San Francisco Estuary and Watershed Science最新文献

{"title":"Movement and Apparent Survival of Acoustically Tagged Juveline Late-Fall Run Chinook Salmon Released Upstream of Shasta Reservoir, California","authors":"J. M. Plumb, Amy C. Hansen, N. Adams, S. Evans, J. Hannon","doi":"10.15447/sfews.2019v17iss3art4","DOIUrl":"https://doi.org/10.15447/sfews.2019v17iss3art4","url":null,"abstract":"Author(s): Plumb, John; Hansen, Amy; Adams, Noah; Evans, Scott; Hannon, John | Abstract: Stakeholder interests have spurred the reintroduction of the critically endangered populations of Chinook Salmon to tributaries upstream of Shasta Dam, in northern California. We released two groups of acoustically tagged, juvenile hatchery, late-fall Chinook Salmon to determine how juvenile salmon would distribute and survive. We measured travel times to Shasta Dam, and the number of fish that moved between locations within Shasta Reservoir. We used mark-recapture methods to determine detection and apparent survival probabilities of the tagged fish as they traveled through five reaches of the Sacramento River from the McCloud River to San Francisco Bay (~590 km) over the two 3-month observation periods. After our first (February) release of 262 tagged fish, 182 fish (70%) were detected at least once at the dam, 41 (16%) were detected at least once downstream of Shasta Dam, and 3 (1%) traveled as far as San Francisco Bay. After the second (November) release of 355 tagged fish, only 4 (1%) were detected at Shasta Dam. No fish were detected below Shasta Dam, so we could not estimate survival for this second release group. The first release of fish was fortuitously exposed to exceptionally high river flows and dam discharges, which may have contributed to the more distant downstream migration and detection of these fish — though other factors such as season, diploid versus triploid, and fish maturation and size may have also contributed to release differences. The reported fish travel times as well as detection and survival rates are the first estimates of juvenile salmon emigration from locations above Shasta Dam in more than 70 years. This information should help inform resource managers about how best to assess juvenile winter-run Chinook Salmon and assist in their reintroduction to watersheds upstream of Shasta Dam.","PeriodicalId":38364,"journal":{"name":"San Francisco Estuary and Watershed Science","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.15447/sfews.2019v17iss3art4","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45138008","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}

{"title":"Effects of Drought and the Emergency Drought Barrier on the Ecosystem of the California Delta","authors":"W. Kimmerer, F. Wilkerson, B. Downing, R. Dugdale, E. Gross, Karen R. Kayfetz, S. Khanna, A. Parker, Janet K. Thompson","doi":"10.15447/sfews.2019v17iss3art2","DOIUrl":"https://doi.org/10.15447/sfews.2019v17iss3art2","url":null,"abstract":"Author(s): Kimmerer, Wim; Wilkerson, Frances; Downing, Bryan; Dugdale, Richard; Gross, Edward S.; Kayfetz, Karen; Khanna, Shruti; Parker, Alexander E.; Thompson, Janet | Abstract: In 2015, the fourth year of the recent drought, the California Department of Water Resources installed a rock barrier across False River west of Franks Tract to limit salt intrusion into the Delta at minimal cost in freshwater. This Barrier blocked flow in False River, greatly reducing landward salt transport by decreasing tidal dispersion in Franks Tract. We investigated some ecological consequences of the Barrier, examining its effects on water circulation and exchange, on distributions of submerged aquatic vegetation (SAV) and bivalves, and on phytoplankton and zooplankton. The Barrier allowed SAV to spread to areas of Franks Tract that previously had been clear. The distributions of bivalves (Potamocorbula and Corbicula) responded to the changes in salinity at time–scales of months for newly settled individuals, to 1 or more years for adults, but the Barrier’s effect was confounded with that of the drought. Nutrients, phytoplankton biomass, and a Microcystis abundance index showed little response to the Barrier. Transport of copepods — determined using output from a particle-tracking model — indicated some intermediate-scale reduction with the Barrier in place, but monitoring data did not show a larger-scale response in abundance. These studies were conducted separately and synthesized after the fact, and relied on reference conditions that were not always suitable for identifying the Barrier’s effects. If barriers are considered in the future, we rcommend a modest program of investigation to replicate study elements, and to ensure suitable reference conditions are available to allow barrier effects to be distinguished unambiguously from other sources of variability.","PeriodicalId":38364,"journal":{"name":"San Francisco Estuary and Watershed Science","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.15447/sfews.2019v17iss3art2","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46710494","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}

