2025 Annual Report on the Salton Sea Management Program

California Natural Resources Agency (CNRA) | March 31st, 2025

The State's Salton Sea restoration and management efforts continued to show significant, demonstrable progress in 2024 – achieving key milestones and accelerating the p

The State's Salton Sea restoration and management efforts continued to show significant, demonstrable progress in 2024 – achieving key milestones and accelerating the pace of critical project delivery functions. With new federal funding, the Salton Sea Management Program (SSMP) broke ground to expand what was already the largest restoration project in the Sea’s history, and further expansion is being initiated to suppress dust and restore habitat on up to 9,000 acres at the south end of the Sea. In other areas along the Sea, over 1,300 acres — spanning roughly five miles of shoreline — now host native vegetation recently planted to suppress dust over the coming decades.

A comparison of the taxonomic and trait structure of macroinvertebrate communities between the riffles and pools of montane headwater streams

Hydrobiologia (Springer) | May 30th, 2018

Macroinvertebrate community taxonomic and trait structure showed consistent differences between riffles and pools across 12 headwater streams in the Sierra Nevada (Cali

Macroinvertebrate community taxonomic and trait structure showed consistent differences between riffles and pools across 12 headwater streams in the Sierra Nevada (California) even as flows varied from wet to dry years and between seasons. Densities of Ephemeroptera, Plecoptera, Trichoptera, Elmidae, Orthocladiinae and Diamesinae midges, and mites were greater in riffles, whereas Tanypodinae, Chironominae, Sialis, and Pisidium were more abundant in pools. Pools had higher densities but estimated biomass was greater in riffles. Collector-gatherer and micropredator abundances were greater in pools whereas grazers, collector-filterers, and macropredators were more abundant in riffles. Stonefly shredders were most abundant in riffles but some caddis shredders were more abundant in pools. Trait state patterns were related to food resource and physical habitat differences between riffles and pools. Of the distinct pool–riffle differences we found among taxa, only about half conformed to expectations from the literature. Pool and riffle assemblages were most dissimilar at intermediate discharge and converged at low and high flows when one or the other habitat dominated. Bioassessment sampling will need to account for these flow-related differences. Benthic invertebrate communities in these mountain streams clearly differ between pools and riffles, but the relative extent of habitats and biological similarity shift with flow regime.

A Conservation Footprint for California Rice

California Rice Commission (CRC) | January 31st, 2025

Rice agriculture, especially winter-flooded rice fields, provides surrogate wetlands that host a diversity of species in the Central Valley. Rice fields are critical for

Rice agriculture, especially winter-flooded rice fields, provides surrogate wetlands that host a diversity of species in the Central Valley. Rice fields are critical for Giant Gartersnakes, wintering waterfowl, wintering and breeding shorebirds, Sandhill Cranes, native fishes, and many other species. However, uncertainties in climate, water availability, agricultural crop markets, and urban expansion are precipitating changes in management practices increased variability and magnitude of fallowing, and, in some cases, crop conversion. 

A Delta Transformed: Ecological Functions, Spatial Metrics, and Landscape Change in the Sacramento-San Joaquin Delta

San Francisco Estuary Institute (SFEI) | October 1st, 2014

In A Delta Transformed, completed in 2014, SFEI researchers used the spatial data generated in the Delta Historical Ecology Investigation, as well as updated modern veget

In A Delta Transformed, completed in 2014, SFEI researchers used the spatial data generated in the Delta Historical Ecology Investigation, as well as updated modern vegetation and land cover datasets, to carry out detailed analyses of how the Delta landscape has been altered since the early-1800s. By quantifying changes in metrics relevant to native wildlife (such as the extent and timing of inundation, habitat patch sizes, length of channel networks), the report provides a foundation for defining, designing, and evaluating landscapes that support desirable ecological functions in the future. See more at: http://www.sfei.org/projects/delta-landscapes-project#sthash.RryQdaII.dpuf

