For many imperiled species, comparisons between wild and cultured populations are invaluable for informing conservation measures, though opportunities to do so may be rare. In this study, we asked whether spawning between and among wild and cultured Delta Smelt varies in terms of behavior or resulting egg fertilization success. We conducted two laboratory experiments in which we allowed wild females to spawn with wild males (wild × wild) and cultured females to spawn with wild males (cultured × wild). Due to small sample sizes, we qualitatively compared our results to published studies of all cultured Delta Smelt (cultured × cultured). Across all three groups, Delta Smelt exhibited spawns that were similar in sequence and manner, varied widely in diel timing, and occurred predominantly between a single female and one or two males. Egg fertilization success was higher in wild × wild trials than in cultured × wild ones, but both fell within the wide range observed among cultured × cultured fish. Thus, spawning was generally similar between cultured and wild Delta Smelt, whether they were in same- or mixed-origin groups. These findings provide rare insight into the spawning behavior of wild Delta Smelt and inform ongoing conservation efforts.
{"title":"A Qualitative Comparison of Spawning Behavior Between Cultured and Wild Delta Smelt (Hypomesus transpacificus)","authors":"Yi-Jun Jean Tsai, Samantha Noel Chase, Evan Carson, Leanna Zweig, Tien-Chieh Hung","doi":"10.15447/sfews.2023v21iss3art2","DOIUrl":"https://doi.org/10.15447/sfews.2023v21iss3art2","url":null,"abstract":"For many imperiled species, comparisons between wild and cultured populations are invaluable for informing conservation measures, though opportunities to do so may be rare. In this study, we asked whether spawning between and among wild and cultured Delta Smelt varies in terms of behavior or resulting egg fertilization success. We conducted two laboratory experiments in which we allowed wild females to spawn with wild males (wild × wild) and cultured females to spawn with wild males (cultured × wild). Due to small sample sizes, we qualitatively compared our results to published studies of all cultured Delta Smelt (cultured × cultured). Across all three groups, Delta Smelt exhibited spawns that were similar in sequence and manner, varied widely in diel timing, and occurred predominantly between a single female and one or two males. Egg fertilization success was higher in wild × wild trials than in cultured × wild ones, but both fell within the wide range observed among cultured × cultured fish. Thus, spawning was generally similar between cultured and wild Delta Smelt, whether they were in same- or mixed-origin groups. These findings provide rare insight into the spawning behavior of wild Delta Smelt and inform ongoing conservation efforts.","PeriodicalId":38364,"journal":{"name":"San Francisco Estuary and Watershed Science","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135816069","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-25DOI: 10.15447/sfews.2023v21iss3art4
Kristen Dybala, Kristin Sesser, Matthew Reiter, W. David Shuford, Gregory Golet, Catherine Hickey, Thomas Gardali
Conserving bird populations is a key goal for management of the Sacramento–San Joaquin Delta ecosystem and is likely to have effects well beyond its boundaries. To inform bird- conservation strategies, we identified Priority Bird Conservation Areas for riparian landbirds and waterbirds in the Delta, defined as the most valuable 5% of the landscape for each group. We synthesized data from 2,547 surveys for riparian landbirds and 7,820 surveys for waterbirds to develop predictive distribution models, which then informed spatial prioritization analyses. We identified a total of 26,019 ha that are a high priority for conserving riparian landbirds, waterbirds, or both, representing the most important places in the Delta to protect and manage, as well as strategic areas where adjacent restoration could expand valuable habitat. These Priority Bird Conservation Areas include the Yolo Bypass Wildlife Area, Consumnes River Preserve, Stone Lakes National Wildlife Refuge, and bufferlands that surround the Sacramento County Regional Sanitation District. However, we also found that over 60% of the Priority Bird Conservation Areas are not currently protected, indicating a vulnerability to changes in land cover or land use. We recommend advancing strategies for bird conservation in the Delta by developing more specific objectives and priorities, extending these analyses to include other bird species, and planning to mitigate the loss of Priority Bird Conservation Areas where they are most vulnerable to land cover change. The predictive models and analysis framework we developed represent the current state of the science on areas important to bird conservation, while also providing a foundation for an evolving bird-conservation strategy that reflects the Delta’s continuously evolving knowledge base and landscape.