{"title":"Geospatial Tools for the Large-Scale Monitoring of Wetlands in the San Francisco Estuary: Opportunities and Challenges","authors":"S. Taddeo, I. Dronova","doi":"10.15447/SFEWS.2019V17ISS2ART2","DOIUrl":"https://doi.org/10.15447/SFEWS.2019V17ISS2ART2","url":null,"abstract":"Author(s): Taddeo, Sophie; Dronova, Iryna | Abstract: Significant wetland losses and continuing threats to remnant habitats have motivated extensive restoration efforts in the San Francisco Bay–Delta estuary of California, the largest in the western United States. Consistent monitoring of ecological outcomes from this restoration effort would help managers learn from past projects to improve the design of future endeavors. However, budget constraints and challenging field conditions can limit the scope of current monitoring programs. Geospatial tools and remote sensing data sets could help complement field efforts for a low-cost, longer, and broader monitoring of wetland resources. To understand where geospatial tools could best complement current field monitoring practices, we reviewed the metrics and monitoring methods used by 42 wetland restoration projects implemented in the estuary. Monitoring strategies within our sample of monitoring plans relied predominantly on field surveys to assess key aspects of vegetation recovery while geospatial data sets were used sparingly. Drawing on recent publications that focus on the estuary and other wetland systems, we propose additional geospatial applications to help monitor the progress made toward site-specific and regional goals. These include the use of ecological niche models to target on-the-ground monitoring efforts, the up-scaling of field measurements into regional estimates using remote sensing data, and the analysis of time-series to detect ecosystem shifts. We discuss challenges and limitations to the broad-scale application of remote sensing data in wetland monitoring. These notably include the need to find a venue to store and share computationally intensive data sets, the often cumbersome pre-processing effort needed for long-term analyses, and multiple confounding factors that can obscure the signal of remote sensing data sets.","PeriodicalId":38364,"journal":{"name":"San Francisco Estuary and Watershed Science","volume":"27 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.15447/SFEWS.2019V17ISS2ART2","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67074287","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}

{"title":"Water Budgets for the Delta Watershed: Putting Together the Many Disparate Pieces","authors":"Jiro Ariyama, G. Boisramé, M. Brand","doi":"10.15447/SFEWS.2019V17ISS2ART3","DOIUrl":"https://doi.org/10.15447/SFEWS.2019V17ISS2ART3","url":null,"abstract":"Author(s): Ariyama, Jiro; Boisrame, Gabrielle F. S.; Brand, Marina Riley | Abstract: Water budgets integrate and summarize the water inputs and outputs that are essential for effective water resources management. Using water data collected from different sources, we constructed three water budgets (a 12-year annual average, a wet year, and a critically dry year) for the Sacramento–San Joaquin Delta (Delta), the Sacramento River (SR) watershed, and the San Joaquin River (SJR) watershed. Although multiple water budgets for the Delta exist, the water budgets presented here are the first to provide all three of the following: (1) water budgets for the entire Delta watershed, divided into management-relevant components, (2) comparisons between wet and dry years and between different regions of the watershed, and (3) discussion of major gaps and uncertainties in the available water data to guide and inform future data collection and water management. Results show that, from 1998 to 2009, the Delta received 24.2 million acre feet (maf) of water each year on average, which primarily exited the Delta as river outflow (71%), water exports (22%), and evapotranspiration (ET; 6%). The SR watershed received 56.9 maf of water (95% as precipitation). The major outputs from the SR watershed were ET (63%) and flows to the Delta (34%). In the SJR watershed, total water input was 28.7 maf composed of precipitation (74%), water imported from the Delta (18%), and storage depletion (7%). The major outputs from the SJR watershed were ET (65%), water exports (19%), and flows to the Delta (14%). Most values varied greatly from year to year. Although streamflows, water exports, and valley precipitation are relatively well measured and estimated, uncertainties are higher for groundwater storage change as well as for ET and precipitation in montane regions. Improvement in data collection and synthesis in these components is necessary to build a more detailed and accurate water budget.","PeriodicalId":38364,"journal":{"name":"San Francisco Estuary and Watershed Science","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.15447/SFEWS.2019V17ISS2ART3","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44871771","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}

