American shad — the Delta’s most-abundant and least-considered anadromous fish

Center for California Water Resources Policy & Management | February 21st, 2022

American shad are the Chinook salmon of herring. Like Chinook salmon, adult American shad spend several years in the ocean before returning to rivers for spawning — the

American shad are the Chinook salmon of herring. Like Chinook salmon, adult American shad spend several years in the ocean before returning to rivers for spawning — they’re anadromous. Also, like salmon, anglers love shad because they’re fun to catch and good to eat. Well, okay, shad are not as good to eat as ocean caught salmon, but they are delicious when prepared well. American shad are native to the east coast of North American. They were introduced to the Sacramento River after repeated releases of shad fry — transported via the then newly completed transcontinental railroad — between 1871 and 1880. Shad quickly became abundant in the Sacramento River and proceeded to colonize many other rivers along the West Coast. In the Columbia River system, shad are now the most abundant anadromous fish species migrating upstream through impoundments on the lower Columbia River. At Bonneville Dam — 140 river miles upstream of the Columbia River mouth — an average of 2.2 million adult shad migrated upstream each year between 1992 and 2003. In contrast, an average of 940,000 adult salmonids migrated annually past Bonneville Dam during the same period.

An Alternative Technique to Quantify the Incidental Take of Listed Anadromous Fishes at the Federal and State Water Export Facilities in the San Francisco Bay-Delta Estuary

National Marine Fisheries Service (NMFS) | July 1st, 2011

An Integrated Surface Water-Groundwater Interaction Model for the Carmel River

California State University, Monterey Bay | April 30th, 2010

The Carmel River supplies fresh water to the residents of the Monterey Peninsula within the water district served by the California American Water company (Cal-Am). The S

The Carmel River supplies fresh water to the residents of the Monterey Peninsula within the water district served by the California American Water company (Cal-Am). The State Water Resources Control Board, in 1995, ordered that Cal-Am reduce their annual diversions from the Carmel River Watershed to within legal right (3,376 acre-feet per year). An alternative water source to the Carmel River has yet to be determined, and as a result, Cal-Am must continue to divert more water than their legal entitlement. The current magnitude of diversions has a negative impact on the spawning and migrating habitat of Steelhead (Oncorhynchus mykiss). Existing software in the Tarsier Environmental Modeling Framework was used to model the spatial distribution of surface water along the Carmel River. The model simulated the flow of water downstream from catchment area to the Pacific Ocean. The river channel was represented by a network data set comprised of links, representing individual reaches of the river, connected by nodes. Prior to my work, systematic error in the model was thought to be partially the result of the model lacking a simulation of the interactions between the surface water and the underlying aquifer. A groundwater sub-model was developed to correct for the systematic error. The groundwater sub-model simulated the movement of water between the river channel and the aquifer. Stock variables representing a shallow and deep aquifer were added to each link of the network data set. Simulated water in the surface water stock of each link percolates to these aquifer stocks until the groundwater reaches aquifer capacity, allowing surface water to continue flowing downstream. The model also allows the lateral flow of groundwater according to Darcy’s Law. Quantitative and qualitative analysis of model output compared to observed data showed an increase in model accuracy. Quantitatively, a Nash- Sutcliff Coefficient was improved from 0.88 to 0.97 with the addition of the groundwater model. Qualitatively, a visualization of the longitudinal profile of the river system showed the simulated aquifer controlling the surface flow. A hypothetical application of this model is presented where reducing the pumping rate from the aquifer allowed the wetted river channel to increase by 2.5 km. Future work on the model should include a reservoir sub-model and accounting for spatial variability in the precipitation throughout the catchment area. With these improvements it will be possible to improve predictions of the spatial distribution of surface water along the Carmel River given hypothetical scenarios such as the rate and spatial distribution of pumping from the Carmel Aquifer. Using these simulations to inform decisions of river management could benefit all stakeholders of the river.