{"title":"Priority Bird Conservation Areas in California's Sacramento-San Joaquin Delta","authors":"Kristen Dybala, Kristin Sesser, Matthew Reiter, W. David Shuford, Gregory Golet, Catherine Hickey, Thomas Gardali","doi":"10.15447/sfews.2023v21iss3art4","DOIUrl":"https://doi.org/10.15447/sfews.2023v21iss3art4","url":null,"abstract":"Conserving bird populations is a key goal for management of the Sacramento–San Joaquin Delta ecosystem and is likely to have effects well beyond its boundaries. To inform bird- conservation strategies, we identified Priority Bird Conservation Areas for riparian landbirds and waterbirds in the Delta, defined as the most valuable 5% of the landscape for each group. We synthesized data from 2,547 surveys for riparian landbirds and 7,820 surveys for waterbirds to develop predictive distribution models, which then informed spatial prioritization analyses. We identified a total of 26,019 ha that are a high priority for conserving riparian landbirds, waterbirds, or both, representing the most important places in the Delta to protect and manage, as well as strategic areas where adjacent restoration could expand valuable habitat. These Priority Bird Conservation Areas include the Yolo Bypass Wildlife Area, Consumnes River Preserve, Stone Lakes National Wildlife Refuge, and bufferlands that surround the Sacramento County Regional Sanitation District. However, we also found that over 60% of the Priority Bird Conservation Areas are not currently protected, indicating a vulnerability to changes in land cover or land use. We recommend advancing strategies for bird conservation in the Delta by developing more specific objectives and priorities, extending these analyses to include other bird species, and planning to mitigate the loss of Priority Bird Conservation Areas where they are most vulnerable to land cover change. The predictive models and analysis framework we developed represent the current state of the science on areas important to bird conservation, while also providing a foundation for an evolving bird-conservation strategy that reflects the Delta’s continuously evolving knowledge base and landscape.","PeriodicalId":38364,"journal":{"name":"San Francisco Estuary and Watershed Science","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135816072","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-25DOI: 10.15447/sfews.2023v21iss3art1
Samuel Bashevkin, Christina Burdi, Rosemary Hartman, Arthur Barros
Zooplankton provide critical food for threatened and endangered fish species in the San Francisco Estuary (estuary). Reduced food supply has been implicated in the Pelagic Organism Decline of the early 2000s, and further changes in zooplankton abundance, seasonality, and distribution may continue to threaten declining fishes. While we have a wealth of monitoring data, we know little about the abundance trends of many estuary zooplankton species. To fill these gaps, we reviewed past research and then examined trends in seasonality and abundance from 1972 to the present of three key but understudied zooplankton species (Bosmina longirostris, Acanthocyclops spp., and Acartiella sinensis) that play important roles in the estuary food web. We fit Bayesian generalized additive mixed models of each taxon’s relationship with salinity, seasonality, year, and geography on an integrated database of zooplankton monitoring in the upper estuary. We found marked changes in the seasonality and overall abundance of each study species. Bosmina longirostris no longer peaks in abundance in the fall months, Acanthocyclops spp. precipitously declined in all months and lost its strong relationship with salinity, and A. sinensis adult abundance has become more strongly related to salinity while juveniles have developed wider seasonal abundance peaks. Through these analyses, we have documented the relationship of each species with salinity and seasonality since the beginning of monitoring or their introduction, thus increasing our understanding of their ecology and importance in the estuary. These results can inform food-web models, be paired with fish data to model the contributions of these species toward fish abundance trends and be mirrored to elucidate other species’ trends in future studies.
