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 10, Issue 4, 2012
Abstract are not presented with Editorials. -SFEWS Editors
We modeled the hydrology of basins draining into the northern portion of the San Francisco Bay Estuary (North San Pablo Bay) using a regional water balance model (Basin Characterization Model; BCM) to estimate potential effects of climate change at the watershed scale. The BCM calculates water balance components, including runoff, recharge, evapotranspiration, soil moisture, and stream flow, based on climate, topography, soils and underlying geology, and the solar-driven energy balance. We downscaled historical and projected precipitation and air temperature values derived from weather stations and global General Circulation Models (GCMs) to a spatial scale of 270 m. We then used the BCM to estimate hydrologic response to climate change for four scenarios spanning this century (2000–2100). Historical climate patterns show that Marin’s coastal regions are typically on the order of 2 °C cooler and receive five percent more precipitation compared to the inland valleys of Sonoma and Napa because of marine influences and local topography. By the last 30 years of this century, North Bay scenarios project average minimum temperatures to increase by 1.0 °C to 3.1 °C and average maximum temperatures to increase by 2.1 °C to 3.4 °C (in comparison to conditions experienced over the last 30 years, 1981–2010). Precipitation projections for the 21st century vary between GCMs (ranging from 2 to 15% wetter than the 20th-century average). Temperature forcing increases the variability of modeled runoff, recharge, and stream discharge, and shifts hydrologic cycle timing. For both high- and low-rainfall scenarios, by the close of this century warming is projected to amplify late-season climatic water deficit (a measure of drought stress on soils) by 8% to 21%. Hydrologic variability within a single river basin demonstrated at the scale of subwatersheds may prove an important consideration for water managers in the face of climate change. Our results suggest that in arid environments characterized by high topo-climatic variability, land and water managers need indicators of local watershed hydrology response to complement regional temperature and precipitation estimates. Our results also suggest that temperature forcing may generate greater drought stress affecting soils and stream flows than can be estimated by variability in precipitation alone.
Delta Flow Factors Influencing Stray Rate of Escaping Adult San Joaquin River Fall-Run Chinook Salmon (Oncorhynchus tshawytscha)
Adult salmon that stray when they escape into non-natal streams to spawn is a natural phenomenon that promotes population growth and genetic diversity, but excessive stray rates impede adult abundance restoration efforts. Adult San Joaquin River (SJR) Basin fall-run Chinook salmon (Oncorhynchus tshawytscha) that return to freshwater to spawn migrate through the San Francisco Bay and Sacramento–San Joaquin River Delta (Delta). The Delta has been heavily affected by land development and water diversion. During the fall time-period for the years 1979 to 2007 Delta pumping facilities diverted on average 340% of the total inflow volume that entered the Delta from the SJR. The hypothesis tested in this paper is that river flow and Delta exports are not significantly correlated with SJR salmon stray rates. Adult coded-wire-tagged salmon recoveries from Central Valley rivers were used to estimate the percentage of SJR Basin salmon that strayed to the Sacramento River Basin. SJR salmon stray rates were negatively correlated (P = 0.05) with the average magnitude of pulse flows (e.g., 10 d) in mid- to late-October and positively correlated (P = 0.10) with mean Delta export rates. It was not possible to differentiate between the effects of pulse flows in October and mean flows in October and November on stray rates because of the co-linearity between these two variables. Whether SJR-reduced pulse flow or elevated exports causes increased stray rates is unclear. Statistically speaking the results indicate that flow is the primary factor. However empirical data indicates that little if any pulse flow leaves the Delta when south Delta exports are elevated, so exports in combination with pulse flows may explain the elevated stray rates. For management purposes, we developed two statistical models that predict SJR salmon stray rate: (1) flow and export as co-independent variables; and (2) south Delta Export (E) and SJR inflow (I) in the form of an E:I ratio.
- 1 supplemental PDF
Pre-Screen Loss and Fish Facility Efficiency for Delta Smelt at the South Delta's State Water Project, California
Water exports have been implicated in the decline of fish populations in the upper San Francisco Estuary, California. We evaluated the relation between delta smelt salvage at the John E. Skinner Delta Fish Protective Facility (SFF) and underlying entrainment losses at the State Water Project (SWP, south Delta). We used cultured delta smelt in mark–recapture experiments in February and March 2009 (adults) and June 2009 (juveniles) to estimate: (1) the percent of fish recaptured at the SFF of the total released at the entrance of the SFF (fish facility efficiency), (2) the percent of fish recaptured at the SFF of the total released in Clifton Court Forebay (CCF), a reservoir for SWP exports, and (3) the fish losses in CCF and before the SFF (pre-screen loss). Mean fish facility efficiency was lower in successive releases: February (53.2%), March (44.0%) and June (24.0%). The mean percent recapture of fish released at the CCF entrance was also lower over time: February (3.01%); March (0.41%) and June (0.03%). Correspondingly higher mean pre-screen losses occurred over time: February (94.3%); March (99.1%) and June (99.9%). We concluded that: (1) entrainment losses of delta smelt could be higher at times, compared to other species previously studied at the SWP; (2) pre-screen loss was the largest source of mortality for delta smelt; (3) increased release distance from the SFF and residence time in CCF—and decreased exports—resulted in a lower percentage of recaptured fish at the SFF; and (4) salvage of delta smelt at the SWP does not seem to be a consistent index of entrainment.
Policy and Program Analysis
This paper presents insights from interviews with over 100 California water policy experts, who answered open-ended questions regarding California’s long-term water policy challenges and potential solutions. Interviews were conducted in the spring and summer of 2010, and interviewees were selected from a range of sectors and regions within California. Top long-term policy problems cited include management of the Sacramento–San Joaquin Delta, dysfunctional institutions and water governance, unsustainable water supplies and flood management, poor environmental protection, and problems with water rights and valuing water. In addition to a range of specific management solutions, respondents emphasized the importance of public education, incentivized cooperation, more holistic water management, local innovation, and removal of regulatory obstacles as primary solutions to California’s long-term water challenges. There was little emphasis on new surface storage projects, except from politicians. Other respondents preferred local and regional approaches to improve water supply, such as conservation, groundwater banking, recycling, or stormwater management. Despite differences in opinion on the problems with implementation of the Endangered Species Act, there was broad agreement that environmental management approaches need to shift away from single-species, piecemeal approaches toward ecosystem-based, multi-species approaches.