An unprecedented coastwide toxic algal bloom linked to anomalous ocean conditions

American Geophysical Union (AGU) | October 9th, 2016

A coastwide bloom of the toxigenic diatom Pseudo-nitzschiain spring 2015 resulted in the largest recorded outbreak of the neurotoxin, domoic acid, along the North Ameri

A coastwide bloom of the toxigenic diatom Pseudo-nitzschiain spring 2015 resulted in the largest recorded outbreak of the neurotoxin, domoic acid, along the North American west coast. Elevated toxins were measured in numerous stranded marine mammals and resulted in geographically extensive and prolonged closures of razor clam, rock crab, and Dungeness crab fisheries. We demonstrate that this outbreak was initiated by anomalously warm ocean conditions. Pseudo-nitzschia australis thrived north of its typical range in the warm, nutrient-poor water that spanned the northeast Pacific in early 2015. The seasonal transition to upwelling provided the nutrients necessary for a large-scale bloom; a series of spring storms delivered the bloom to the coast. Laboratory and field experiments confirming maximum growth rates with elevated temperatures and enhanced toxin production with nutrient enrichment, together with a retrospective analysis of toxic events, demonstrate the potential for similarly devastating ecological and economic disruptions in the future.

Anadromous Salmonid Fish Passage Facility Design

National Marine Fisheries Service (NMFS) | July 26th, 2011

The primary effect of barriers (e.g., hydroelectric dams, water storage projects, irrigation diversions, impassable culverts, etc.) on Pacific salmonids is the reduction

The primary effect of barriers (e.g., hydroelectric dams, water storage projects, irrigation diversions, impassable culverts, etc.) on Pacific salmonids is the reduction in population abundance and productivity through excessive mortality and reduction in habitat quantity and quality. Individuals are lost to the population due to death from passing through turbines, disproportionate predation in reservoirs, entrainment at unscreened or improperly screened diversions, etc. Spatial structure and diversity have also been reduced by the loss of nearly 40% of salmon habitat from dams (NRC 1996), either through complete blockage or inundation. This document is intended to assist with improving conditions for salmonids that must migrate past barriers to complete their life cycle. The task involved in successfully passing fish upstream or downstream of an in-river impediment is a dynamic integration of fish behavior, physiology, and bio-mechanics with hydraulic analysis, hydrologic study, and engineering. Installing a fish passage structure does not constitute providing satisfactory fish passage unless all of the above components are adequately factored into the design. The following document provides criteria, rationale, guidelines, and definitions for the purpose of designing proper fish passage facilities for the safe, timely, and efficient upstream and downstream passage of anadromous salmonids at impediments created by artificial structures, natural barriers (where provision of fish passage is consistent with management objectives), or altered instream hydraulic conditions. This document provides fishway facility design standards for the National Marine Fisheries Service, and is to be used for actions pertaining to the various authorities and jurisdictions of NMFS, including Section 18 of the Federal Power Act (FPA), the Endangered Species Act (ESA), and the Magnuson-Stevens Fishery Conservation and Management Act (MSA) in the Northwest Region (NWR). This document intends to provide generic guidance as an alternative to active participation by NMFS engineers in a design process, for the purpose of providing designs that will be acceptable for fishways that fall within NMFS jurisdictions. If passage facilities are designed and constructed in a manner consistent with these criteria, adverse impacts to anadromous fish migration will be minimized. Instances will occur where a fish passage facility may not be a viable solution for correcting a passage impediment, due to biological, sociological, or economic constraints. In these situations, removal of the impediment or altering operations may be a suitable surrogate for a constructed fish passage facility. In other situations, accomplishing fish passage may not be an objective of NMFS because of factors such as limited habitat or lack of naturally occurring runs of anadromous fish upstream of the site. To determine whether NMFS will use its various authorities to promote or to prescribe fish passage, NMFS will rely on a collaborative approach, considering the views of other fisheries resource agencies, Native American Tribes, non-government organizations, and citizen groups, and will strive to accomplish the objectives in watershed plans for fisheries restoration and enhancement. This document does not address aspects of design other than those that provide for safe and timely fish passage, and to some extent, preservation of aquatic habitat. Structural integrity, public safety, and other aspects of facility design are the responsibility of the principal design engineer, who should ensure that the final facility design meets all other requirements in addition to the fish passage criteria and guidelines contained in this document.

