Research  

Food Webs as Essential Components of Fish Habitat - historically, there has been a predominate focus on the restoration of physical habitat features (e.g., water temperature, large wood and habitat complexity) to recover endangered fishes.  Much of our work examines the role of river food webs (and their interactions with physical habitat) to determine coldwater fish habitat suitability.  Currently, we have several projects examining the influence of food webs on the growth and survival of threatened and endangered fishes including the assessment of rearing habitat in the McCloud River (for reintroduction purposes), the influence of reservoir releases (including nutrients and zooplankton) on native and endemic fishes in the Sacramento River, and the influence of food and temperature on the growth of Southern Oregon Northern California Coast coho salmon from the Klamath River watershed. Read our recent paper on the influence of food on the growth of juvenile coho salmon.

Core partners: USBR, California Trout, The Nature Conservancy, NMFS Southwest Science Center, UC Davis

Climate Resilient Aquatic Habitats - spring-fed rivers are relatively rare compared to their runoff counterparts, however, they may be disproportionally important for the long-term persistence of native fishes and other coldwater taxa under a rapidly changing climate.  We are interested in differences in hydrology, thermal regimes, geomorphology, and several other environmental variables between runoff dominated rivers and spring-fed rivers and how these differences affect food webs, stream biota, and growth and life history of resident and migratory fishes.  Currently, our research suggests that spring-fed rivers represent climate resilient habitats and exhibit a diversity of habitat features that will be critical to the long-term persistence of native coldwater fish under global change.  See our recent publications: Lusardi et al. 2016, Lusardi et al. 2018, Lusardi et al. 2021, Lusardi et al. 2023.

Core partners: California Trout, USBR, The Nature Conservancy, University of Arizona, UC Davis Center for Watershed Sciences

Reintroduction of Native Fishes to Historical Habitat - climate change, aging water infrastructure, periods of drought, and increasing demand for water resources has precipitated strong declines in salmonids throughout California.  Compounding this, longitudinal and lateral disconnections from historical spawning and rearing habitat has triggered a loss of salmonid life history diversity, making species less resilient to change.  As a result, reintroductions of salmonids to historical habitat has occurred or is currently proposed as a viable recovery strategy.   We seek to understand the feasibility of reintroductions and to track the reintroduction of salmonids to historical habitat post dam removal.  Using novel techniques, we are  working with others to define the the Klamath basin 'isoscape' in order to track the movement and use of habitat throughout the Klamath River watershed pre- and post-dam removal. 

Core partners: Yurok Tribe, California Trout, Oregon Department of Fish and Wildlife, Humboldt State University, and University of Montana, Center for Watershed Sciences, and the National Marine Fisheries Service.

Rural Working Landscapes and Reconciliation Ecology - much of our work occurs in rural working landscapes throughout northern California and Oregon.  We work closely with farmers and ranchers on science-based solutions to achieve sustainable agricultural practices and enhance habitat for threatened and endangered species, such as SONCC coho.  This work is not possible without strong on the ground partnerships between landowners, California Trout, the Nature Conservancy, and the UC Davis Center for Watershed Sciences.  Specifically, we are working with our partners to upgrade aging water infrastructure and, with the savings in water, put that water back into the river to support threatened species.  Determining the magnitude and timing of certain flows for fish and other aquatic biota are key research questions we are investigating.   Watch this video from California Trout to get a better understanding of what we do (and why): https://www.youtube.com/watch?v=8IZf4M0lHIE . Please see our recent paper on water prioritization in working lanscapes.

Core Partners: California Trout, Blaire and Susan Hart, The Nature Conservancy, Center for Watershed Sciences, UC Davis.

California Environmental Flows Framework -  one of the major factors affecting the decline of native fishes in California is insufficient streamflow.  Streamflow has been referred to as the ‘master variable’ because it controls so many different aspects of the aquatic environment.  A question often asked is "how much water do fish need?" In 2016, a group of scientists from UC Davis, California Trout, UC Berkeley, The Nature Conservancy, Utah State University and the Southern California Coastal Water Research Project, began to delve into this question and others.  They formed what is collectively known as the California Environmental Flows Framework (CEFF or the Framework) which, ultimately, seeks to determine ecological flow criteria for native fishes and other aquatic species throughout the state. CEFF uses a functional flows approach to better understand how much water fish need and, importantly, when they need it. The science behind functional flows is relatively new, but strong empirical evidence exists to suggest that implementation of this approach will benefit native fishes and other stream biota.  Please see a series of papers published in 2022 (Stein et al. 2022, Peek et al. 2022, Yarnell et al. 2022, and Grantham et al. 2022).

