Project, funded by a Prop 1 Watershed Restoration Grant, wants the public’s opinion on the importance of 10 possible land-use objectives leading to the selection of one of the four islands for improvements. As your blinking cursor hovers over a satellite image of Bouldin, Bacon, Webb, and Holland Tracts, the survey lays out all that the experts...
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chart by Hutton

An examination of 50 years of records reveals an apparent seasonal bias in estimates of freshwater flow from the Delta to the San Francisco Estuary.

The seasonal bias suggests flows were overestimated during the summer months and underestimated during the winter. Estimates of Delta outflow use a measurement called net Delta outflow index (NDOI), which is determined by taking the amount of Delta inflow, from sources such as the Calaveras, Sacramento, and San Joaquin rivers, and subtracting Delta exports, a direct measurement, and net Delta channel depletions. A team led by TetraTech’s Paul Hutton compared NDOI estimates against measured Delta outflow at four points, as...
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diagram of fish net trawl

Fish monitoring surveys in the San Francisco Estuary net different numbers of different fish species depending upon when and how they sample.

According to a new study published in San Francisco Estuary and Watershed Science, even surveys that target the same part of the water column can come up with significantly different catches. The study’s authors analyzed decades worth of data from the California Department of Fish and Wildlife (CDFW) Fall Midwater Trawl, which spans from San Pablo Bay to the upper Delta; CDFW’s San Francisco Bay Study midwater and otter trawls, covering the South Bay to the central Delta; and the...
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field in delta with irrigation

Rain or shine, farmers in California use about the same amount of water every year, while residential water use varies considerably with precipitation.

A research team led by UC San Diego’s John Helly processed 15 years’ worth of water-use data from the state’s Department of Water Resources, reporting in the March 2022 issue of San Francisco Estuary and Watershed Science that while “the annually precipitated water supply in the Bay-Delta” varied by 30%, agricultural water use scarcely changed year to year. “The water management system maintained nearly constant agricultural water use even in periods of intense drought, with year-to-year variation of about 7%,”...
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West Coast Salmonids All Tired Out?

West Coast salmon and steelhead populations have declined steeply in the past century – a plight that biologists have primarily blamed on habitat loss. Dams, for instance, block adult fish’s access to historic spawning grounds, and juvenile survival is impacted by streamside development and water diversions. Now, it turns out, microplastic pollution may be a much bigger factor than anyone knew just several years ago. In 2019, scientists with the San Francisco Estuary Institute and the Los Angeles-based nonprofit 5...
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Will Salmon Simmer Again?

After two critically dry years that coincided with Trump-era rollbacks to environmental protections, some iconic Delta fish are closer than ever to the point of no return. Last fall, for the second year in a row, the fall midwater trawl found zero wild Delta smelt, while a coalition of environmentalists and fishermen is asking a federal court to help prevent a repeat of 2021’s near-obliteration of endangered winter-run Chinook salmon. Their lawsuit is just one of the balls to watch...
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Gone Fishing

As the weekend dawns and California slumbers, the sportfishers descend, like clockwork, on the banks and waves of the San Francisco Bay and Sacramento-San Joaquin Delta. They carry nets for herring or poles for sturgeon, heavy and light tackle, bloodworms or anchovy or any number of delectable morsels to attract the desired target. They tread industrialized East Bay shorelines and marshy Delta banks, hop aboard sporty six-pack boats for more ambitious trips or humbler craft for a leisurely solo excursion....
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Natives Who Can Rough It

Name a native fish. One that spends lots of time in the Delta. One that’s not a salmon, smelt, or sturgeon. One whose population isn’t plummeting, and in fact seems to be doing just fine. By now the list of possibilities has been shortened severely — though not exhausted. A number of native fish still ply Delta waters in stable numbers, but precisely because there are no restoration projects, monitoring programs, or conservation efforts designed to save them — or...
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Let’s Not Forget Suisun Marsh

