scholarly journals Determining the Exposure Pathway and Impacts of Microcystis on Threadfin Shad, Dorosoma petenense , in San Francisco Estuary

2020 ◽  
Vol 39 (4) ◽  
pp. 787-798
Author(s):  
Shawn Acuña ◽  
Dolores Baxa ◽  
Peggy Lehman ◽  
Foo‐Ching Teh ◽  
Dong‐Fang Deng ◽  
...  
Keyword(s):  
San Francisco ◽  
San Francisco Estuary ◽  
Exposure Pathway ◽  
Dorosoma Petenense ◽  
Threadfin Shad

Trophic ecology of two non-native hydrozoan medusae in the upper San Francisco Estuary

2011 ◽  
Vol 62 (8) ◽  
pp. 952 ◽  
Author(s):  
Alpa P. Wintzer ◽  
Mariah H. Meek ◽  
Peter B. Moyle
Keyword(s):  
San Francisco ◽  
Trophic Ecology ◽  
Fish Larvae ◽  
San Francisco Estuary ◽  
Ecological Interactions ◽  
Calanoid Copepods ◽  
Dorosoma Petenense ◽  
Gut Fullness ◽  
Threadfin Shad ◽  
Temporal Overlap

Blooms of some gelatinous zooplankton are increasing worldwide, often disrupting foodwebs. Invasions of non-native jellyfish are a growing problem in many estuaries, including the San Francisco Estuary, where at least two species of Ponto-Caspian hydrozoans, Maeotias marginata Modeer, 1791 and Moerisia sp., are abundant. The present study investigated their trophic ecology, testing the following hypotheses: (1) diets over the bloom and at the diel scale are comprised of a variety of prey items; (2) hydrozoans are generalist feeders; (3) hydrozoans feed on the larvae of declining fish species; and (4) the potential for prey competition exists between the hydrozoans and two declining planktivorous fishes, striped bass (Morone saxatilis) and threadfin shad (Dorosoma petenense). Both hydrozoans ate a variety of crustaceans, most notably calanoid copepods, which were found in greater proportion in the guts than in the environment. The only fish larvae consumed were gobies. Density of Moerisia sp., was negatively correlated with gut fullness for both fishes, and diet overlap was high between shad and hydrozoans, but low for bass. Because of strong spatial and temporal overlap between hydrozoans and shad, competition for zooplankton may be occurring. These hydrozoans have invaded other systems, and should be monitored to assess potential ecological interactions in these locations.

Early Life History of Fishes in the San Francisco Estuary and Watershed

2004 ◽  
Keyword(s):  
San Francisco ◽  
Striped Bass ◽  
Open Water ◽  
Minimum Length ◽  
Ontogenetic Changes ◽  
Delta Smelt ◽  
Diel Cycles ◽  
Dorosoma Petenense ◽  
Threadfin Shad ◽  
Inland Silverside

<em>Abstract.</em>—In July 2000 and 2001, we sampled adjacent screened and unscreened agricultural irrigation diversions in the Sacramento River, California to (1) evaluate the effectiveness of a custom fish screen for excluding four open-water fishes: native delta smelt <em>Hypomesus transpacificus </em>and alien threadfin shad <em>Dorosoma petenense</em>, inland silverside <em>Menidia beryllina</em>, and striped bass <em>Morone saxatilis</em>; and (2) examine factors affecting entrainment of each species. We also compiled trawl and beach seine data from contemporaneous monitoring programs to make inferences about microhabitat use by these fishes and its implications for entrainment vulnerability. The fish screen reduced entrainment of each species by 99% or more and excluded many fish less than 25 mm, the approximate minimum length it was designed to exclude. Tidal and diel influences on entrainment through the unscreened diversion were observed, but diel cycles appeared to be more important, as most entrainment occurred at night or during crepuscular periods. Except for delta smelt, our results suggested that open-water fishes may undergo ontogenetic changes in vulnerability to unscreened irrigation diversions. Fishes entrained during daylight (threadfin shad and striped bass) averaged only 15–16 mm in length. At night, average lengths of entrained threadfin shad and inland silverside were 22–25 mm, even though larvae continued to be entrained. Similarly, a diel influence on striped bass entrainment was observed only in 2000, when individuals larger than 20 mm were consistently collected. No striped bass were collected at sizes greater than 35 mm, even though larger individuals occupied the study area. We found no evidence of size-related changes in delta smelt vulnerability to entrainment, but the monitoring data indicated that delta smelt were abundant offshore, whereas the other three species were most abundant nearshore. We think that low and inconsistent entrainment of delta smelt reflected (1) predominantly offshore habitat use by delta smelt, and (2) the relatively small hydrodynamic influence of the diversion.

