Quantification of pre-screen loss of juvenile steelhead in Clifton Court Forebay

California Department of Water Resources (DWR) | August 26th, 2008

Rapid decline of California’s native inland fishes: a status assessment

University of California, Davis (UC Davis) | November 1st, 2010

Degradation of freshwater ecosystems is a global crisis best understood through intensive study of well-studied regional faunas. A quantitative protocol was used

Degradation of freshwater ecosystems is a global crisis best understood through intensive study of well-studied regional faunas. A quantitative protocol was used to determine conservation status of all 129 freshwater fishes native to California. Seven (5%) are extinct; 34 (26%) qualified for listing as endangered or threatened species; 32 (25%) were rated as imperiled, qualifying as California Species of Special Concern, with potential for listing; 34 (26%) rated being on a watch list and 22 (17%) were found to be relatively secure. Of 31 species officially listed under federal and state endangered species acts, 17 (55%) clearly qualified for listing under our criteria and 12 (39%) were rated as species of special concern. Conversely, of 34 extant species with the lowest ratings under our criteria, only 17 (50%) were officially listed. Climate change, area occupied and anthropogenic threats had the largest negative impact on status. Of the 15 categories of anthropogenic threats analyzed, those most likely to diminish status were alien species, agriculture and dams. Overall, 83% of California’s freshwater fishes are extinct, endangered, or in decline, a 16% increase since 1995 and a 21% increase since 1989. The decline seen in California’s inland fishes is probably typical of declines in areas that are less well documented, indicating a strong need for better methods of conservation of freshwater ecosystems.

Rapid emergence of climate change in environmental drivers of marine ecosystems

Nature Portfolio (Springer Nature) | March 7th, 2017

Climate change is expected to modify ecological responses in the ocean, with the potential for important effects on the ecosystem services provided to humankind

Climate change is expected to modify ecological responses in the ocean, with the potential for important effects on the ecosystem services provided to humankind. Here we address the question of how rapidly multiple drivers of marine ecosystem change develop in the future ocean. By analysing an ensemble of models we find that, within the next 15 years, the climate change-driven trends in multiple ecosystem drivers emerge from the background of natural variability in 55% of the ocean and propagate rapidly to encompass 86% of the ocean by 2050 under a ‘business-as-usual’ scenario. However, we also demonstrate that the exposure of marine ecosystems to climate change-induced stress can be drastically reduced via climate mitigation measures; with mitigation, the proportion of ocean susceptible to multiple drivers within the next 15 years is reduced to 34%. Mitigation slows the pace at which multiple drivers emerge, allowing an additional 20 years for adaptation in marine ecological and socio-economic systems alike.

Rapid progression of ocean acidification in the California current system

American Association for the Advancement of Science (AAAS) | June 14th, 2012

Nearshore waters of the California Current System (California CS) already today have a low carbonate saturation state, making them particularly susceptible to o

Nearshore waters of the California Current System (California CS) already today have a low carbonate saturation state, making them particularly susceptible to ocean acidification. Here, we use eddy-resolving model simulations to study the potential development of ocean acidification in this system up to 2050 under the SRES A2 and B1 scenarios. In both scenarios, the saturation state of aragonite Ωaragis projected to drop rapidly, with much of the nearshore regions developing summer-long undersaturation in the top 60 m within the next 30 years. By the year 2050, waters with Ωarag above 1.5 have largely disappeared and more than half of the waters are undersaturated year-round. Habitats along the seafloor become exposed to year-round undersaturation within the next 20 to 30 years. This has potentially major implications for the rich and diverse ecosystem that characterizes the California CS.

Recent declines in salmon body size impact ecosystems and fisheries

Nature Portfolio (Springer Nature) | August 19th, 2020

Declines in animal body sizes are widely reported and likely impact ecological interactions and ecosystem services. For harvested species subject to multiple stressors, l

Declines in animal body sizes are widely reported and likely impact ecological interactions and ecosystem services. For harvested species subject to multiple stressors, limited understanding of the causes and consequences of size declines impedes prediction, prevention, and mitigation. We highlight widespread declines in Pacific salmon size based on 60 years of measurements from 12.5 million fish across Alaska, the last largely pristine North American salmon-producing region. Declines in salmon size, primarily resulting from shifting age structure, are associated with climate and competition at sea. Compared to salmon maturing before 1990, the reduced size of adult salmon after 2010 has potentially resulted in substantial losses to ecosystems and people; for Chinook salmon we estimated average per-fish reductions in egg production (−16%), nutrient transport (−28%), fisheries value (−21%), and meals for rural people (−26%). Downsizing of organisms is a global concern, and current trends may pose substantial risks for nature and people.