I started sampling the fishes of Suisun Marsh in 1979 because one of my UC Davis graduate students was looking for a place to study tule perch, a live-bearing native fish. We found not only a lot of tule perch in the marsh, but also an abundance of other native fishes. Clearly, this was a good place to study species for which we had little information at that time. Two things helped with our new project. First, sampling boats could...
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Hatchery Delta Smelt Released to Wild

On a mild day between rainstorms in mid-December, wildlife biologists outfitted in rubber boots and orange lifejackets load drum after drum of precious cargo onto a small boat docked in Rio Vista, a town on the Sacramento River in the Sacramento-San Joaquin Delta. There is little fanfare but the occasion is nonetheless momentous. The shiny silver drums contain thousands of Delta smelt — finger-size imperiled fish unique to the Delta — that were raised in a conservation hatchery. Today marks...
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Sturdy Sturgeon

A 90-year-old Australian lungfish at San Francisco’s Academy of Sciences has received a lot of press lately, but there is a wild fish species living in the San Francisco Bay that has the potential to live that long or longer — or so we think. While one white sturgeon caught in the Columbia River Basin was estimated to be 104 years old, the life expectancy of white sturgeon, Acipenser transmontanus, which includes the Central Valley population endemic to the San...
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Scientists in the Central Valley are honing a novel way of giving young salmon the nourishing benefits of wintertime floodwaters without undertaking costly floodplain restoration work.

The method, being practiced along the Sacramento River, mimics the flood patterns of natural Sacramento Valley wetlands by diverting water onto floodplain farm fields, retaining it there for three weeks, and finally flushing the water—now rich with zooplankton and invertebrate protein—back into the river. Onsite studies have shown that salmon smolts grow faster when provided with this supplemental nutrition source, giving the method promise as a tool for boosting survival rates of outmigrating juveniles and, ultimately, helping sustain imperiled Chinook...
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Hot off the press, Sacramento County Breeding Birds: A Tale of Two Atlases and Three Decades of Change raises red flags for some of the county’s wetland species.

Breeding bird atlases use field observations to record possible, probable, or confirmed nesting in uniform-sized blocks within a county or state. Biologist/artist Tim Manolis led a Sacramento County atlas project in 1988-93, but the results were never published. When Edward Pandolfino of Western Field Ornithologists heard about it he suggested repeating the effort and packaging the two data sets together. The second Sacramento atlas, covering 2016-20, followed the lead of recent state atlases in the eastern US in using data...
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A large pulse of water sent through the Yolo Bypass in summer 2016 boosted phytoplankton biomass and food web conditions in Cache Slough and the lower Sacramento River, a new report confirms.

 “Our goal was to improve estuarine habitat by increasing net flows through the Cache Slough Complex to enhance downstream transport of lower trophic-level resources, an important driver for fish such as the endangered Delta Smelt,” write the authors—including esteemed (and recently retired) California Department of Water Resources lead scientist Ted Sommer—in the latest issue of San Francisco Estuary and Watershed Science. The pulse occurred over three weeks in July, a time when flows in the region above Cache Slough are...
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New Way to Sleuth Out Fish IDs in the Field

The CRISPR technique used to edit DNA has been formulated into a tool that can distinguish between similar-looking California fish species for conservation research. Called SHERLOCK (Specific High-sensitivity Enzymatic Reporter unLOCKing), the tool can tell the difference between species with speed and accuracy. Better yet, it is both inexpensive and can be run while researchers are in the field. “It puts the power in the hands of the field biologist to make the most informed decision versus waiting sometimes days...
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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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Loss of wetland habitat in the Delta has reduced net primary productivity by 94%, but achieving current restoration goals could restore 12% of this loss.

In a new study published in the September 2021 issue of Science of The Total Environment, researchers modeled net primary production of the Delta under historical and contemporary conditions in order to project the potential benefits of restoration. The loss of net primary productivity—the amount of energy available to pass up the food chain—associated with human modification of the Delta since the early 19th century has reduced the energy available to support biodiversity and ecosystem services. Using the San Francisco Estuary Institute’s Historical...
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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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