A Framework for Research Addressing the Role of Ammonia/Ammonium in the Sacramento-San Joaquin Delta and the San Francisco Bay Estuary Ecosystem

CALFED | April 13th, 2009

The Sacramento-San Joaquin Delta and the San Francisco Bay Estuary ecosystem has been drastically altered by human activity since at least the mid-1800s, leading to numer

The Sacramento-San Joaquin Delta and the San Francisco Bay Estuary ecosystem has been drastically altered by human activity since at least the mid-1800s, leading to numerous physical, chemical and biological changes [e.g., see Healey (2008) and Healey et al. (2008) for overviews]. Recent concerns include (1) the precipitous decline of four fish species that inhabit the Delta (collectively referred to as the pelagic organism decline, or POD) and (2) apparent major shifts in community composition of algae and higher trophic levels in the Delta and downstream in Suisun Bay. The four POD species of concern are delta smelt (longfin smelt), threadfin shad and striped bass. One of the potential causes of the POD and the community changes is the discharge of increasing concentrations of a combination of ammonia (NH3) and ammonium (NH4+) into the Delta ecosystem and eventually into Suisun Bay. For brevity, we hereafter abbreviate the ammonia/ammonium combination as ammonia/um. To address the potential for adverse effects of ammonia/um on the Bay-Delta ecosystem, a ammonia/um workshop was convened by the CALFED Science Program on 10 and 11 March 2009 in Sacramento, California. We participated as an expert panel and were charged with preparing a framework for research that will address the role of ammonia/um in the Bay-Delta ecosystem. In this report, we present our perception and interpretation of the major concerns related to ammonia/um in the Bay-Delta ecosystem; a conceptual framework of the major physical, chemical and biological drivers controlling the ecosystem (including POD populations); our assessment of the major research needs; and concluding remarks. For some research needs, we recommend specific types of research and provide literature citations; however, for other research needs we recommend general approaches for which targeted research will be determined later. In many ways, Bay-Delta research is breaking new ground by tackling a large-scale, complex freshwater-estuarine ecosystem affected by multiple, interactive stressors. Consequently, the Bay-Delta research program will establish a template for future research and management decisions in other hydrologically, biogeochemically, and trophically-similar systems, rather than relying on paths trodden by others.

A freshwater conservation blueprint for California: prioritizing watersheds for freshwater biodiversity

Society for Freshwater Science | April 18th, 2018

Conservation scientists have adapted conservation planning principles designed for protection of habi- tats ranging from terrestrial to freshwater ecosystems. We

Conservation scientists have adapted conservation planning principles designed for protection of habi- tats ranging from terrestrial to freshwater ecosystems. We applied current approaches in conservation planning to prioritize California watersheds for management of biodiversity. For all watersheds, we compiled data on the pre- sence/absence of herpetofauna and fishes; observations of freshwater-dependent mammals, selected invertebrates, and plants; maps of freshwater habitat types; measures of habitat condition and vulnerability; and current manage- ment status. We analyzed species-distribution data to identify areas of high freshwater conservation value that op- timized representation of target taxa on the landscape and leveraged existing protected areas. The resulting priority network encompasses 34% of the area of California and includes ≥10% of the geographic range for all target taxa. High-value watersheds supported nontarget freshwater taxa and habitats, and focusing on target taxa may provide broad conservation value. Most of the priority conservation network occurs on public lands (69% by area), and 46% overlaps with protected areas already managed for biodiversity. A significant proportion of the network area is on private land and underscores the value of programs that incentivize landowners to manage freshwater species and habitats. The priority conservation areas encompass more freshwater habitats/ha than existing protected areas. Land use (agriculture and urbanization), altered fire regimes, nonnative fish communities, and flow impairment are the most important threats to freshwater habitat in the priority network, whereas factors associated with changing climate are the key drivers of habitat vulnerability. Our study is a guide to a comprehensive approach to freshwater conservation currently lacking in California. Conservation resources are often limited, so prioritiza- tion tools are valuable assets to land and water managers.

