Tailing a Thrush

Tailing a Thrush

By Joe Eaton Researchers like Point Blue Conservation Science ecologist Tom Gardali have equipped Swainson’s thrushes, weighing just over an ounce, with tiny, one-gram GPS tags. If recovered, the tag shows the thrush’s exact winter destination, information vital to border-crossing conservation efforts. “You only get a few readings,” says Gardali, “and you still need to get the tag back. But GPS goes to a spot on the map. This is Holy Grail stuff.”  Sierra/Cascade thrushes were presumed to migrate to...
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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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High Road or High Water for Wildlife

By Ashleigh Papp While we were cooped up inside waiting out February’s storms, many animals were on the move. Cameras positioned along a creek in the Pacheco Pass wildlife corridor captured footage of animals passing through a culvert under a bridge on SR-152 that crosses Pacheco Creek. “We caught a bobcat on camera walking through the creek,” says Tanya Diamond, researcher with Pathways for Wildlife. “With her ears back and elbow-deep in water, you can tell she’s miserable.” As storms...
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Putah Creek Pipeline for Salmon

By Robin Meadows “The dream is to reestablish a natural run of salmon in Putah Creek,” says UC Davis professor emeritus Peter Moyle. In 1972 Putah creek was a trickle of water between heavy machinery mining gravel for the campus roads. Moyle and others urged the university to cease mining and by the end of the decade the machinery was gone and the administration designated a riparian reserve along the creek on campus. After droughts and an ensuing long legal...
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SOS for Finicky Native

By Lisa Owens Viani In 2016, restoration managers with The Nature Conservancy discovered that western sycamores planted along the Sacramento River had hybridized with the non-native London plane tree. The native sycamore is “kind of a messy tree,” says project manager Ryan Luster. “The branches break off and create cavities that wildlife love to use.” Concerns about the tree’s status first arose in the 1990s when the California Department of Fish and Wildlife found only 17 sycamore stands larger than...
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Estuary’s Question of the Month: What is the weirdest species in the Estuary and why?

A fall flight over the Mexican coast where the Colorado River meets the Sea of Cortez offered me a gut-punching, eye-screwing, visual on the results of impaired flow. The semantics of ‘unimpaired’ and ‘impaired’ flow have laced the language of California water management debates since some engineer invented these politically ‘neutral’ terms long ago. The terms refer to our alteration of freshwater flows from snowmelt and runoff by dams and diversions. But whatever the labels, or whichever estuary you’re referring...
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Pied-billed grebes are providing valuable biocontrol services in the Estuary by consuming red swamp crayfish, an invasive crustacean known to disrupt ecosystems.

Although grebes are primarily fish-eaters (they swallow their own feathers to cushion the sharp bones), this species also consumes significant numbers of crayfish, sometimes detaching the pincers before swallowing the good part. Native to southern swamps and bayous, the red swamp crayfish has been introduced in the Sacramento Valley and San Francisco Delta. According to the US Geological Survey, the species is established at Coyote Hills Regional Park and elsewhere around the Bay. The crayfish preys on the larval stages of...
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A gene tells Chinook salmon whether to return to their native streams to spawn in spring, fall, or sometime in-between, according to new research.

The finding, by UC Davis graduate student Tasha Thompson and colleagues, helps distinguish between spring- and fall-run fish—and could help save spring-run salmon from human-hastened extinction. Fall-run populations enter rivers in autumn and spawn immediately. By contrast, spring-run fish return during peak snowmelt, linger in tributaries through summer, and spawn around the same time as their fall-run brethren. “Spring-run fish are special for a lot of reasons,” Thompson says. Spring-run salmon historically spawned in the upper portion of watersheds, nourishing...
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For the first time ever, an annual fish-counting survey has turned up zero Delta smelt—a dire milestone in Bay Area aquatic biology.

This does not mean the fish is extinct—yet—but it does mean that the Sacramento-San Joaquin Delta ecosystem is in disarray. The species, which lives its entire life in the estuary, is a key ecological indicator—and it was prolific until just a couple of decades ago. According to the California Department of Fish and Wildlife’s Fall Midwater Trawl survey, which provides an annual index on abundance for several fish species in the Delta, the Delta smelt index generally averaged several hundred fish...
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Reflowing the Sierra to the Sea

A fall flight over the Mexican coast where the Colorado River meets the Sea of Cortez offered me a gut-punching, eye-screwing, visual on the results of impaired flow. The semantics of ‘unimpaired’ and ‘impaired’ flow have laced the language of California water management debates since some engineer invented these politically ‘neutral’ terms long ago. The terms refer to our alteration of freshwater flows from snowmelt and runoff by dams and diversions. But whatever the labels, or whichever estuary you’re referring...
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Sleuthing Sturgeon Snags

