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Pearls in the ocean of information that our reporters didn’t want you to miss
Vulnerable homes and office parks in San Mateo County.
August 6, 2017
Cariad Hayes Thronson

Simultaneous lawsuits filed against 37 fossil fuel companies by Marin and San Mateo Counties, along with the City of Imperial Beach, over sea level rise may open new front in climate battle.

The suits, filed in California Superior Court, seek compensatory and punitive damages and other remedies for the ongoing harm that oil, gas and coal cause by contributing to global warming and sea level rise. A 2009 Pacific Institute study calculated that San Mateo has more property and people at risk from sea level rise than any California county, while in Marin more than 12,000 homes, businesses and institutions, with an assessed value of $16 billion could be at risk from tides and surge flooding by the end of the century. The suits claim that the companies have known about the dangers posed by greenhouse gases for nearly fifty years and sought to conceal them from the public and encourage the use of fossil fuels while protecting the companies’ own assets and developing plans to profit from a warmer world. According to some legal experts, the suits may succeed where other efforts to hold fossil fuel companies accountable for climate change damage have failed, thanks to advances in climate science and recent revelations about what the companies knew about global warming and when they knew it. CHT

Man’s best friend is being enlisted in efforts to detect the soil-born pathogen responsible for sudden oak death and other rapidly spreading plant and tree diseases.

Phytophthora is difficult to detect in nurseries, plant materials, and planting sites until it has done its damage. To develop early-detection options, H.T. Harvey and Associates are training a female cattle dog/border collie mix named Bolt to sniff out Phytophthora. Part of the Harvey Dog ecological-scent detection program, Bolt has accurately identified four species of Phytophthora in the lab. If her training in a natural setting is successful, Bolt could get to work helping minimize the spread of Phytophthora. Potential beneficiaries would likely include those working to re-oak the parks, open spaces, and backyards of Silicon Valley to improve habitat for native plants and animals.  KMW