Reconciling fish and farms: Methods for managing California rice fields as salmon habitat

PLOS | February 24th, 2021

Rearing habitat for juvenile Chinook Salmon (Oncorhynchus tshawytscha) in California, the southernmost portion of their range, has drastically declined throughout the pa

Rearing habitat for juvenile Chinook Salmon (Oncorhynchus tshawytscha) in California, the southernmost portion of their range, has drastically declined throughout the past century. Recently, through cooperative agreements with diverse stakeholders, winter-flooded agricultural rice fields in California’s Central Valley have emerged as ecologically functioning floodplain rearing habitat for juvenile Chinook Salmon. From 2013 to 2016, we conducted a series of experiments examining methods to enhance habitat benefits for fall-run Chinook Salmon reared on winter-flooded rice fields in the Yolo Bypass, a modified floodplain managed for flood control, agriculture, and wildlife habitat in the Sacramento River Valley of California. Investigations included studying the effect of 1) post-harvest field substrate; 2) depth refugia; 3) duration of field drainage; and 4) duration of rearing occupancy on in-situ diet, growth and survival of juvenile salmon. Post-harvest substrate treatment had only a small effect on the lower trophic food web and an insignificant effect on growth rates or survival of rearing hatchery-origin, fall-run Chinook Salmon. Similarly, depth refugia, created by trenches dug to various depths, also had an insignificant effect on survival. Rapid field drainage yielded significantly higher survival compared to drainage methods drawn out over longer periods. A mortality of approximately one third was observed in the first week after fish were released in the floodplain. This initial mortality event was followed by high, stable survival rates for the remainder of the 6-week duration of floodplain rearing study. Across years, in-field survival ranged 7.4–61.6% and increased over the course of the experiments. Despite coinciding with the most extreme drought in California’s recorded history, which elevated water temperatures and reduced the regional extent of adjacent flooded habitats which concentrated avian predators, the adaptive research framework enabled incremental improvements in design to increase survival. Zooplankton (fish food) in the winter-flooded rice fields were 53-150x more abundant than those sampled concurrently in the adjacent Sacramento River channel. Correspondingly, observed somatic growth rates of juvenile hatchery-sourced fall-run Chinook Salmon stocked in rice fields were two to five times greater than concurrently and previously observed growth rates in the adjacent Sacramento River. The abundance of food resources and exceptionally high growth rates observed.

Record of Decision, Trump Administration Action 5 Operations Plan for the Central Valley and State Water Projects, per Executive Order 14181

U.S. Bureau of Reclamation (USBR) | December 4th, 2025

On January 24, 2025, President Donald J. Trump issued Executive Order 14181 “Emergency Measures To Provide Water Resources In California And Improve Disaster Response I

On January 24, 2025, President Donald J. Trump issued Executive Order 14181 “Emergency Measures To Provide Water Resources In California And Improve Disaster Response In Certain Areas.” A Presidential Memorandum titled “Putting People Over Fish” was signed four days before the Executive Order and references a reliable water supply, but the specific direction to the CVP is found in Executive Order 14181. Section 2 of Executive Order 14181 requires, among other measures, (c) The Secretary of the Interior, including through the Bureau of Reclamation, shall utilize his discretion to operate the CVP to deliver more water and produce additional hydropower, including by increasing storage and conveyance, and jointly operating federal and state facilities, to high­need communities, notwithstanding any contrary State or local laws. The Bureau of Reclamation shall take all available measures to ensure that State agencies — including the California Department of Water Resources — do not interfere with the Bureau of Reclamation’s operation of the project to maximize water delivery to high­need communities or otherwise, including but not limited to the issuance of a new Record of Decision maximizing water deliveries and consistent with the 2020 Record of Decision. Subsection (g) calls for a “proposed plan, for review by the Secretaries, to appropriately suspend, revise, or rescind any regulations or procedures that unduly burden such projects and are not necessary to protect the public interest or otherwise comply with the law.” This ROD implements initial actions in response to Executive Order 14181. Click here for the Reclamation Long Term Operations page,  here for response to the Trump Action 5 gambit from California Department of Water Resources, and here for the response from the State Water Resources Control Board

Recovery Plan for Sacramento-San Joaquin Delta native fishes

U.S. Fish and Wildlife Service (FWS) | November 26th, 1996

Eight fish species are included in the Sacramento-San Joaquin Delta Native Fishes Recovery Plan. The delta smelt is listed as a threatened species. The Sacramento splitta