Local green sturgeon are struggling. The population that spawns in the Sacramento –San Joaquin River Delta was declared federally threatened in 2006. Researchers at UC Davis, which hosts the world’s only green sturgeon rearing program, are now trying to figure out why the fish is in trouble. “If we knew how large they are when they’re moving through each portion of the system, we’d know a lot more about the threats they face at each life state, and where we...
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Hauling Out on Higher Ground

Harbor Seals “have this dual existence,” says Sarah Allen, National Park Service ecologist. “They’re tied to the land physiologically and tied to the bay waters for food and travel.” From rocky islets to tidal marshes, the Bay shoreline offers respite to these native marine mammals. Rocky islets like the Castro Rocks, located near the Richmond-San Rafael Bridge, are particularly important refuges -- but more than half the islets that exist throughout the Bay are likely to be erased by sea-level...
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Shark Hunt Stand Off

In the spring and summer months, anglers armed with heavy line and large hooks drop anchor in the murky, current-torn waters between Alcatraz and the Golden Gate Bridge seeking the elusive, and occasionally gigantic, broadnose sevengill shark. As social-media hype stokes excitement among trophy seekers, some other fisherfolk and conservationists want to see the pursuit ended before it depletes shark numbers. While interest in catching large, breeding-age sevelgills has risen in recent years, it remains unclear whether the population can...
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Incidental findings of a long-term study of brown bear predation on salmon have revealed a hidden link between the fish and forest health.

For 20 years, Tom Quinn, a professor in Aquatic and Fishery Sciences at the University of Washington, waded in southwestern Alaska’s Hansen Creek with his students, counting and measuring sockeye salmon carcasses in the stream. Quinn asked his students to toss the bodies on the north bank of the creek to avoid double counting; over the years, they tossed close to 295 tons of salmon onto the north bank. In 2016, Quinn and his colleagues and students took core samples...
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Floods and droughts can cause pools and riffles—and the bugs that live in them—to become more homogenous.

For years, scientists monitoring water quality in streams and rivers have collected mixed samples of aquatic invertebrates from riffles, pools, and transition zones. But UC Santa Barbara stream ecologist David Herbst and his colleagues recently finished a 15-year study of the benthic life in small streams of the central Sierra that examined pools and riffles separately. They found that during flood and drought events, these habitats and their inhabitants become more uniform. But while floods come and go, droughts can...
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MEGA-PEARLS, Oct 2018

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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Spring-run Salmon Need More Than Simple Answers

Salmon once flourished in California despite huge swings in climate – from mega-droughts to massive floods – that were far more extreme than those today. But then people re-engineered the state’s waterways to meet their own needs. “Complexity is what salmon thrive on, and we’ve been making their habitat simpler and simpler,” says biologist Bruce Herbold.  “We haven’t been playing to their strengths.” Habitat diversity is key to restoring salmon, and the prospects for restoring Central Valley wetlands to benefit...
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Following the Water: Bobcats in Coyote Valley

By Ashleigh Papp From a bird’s eye view, the area between the Santa Cruz and Diablo mountain ranges looks like any typical valley. But the work being done by Tanya Diamond, a wildlife biologist with Pathways for Wildlife, shows that the Coyote Valley offers much more to native wildlife and conservationists than mere open space. With satellite tracking collars and footage captured by hidden cameras, Diamond’s team has confirmed just how much water – Coyote and Fisher Creeks in particular...
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Kitchen Sink Update on Every Last Invader

On multiple fronts, with multiple forces and weapons, California’s battle against invasive aquatic organisms continues. Notoriously, San Francisco Bay is the world’s most invaded estuary. The state’s lakes, rivers, and other freshwater wetlands have their own problematic exotics. Keeping them out, and preventing their spread once established, requires coordination among agencies and levels of government. At best, meshing jurisdictional gears can be a challenge. Legislation pending in Congress could make treating ships’ ballast water to remove invasives yet another source...
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Help may be on the way for critically endangered southern resident killer whales.

NOAA Fisheries and the Washington Department of Fish and Wildlife have partnered to produce a list of the west coast Chinook salmon stocks most important to the whale’s survival. This list comes as a part of a special action plan by NOAA to address the three primary threats to the southern resident killer whales: Chemical contaminants, vessel traffic, and lack of prey. The salmon, themselves endangered, are the preferred food source for the whales, and identifying the salmon runs—which include...
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