Core Partners: UC Davis Center for Watershed Sciences (Dr. Sarah Yarnell) and Hydrology, UC Berkelely, California Trout, The Nature Conservancy, Southern California Coastal Water Research Project, and Utah State University.

Reconciliation Ecology and Beaver Dam Analogs - recent evidence suggests that beavers positively affect juvenile salmon through changes in physical habitat, primarily through improving habitat complexity and coldwater refuge.  Little is known, however, about the effects of beaver dams or beaver dam analogs on stream food webs and potential benefits to rearing fishes.  In partnership with the Scott River Watershed Council, we are examining changes in food web structure associated with the implementation of beaver dam analogs on Sugar Creek and French Creek (tributaries to the Scott River, CA).   Specifically, we are using carbon and nitrogen isotopes to investigate shifts in trophic pathways to threatened coho salmon and the potential differences in those pathways between habitats. We are also collecting data to examine potential changes in the density and diversity of food webs.  The research has important implications for habitat diversity, climate change, and ecosystem resilience.  Please see our recent paper in Restoration Ecology.

Core Partners: Scott River Watershed Council and Michael Pollock (NMFS Northwest Science Center).

Life Cycle Production Models for Threatened and Endangered Species - management of threatened and endangered species requires forethought and insight on the types of habitat that may be most beneficial to their long-term success. Through direct collaboration with Francisco Bellido-Leiva (PhD candidate, Dept. of Civil and Environmental Engineering) and Dr. Jay Lund, we are working on optimizing the production and growth of Sacramento Winter-run Chinook from Keswick Dam to the Delta using life cycle production models.  Such modelling allows us to define certain types of habitats throughout the Central Valley and, using empirical data, define rules of habitat use based on river conditions.  Importantly, and as part of this research, we are also developing a bioenergetic model to better understand the influence of water temperature and prey on the growth of juvenile fishes across different habitats.  The overall objective of the research is to better understand the relationship between habitat quality and quantity and how that translates to juvenile salmon development in order to assist recovery efforts.

Core Partners: California Trout, UC Davis Engineering, Center for Watershed Sciences, UC Davis.

Other Research Projects:

Walker Creek Ecology and Habitat for Endangered Coho Salmon - in a new partnership with California Trout, we are looking at potential limiting factors on endangered coho salmon in Walker Creek, Marin County.  Historically, Walker Creek, similar to Lagunitas Creek, was critical to the life history of both endangered coho salmon and threatened steelhead in the greater Tomales Bay area.  Understanding how Walker Creek is used by coho salmon and identifying limiting factors on their success is key to population recovery.

Partners: California Trout, Marin Water District, Walker Creek Outdoor School.

Thermal Diversity and Salmon Physiology  - in collaboration with Dr. Nann Fangue and Ken Zillig at UC Davis, we are examining differences in thermal physiology between salmon populations.  From an evolutionary perspective, differences in thermal physiology and tolerance between salmon populations contributed to stock resiliency across the Pacific Northwest. Conserving remaining diversity has important management implications, particularly in the face of a shifting climate.  

Partners: UC Davis Wildlife, Fish, and Conservation Biology, Environmental Protection Agency, North Coast Regional Board

Past Research Projects:

State of the Salmonids (2017) -  in partnership with California Trout, we reviewed the status of all native salmonids in California (n = 32) and quantitatively scored them based on a seven-metric rubric which included geographic area occupied, adult abundance, dependence on human intervention, environmental tolerance, genetic risks, vulnerability to climate change, and additional anthropogenic threats. We then made a series of recommendations based on our findings in order to improve the conservation status of each species.  This 600 page status review was peer reviewed by ~50 state and federal agency scientists prior to publication and received significant media attention, including the front page of the San Francisco Chronicle.

Shasta River and Big Springs Creek (2008-2013) - the Shasta River, a volcanic spring-fed river, is one of the four primary tributaries to the Klamath River.  Despite accounting for less than 2% of the  annual discharge of the lower Klamath River, the Shasta River historically accounted for greater than 50% of the entire Klamath River Chinook run.  Numerous manuscripts (and friendships) have come from this work over the last decade.  To see some of our work and those of my collaborators please visit the Center for Watershed Sciences at UC Davis. 

Threatened Inland trout (2015-2017) - working with our partners at the US Fish and Wildlife Service, California Department of Fish and Game,  and California Trout, we examined the long-term effects of intensive resource management (e.g., hatchery stocking, influence of chemical treatments) on Little Kern golden trout genetics, a federally threatened species.

Kobuk River, Gates of the Arctic National Park (2008-2011) - in partnership with numerous colleagues, including the Alaska Department of Fish and Game, we investigated the effects of climate change on the Kobuk River (Ak) and predicted future shifts in environmental baselines, with implications for resource management and indigenous peoples.