Anadromous Salmonids in the Delta: New Science 2006-2016

University of California, Davis (UC Davis) | July 1st, 2016

As juvenile salmon enter the Delta, they disperse among its complex channel network where they are subject to channel-specific processes that affect their rate of migrati

As juvenile salmon enter the Delta, they disperse among its complex channel network where they are subject to channel-specific processes that affect their rate of migration, vulnerability to predation, feeding success, growth rates, and ultimately, survival. In the decades before 2006, tools available to quantify growth, dispersal, and survival of juvenile salmon in this channel network were limited. Fortunately, thanks to technological advances, much has been learned over the past decade about the role of the Delta in the life cycle of juvenile salmon. One of the most important advances during the past decade has been the widespread adoption of acoustic telemetry techniques. Use of telemetry has shed light on how survival varies among alternative migration routes and the proportion of fish that use each migration route. Chemical and structural analysis have provided insights about when juveniles left their natal river and provided evidence of extended rearing in the brackish or saltwater regions of the Delta. New advancements in genetics now allow individuals captured by trawls to be assigned to specific runs. Detailed information about movement and survival in the Delta has spurred development of agent-based models of juvenile salmon that are coupled to hydrodynamic models. Although much has been learned, knowledge gaps remain about how very small juvenile salmon (fry and parr) use the Delta. Understanding how all life stages of juvenile salmon grow, rear, and survive in the Delta is critical for devising management strategies that support a diversity of life history strategies.

Analyses of Rotary Screw Trap Sampling of Migrating Juvenile Chinook Salmon in the Stanislaus River, 1996-2005

Delta Stewardship Council (Delta Council) | August 1st, 2006

Anatomy of a range contraction: Flow–phenology mismatches threaten salmonid fishes near their trailing edge

National Academy of Sciences (NAS) | March 31st, 2025

Climate change is redistributing life on Earth, with profound impacts for ecosystems and human well-being. While repeat surveys separated by multidecadal intervals can de

Climate change is redistributing life on Earth, with profound impacts for ecosystems and human well-being. While repeat surveys separated by multidecadal intervals can determine whether observed shifts are in the expected direction (e.g., poleward or upslope due to climate change), they do not reveal their mechanisms or time scales: whether they were gradual responses to environmental trends or punctuated responses to disturbance events. Here, we document population reductions and temporary range contractions at multiple sites resulting from drought for three Pacific salmonids at their ranges’ trailing edge. During California’s 2012 to 2016 historic multiyear drought, the 2013 to 2014 winter stood apart because rainfall was both reduced and delayed. Extremely low river flows during the breeding season (“flow–phenology mismatch”) reduced or precluded access to breeding habitat. While Chinook (Oncorhynchus tshawytscha) experienced a down-river range shift, entire cohorts failed in individual tributaries (steelhead trout, O. mykiss) and in entire watersheds (coho salmon, O. kisutch). Salmonids returned to impacted sites in subsequent years, rescued by reserves in the ocean, life history diversity, and, in one case, a conservation broodstock program. Large population losses can, however, leave trailing-edge populations vulnerable to extinction due to demographic stochasticity, making permanent range contraction more likely. When only a few large storms occur during high flow season, the timing of particular storms plays an outsized role in determining which migratory fish species are able to access their riverine breeding grounds and persist.

Annual Report of Activities October 1, 2013 to September 30, 2014, American River Group (ARG)

Delta Stewardship Council (Delta Council) | September 30th, 2014

Anthropogenic carbon and ocean pH: Oceanography

Nature Portfolio (Springer Nature) | September 25th, 2003

Most carbon dioxide released into the atmosphere as a result of the burning of fossil fuels will eventually be absorbed by the ocean1, with potentially adverse co

Most carbon dioxide released into the atmosphere as a result of the burning of fossil fuels will eventually be absorbed by the ocean1, with potentially adverse consequences for marine biota. Here we quantify the changes in ocean pH that may result from this continued release of CO2 and compare these with pH changes estimated from geological and historical records. We find that oceanic absorption of CO2 from fossil fuels may result in larger pH changes over the next several centuries than any inferred from the geological record of the past 300 million years, with the possible exception of those resulting from rare, extreme events such as bolide impacts or catastrophic methane hydrate degassing.