{"title":"Ten Essential Bay‒Delta Articles","authors":"Ted R. Sommer, J. L. Conrad, S. Culberson","doi":"10.15447/SFEWS.2019V17ISS2ART1","DOIUrl":"https://doi.org/10.15447/SFEWS.2019V17ISS2ART1","url":null,"abstract":"For newcomers and veteran scientists alike, Bay– Delta science is daunting. The number of research and management issues is exceptional, and the scientific literature is well developed but fragmented. There is a substantial history of periodic reviews of Bay–Delta science and policy issues. Between 1979 and 1986 the first widely circulated reviews were published, focused on Bay processes (Conomos 1979) and issues (Kockelman et al 1982; Nichols et al 1986). Similar publications in the midto late1990s built substantially on this body of knowledge (e.g., Hollibaugh 1996; van Geen and Luoma 1999). The CALFED Bay–Delta program shifted much of the focus to the Delta, resulting in sponsored white papers on major issues in the mid-2000s (e.g., Brown 2003; Kimmerer 2004; Bennett 2005; Williams 2006). The first “State of Bay–Delta Science” was published in 2008 (Healey et al. 2008). The most recent update of the State of Bay–Delta Science (Healey et al. 2016a, 2016b, and accompanying articles) considered species of concern (Delta Smelt, Chinook Salmon), processes (fish predation, nutrient dynamics, food webs, flow and transport), stressors (contaminant effects, climate change), tools (multidimensional models), and human uses and effects on the Delta (Delta landscapes, climate change, agricultural and urban water supply, and the levee system). Other comprehensive overviews are also available; for example, IEP (2015), Johnson et al. (2017), and Sherman et al. (2017). Together, these reviews and the studies they cite give a sense of the historical development of scientific understanding in the Bay–Delta, and provide conceptual models for species’ or system ecology. Many of the papers are themselves scientific milestones, and provided a science foundation for current Bay–Delta current management actions (e.g., Delta Smelt Resiliency Strategy, CNRA 2016; and Sacramento Valley Salmon Resiliency Strategy, CNRA 2017). ESSAY","PeriodicalId":38364,"journal":{"name":"San Francisco Estuary and Watershed Science","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.15447/SFEWS.2019V17ISS2ART1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47317898","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}

{"title":"Characterizing Early 20th Century Outflow and Salinity Intrusion in the San Francisco Estuary","authors":"P. Hutton, Sujoy B. Roy","doi":"10.15447/SFEWS.2019V17ISS2ART4","DOIUrl":"https://doi.org/10.15447/SFEWS.2019V17ISS2ART4","url":null,"abstract":"Author(s): Hutton, Paul H.; Roy, Sujoy B. | Abstract: We evaluated two historically important data sets to characterize the San Francisco Estuary’s salinity regime before the State of California began systematic data collection in the early 1920s. One set documents barge travel along the Sacramento and San Joaquin rivers to obtain water of adequate quality for local industry; a second set documents Delta inflow used to compute antecedent outflow. The barge travel distance reported over 2 decades (1908–1929) was well explained by flow–salinity modeling, indicating internal consistency in these measurements. However, absolute salinity intrusion estimated through the barge travel data is systematically lower than suggested by contemporaneous water-quality measurements available since 1921. Through integration of these data sets, our work showed substantial similarities between 1908–1921 and the subsequent period before construction of Shasta Dam (1922–1944). Our analysis reveals an apparent shift in the estuary’s salinity regime, with lesser salinity intrusion occurring in pre-1919 summer and fall months as a result of higher summer Delta outflow; this shift may be related to lower storage and irrigation diversions as well as a preponderance of wet years with higher summer runoff in the pre–1919 period. We found seasonal patterns of wet year salinity intrusion to be comparable over the full study period (1908–1944), indicating that the relative effect of upstream water management is minimal when flows are high, consistent with findings reported in later periods. The barge and flow data provide qualitative insights on early 20th century conditions, when limited data are available. Post–1920 hydrology and salinity data are preferable for quantitative analyses because of better documentation associated with collection and analysis, and sustained reporting over several decades. This work provides a foundation for future efforts to characterize the hydrologic and hydrodynamic changes that occurred in the system between the 1850s (i.e., natural or pre-development conditions) and the 1920s.","PeriodicalId":38364,"journal":{"name":"San Francisco Estuary and Watershed Science","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.15447/SFEWS.2019V17ISS2ART4","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44314720","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}

