Freshwater and Estuaries


Estuaries and Lagoons are rare, but critical habitats in California. These systems are some of the most productive and species rich environments on the planet and provide numerous ecosystem functions and services. For estuarine research, it is largely conducted by graduate students co-advised with Dr. Kerstin Wasson at the Elkhorn Slough Foundation.

Currently, estuarine research in the RC Lab focuses on three major themes:
(1) The role of bottom up effects (nutrient inputs and eutrophication) on shaping estuarine communities;
(2) the dynamics of invasive species; and
(3) the functional role of estuaries as habitat and nursery grounds for coastal fish populations.



Freshwater habitats range from small ephemeral ponds and streams to continental rivers and inland seas. Even though free flowing and standing freshwaters comprise less than 1% of the world’s water, they support greater than 41% of all fish diversity. Furthermore, most civilizations are adjacent to bodies of freshwater giving rise to direct conservation implications for these diverse systems.

The majority of freshwater ecology in our lab is conducted by our graduate students who are funded by the National Marine Fisheries Service Santa Cruz Lab here at the Coastal Science Campus at UCSC.  These students almost always work on aspects of ecology and evolution of salmonids.  Because NMFS researchers support our students, it is best to contact them directly to inquire about possibilities with them. At NMFS, you should contact Drs. Eric DannerSean Hayes, and Devon Pearse.  They may be able to direct you to others at the NMFS lab interested in sponsoring graduate students.  Also, you should contact  Dr. Eric Palkovacs in our department (EEB).

Freshwater topics that RC lab graduate students have addressed include:

Water Temperature Effects

Water temperature affects the basic physiology of poikilothermic organisms, including growth and survival. We know surprisingly little about these details, their spatio-temporal variation, and how they might affect demographic processes of threatened populations of salmonids.

Kim Brewitt: “Steelhead (Oncorhynchus mykiss) use of thermal refugia: A bioenergetics approach.”
Maya Friedman: “Chinook (O. tshawytscha) emigration strategy and thermal refugia use.”
Walter Heady: “Regional differences in temperature dependent growth.”
Ann-Marie Osterback: “Processes influencing stream temperature and habitat for southern steelhead.”


We use a combination of tagging technologies, including radio, acoustic, and Passive Integrated Transponder (PIT) tags, to track the movement patterns of salmonids. By using these technologies, we are able to better understand what drives life-history decisions and freshwater habitat use.

Kim Brewitt: “Using radio telemetry to assess steelhead use of thermal refugia.”
Maya Friedman: “Using otolith microchemistry to understand emigration patterns of juvenile Chinook.”
Walter Heady: “Resident versus anadromous life-history decisions in the Mokolumne River.”
Ann-Marie Osterback: “Using PIT antennas to determine life-history decisions of juvenile steelhead.”

Species Interactions

Predators can exert strong top-down control on their prey, which can have cascading effects throughout the ecosystem. Understanding predator-prey interactions, and whether predator populations are being artificially subsidized, is important for our understanding of community dynamics.

Kim Brewitt: “Investigating differences in prey availability for steelhead across thermal zones.”
Walter Heady: “Using stable isotopes and tissue turnover rates to infer diet and differential habitat use.”
Ann-Marie Osterback: “Subsidized predators and imperiled prey: the impact of avian predators on salmonids.”
Megan Sabal: “Indirect effects of introduced prey species on native prey species through a shared predator.”

Juvenile Salmonids in California Coastal Lagoons

Ann-Marie Osterback: “Evaluating the impact of avian predators on juvenile salmonids.”
Walter Heady: “Using stable isotopes to track the timing of resource switches.”
Morgan Bond, “The importance of lagoons for salmonid growth and implications for marine survival.”
Chad Hanson, “The importance of lagoon habitat to salmon population viability.”