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Fish and Aquatic Sciences

The ICF Fish and Aquatic Science team helps resource managers successfully address their most pressing water-related issues through:

  • applied scientific research studies, often with an emphasis on endangered species
  • project planning and environmental impact assessment using quantitative tools and other novel techniques
  • ensuring compliance with regulations through monitoring and analysis, and
  • facilitating stakeholder involvement with a variety of data visualization techniques and tools

men fishing in a boat on the creek

Our Work

The California Department of Water Resources (CA-DWR) is mandated to investigate engineering solutions to reduce juvenile salmonid migration into the low-survival interior Sacramento-San Joaquin Delta. To this end, various barriers have been investigated at important channel junctions — but many pose an increased predation risk because of the predator habitat provided by the in-water structures or because of changed juvenile salmonid behavior. 

With these objectives and factors in mind, our experts worked closely with CA-DWR to develop the present study (co-authored by ICF’s Marin Greenwood) and investigate the survival of acoustically tagged juvenile salmonids at the San Joaquin River-Head of Old River (HOR) and Sacramento River-Georgiana Slough junctions. Overall, we found that site-specific considerations are key because barriers and other factors can affect survival at important channel junctions. 

Our team deployed bioenergetics modeling to illustrate that the potential proportional consumption of juvenile salmon entering HOR by Striped Bass could have been greater in 2012 than 2011 because 2012 had higher predator density, lower prey density, and higher temperature. We found that the predation probability of juvenile Chinook Salmon at HOR was significantly greater with a bioacoustic fish fence (BAFF) turned on and a rock barrier in place than with the BAFF turned off, largely because the barriers guided the juvenile salmon as intended away from the low-survival route, but inadvertently toward a predator-dense ambush location.

Understanding how fish move in estuarine ecosystems is pivotal for determining how freshwater flow and tidal hydrodynamics affect behavior that leads to increased risk to predation, habitat access or entrainment. For the endangered Delta Smelt, little is known about their movements during onset of their spawning season when some move upstream to habitats in the vicinity of the SWP and CVP water diversion facilities. 

Our experts, however, are determined to resolve that knowledge gap by pioneering the application of Passive Integrative Transponder (PIT) and Juvenile Salmon Acoustic Telemetry Systems (JSATS) for application of small forage fish, such as the endangered Delta Smelt. 

In 2014, our researchers conducted a laboratory study to determine the feasibility of tagging adult Delta Smelt for use in future tracking studies in the Delta. The study successfully demonstrated that adult Delta Smelt could be implanted with PIT tags with minimal effects on their survival. We found that the smallest commercially available acoustic tags are too big for adult Delta Smelt’s body cavity, as only 50 percent of the fish implanted with miniature JSATS survived the 30-day evaluation period. However, through our research (published in North American Journal of Fisheries Management), we were able to determine the appropriate tag size and weight that acoustic tags would need to be to improve survival on par with PIT tags. 

What’s next? Our team has plans to work with UC Davis and Pacific Northwest National Laboratory researchers to develop additional studies on acoustic tagging technology for Delta Smelt and other small fish (e.g., Longfin Smelt, Chinook salmon fry) in the San Francisco Estuary. The ability to tag and track Delta Smelt will enhance our ability to understand their responses to management actions. 


State Water Project (SWP) and Central Valley Project (CVP) water exports from the Sacramento-San Joaquin Delta help support California’s large agricultural economy (approximately $4 billion per year) and provide municipal water for over 23 million people. 

To improve an understanding of factors that affect entrainment of listed fish species-a critical piece of management for the Bay-Delta-our experts developed models to evaluate project exports on ESA and CESA listed species, including Delta Smelt, winter-run Chinook Salmon, and steelhead. 

Our Fish and Aquatic Science Practice Lead, Lenny Grimaldo, currently leads a team of scientists on a set of entrainment studies aimed to better understand and predict Delta Smelt salvage and entrainment at SWP and CVP fish screens. Models developed by these studies will be used to reduce uncertainty over fish protection measures in hopes of improving both species conservation and water diversion management of the SWP and CVP. 

Estuarine habitats are shaped by the influence of freshwater flow, water quality, and other stationary features. In the San Francisco Estuary, there is a strong desire to better understand how freshwater flow affects habitat and prey abundance for the listed fish species, including the endangered Delta Smelt. To that end, we recently completed an effects analysis on the management action to improve fall outflows to benefit Delta Smelt. 

Additionally, our team is leading a lower trophic monitoring study for Reclamation’s Delta Outflow Adaptive Management Plan for Delta Smelt. This work is critical for identifying how Delta Smelt respond to changes to their habitat under increased fall outflows prescribed by the USFWS Biological Opinion for the State Water Project (SWP) and Central Valley Project (CVP). Working hand-in-hand with scientists from Reclamation, the U.S. Fish and Wildlife Service, and UC Davis, we are collecting phytoplankton, Chlorophyll a, nutrient, water velocity, zooplankton, and macrocrustacean data to better understand potential mechanisms affecting Delta Smelt and their habitat. 

Our expert taxonomy team (led by Colin Brennan, Athena Maguire, and Andrew Kalmbach) is conducting in-house identifications of phytoplankton, zooplankton and macrocrustaceans. Ultimately, information from this study will be used to help guide management decisions about outflow needs for Delta Smelt and their prey and habitat. 

As restoration efforts ramp up in coastal landscapes threatened by climate change and urbanization, a critical information gap has emerged. Though many communities are looking to better understand the role of tidal marshes play in supporting native fishes, information about how fish benefit from restoration remains outstanding. 

This knowledge gap has come to the forefront in the San Francisco Estuary where our team has been conducting research on how fish benefit from restored marshes using field, lab, and modeling applications.

We conducted a study to determine if the endangered Longfin Smelt were rearing in tidal marshes and shallow habitats of the upper San Francisco Estuary. These habitats have been overlooked by the long-term monitoring efforts in the region. Published in Estuaries and Coasts, our work was important in demonstrating that Longfin Smelt larvae were indeed hatching and rearing in shallow and marsh habitats of the estuary. Ultimately, this study provides insights for potential restoration actions that can improve spawning and rearing habitat for the endangered Longfin Smelt in estuarine ecosystems. 

Our work doesn’t end here. Through a multi-agency partnership led by the California Department of Water Resources, our experts will head up a field investigation to examine juvenile Chinook Salmon fry rearing in tidal marshes of the upper San Francisco Estuary. This work will be carried out through a science grants awarded from the California Department of Fish and Wildlife Proposition 1 and State and Federal Contractor Water Agency (SFCWA). In collaboration with scientists from the National Oceanic and Atmospheric Association (NOAA) and UC Berkeley, we will seek to determine the residence time (otolith microchemistry), growth rates (otolith analysis), and feeding (stomach content analysis) of juvenile Chinook Salmon as they head to the ocean. Ultimately, this work aims to provide key information on the importance of estuarine rearing for Chinook Salmon for application in life cycle model assessments and for guiding restoration efforts in the San Francisco Estuary.