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California Water Science Center (CAWSC) scientists will present their latest research at California’s 2023 Interagency Ecological Program (IEP) Workshop to be held in Sacramento, California from March 21-24. Five talks, along with several poster presentations, will be given by CAWSC scientists.

The 2023 IEP Workshop will be held in the California Natural Resources Headquarters building in downtown Sacramento. The workshop will follow a hybrid “in-person/virtual” model and will mark the first in-person IEP Workshop gathering since the onset of the COVID pandemic in 2020.


CAWSC featured speakers are:

Title: Fish Behavior During Delta Smelt Experimental Releases Inferred from ARIS Sonar

CAWSC presenter: Frederick Feyrer, USGS Research Fish Biologist

Day/time: March 21st, 10:30am-10:50am

Background: Delta smelt is a federally endangered fish species that is endemic to the Sacramento-San Joaquin Delta. USGS researchers conducted short-term underwater observations of delta smelt behavior and potential predatory fishes in the immediate vicinity of release using Adaptive Resolution Imaging Sonars (ARIS). The ARIS transforms sound waves into near-video quality images, making it possible to obtain continuous underwater observations that can be viewed in real-time and recorded for subsequent analysis. Preliminary results show a difference in potential predatory fish abundance across release locations and indicate that river velocity influences delta smelt behavior and their ability to actively move in a direction. Resource managers can use study results to design plans for future supplemental releases that maximize the likelihood of successful survival and recruitment of delta smelt.

Fred Feyrer
Title: A multi-parameter approach to modeling light attenuation in the Sacramento-San Joaquin Delta using commonly available data

CAWSC presenter: Emily Richardson, Physical Scientist

Day/time: March 21st, 2:54pm-2:59pm

Background:  Modeling productivity in aquatic habitats requires information about available light, which is attenuated (reduced) by particulates and dissolved materials. The decrease in light with depth is understood to be caused by the amount of light hitting the water surface and its reduction due to photosynthetically active radiation (KdPAR) -- an inherent physical property. KdPAR is difficult to determine in real time because measurements of light with depth are needed. In this study, scientists assessed if KdPAR may be modeled using real-time surface-water measurements that are collected throughout the Sacramento-San Joaquin River Delta (Delta).

In her presentation, Emily Richardson will discuss data collection methods and the creation of a Delta-specific model for predicting KdPAR, and how such modeling is used for a variety of purposes throughout the Delta.

Emily Richardson
Title Spilling the Allelopathic “Tea”: The Potential Role of Allelochemicals in Water Primrose Invasion of the Delta

CAWSC presenter: Michael Gross, Research Chemist

Day/time: March 22nd, 4:28pm-4:44pm

Background: Water primrose (Ludwigia spp.) is an invasive aquatic vegetation that has rapidly increased in coverage throughout the Sacramento-San Joaquin Delta (“the Delta”). Water primrose has invaded wetlands and may contribute towards mortality in native tule and cattail vegetation. Previous studies have suggested that water primrose contains allelopathic chemicals that could cause plant mortality. Three major allelopathic polyphenols (myricitrin, prunin, and quercitrin) were measured in leaf, water, and soil samples from Delta marshes infested with water primrose. 

In his presentation, Michael Gross will discuss the methods used for sample collection and the data gathered from testing and analyses.

Photo of Research Chemist Michael Gross on LC/MS/MS
Title: Variability in Coastal Habitat Available for Longfin Smelt in the Northeastern Pacific Ocean

CAWSC presenter: Matthew Young, Fish Biologist

Day/time: March 23rd, 11:10am-11:30am

Background: Longfin Smelt (Spirinchus thaleichthys) is a pelagic fish species found in waters along the Pacific coast, from Alaska to central California. Its complex life cycle makes it vulnerable to threats in both freshwater and at sea. Substantial species declines in California’s San Francisco Estuary, where Longfin Smelt is listed as Threatened under California’s Endangered Species Act, have prompted evaluation of Longfin Smelt population trends and drivers.  In this research, USGS scientists examined the distribution and habitat associations of Longfin Smelt in the northeast Pacific Ocean to better understand coastal factors affecting Longfin Smelt populations. Coastal observations from numerous sources were compiled and used to estimate the range-wide coastal marine distribution of Longfin Smelt. 

In his presentation, Matthew Young, will discuss his research detailing the distribution and habitation conditions of the smelt population in the study area.

