Day

March 1, 2021
01
Mar

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 population use coastal habitats to some degree, but typically remain in the Estuary and lower Sacramento and San Joaquin rivers. There they congregate in deep areas with fine-sediment substrate, and are thought to move into shallow subtidal habitats to feed...
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01
Mar

As agencies wrangle over how best to protect the Delta’s dwindling native fish species, researchers want to see more consideration to the needs of the estuary’s birds.

 “If we want to restore the ecology of the Delta, we can’t just be looking in the water,” says Kristen E. Dybala of Point Blue Conservation Science. In a paper published in San Francisco Estuary and Watershed Science, Dybala and two co-authors make the case that “birds and their habitat needs are often not addressed in science syntheses, conservation planning, and large-scale restoration initiatives in the Delta.” While some birds use the same sloughs and channels that support such high-profile fishes as Chinook salmon and Delta smelt, other bird species rely on habitat types that fringe the Delta’s waterways. Indeed, while general habitat restoration in the Delta can provide multiple benefits for humans, fish and many birds, the authors observe...
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01
Mar

Filling significant recently identified gaps in monitoring spring-run Chinook is critical to protecting these threatened Central Valley salmon.

“There’s no way we can manage them for recovery if we don’t understand the biological processes that govern their dynamics through time and space,” says UC Santa Cruz/NOAA salmon expert Flora Cordoleani, lead author of a study reported in the December 2020 issue of San Francisco Estuary and Watershed Science. Cordoleani and colleagues identified the monitoring gaps while building a model of the spring-run Chinook life cycle. The model accounts for three self-sustaining populations of these at-risk fish, assessing survival of key life stages (eggs, fry, smolts and adults) as well as in key habitats (natal creeks, the Sacramento River, floodplains in the Sutter and Yolo bypasses, the Sacramento-San Joaquin Delta, and San Francisco Bay). “It’s a complex model, and...
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01
Mar

Human activity could undermine the success of efforts to reintroduce sea otters to San Francisco Bay.

 Although past studies have found that the Bay could support 1.5 times the entire current southern sea otter population, a new study from the Estuary & Ocean Science Center at San Francisco State University and published by PeerJ last November indicates that anthropogenic risks like contaminants, vessel traffic, and oil spills may constrain the otter’s ability to gain a foothold. The study, led by Jane Rudebusch, at the time graduate student at SFSU, looked at the types of human stressors present and ranked them according to factors like temporal overlap (frequency of its interaction with otters), intensity (consequence of that interaction), and management effectiveness (how well the stressor is mitigated by human regulation). The study concluded that high-speed vessel traffic,...
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01
Mar

The increasing flow of microplastics entering San Francisco Bay from trash, fleece clothing, car tires, and myriad other sources is likely being trapped by a surprising filter: native eelgrass (Zostera marina).

Miniscule polymer pieces the size of a sesame seed or tinier, microplastics pose a growing pollution threat to marine environments worldwide. To understand how microplastics accumulate in nearshore, urbanized environments, researchers quantified the prevalence of microplastics in and around the Zostera marina meadows of Deerness Sound, in the Orkney Islands of Scotland. Mark Hartl and colleagues at Heriot-Watt University found that microplastic flakes, fibers, and fragments were twice as concentrated in the water above eelgrass meadows as in adjacent control areas of sandy sediments. Sediments within the meadows contained 40% more microplastics than in the sandy areas. The scientists also found plastics attached to every one of the 60 blades of eelgrass they examined; in fact, microplastics were 20% more...
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