{"title":"Long-Term Trends in Seasonality and Abundance of Three Key Zooplankters in the Upper San Francisco Estuary","authors":"Samuel Bashevkin, Christina Burdi, Rosemary Hartman, Arthur Barros","doi":"10.15447/sfews.2023v21iss3art1","DOIUrl":"https://doi.org/10.15447/sfews.2023v21iss3art1","url":null,"abstract":"Zooplankton provide critical food for threatened and endangered fish species in the San Francisco Estuary (estuary). Reduced food supply has been implicated in the Pelagic Organism Decline of the early 2000s, and further changes in zooplankton abundance, seasonality, and distribution may continue to threaten declining fishes. While we have a wealth of monitoring data, we know little about the abundance trends of many estuary zooplankton species. To fill these gaps, we reviewed past research and then examined trends in seasonality and abundance from 1972 to the present of three key but understudied zooplankton species (Bosmina longirostris, Acanthocyclops spp., and Acartiella sinensis) that play important roles in the estuary food web. We fit Bayesian generalized additive mixed models of each taxon’s relationship with salinity, seasonality, year, and geography on an integrated database of zooplankton monitoring in the upper estuary. We found marked changes in the seasonality and overall abundance of each study species. Bosmina longirostris no longer peaks in abundance in the fall months, Acanthocyclops spp. precipitously declined in all months and lost its strong relationship with salinity, and A. sinensis adult abundance has become more strongly related to salinity while juveniles have developed wider seasonal abundance peaks. Through these analyses, we have documented the relationship of each species with salinity and seasonality since the beginning of monitoring or their introduction, thus increasing our understanding of their ecology and importance in the estuary. These results can inform food-web models, be paired with fish data to model the contributions of these species toward fish abundance trends and be mirrored to elucidate other species’ trends in future studies.","PeriodicalId":38364,"journal":{"name":"San Francisco Estuary and Watershed Science","volume":"111 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135816073","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-25DOI: 10.15447/sfews.2023v21iss3art3
William Satterthwaite
The escapement objective used to manage fisheries on Sacramento River Fall Chinook (SRFC) was established in 1984. Despite substantial changes to the system and multiple calls to re-evaluate the objective, data and analytical limitations have slowed progress. Synthesizing the available information is further complicated by the different measurement scales employed by relevant studies. Here, I offer a modeling framework for integrating consideration of established hatchery spawning goals, natural-area production or habitat capacities measured at varying spatial scales, and policy decisions about what fraction of potential natural production is desired along with risk tolerance. The model allows evaluating how likely a potential escapement goal (measured at the currently-used scale of fall run adults returning to both hatcheries and natural areas throughout the Sacramento Basin) is to both meet hatchery goals and to produce at least a specified fraction of potential natural production. The framework also incorporates consideration of forecasting and harvest planning error into identifying a pre-season planning target and its probability of resulting in escapement at least as high as the goal. The model indicates that the low end of the current escapement goal range of 122,000-180,000 adults, if achieved, would be more likely than not to achieve hatchery goals while achieving around 50% of potential natural production. Realized escapement equal to the high end is modeled to be highly likely to achieve hatchery goals and likely to achieve around 75% of potential basin-wide natural production or around 60% of Upper Sacramento potential production. The model indicates diminishing returns from total adult SRFC escapements higher than about 300,000 adults. However, past performance of forecast and harvest planning models suggest that a preseason target higher than the ultimate escapement goal is needed to have even a 50% chance of achieving the escapement goal.