{"title":"Management of Invasive Water Hyacinth as Both a Nuisance Weed and Invertebrate Habitat","authors":"E. Marineau, Matthew J. Perryman, S. Lawler, R. Hartman, P. Pratt","doi":"10.15447/SFEWS.2019V17ISS2ART5","DOIUrl":"https://doi.org/10.15447/SFEWS.2019V17ISS2ART5","url":null,"abstract":"Author(s): Donley Marineau, Erin; Perryman, Matthew J.; Lawler, Sharon P.; Hartman, Rosemary K.; Pratt, Paul D. | Abstract: Invasive species have many detrimental ecological and socio-economic effects. However, invasive species can also provide novel habitat for native species. The growing rate of biological invasions world-wide presents an urgent dilemma: how can natural resource managers minimize negative effects of invasive species without depleting native taxa that have come to rely on them? Adaptive management can provide a means to address this dilemma when invasive species management plans are crafted in novel environments. We present a case study of research in support of adaptive management that considers the role of invasive water hyacinth (Eichhornia crassipes [Mart.] Solms [Pontederiaceae]) management, using herbicides, in aquatic food web functioning in the Sacramento–San Joaquin River Delta of California, USA (the “Delta”). We hypothesized that herbicide applications under current management protocols would reduce the abundance and diversity of aquatic invertebrates because they would alter both structural and biological habitat. Using a Before, After, Control, Intervention (BACI) experiment, we sampled invertebrates per gram plant biomass before and 4 weeks after glyphosate applications in treated and untreated locations. There was more plant biomass in the late-season samples because dead, dying, and living plant materials were compacted. However, there were no detectable differences between control and treated sites — or for samples before versus after the treatment date—for invertebrate abundance, species richness, or evenness. This case study demonstrates that even decaying water hyacinth serves as habitat for invertebrates that may be forage for Delta fishes. We concluded that current management practices using glyphosate do not affect invertebrate abundance during a month-long period of weed decay. These results provide valuable feedback for the “evaluate and respond” component of the adaptive management process for water hyacinth control, and demonstrate how managers globally can and should consider potential food web effects in the course of their invasive species management efforts.","PeriodicalId":38364,"journal":{"name":"San Francisco Estuary and Watershed Science","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.15447/SFEWS.2019V17ISS2ART5","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42554937","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}

{"title":"Clarifying Effects of Environmental Protections on Freshwater Flows to—and Water Exports from—the San Francisco Bay Estuary","authors":"G. Reis, J. Howard, J. Rosenfield","doi":"10.15447/SFEWS.2019V17ISS1ART1","DOIUrl":"https://doi.org/10.15447/SFEWS.2019V17ISS1ART1","url":null,"abstract":"Understanding and resolving conflicts over management of scarce natural resources requires access to information that helps characterize the problem. Where information is lacking, perceived differently by stakeholders, or provided without relevant context, these conflicts can become intractable. We studied water management practices and constraints that affect the flow of water into and through the San Francisco Bay estuary — home to six endangered fish species and two water export facilities owned by the state and federal governments that serve millions of people and large expanses of agricultural land in California. Media reports reflect widely held beliefs that environmental regulations, and particularly protections for endangered fish species, frequently limit water diversions and substantially increase freshwater flow to San Francisco Bay. We analyzed long-term trends in freshwater flow to San Francisco Bay relative to annual runoff from its Central Valley watershed, and the frequency and magnitude of specific regulatory and physical constraints that govern operations of the water export facilities. We found that the percentage of Central Valley runoff that reached San Francisco Bay during the ecologically sensitive winter-spring period declined over the past several decades, such that the estuary experienced drought conditions in most years. During a 9-year period that included a severe natural drought, exports were constrained to maintain salinity control as often as to protect endangered fish populations. Salinity-control and system-capacity constraints were responsible for Delta outflow volumes that dwarfed those related to protection of fish and wildlife populations, endangered or otherwise. These results run counter to common media narratives. We recommend rapid synthesis and easily accessible presentation of data on Central Valley water diversions and constraints on them; such data should be contextualized via comparison to regional hydrology and water management system capacity.","PeriodicalId":38364,"journal":{"name":"San Francisco Estuary and Watershed Science","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.15447/SFEWS.2019V17ISS1ART1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42061738","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}