Eight fish species are included in the Sacramento-San Joaquin Delta Native Fishes Recovery Plan. The delta smelt is listed as a threatened species. The Sacramento splittail (splittail) was proposed as a threatened species on January 6, 1994. This recovery plan will recommend restoration criteria for the splittail that would be appropriate recovery criteria should the species be listed. Longfin smelt, green sturgeon, spring-run, late fall-run, and San Joaquin fall-run chinook salmon are species of concern for which restoration criteria are recommended. Information is also included on Sacramento perch, a species believed to be extirpated from the Delta at this time. Habitat Requirements and Limiting Factors: The eight species included in this recovery plan depend on the Sacramento-San Joaquin Delta for a significant segment of their life history. Threats to the Delta ecosystem and these species include loss of habitat due to increased freshwater exports resulting in increased salinity, loss of shallow-water habitat due to dredging, diking and filling, introduced aquatic species that have disrupted the food chain, and entrainment (movement offish by currents produced by diversions) in State, Federal and private water diversion. State and Federal water projects have also changed the pattern and timing of flows through the Delta. The salmon races are affected by sport and commercial harvest as well as by interactions with hatchery stocks. Recovery and Restoration Objective: Delisting of delta smelt. Restoration of splittail, longfin smelt, green sturgeon, spring-run, late fall-run, San Joaquin fall-run chinook salmon, and Sacramento perch. Recovery and Restoration Criteria: Recovery criteria are quantifiable and species specific and can be used to (1) monitor effectiveness of recovery actions, (2) determine when a species has recovered to a secure level (stabilized), and (3) determine when a species qualifies for delisting. In many cases, criteria are based on two independent measures: population abundance and geographic distribution. For each species a historic base period was established using available data to characterize abundance and distribution during a pre-decline period. The time period over which abundance and distribution criteria must be met was set at five generations. For five of the eight species there is an additional requirement of meeting the criteria through a minimum number of years of stressful environmental conditions. Action Needed: 1. Enhance and restore aquatic and wetland habitat in the Sacramento-San Joaquin River estuary. 2. Reduce effects of commercial and recreational harvest. 3. Reduce effects of introduced aquatic species on Delta native fishes. 4. Change and improve enforcement ofregulatory mechanisms. 5. Conduct monitoring and research on fish biology and management requirements. 6. Assess recovery management actions and re-assess prioritization of actions. 7. Increase public awareness of importance of Delta native fishes.

Regional Monitoring Program (RMP) Field Sampling Report 2016

San Francisco Estuary Institute (SFEI) | June 1st, 2017

The Regional Monitoring Program for Water Quality in San Francisco Bay (RMP) is the primary source for long-term contaminant monitoring information for the Bay. The RMP

The Regional Monitoring Program for Water Quality in San Francisco Bay (RMP) is the primary source for long-term contaminant monitoring information for the Bay. The RMP is an innovative and collaborative effort among the scientific community, the San Francisco Bay Regional Water Quality Control Board (Water Board), and the regulated discharger community. The Program was initiated by the Water Board as a pilot study in 1989 and has been collecting water, sediment, and bivalve tissue data since its official inception in 1993. Regular monitoring of sport fish tissue and bird eggs for toxic contaminants was incorporated into the Program in 1997 and 2006, respectively.

Regional Monitoring Program (RMP) for Water Quality in the San Francisco Bay, Multi-Year Plan 2020 Annual Update

San Francisco Estuary Institute (SFEI) | January 6th, 2020

In 1992 the San Francisco Bay Regional Water Board passed Resolution No. 92-043 directing the Executive Officer to send a letter to regulated dischargers requiring the

In 1992 the San Francisco Bay Regional Water Board passed Resolution No. 92-043 directing the Executive Officer to send a letter to regulated dischargers requiring them to implement a regional multi-media pollutant monitoring program for water quality (RMP) in San Francisco Bay. The Water Board’s regulatory authority to require such a program comes from California Water Code Sections 13267, 13383, 13268 and 13385. The Water Board offered to suspend some effluent and local receiving water monitoring requirements for individual discharges to provide cost savings to implement baseline portions of the RMP, although they recognized additional resources would be necessary. The Resolution also included a provision that the requirement for a RMP be included in discharger permits. The RMP began in 1993, and over ensuing years has been a successful and effective partnership of regulatory agencies and the regulated community.