{"title":"An Approach to Defining a Sacramento River Fall Chinook Escapement Objective Considering Natural Production, Hatcheries, and Risk Tolerance","authors":"William Satterthwaite","doi":"10.15447/sfews.2023v21iss3art3","DOIUrl":"https://doi.org/10.15447/sfews.2023v21iss3art3","url":null,"abstract":"The escapement objective used to manage fisheries on Sacramento River Fall Chinook (SRFC) was established in 1984. Despite substantial changes to the system and multiple calls to re-evaluate the objective, data and analytical limitations have slowed progress. Synthesizing the available information is further complicated by the different measurement scales employed by relevant studies. Here, I offer a modeling framework for integrating consideration of established hatchery spawning goals, natural-area production or habitat capacities measured at varying spatial scales, and policy decisions about what fraction of potential natural production is desired along with risk tolerance. The model allows evaluating how likely a potential escapement goal (measured at the currently-used scale of fall run adults returning to both hatcheries and natural areas throughout the Sacramento Basin) is to both meet hatchery goals and to produce at least a specified fraction of potential natural production. The framework also incorporates consideration of forecasting and harvest planning error into identifying a pre-season planning target and its probability of resulting in escapement at least as high as the goal. The model indicates that the low end of the current escapement goal range of 122,000-180,000 adults, if achieved, would be more likely than not to achieve hatchery goals while achieving around 50% of potential natural production. Realized escapement equal to the high end is modeled to be highly likely to achieve hatchery goals and likely to achieve around 75% of potential basin-wide natural production or around 60% of Upper Sacramento potential production. The model indicates diminishing returns from total adult SRFC escapements higher than about 300,000 adults. However, past performance of forecast and harvest planning models suggest that a preseason target higher than the ultimate escapement goal is needed to have even a 50% chance of achieving the escapement goal.","PeriodicalId":38364,"journal":{"name":"San Francisco Estuary and Watershed Science","volume":"186 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135816074","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-15DOI: 10.15447/sfews.2023v21iss2art2
Francisco Bay, Estuary Permalink, Carley Schacter, C. A. Hartman, M. Herzog, S. Peterson, L. Tarjan, Yiwei Wang, Cheryl M. Strong, R. Tertes, Nils Warnock, J. Ackerman
The South Bay Salt Pond Restoration Project aims to restore many former salt production ponds, now managed for wildlife and water quality, to tidal marsh. However, because managed ponds support large densities of breeding waterbirds, reduction of pond habitat may influence breeding waterbird distribution and abundance. We investigated habitat use associated with breeding, feeding, and roosting behaviors during the breeding season for American Avocets (Recurvirostra americana), Black-necked Stilts (Himantopus mexicanus), Forster’s Terns (Sterna forsteri), and Caspian Terns (Hydroprogne caspia) in south San Francisco Bay in 2019 after substantial tidal marsh restoration, and compared results to a 2001 survey (before restoration). In 2019, managed ponds (26% of currently available habitat) were selected by waterbirds engaged in breeding behaviors (> 39% of observations), foraging (> 42%), and roosting (> 73%). Waterbirds avoided tidal habitats (43% of available habitat), comprising < 17% of observations of breeding behavior, < 28% of foraging observations, and < 13% of roosting observations. Waterbird densities increased in managed ponds between 2001 and 2019, and decreased in active salt ponds, especially among feeding Avocets (92% decrease) and Stilts (100% decrease). Islands were important for waterbirds observed breeding and roosting (45% of Avocet and 53% of Tern observations). Avocets and Stilts fed primarily on wet bare ground (65% and 58%, respectively), whereas feeding Forster’s Terns and Caspian Terns used mostly open water (82% and 93%, respectively). Within ponds, Avocets were associated with islands (131 m closer than expected). Stilts and Forster’s Terns were also associated with islands (68 m and 161 m closer than expected), except when feeding (1 m closer and 90 m farther than expected). Avocets and Stilts were associated with pond levees (39 m and 41 m closer than expected), but Forster’s Terns were not (9 m closer than expected). Our results emphasize the importance of managed ponds for breeding and foraging waterbirds, including islands for breeding and roosting and levees for foraging.