LIGHTENING TALK: Molecular monitoring for harmful algae in the San Francisco Bay-Delta and beyond

CAWSC presenter: Keith Bouma-Gregson, Biologist

Day/time: Tuesday, March 21st, 2:06pm-2:11pm

Background: The California Water Science Center Biogeochemistry Group (BGC) was funded by the California Department of Water Resources to study the water age, nutrients, and phytoplankton community in Franks Tract to help understand how the Emergency Drought Barrier (EDB) in West False River was influencing cyanobacterial blooms in Franks Tract. The EDB was installed to prevent salt water from intruding into Franks Tract. The hypothesis is that water age (residence time) increased in Franks Tract, due to the barrier, which created conditions favorable for cyanobacteria to grow and bloom. To study conditions in Franks Tract, BGC scientists and hydrologic technicians collected high-resolution mapping data to measure the spatial distribution of water age in Franks Tract. Data and conclusions from this research will help inform how drought management actions in the Delta are influencing cyanobacterial growth, to reduce the probability of management actions contributing to bloom formation.

Keith Bouma-Gregson, Ph.D.


In addition to CAWSC featured speakers, the following scientists will be giving poster presentations about their research. 2023 CAWSC poster presentations are:

Title: A Preliminary Look at Fine-Scale Drivers of Pelagic Fish Distribution in Suisun Bay, CA

CAWSC presenters: Danielle Palm and Anthony Martinez

Physical factors such as tide, turbidity, and salinity can influence the spatiotemporal distribution of estuarine fish. Fine-scale sampling is needed to further contextualize fish-habitat relationships to guide targeted management efforts. We initiated a multi-year high-resolution sampling effort across varying environmental conditions in Suisun Bay to address fish-habitat relationships on tidal time scales with the goal of evaluating how habitat impacts can influence vulnerable resident fish populations.

Title: Can delta island ponds be used as a tool to support Delta Smelt supplementation?

CAWSC presenters: Jordan Buxton and Jeff Gronemyer

The population of endemic delta smelt (Hypomesus transpacificus) in the Sacramento-San Joaquin Delta began declining in the 1980s and has shown no signs of recovery. Therefore, plans to supplement the wild population with hatchery raised fish are being explored and implemented. One possible tool to aid supplementation is the use of semi-natural ponds on delta islands. The goal of this study is to examine how environmental conditions vary seasonally among ten ponds. 


Title: Investigating island drainage canals in the Sacramento-San Joaquin Delta for pesticides

CAWSC presenter: Matthew Uychutin

Sacramento-San Joaquin Delta surface waters frequently contain toxic pesticides. One source of these pesticides are Delta islands used for agriculture. In this study, USGS scientists measured pesticide concentrations in surface-water samples collected from two Delta islands, an island used mostly for agriculture (‘farmed island’) and an island used partially for wetland restoration (‘managed island’). Overall, water samples from the farmed island exceeded U.S. EPA aquatic life benchmarks for four pesticides. Water samples from the managed island exceeded EPA aquatic life benchmarks for one. These results help to better understand the transport and fate of contaminants that can affect the food web in the Delta.

Title: Pesticide concentrations in Delta island ponds assessed for Delta Smelt supplementation habitat

CAWSC presenter: James Orlando

Resource managers are pursuing supplementation of the wild endangered Delta Smelt population with fish from a refuge population. Identifying suitable natural habitats is a challenge for conducting research on delta smelt supplementation. To address this, scientists measured the presence of over 170 current-use pesticides in water and sediments in the ponds and pond water sources of natural pond habitats on four Delta islands.

Title: Identifying Microcystin Sources and Producers In San Francisco Bay

CAWSC presenter: Andrea Jaegge

Microcystins have been detected in San Francisco Bay (SFB) since 2011; however, the primary source(s) and taxa responsible for production remain unknown. Cyanotoxins negatively affect human and ecosystem health and understanding how cyanotoxins enter SFB can help managers plan mitigation efforts. This project aims to determine the sources and taxa response for microcystins in San Francisco Bay. These cyanotoxins can negatively impact human and ecosystem health and understand who and where they come from is important for management and mitigation efforts.

The Annual IEP Workshop is an informal event is held each spring for sharing new research results that advance science important to IEP and the larger Delta science community.

To learn more, visit the Annual IEP Workshop website.











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