SFEWS Vol. 20, Issue 1 | March 2021
#CentralValley #ChinookSalmon #otolithchemistry #Steelhead #monitoring #surveys #catchability #detectionefficiency #DeltaSmelt #supplementation #Ich #pathogens #organiccarbon #stablecarbon #nitrogen #inputs #YubaRiver #watersheds
Variation in Juvenile Salmon Growth Opportunities Across a Shifting Habitat Mosaic
Coleman et al. found that juvenile Chinook Salmon grew faster in the Delta in some years (2016), but slower in the Delta during drought conditions (2014 to 2015). Habitat that featured faster growth rates varied within and among years, suggesting the importance of maintaining a habitat mosaic for juvenile salmonids, particularly in a dynamic environment such as the California Central Valley.
Counting the Parts to Understand the Whole: Rethinking Monitoring of Steelhead in California’s Central Valley
Eschenroeder et al. argue that a reallocation of monitoring resources to better understand the interaction between resident and anadromous Steelhead would provide better data to estimate the vital rates needed to evaluate the effects of recovery actions.
Relative Bias in Catch Among Long-Term Fish Monitoring Surveys Within the San Francisco Estuary
Huntsman et al. assessed relative catchability differences among four long-term fish monitoring surveys from the San Francisco Estuary. Their results demonstrate that catchability is a source of bias among monitoring efforts within the San Francisco Estuary, and assuming equal catchability among surveys, species, and size classes could result in significant bias when describing spatio-temporal patterns in catch if ignored.
Investigation of Molecular Pathogen Screening Assays for Use in Delta Smelt
Gille et al. conducted a pilot study that applied molecular assays originally developed in salmonids to assess the presence of a wide variety of pathogens in the gill tissue of cultured and wild Delta Smelt—as well as cultured fish—deployed in enclosures in the estuary. Although disease is not an overt cause of population decline of Delta Smelt in the San Francisco Estuary, comprehensive pathogen presence and prevalence data are lacking, and unintended transmission of pathogens can have devastating effects on populations already at-risk or on the natural ecosystem at large. Their results corroborate previous work that cultured Delta Smelt do not appear to present a high risk for pathogen transmission during population supplementation or reintroduction.
Multi-Biomarker Analysis for Identifying Organic Matter Sources in Small Mountainous River Watersheds: A Case Study of the Yuba River Watershed
Pondell and Canuel's study focused on identifying the composition of watershed-derived organic matter (OM). To better understand inputs to inland waters and improve distinguish between terrigenous and aquatic sources in downstream systems, such as estuaries and coasts, they surveyed OM sources from the Yuba River watershed in northern California to identify specific biomarkers that represent aquatic and terrigenous OM sources. Results demonstrate the utility of multi-biomarker studies for distinguishing between OM from different sources and land uses, offering new insights for biogeochemical studies in aquatic systems.
Volume 17, Issue 4, 2019
Sixteen years ago, in October 2003, San Francisco Estuary and Watershed Science (SFEWS) published its first article. An anniversary like this is a good time to remind ourselves of our history, and to ask if the journal is living up to the goals we set in 2003. And if so, are those goals consistent with today’s needs? In 2004, CDL’s eScholarship Publishing Group counted an average of 254 requests per month for SFEWS online articles. In 2010, that increased to 1,232 requests per month, and in 2014 to 1,764 per month. In the first 10 months of 2019, 4,420 articles were requested per month. Downloads have been consistently 35% to 40% of requests. Taking data from 2014 through 2017, the search engine Scopus’ CiteScore for SFEWS increased from 0.32 to 1.64; its rank is 82nd of 203 journals in the Water Science and Technology category for 2018, a remarkable climb from being ranked 120 of 179 in 2014. SFEWS is ranked fifth among 53 open access journals in the aquatic sciences, according to the Science Journal Ranking index; and in the top 25% among all 218 aquatic science journals ranked by that index. Thus, SFEWS has grown from an outlet designed to expand access to regional science to a well-respected scientific journal in its own right. Our look back shows that SFEWS has probably grown beyond our original expectations in size, influence, and stature.
