SFEWS Vol. 20, Issue 2 | June 2022
#ChinookSalmon #SacramentoSplittail #tidalmarsh #floodplain #openwater #drought #flood #juvenileproductionestimate #JPE #lifehistory #raceidentification #springrun #SacramentoRiver #CADelta #quantile #regressionforest #Steelhead #machinelearning #entrainmentloss #SanFrancisco #estuary #SFE #BayDelta #gillnet #gearselectivity #Drainage #waterquality #agriculturaldrainage #returnflow #diversions #Delta #island #groundwater #nitrogen #phosphorous #metals
Considerations for the Development of a Juvenile Production Estimate for Central Valley Spring-Run Chinook Salmon
Effective species management depends on accurate estimates of population size. There are, however, no estimates of annual juvenile production for Central Valley spring-run Chinook Salmon (“spring run”), a highly imperiled species in California, making it difficult to evaluate population status and effectively manage key issues such as entrainment of this species at water diversions. In recognition of this critical information gap, we initiated an effort to develop a juvenile production estimate (JPE) for spring run, defined here as an annual forecast of the number of juvenile Central Valley spring-run Chinook Salmon that enter the Sacramento–San Joaquin Delta (“Delta”) from the Sacramento Valley.
Machine Learning Forecasts to Reduce Risk of Entrainment Loss of Endangered Salmonids at Large-Scale Water Diversions in the Sacramento–San Joaquin Delta, California
Incidental entrainment of fishes at large-scale state and federal water diversion facilities in the Sacramento-San Joaquin Delta, California, can trigger protective management actions when limits imposed by environmental regulations are approached or exceeded. These actions can result in substantial economic costs, and likewise they can affect the status of vulnerable species. Here, we examine data relevant to water management actions during January–June; the period when juvenile salmonids are present in the Delta.
Gill Net Selectivity for Fifteen Fish Species of the Upper San Francisco Estuary
Gill-net size selectivity for 15 fish species occurring in the upper San Francisco Estuary was estimated from a data set compiled from multiple studies which together contained 7,096 individual fish observations from 882 gill net sets. The gill nets considered in this study closely resembled the American Fisheries Society’s recommended standardized experimental gill nets for sampling inland waters. Relationships between gill-net mesh sizes and the sizes for each fish species retained in them were estimated indirectly using generalized linear modeling and maximum likelihood.
Nutrient and Trace Element Contributions from Drained Islands in the Sacramento–San Joaquin Delta, California
Inventorying nutrient and trace element sources in the Sacramento-San Joaquin Delta (the Delta) is critical to understanding how changes—including alterations to point source inputs such as upgrades to the Sacramento Regional Wastewater Treatment Plant (SRWTP) and landscape-scale changes related to wetland restoration—may alter the Delta’s water quality. While island drains are a ubiquitous feature of the Delta, limited data exist to evaluate island drainage mass fluxes in this system. To better constrain inputs from island drains, we measured monthly discharge along with nutrient and trace element concentrations in island drainage on three Delta islands and surrounding rivers from June 2017 to September 2018.
Climate Change Impacts on San Francisco Estuary Aquatic Ecosystems: A Review ample header
In the San Francisco Estuary, signals of climate change are apparent in the long-term monitoring record. Here we synthesize current and potential future climate change effects on three main ecosystems (floodplain, tidal marsh, and open water) in the upper estuary and two representative native fishes that commonly occur in these ecosystems (anadromous Chinook Salmon, Oncorhynchus tshawytscha and estuarine resident Sacramento Splittail, Pogonichthys macrolepidotus).
Volume 10, Issue 3, 2012
Special Issue: Conceptual Models to Support Restoration Planning: the DRERIP Approach
Research Article
Using Conceptual Models in Ecosystem Restoration Decision Making: An Example from the Sacramento-San Joaquin River Delta, California
The Sacramento–San Joaquin Delta (the Delta) is located on the western edge of California’s Central Valley and is of critical ecological and economic importance. However, ecosystem alterations for human uses changed many of the Delta’s natural processes, and it is now considered in need of restoration. An approach was developed to evaluate and rank restoration actions in the Delta under the Ecosystem Restoration Program’s Delta Regional Ecosystem Restoration Implementation Plan (DRERIP). The DRERIP approach provides an explicit framework for evaluating restoration actions, using linked conceptual models, an action evaluation procedure, and a decision-support tool. Conceptual models allow scientists and managers to synthesize scientific information and make qualitative predictions about ecosystem function and restoration outcomes to guide and focus restoration efforts. The action evaluation procedure is a structured assessment of restoration actions. The procedure clearly describes actions to be evaluated, assesses the magnitude (importance and scale) and certainty of anticipated ecological outcomes, estimates degrees of worth (achieving intended outcomes) and risk (causing adverse consequences), evaluates the reversibility of the action, and identifies opportunities for learning. The values for worthiness, risk, reversibility, and learning opportunity are used in the decision- support tool to determine the fate of a proposed action. The decision-support tool is a structured decision tree that determines the disposition of an action: whether a restoration project should be discarded, revised with a different approach and re-evaluated, or implemented; and, if implemented, at what scale (targeted research, pilot project, or full implementation). The DRERIP approach provides managers with a valuable tool for restoration planning, and a foundation for integration with quantitative methods for a comprehensive ecosystem restoration plan.