Multidecadal trends for three declining fish species: habitat patterns and mechanisms in the San Francisco Estuary, California, USA

2007 ◽  
Vol 64 (4) ◽  
pp. 723-734 ◽  
Author(s):  
Frederick Feyrer ◽  
Matthew L Nobriga ◽  
Ted R Sommer
Keyword(s):  
Water Quality ◽  
San Francisco ◽  
Striped Bass ◽  
Fish Species ◽  
Habitat Suitability ◽  
Specific Conductance ◽  
San Francisco Estuary ◽  
Delta Smelt ◽  
Threadfin Shad

We examined a 36-year record of concurrent midwater trawl and water quality sampling conducted during fall to evaluate habitat trends for three declining fish species in the San Francisco Estuary, California, USA: delta smelt (Hypomesus transpacificus), striped bass (Morone saxatilis), and threadfin shad (Dorosoma petenense). Generalized additive modeling revealed that Secchi depth and specific conductance were important predictors of occurrence for delta smelt and striped bass, while specific conductance and water temperature were important for threadfin shad. Habitat suitability derived from model predictions exhibited significant long-term declines for each species; the southeastern and western regions of the estuary exhibited the most dramatic changes. Declines in habitat suitability were associated with anthropogenic modifications to the ecosystem. For delta smelt, an imperiled annual species endemic to the estuary, the combined effects of fall stock abundance and water quality predicted recruit abundance during recent years of chronically low food supply. Our results are consistent with existing evidence of a long-term decline in carrying capacity for delta smelt and striped bass and demonstrate the utility of long-term data sets for evaluating relationships between fish and their habitat.

scholarly journals Supporting Restoration Decisions through Integration of Tree-Ring and Modeling Data: Reconstructing Flow and Salinity in the San Francisco Estuary over the Past Millennium

Water ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2139
Author(s):  
Paul H. Hutton ◽  
David M. Meko ◽  
Sujoy B. Roy
Keyword(s):  
San Francisco ◽  
Tree Ring ◽  
San Francisco Estuary ◽  
Salinity Intrusion ◽  
Estuarine Ecosystem ◽  
Freshwater Flow ◽  
The Past ◽  
Decadal Scale ◽  
Tree Ring Data ◽  
Past Millennium

This work presents updated reconstructions of watershed runoff to San Francisco Estuary from tree-ring data to AD 903, coupled with models relating runoff to freshwater flow to the estuary and salinity intrusion. We characterize pre-development freshwater flow and salinity conditions in the estuary over the past millennium and compare this characterization with contemporary conditions to better understand the magnitude and seasonality of changes over this time. This work shows that the instrumented flow record spans the range of runoff patterns over the past millennium (averaged over 5, 10, 20 and 100 years), and thus serves as a reasonable basis for planning-level evaluations of historical hydrologic conditions in the estuary. Over annual timescales we show that, although median freshwater flow to the estuary has not changed significantly, it has been more variable over the past century compared to pre-development flow conditions. We further show that the contemporary period is generally associated with greater spring salinity intrusion and lesser summer–fall salinity intrusion relative to the pre-development period. Thus, salinity intrusion in summer and fall months was a common occurrence under pre-development conditions and has been moderated in the contemporary period due to the operations of upstream reservoirs, which were designed to hold winter and spring runoff for release in summer and fall. This work also confirms a dramatic decadal-scale hydrologic shift in the watershed from very wet to very dry conditions during the late 19th and early 20th centuries; while not unprecedented, these shifts have been seen only a few times in the past millennium. This shift resulted in an increase in salinity intrusion in the first three decades of the 20th century, as documented through early records. Population growth and extensive watershed modification during this period exacerbated this underlying hydrologic shift. Putting this shift in the context of other anthropogenic drivers is important in understanding the historical response of the estuary and in setting salinity targets for estuarine restoration. By characterizing the long-term behavior of San Francisco Estuary, this work supports decision-making in the State of California related to flow and salinity management for restoration of the estuarine ecosystem.

scholarly journals Managed Wetlands Can Benefit Juvenile Chinook Salmon in a Tidal Marsh