{"title":"Habitat Use by Breeding Waterbirds in Relation to Tidal Marsh Restoration in the San Francisco Bay Estuary","authors":"Francisco Bay, Estuary Permalink, Carley Schacter, C. A. Hartman, M. Herzog, S. Peterson, L. Tarjan, Yiwei Wang, Cheryl M. Strong, R. Tertes, Nils Warnock, J. Ackerman","doi":"10.15447/sfews.2023v21iss2art2","DOIUrl":"https://doi.org/10.15447/sfews.2023v21iss2art2","url":null,"abstract":"The South Bay Salt Pond Restoration Project aims to restore many former salt production ponds, now managed for wildlife and water quality, to tidal marsh. However, because managed ponds support large densities of breeding waterbirds, reduction of pond habitat may influence breeding waterbird distribution and abundance. We investigated habitat use associated with breeding, feeding, and roosting behaviors during the breeding season for American Avocets (Recurvirostra americana), Black-necked Stilts (Himantopus mexicanus), Forster’s Terns (Sterna forsteri), and Caspian Terns (Hydroprogne caspia) in south San Francisco Bay in 2019 after substantial tidal marsh restoration, and compared results to a 2001 survey (before restoration). In 2019, managed ponds (26% of currently available habitat) were selected by waterbirds engaged in breeding behaviors (> 39% of observations), foraging (> 42%), and roosting (> 73%). Waterbirds avoided tidal habitats (43% of available habitat), comprising < 17% of observations of breeding behavior, < 28% of foraging observations, and < 13% of roosting observations. Waterbird densities increased in managed ponds between 2001 and 2019, and decreased in active salt ponds, especially among feeding Avocets (92% decrease) and Stilts (100% decrease). Islands were important for waterbirds observed breeding and roosting (45% of Avocet and 53% of Tern observations). Avocets and Stilts fed primarily on wet bare ground (65% and 58%, respectively), whereas feeding Forster’s Terns and Caspian Terns used mostly open water (82% and 93%, respectively). Within ponds, Avocets were associated with islands (131 m closer than expected). Stilts and Forster’s Terns were also associated with islands (68 m and 161 m closer than expected), except when feeding (1 m closer and 90 m farther than expected). Avocets and Stilts were associated with pond levees (39 m and 41 m closer than expected), but Forster’s Terns were not (9 m closer than expected). Our results emphasize the importance of managed ponds for breeding and foraging waterbirds, including islands for breeding and roosting and levees for foraging.","PeriodicalId":38364,"journal":{"name":"San Francisco Estuary and Watershed Science","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41399051","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-15DOI: 10.15447/sfews.2023v21iss2art3
P. Hutton, Sujoy B. Roy
The deviation of specific electrical conductance (EC) from conservative mixing behavior is well-established in the scientific literature. This principle is based on the observation that, as salt concentration in a water sample increases, the mobility of individual ions in the sample decreases, and thus their ability to conduct electricity decreases. Despite this fact, some commonly used models for salinity transport in the San Francisco Estuary (estuary) utilize EC as a primary simulation constituent, treating it as a conservative quantity. Such a modeling approach has likely been followed to exploit the wide availability of EC data for model calibration and validation, and to obviate the need to translate between EC and salinity in a domain characterized by multiple source waters with varying ionic make-ups. Arguably, this approach provides a reasonable trade-off between data translation error and model simulation error. In this paper, we critically evaluate this approach, employing an extensive salinity data set that includes measurements of EC and major ion concentrations in the estuary. We demonstrate and quantify EC deviation from steady-state, conservative mixing behavior; review the conservative mixing behavior of three bulk salinity measures (practical salinity, ionic strength, and limiting equivalent conductance); and evaluate their source-dependent correlations with EC in the estuary. We find limiting equivalent conductance—a value that assumes uninhibited mobility among individual ions in a water sample—to be an attractive alternative for salinity transport in the estuary. In addition to being a conservative quantity, it is consistently correlated with EC in the estuary’s dominant source waters, and thus addresses concerns related to data-translation error. We conclude this paper discussing pros and cons of adopting various salinity-transport model constituents.
{"title":"A Note on Conservative Mixing: Implications for Selecting Salinity-Transport Model Constituents in the San Francisco Estuary","authors":"P. Hutton, Sujoy B. Roy","doi":"10.15447/sfews.2023v21iss2art3","DOIUrl":"https://doi.org/10.15447/sfews.2023v21iss2art3","url":null,"abstract":"The deviation of specific electrical conductance (EC) from conservative mixing behavior is well-established in the scientific literature. This principle is based on the observation that, as salt concentration in a water sample increases, the mobility of individual ions in the sample decreases, and thus their ability to conduct electricity decreases. Despite this fact, some commonly used models for salinity transport in the San Francisco Estuary (estuary) utilize EC as a primary simulation constituent, treating it as a conservative quantity. Such a modeling approach has likely been followed to exploit the wide availability of EC data for model calibration and validation, and to obviate the need to translate between EC and salinity in a domain characterized by multiple source waters with varying ionic make-ups. Arguably, this approach provides a reasonable trade-off between data translation error and model simulation error. In this paper, we critically evaluate this approach, employing an extensive salinity data set that includes measurements of EC and major ion concentrations in the estuary. We demonstrate and quantify EC deviation from steady-state, conservative mixing behavior; review the conservative mixing behavior of three bulk salinity measures (practical salinity, ionic strength, and limiting equivalent conductance); and evaluate their source-dependent correlations with EC in the estuary. We find limiting equivalent conductance—a value that assumes uninhibited mobility among individual ions in a water sample—to be an attractive alternative for salinity transport in the estuary. In addition to being a conservative quantity, it is consistently correlated with EC in the estuary’s dominant source waters, and thus addresses concerns related to data-translation error. We conclude this paper discussing pros and cons of adopting various salinity-transport model constituents.","PeriodicalId":38364,"journal":{"name":"San Francisco Estuary and Watershed Science","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49200727","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-15DOI: 10.15447/sfews.2023v21iss2art1