Policy and Program Analysis
Review of and Recommendations for Monitoring Contaminants and their Effects in the San Francisco Bay−Delta
Legacy and current-use contaminants enter into and accumulate throughout the San Francisco Bay−Delta (Bay−Delta), and are present at concentrations with known effects on species important to this diverse watershed. There remains major uncertainty and a lack of focused research able to address and provide understanding of effects across multiple biological scales, despite previous and ongoing emphasis on the need for it. These needs are challenging specifically because of the established regulatory programs that often monitor on a chemical-by-chemical basis, or in which decisions are grounded in lethality-based endpoints. To best address issues of contaminants in the Bay−Delta, monitoring efforts should consider effects of environmentally relevant mixtures and sub-lethal impacts that can affect ecosystem health. These efforts need to consider the complex environment in the Bay−Delta including variable abiotic (e.g., temperature, salinity) and biotic (e.g., pathogens) factors. This calls for controlled and focused research, and the development of a multi-disciplinary contaminant monitoring and assessment program that provides information across biological scales. Information gained in this manner will contribute toward evaluating parameters that could alleviate ecologically detrimental outcomes. This review is a result of a Special Symposium convened at the University of California−Davis (UCD) on January 31, 2017 to address critical information needed on how contaminants affect the Bay−Delta. The UCD Symposium focused on new tools and approaches for assessing multiple stressor effects to freshwater and estuarine systems. Our approach is similar to the recently proposed framework laid out by the U.S. Environmental Protection Agency (USEPA) that uses weight of evidence to scale toxicological responses to chemical contaminants in a laboratory, and to guide the conservation of priority species and habitats. As such, we also aimed to recommend multiple endpoints that could be used to promote a multi-disciplinary understanding of contaminant risks in Bay−Delta while supporting management needs.
The Sacramento–San Joaquin Delta has been invaded by several species of non-native predatory fish that are presumed to be impeding native fish population recovery efforts. Since eradication of predators is unlikely, there is substantial interest in removing or altering manmade structures in the Delta that may exacerbate predation on native fish (contact points). It is presumed that these physical structures influence predator-prey dynamics, but how habitat features influence species interactions is poorly understood, and physical structures in the Delta that could be remediated to benefit native fish have not been inventoried completely. To inform future research efforts, we reviewed literature that focused on determining the effects of predator-prey interactions between fish, based on contact points that are commonly found in the Delta. We also performed a geospatial analysis to determine the extent of potential contact points in the Delta. We found that the effects of submerged aquatic vegetation (SAV) and artificial illumination are well studied and documented to influence predation in other freshwater systems worldwide. Conversely, other common structures in the Delta—such as docks, pilings, woody debris, revetment, and water diversions—did not have the same breadth of research. In the Delta, the spatial extent of the different types of contact points differed considerably. For example, 22% of the Delta water surface area is occupied by SAV, whereas docks only cover 0.44%. Our conclusion, based on both the literature review and spatial analysis, is that the effects of SAV and artificial illumination on predation warrant the most immediate future investigation in the Delta.
A Bayesian hierarchical model that integrated information about state and observation processes was used to estimate the number of adult Delta Smelt entrained into the southern Sacramento−San Joaquin Delta during water export operations by the California State Water Project and the Central Valley Project. The model hierarchy accounted for dynamic processes of transport, survival, sampling efficiency, and observation. Water export, mark−recapture, and fish facility count data informed each process. Model diagnostics and simulation testing indicated a good fit of the model, and that parameters were jointly estimable in the Bayesian hierarchical model framework. The model was limited, however, by sparse data to estimate survival and State Water Project sampling efficiency. Total December to March entrainment of adult Delta Smelt ranged from an estimated 142,488 fish in 2000 to 53 fish in 2014, and the efficiency of louvers used to divert entrained fish to fish facilities appeared to decline at high and low primary intake channel velocities. Though applied to Delta Smelt, the hierarchical modeling framework was sufficiently flexible to estimate the entrainment of other pelagic species.
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