{"title":"Diets of Largemouth Bass (Micropterus salmoides) in the Sacramento San Joaquin Delta","authors":"K. Weinersmith, Denise D. Colombano, Andrew J. Bibian, M. Young, A. Sih, J. L. Conrad","doi":"10.15447/SFEWS.2019V17ISS1ART3","DOIUrl":"https://doi.org/10.15447/SFEWS.2019V17ISS1ART3","url":null,"abstract":"Largemouth Bass (Micropterus salmoides) were introduced into the Sacramento-San Joaquin Delta (the Delta) over 100 years ago. In the last 2 decades, the abundance of centrarchids (including Largemouth Bass) in the littoral zone has increased, while some native fish and fish that were previously abundant in the pelagic zone have declined. Largemouth Bass are now one of the most abundant piscivores in the Delta. Understanding the ecology of this top predator — including a comprehensive understanding of what prey are important in Largemouth Bass diets — is important to understanding how this species may affect the Delta fish community. To address this need, we conducted electrofishing surveys of Largemouth Bass at 33 sites every 2 months from 2008 to 2010, measuring fish fork lengths and collecting stomachs contents at each site. We characterized diets using Percent Index of Relative Importance for 3,004 Largemouth Bass, with samples that spanned all seasons. Amphipods dominated the diets of Largemouth Bass ≤175 mm FL year-round, with dipterans, odonates, and copepods and cladocerans representing other important diet items. Non-native red swamp crayfish (Procambarus clarkii) were the most important prey for Largemouth Bass >175 mm FL. Non-native centrarchids (including Largemouth Bass) and amphipods were important prey items as well. Prickly Sculpin (Cottus asper) were the most frequently consumed native fish. Other native fish and pelagic fish species rarely occurred in Largemouth Bass diets, and we discuss trends in how the frequency of co-occurrence of these fishes with Largemouth Bass in the electrofishing surveys was associated with their frequency in Largemouth Bass diets. The Largemouth Bass in the Delta appear to be sustained largely on a diet of other non-natives that reside in the littoral zone.","PeriodicalId":38364,"journal":{"name":"San Francisco Estuary and Watershed Science","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.15447/SFEWS.2019V17ISS1ART3","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46903414","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}

{"title":"Evaluation of Long-Term Mark-Recapture Data for Estimating Abundance of Juvenile Fall-Run Chinook Salmon on the Stanislaus River from 1996 to 2017","authors":"Tyler J Pilger, Matthew L. Peterson, Dana J. Lee, A. Fuller, D. Demko","doi":"10.15447/SFEWS.2019V17ISS1ART4","DOIUrl":"https://doi.org/10.15447/SFEWS.2019V17ISS1ART4","url":null,"abstract":"Conservation and management of culturally and economically important species rely on monitoring programs to provide accurate and robust estimates of population size. Rotary screw traps (RSTs) are often used to monitor populations of anadromous fish, including fall-run Chinook Salmon (Oncorhynchus tshawytscha) in California’s Central Valley. Abundance estimates from RST data depend on estimating a trap's efficiency via mark-recapture releases. Because efficiency estimates are highly variable and influenced by many factors, abundance estimates can be highly uncertain. An additional complication is the multiple accepted methods for how to apply a limited number of trap efficiency estimates, each from discrete time-periods, to a population’s downstream migration, which can span months. Yet, few studies have evaluated these different methods, particularly with long-term monitoring programs. We used 21 years of mark-recapture data and RST catch of juvenile fall-run Chinook Salmon on the Stanislaus River, California, to investigate factors associated with trap efficiency variability across years and mark-recapture releases. We compared annual abundance estimates across five methods that differed in treatment of trap efficiency (stratified versus modeled) and statistical approach (frequentist versus Bayesian) to assess the variability of estimates across methods, and to evaluate whether method affected trends in estimated abundance. Consistent with short-term studies, we observed negative associations between estimated trap efficiency and river discharge as well as fish size. Abundance estimates were robust across all methods, frequently having overlapping confidence intervals. Abundance trends, for the number of increases and decreases from year to year, did not differ across methods. Estimated juvenile abundances were significantly related to adult escapement counts, and the relationship did not depend on estimation method. Understanding the sources of uncertainty related to abundance estimates is necessary to ensure that high-quality estimates are used in life cycle and stock-recruitment modeling.","PeriodicalId":38364,"journal":{"name":"San Francisco Estuary and Watershed Science","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.15447/SFEWS.2019V17ISS1ART4","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46382895","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}