Calvin Yee, April Smith, Jason L. Hassrick, A. Kalmbach, Megan C. Sabal, D. Cox, L. Grimaldo, Andrew A. Schultz
Zooplankton density and community composition in estuaries can be affected by variation in freshwater inputs, with important implications for higher trophic levels. In the San Francisco Estuary, management agencies have initiated autumn flow augmentations in the form of changes to reservoir releases or to exported water from the South Delta to increase and improve available habitat for endangered Delta Smelt, Hypomesus transpacificus, during the season when their body condition most influences fecundity. Autumn flow augmentation only occurs in years with higher precipitation, effectively moving the Low-Salinity Zone (LSZ) downstream to key foraging habitats for Delta Smelt in Suisun Bay and Suisun Marsh. To assess whether augmented flow enhanced prey resources for Delta Smelt, we compared autumn zooplankton abundance, biomass, spatial distribution, and community composition in years when flow was augmented (2017, 2019) with reference years when flow was not augmented (2018, 2020). In augmented years, we detected higher total zooplankton abundance and altered community composition in Suisun Bay and Suisun Marsh. Increased freshwater in these regions was associated with higher abundance of Pseudodiaptomus forbesi, a preferred prey of Delta Smelt, while species associated with higher salinities—Acartiella sinensis and Tortanus dextrilobatus—were less abundant. Thus, autumn flow augmentations can influence foraging habitat and prey availability for Delta Smelt, underscoring the complex responses of estuarine zooplankton communities to changes in response to flow and salinity regimes. This study is management- relevant because it shows that important Delta Smelt prey items increase in downstream regions when X2 is lower. Whether that results in a response in Delta Smelt abundance remains to be seen.
{"title":"Flow Augmentations Modify an Estuarine Prey Field","authors":"Calvin Yee, April Smith, Jason L. Hassrick, A. Kalmbach, Megan C. Sabal, D. Cox, L. Grimaldo, Andrew A. Schultz","doi":"10.15447/sfews.2023v21iss2art1","DOIUrl":"https://doi.org/10.15447/sfews.2023v21iss2art1","url":null,"abstract":"Zooplankton density and community composition in estuaries can be affected by variation in freshwater inputs, with important implications for higher trophic levels. In the San Francisco Estuary, management agencies have initiated autumn flow augmentations in the form of changes to reservoir releases or to exported water from the South Delta to increase and improve available habitat for endangered Delta Smelt, Hypomesus transpacificus, during the season when their body condition most influences fecundity. Autumn flow augmentation only occurs in years with higher precipitation, effectively moving the Low-Salinity Zone (LSZ) downstream to key foraging habitats for Delta Smelt in Suisun Bay and Suisun Marsh. To assess whether augmented flow enhanced prey resources for Delta Smelt, we compared autumn zooplankton abundance, biomass, spatial distribution, and community composition in years when flow was augmented (2017, 2019) with reference years when flow was not augmented (2018, 2020). In augmented years, we detected higher total zooplankton abundance and altered community composition in Suisun Bay and Suisun Marsh. Increased freshwater in these regions was associated with higher abundance of Pseudodiaptomus forbesi, a preferred prey of Delta Smelt, while species associated with higher salinities—Acartiella sinensis and Tortanus dextrilobatus—were less abundant. Thus, autumn flow augmentations can influence foraging habitat and prey availability for Delta Smelt, underscoring the complex responses of estuarine zooplankton communities to changes in response to flow and salinity regimes. This study is management- relevant because it shows that important Delta Smelt prey items increase in downstream regions when X2 is lower. Whether that results in a response in Delta Smelt abundance remains to be seen.","PeriodicalId":38364,"journal":{"name":"San Francisco Estuary and Watershed Science","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46741419","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-03-24DOI: 10.15447/sfews.2023v21iss1art3
T. Mussen, S. Driscoll, M. Cook, Justin Nordin, M. Guerin, R. Rachiele, Don Smith, G. Berg, Lisa Thompson