Juvenile Chinook Salmon (Oncorhynchus tshawytscha) in and Around the San Francisco Estuary
Central Valley Chinook must pass through the San Francisco Estuary as juveniles and again as maturing adults. Much attention has been given to the effects on Chinook of management of the freshwater part of the estuary, and the Sacramento–San Joaquin Delta, and especially to the effects on Chinook of diversions of water from the Delta. Here, I review available information on juvenile Chinook in and around the estuary that seems most relevant to management of the estuary and of Chinook. Most naturally produced juvenile fall Chinook enter the estuary as small fish (<50 mm) that typically use tidal habitats, and anthropogenic changes in the Delta and around the bays have sharply reduced that habitat. Nevertheless, there is evidence that many surviving naturally produced fall Chinook leave fresh water at <55 mm length. Juvenile Chinook from other runs are older and larger when they enter the estuary, and probably pass through it more rapidly. Presumably, these have been less directly affected by loss of tidal habitat, but are also affected by degradation of the estuarine ecosystem. The effects of Delta diversions on Chinook vary strongly by run and river of origin; surprisingly few Sacramento River fall Chinook have been recovered at the diversions. Central Valley Chinook, especially fall Chinook, are strongly affected by hatchery culture that reduces juvenile life-history diversity, probably results in density-dependent mortality in the estuary, and presumably reduces fitness for natural reproduction. Hatchery culture diverts juvenile fall Chinook away from, and precludes for selection for, the life history trajectories followed by most naturally produced fish, to which more attention should be given.
A Conceptual Model of Sedimentation in the Sacramento–San Joaquin Delta
Sedimentation in the Sacramento–San Joaquin River Delta builds the Delta landscape, creates benthic and pelagic habitat, and transports sediment-associated contaminants. Here we present a conceptual model of sedimentation that includes submodels for river supply from the watershed to the Delta, regional transport within the Delta and seaward exchange, and local sedimentation in open water and marsh habitats. The model demonstrates feedback loops that affect the Delta ecosystem. Submerged and emergent marsh vegetation act as ecosystem engineers that can create a positive feedback loop by decreasing suspended sediment, increasing water column light, which in turn enables more vegetation. Sea-level rise in open water is partially countered by a negative feedback loop that increases deposition if there is a net decrease in hydrodynamic energy. Manipulation of regional sediment transport is probably the most feasible method to control suspended sediment and thus turbidity. The conceptual model is used to identify information gaps that need to be filled to develop an accurate sediment transport model.
A Conceptual Model for Floodplains in the Sacramento-San Joaquin Delta
Floodplains are among the most biologically productive and diverse ecosystems on Earth and they provide significant benefits to society such as attenuation of floodwaters, groundwater recharge, filtration of nutrients and sediments, carbon sequestration, fisheries productivity and recreation. However, floodplains are also among the most converted and threatened ecosystems. Floodplain habitats in the Sacramento-San Joaquin Delta, and throughout California’s Central Valley, have been greatly reduced from their historic extent and key processes that create and maintain floodplains, such as flood flows and meander migration, have been greatly altered. These widespread alterations to habitats and processes have lead to declines in many species’ populations in California’s Central Valley and Delta, creating challenges for both environmental and water management. To address these challenges numerous entities and programs are now focused on restoring floodplains and other Delta habitats. This paper provides a conceptual model for floodplains that characterizes the key features and identifies the critical processes, drivers, and linkages that allow floodplains to produce a variety of functional outputs of management importance. These outputs include: (1) the floodplain habitat mosaic, including riparian vegetation and its associated wildlife; (2) spawning and rearing habitat for native fish; and (3) food-web productivity that can support native fish on the floodplain as well as be exported to downstream ecosystems. The model emphasizes that the production of these outputs from floodplains requires vertical and lateral hydrological connectivity across a broad range of flow conditions. For example, long-duration flooding in the spring promotes native fish spawning and food-web productivity that benefits native species.