2021 ◽  
Author(s):  
Nicole M. Aha ◽  
Peter B. Moyle ◽  
Nann A. Fangue ◽  
Andrew L. Rypel ◽  
John R. Durand
Keyword(s):  
San Francisco ◽  
Growth Rates ◽  
Chinook Salmon ◽  
Oncorhynchus Tshawytscha ◽  
Nursery Habitat ◽  
San Francisco Estuary ◽  
Rice Fields ◽  
Fish Growth ◽  
Juvenile Chinook Salmon ◽  
Juvenile Chinook

AbstractLoss of estuarine and coastal habitats worldwide has reduced nursery habitat and function for diverse fishes, including juvenile Chinook salmon (Oncorhynchus tshawytscha). Underutilized off-channel habitats such as flooded rice fields and managed ponds present opportunities for improving rearing conditions and increasing habitat diversity along migratory corridors. While experiments in rice fields have shown enhanced growth rates of juvenile fishes, managed ponds are less studied. To evaluate the potential of these ponds as a nursery habitat, juvenile Chinook salmon (~ 2.8 g, 63 mm FL) were reared in cages in four contrasting locations within Suisun Marsh, a large wetland in the San Francisco Estuary. The locations included a natural tidal slough, a leveed tidal slough, and the inlet and outlet of a tidally muted managed pond established for waterfowl hunting. Fish growth rates differed significantly among locations, with the fastest growth occurring near the outlet in the managed pond. High zooplankton biomass at the managed pond outlet was the best correlate of salmon growth. Water temperatures in the managed pond were also cooler and less variable compared to sloughs, reducing thermal stress. The stress of low dissolved oxygen concentrations within the managed pond was likely mediated by high concentrations of zooplankton and favorable temperatures. Our findings suggest that muted tidal habitats in the San Francisco Estuary and elsewhere could be managed to promote growth and survival of juvenile salmon and other native fishes.

Atmospheric Concentrations and Fluxes of Organic Compounds in the Northern San Francisco Estuary

2002 ◽  
Vol 36 (22) ◽  
pp. 4741-4747 ◽  
Author(s):  
Pam Tsai ◽  
Rainer Hoenicke ◽  
Donald Yee ◽  
Holly A. Bamford ◽  
Joel E. Baker
Keyword(s):  
Organic Compounds ◽  
San Francisco ◽  
San Francisco Estuary ◽  
Atmospheric Concentrations

scholarly journals The effects of dietary Microcystis aeruginosa and microcystin on the copepods of the upper San Francisco Estuary

2010 ◽  
Vol 55 (7) ◽  
pp. 1548-1559 ◽  
Author(s):  
KEMAL A. GER ◽  
SWEE J. TEH ◽  
DOLORES V. BAXA ◽  
SARAH LESMEISTER ◽  
CHARLES R. GOLDMAN
Keyword(s):  
San Francisco ◽  
Microcystis Aeruginosa ◽  
San Francisco Estuary

Carbon-Isotope, Diatom, and Pollen Evidence for Late Holocene Salinity Change in a Brackish Marsh in the San Francisco Estuary

2001 ◽  
Vol 55 (1) ◽  
pp. 66-76 ◽  
Author(s):  
Roger Byrne ◽  
B. Lynn Ingram ◽  
Scott Starratt ◽  
Frances Malamud-Roam ◽  
Joshua N. Collins ◽  
...  
Keyword(s):  
San Francisco ◽  
High Salinity ◽  
Carbon Isotopic Composition ◽  
Brackish Marsh ◽  
San Francisco Estuary ◽  
Freshwater Inflow ◽  
Water Diversion ◽  
Freshwater Flow ◽  
Low Salinity ◽  
Carbon Isotopic

AbstractAnalysis of diatoms, pollen, and the carbon-isotopic composition of a sediment core from a brackish marsh in the northern part of the San Francisco Estuary has provided a paleosalinity record that covers the past 3000 yr. Changes in marsh composition and diatom frequencies are assumed to represent variations in freshwater inflow to the estuary. Three periods of relatively high salinity (low freshwater inflow) are indicated, 3000 to 2500 cal yr B.P., 1700 to 730 cal yr B.P., and ca. A.D. 1930 to the present. The most recent period of high salinity is primarily due to upstream storage and water diversion within the Sacramento–San Joaquin watershed, although drought may also have been a factor. The two earlier high-salinity periods are likely the result of reduced precipitation. Low salinity (high freshwater flow) is indicated for the period 750 cal yr B.P. to A.D. 1930.

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