Phytoplankton subsidies from river inputs and wetland habitats can be important food sources for pelagic organisms in the Sacramento–San Joaquin Delta (Delta). However, while the Sacramento River is a key contributor of water to the Delta, providing 80% of the mean annual inflow, the river is only a minor source of phytoplankton to the system. The reason for low phytoplankton biomass in the Sacramento River is not well understood but appears to be associated with a 65- km stretch of the lower river where chlorophyll-a (Chl-a) concentrations can decline by as much as 90%. We conducted two surveys along the lower Sacramento River, in spring and fall of 2016, to investigate the relative contributions of different factors potentially driving this Chl-a decline. Our study evaluated the change in Chl-a concentrations as a result of dilution from tributaries, light availability, nutrient concentrations, nutrient uptake, phytoplankton productivity, zooplankton grazing, and clam grazing. Chl-a concentration decreased from 14 µg L–1 to 1.8 µg L–1 in the spring and from 4.0 µg L–1 to 1.2 µg L–1 in the fall. Dilutions from the Feather River and American River contributed to 39% and 11% of Chl-a decline, respectively, during the spring. Average water depths roughly doubled downstream of the American River confluence, reducing water column light availability and lowering productivity. Zooplankton and clam grazing rates were generally low. Using a mass balance analysis, the measured variables explained 76% of the observed decline in Chl-a in the spring, suggesting additional losses from unidentified factors. We found that phytoplankton biomass is regulated by multiple potential factors in the lower Sacramento River, emphasizing the need for practitioners of restoration and management programs to evaluate multiple potential factors when attempting to enhance phytoplankton production in the Delta, or other large river systems.
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Pub Date : 2023-03-24DOI: 10.15447/sfews.2023v21iss1art1
Ted R. Sommer, J. L. Conrad, S. Culberson
Science is the foundation for a wide range of activities, including evaluation, innovation, and technology, which in turn support management. Without good science, resource management in regions such as the estuary is handicapped, and must proceed with outdated conceptual models, operating strategies, and technologies. At the same time, we recognize that poor communication can interfere with conversations between scientists and managers, even when high-quality data and publications are available. In this essay, we have tried to address an important part of this issue: helping scientists to understand how to produce actionable science. Our hope is that these suggestions will, at the least, help improve dialog between scientists and the managers responsible for the estuary’s resources.
{"title":"Data to Decisions: How to Make Science More Relevant for Management of the San Francisco Estuary","authors":"Ted R. Sommer, J. L. Conrad, S. Culberson","doi":"10.15447/sfews.2023v21iss1art1","DOIUrl":"https://doi.org/10.15447/sfews.2023v21iss1art1","url":null,"abstract":"Science is the foundation for a wide range of activities, including evaluation, innovation, and technology, which in turn support management. Without good science, resource management in regions such as the estuary is handicapped, and must proceed with outdated conceptual models, operating strategies, and technologies. At the same time, we recognize that poor communication can interfere with conversations between scientists and managers, even when high-quality data and publications are available. In this essay, we have tried to address an important part of this issue: helping scientists to understand how to produce actionable science. Our hope is that these suggestions will, at the least, help improve dialog between scientists and the managers responsible for the estuary’s resources.","PeriodicalId":38364,"journal":{"name":"San Francisco Estuary and Watershed Science","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45399147","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-03-24DOI: 10.15447/sfews.2023v21iss1art4
J. Lacy, Evan T. Dailey, Tara L. Morgan-King
We investigated wind-wave and suspended-sediment dynamics in Little Holland Tract and Liberty Island, two subsided former agricultural tracts in the Cache Slough complex in the northern Sacramento-San Joaquin Delta which were restored to tidal shallows to improve habitat. Turbidity, and thus suspended-sediment concentration (SSC), is important to habitat quality because some species of native fishes, including the Delta Smelt, are found preferentially in more turbid waters. Data from October 2015 to August 2016 show that average SSC was greater within Little Holland Tract than in the primary breach that connects the basin to surrounding channels: approximately twice as great at a shallower station farther from the breach and 15% greater at a deeper station closer to the breach. Suspended-sediment concentration within Little Holland Tract was directly related to wave shear stress and inversely related to water depth, based on linear regression. We used measurements of suspended-sediment flux (SSF) through the largest levee breaches to assess whether the enhanced SSC within Little Holland Tract is exported to surrounding waters, thus potentially increasing turbidity over a wider region. Cumulatively, sediment is exported through the Little Holland Tract breaches in winter and imported in summer, consistent with regional patterns in sediment flux, indicating that wind-wave re-suspension within the basin does not control sediment flux from Little Holland Tract on seasonal time-scales. Some sediment was exported during wind-wave events, and results show that sediment export is greater when primary breaches are located downwind of the basin rather than upwind.