Photo: H.T. Harvey

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 resource managers the difficult task of designing flows intended to help salmon without clear guidance on flow targets,” write the authors, led by Cyril Michel of the Institute of Marine Sciences at UC Santa Cruz. Studying migrating Chinook salmon smolts under a wide range of hydrologic conditions, they found that fewer than three percent of fish carrying acoustic tags were detected after release at flows weaker than about 4,260 cubic feet per second. However, survival jumped to 19 percent at flows ranging between 4,260 and 10,700 cfs; they jumped again to more than 50 percent when the river was carrying between 10,700 and 22,870 cfs. However, fish survival did not improve at even greater flows. “It looks like survival plateaus beyond a...
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 support long-term conservation planning. Electrofishing, or e-fishing as it’s sometimes known, uses a generator aboard a small boat to pass electricity through the water beneath and in front of the boat. “When the electricity moves through the water, it can immobilize the fish within the zone of being shocked,” says McKenzie. “It’s a really cool method. You’re looking down at the water, and then all of a sudden fish pop out of the water.” Briefly incapacitated, fish are collected via dip net and placed into a holding tank, where they come to their senses within a minute or so and can be identified, measured, and otherwise studied before being returned to the water. Electrofishing has been used intermittently by various...
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 multi-million dollar Delta smelt survey] has not really been seen before in the Estuary,” says lead author Brian Mahardja, a biologist with the US Bureau of Reclamation, “that’s why there was a call to see what else we can gain out of this program.” The study team, also representing the US Fish and Wildlife Service and the California Department of Water Resources, analyzed juvenile Chinook salmon bycatch data collected through the EDSM to assess its potential to augment data obtained through other fish surveys. They found that some under-sampled regions of the Delta see improved coverage through EDSM, and that the program’s boat-based, labor-intensive random sampling technique “can provide more statistically robust abundance estimates relative to traditional methods.” That said,...
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. At the other end of the spectrum, the smelt respond to both turbidity and salinity cues. After assigning a behavior to simulated smelt distributed across the Delta, researchers ran a 133-day simulation of water year 2002, then compared the modeled movements with observations from the 2002 Spring Kodiak Trawl Survey. The movement models that most closely matched distributions indicated by the survey data were those that incorporated some form of salinity response triggering migration (either overall salinity in the surrounding water or the rate of salinity increase). The study acknowledges that further refinements are needed to assess the influence of turbidity on smelt movement, due to the challenge of accurately predicting what is essentially a localized, constantly changing effect. In...
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 hydrodynamics, water clarity (turbidity), precipitation, and sub-adult abundance,” the authors write. Historically, when large numbers of smelt began to appear in the salvage screens of the Delta pumps, pumping would be curtailed. Today, Grimaldo says, the fish are so rare that it is almost impossible to rely on salvaged fish as indicators of total entrainment losses. “But we found that turbidity can be used as an important factor to help manage real-time entrainment losses,” he says. The theory behind this, he explains, is that when the water becomes turbid, the fish—which prefer murky water to clear—migrate upstream and into the pumps. The new findings will help resource agencies better manage Delta exports to help protect the rapidly vanishing species.
moss ball oregon USFWS
Almost two months after invasive zebra mussels were discovered in imported “moss balls” (actually algae) in a Seattle PetCo store, federal and state agencies are still trying to track the Trojan moss balls and keep the mussels out of vulnerable water bodies, including California’s. So far, contaminated moss balls have been found in 46 states (Virginia, Delaware, Rhode Island, and Hawaii are the exceptions) and most of Canada’s provinces. The US Fish & Wildlife Service has issued detailed guidance for getting rid of the moss balls, summarized as “Destroy, Dispose, Drain,” and the Pet Industry Joint Advisory Council has followed suit.  The Animal and Plant Health Inspection Service (APHIS), Customs and Border Protection, and the US Geological Survey are also involved. Authorities have identified multiple moss ball importers in seven states, some of them in California.  Some importers get their stock from Ukraine, a known source of both moss and mussels.  Meanwhile, another worrisome invader, the Mediterranean marine alga Caulerpa prolifera, recently turned up in Newport Bay, reinforcing the need for vigilant early detection work. A related species, C. taxifolia, appeared in Southern California earlier, but a multi-agency effort eradicated it in 2006. How to Dispose of Mussels and Moss Balls,...
northern harrier-hull lab-UC Davis
Northern harriers, long-winged rodent-hunting hawks, make impressive migrant journeys. Research by UC Davis’ Hull Lab sheds new light on these journeys. Harriers are a familiar sight in California’s wetlands, especially in winter. Researchers captured fifteen female harriers–ten in winter, five in spring–in Suisun Marsh and equipped with 14-gram GPS backpack transmitters, too heavy for use with the smaller males. Telemetry data from seven of the ten winter females revealed migrations of up to 600 miles, to nesting sites from the San Joaquin Valley to Washington State and Idaho.  The eighth, nicknamed Blanca for her pale yellow eyes, flew through British Columbia and Alaska all the way to the Arctic tundra, a 7,000-mile round trip that set a distance record for her species. She and her fellow travelers used wildlife refuge wetlands as stopovers. The five spring-caught females stayed closer to Suisun. Lead researcher Joshua Hull plans to use newly available 10-gram transmitters to track male harriers.  The project will help wildlife managers better understand the habitat needs of this raptor, a California Species of Special Concern whose numbers in Suisun Marsh and elsewhere have declined.  Read More Hull Lab Harrier News Plus Three Great Migration Stories by Joe Eaton. 
sunset delta climate map
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.
pesticide resistance delta map
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.

REBALANCING THE BAY

Former Chronicle reporter Jane Kay spent a year exploring the San Francisco Bay’s 1,000-mile shoreline, focusing on efforts to restore the balance of the bay she loves. She reports that the rising seas and intensified storm surges of climate change may be mitigated by natural buffers, including tidal marsh from reclaimed hayfields and commercial salt ponds as well as restored eelgrass and oyster reefs in subtidal zones. Kay also highlights the ecological role of freshwater flowing though Delta, which benefits species in the Estuary and helps flush treated sewage out of the South Bay. Her story was posted by National Geographic on June 13, 2017. Photo by Ariel Okamoto.

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