A functional flows approach to selecting ecologically relevant flow metrics for environmental flow applications

River Research and Applications (Wiley) | January 8th, 2020

A geohydrologic reconnaissance of the Saratoga Spring area, Death Valley National Monument, California

U.S. Geological Survey (USGS) | March 1st, 1966

A global spatial analysis reveals where marine aquaculture can benefit nature and people

PLOS | October 9th, 2019

Aquaculture of bivalve shellfish and seaweed represents a global opportunity to simultaneously advance coastal ecosystem recovery and provide substantive benefits to hum

Aquaculture of bivalve shellfish and seaweed represents a global opportunity to simultaneously advance coastal ecosystem recovery and provide substantive benefits to humanity. To identify marine ecoregions with the greatest potential for development of shellfish and seaweed aquaculture to meet this opportunity, we conducted a global spatial analysis using key environmental (e.g., nutrient pollution status), socioeconomic (e.g., governance quality), and human health factors (e.g., wastewater treatment prevalence). We identify a substantial opportunity for strategic sector development, with the highest opportunity marine ecoregions for shellfish aquaculture centered on Oceania, North America, and portions of Asia, and the highest opportunity for seaweed aquaculture distributed throughout Europe, Asia, Oceania, and North and South America. This study provides insights into specific areas where governments, international development organizations, and investors should prioritize new efforts to drive changes in public policy, capacity-building, and business planning to realize the ecosystem and societal benefits of shellfish and seaweed aquaculture.

A Literature Review and Hypsometric Analysis to Support Decisions on Trout Management Flows on the Colorado River Downstream from Glen Canyon Dam

U.S. Geological Survey (USGS) | August 7th, 2024

Fish stranding has been studied in select rivers worldwide, often with the purpose of determining how to mitigate adverse effects of dam operations on highly valued salmo

Fish stranding has been studied in select rivers worldwide, often with the purpose of determining how to mitigate adverse effects of dam operations on highly valued salmon and trout populations. However, where a reduction in trout population size is desired by resource managers, as is the case downstream of the Glen Canyon Dam on the Colorado River, flow manipulations termed trout management flows (TMFs) may be used to optimize fish stranding and mortality. To inform the design and implementation of potential future TMFs, we reviewed relevant literature to identify key factors that influence fish stranding. We found that key factors were highly interdependent and site-specific, but general trends suggest that down-ramping (decreasing flow) at rapid rates in daytime during the late spring to summer emergence period would lead to stranding of age-0 rainbow trout in shallow shoreline habitat. A hypsometric analysis was then used to predict stranding risk for age-0 rainbow trout in Glen Canyon for a range of TMFs, which incorporated existing bathymetric data and flow and habitat suitability models. Our results indicate that a TMF with a steady high flow ranging from 12,000 to 16,000 cubic feet per second (ft3/s) combined with a minimum flow ranging from 3,000 to 5,000 ft3/s may effectively strand age-0 fish while also minimizing risk to water storage in Lake Powell and other resources. This strategy implemented under normal hydropeaking operations was predicted to lead to a substantive stranding risk when paired with low flows of 5,000 ft3/s, and especially 3,000 ft3/s. However, there remains uncertainty associated with elements of implementing an effective TMF downstream from Glen Canyon Dam. The main uncertainties include (1) the down-ramp rate that maximizes stranding of age-0 trout, (2) the duration of drawdown to maximize stranding mortality while minimizing impact to downstream resources, (3) duration of high flows required for age-0 fish to colonize newly created shoreline habitat (this is only for certain TMF hydrographs), (4) number of repetitions of TMF cycles to minimize compensatory survival response, and (5) recruitment threshold of both rainbow and brown trout populations to trigger TMF implementation.