为了改善栖息地，我们在萨克拉曼托-圣华金三角洲北部Cache Slough建筑群的两个下沉农业区Little Holland Tract和Liberty Island调查了风浪和悬浮泥沙动力学。浑浊度和悬浮沉积物浓度(SSC)对栖息地质量很重要，因为一些本地鱼类，包括三角洲冶炼鱼，优先在更浑浊的水域中被发现。2015年10月至2016年8月的数据显示，小荷兰水道内的平均SSC高于连接盆地与周围河道的主要裂口:距离裂口较浅的站点大约是其两倍，靠近裂口的较深站点则高出15%。线性回归结果表明，小荷兰水道内悬沙浓度与波浪剪切应力成正相关，与水深成反比。我们通过最大的堤防裂口测量悬浮泥沙通量(SSF)来评估小荷兰水道内增强的悬浮泥沙通量是否会输出到周围水域，从而可能增加更广泛地区的浊度。累积来看，泥沙冬季通过小荷兰道的破口输出，夏季通过小荷兰道的破口输入，与泥沙通量的区域格局一致，说明在季节时间尺度上，盆地内的风浪再悬浮对小荷兰道的输沙通量没有控制作用。在风浪过程中有一定的输沙量，结果表明，当主要溃口位于盆地的下风位置时，输沙量大于逆风位置。
{"title":"What Controls Suspended-Sediment Concentration and Export in Flooded Agricultural Tracts in the Sacramento–San Joaquin Delta?","authors":"J. Lacy, Evan T. Dailey, Tara L. Morgan-King","doi":"10.15447/sfews.2023v21iss1art4","DOIUrl":"https://doi.org/10.15447/sfews.2023v21iss1art4","url":null,"abstract":"We investigated wind-wave and suspended-sediment dynamics in Little Holland Tract and Liberty Island, two subsided former agricultural tracts in the Cache Slough complex in the northern Sacramento-San Joaquin Delta which were restored to tidal shallows to improve habitat. Turbidity, and thus suspended-sediment concentration (SSC), is important to habitat quality because some species of native fishes, including the Delta Smelt, are found preferentially in more turbid waters. Data from October 2015 to August 2016 show that average SSC was greater within Little Holland Tract than in the primary breach that connects the basin to surrounding channels: approximately twice as great at a shallower station farther from the breach and 15% greater at a deeper station closer to the breach. Suspended-sediment concentration within Little Holland Tract was directly related to wave shear stress and inversely related to water depth, based on linear regression. We used measurements of suspended-sediment flux (SSF) through the largest levee breaches to assess whether the enhanced SSC within Little Holland Tract is exported to surrounding waters, thus potentially increasing turbidity over a wider region. Cumulatively, sediment is exported through the Little Holland Tract breaches in winter and imported in summer, consistent with regional patterns in sediment flux, indicating that wind-wave re-suspension within the basin does not control sediment flux from Little Holland Tract on seasonal time-scales. Some sediment was exported during wind-wave events, and results show that sediment export is greater when primary breaches are located downwind of the basin rather than upwind.","PeriodicalId":38364,"journal":{"name":"San Francisco Estuary and Watershed Science","volume":"56 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41300013","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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