Walter Heady

Current Position: Coastal Marine Ecologist, The Nature Conservancy, Santa Cruz, CA

Longer Marine Lab
100 Shaffer Rd.
Santa Cruz, CA 95060
(831) 459.5783
heady@biology.ucsc.edu

 

Education:

BS University of California, Santa Cruz

PhD University of California, Santa Cruz (2012)

Research Interests

Broadly I am interested in basic and applied aquatic ecology; population and community ecology of invertebrates, amphibians, and freshwater fishes; fisheries and aquatic resource management, conservation and restoration ecology.

I use a combination of field investigations, laboratory experiments and mathematical modeling to investigate the consequences of biotic and abiotic factors on the growth, movement and survival of juvenile steelhead (Oncorhynchus mykiss). I have conducted field research in many of the small coastal streams of central California, as well as larger rivers of the Sacramento-San Joaquin basin and San Francisco Bay-Delta area. I have used hatchery fish from throughout California to investigate critical physiology and how this varies regionally. My research is in cooperation with the National Marine Fisheries Service, Santa Cruz Laboratory, the East Bay Municipal Utilities District, and local agencies such as Santa Cruz County. My research is motivated by the need for sound science to inform management.

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ECOLOGY OF ANADROMOUS RAINBOW TROUT / STEELHEAD (Oncorhynchus mykiss)

Consequences of habitat use and movement for survival and anadromy of California steelhead (Oncorhynchus mykiss): I used acoustic telemetry in standardized transects to monitor steelhead degree of anadromy, movement, spatial distribution, survival and habitat associations.  In prep for publication.

 

Regional differences in temperature dependent growth of juvenile steelhead (Oncorhynchus mykiss): Using a laboratory experiment I investigated steelhead growth at 14, 20 and 24C. I used steelhead from three populations from two different distinct population segments. I then compared my results to previous studies. Results show differences in steelhead temperature dependent growth both within and among regions of California and Oregon. I also found no evidence for legacy effects of temperature dependent growth. In prep for publication.


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SABLE ISOTOPE ECOLOGY

Stable isotopes are an increasingly important tool in ecologists’ toolboxes, yet proper analysis and interpretation is predicated on proper model formulation and model inputs. Jonathan Moore and I collaborated to address these key gaps in a common application–using isotopes to estimate timing of resource change. Using a diet switch experiment on rainbow trout and measured isotope values of seven of their tissues, we compared competing tissue turnover model structures, quantitatively evaluated different methods of estimating resource switch, and applied this to wild-caught trout to estimate their timing of anadromous migration.

We also use stable isotope analysis in many of the ecological investigations on this page.

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SPECIES ASSEMBLAGES / SPECIES INTERACTIONS

Juvenile salmonid rearing habitat restoration influences on fish and fish prey community structure and spatial distribution through time: We investigated how macroinvertebrate community structure varied among sites within two restored side channel habitats and through time. We also looked at how juvenile Chinook salmon and steelhead used these habitats and how gut content of these fish related to macroinvertebrate community assemblages. Results were written in a management report to the CVPIA Anadromous Fish Restoration Program.

INVASIVE SPECIES

Invasive species have the potential to dramatically alter ecosystem functioning, species interactions, and species assemblages.

New Zealand mudsnail: This small snail (the size of a grain of rice) may have large impacts to aquatic ecosystems. It is a recent invader to North America. Its ability to withstand extensive periods of desiccation, reproduce asexually and protection from predation gives this species great invasion potential. Using stable isotope and community assemblage analyses we are investigating how this snail affects macroinvertebrate communities.

Signal crayfish: This arthropod was introduced to California in the early 1900s and now is found widespread throughout many freshwater habitats. It’s low energy requirements through time, and broad omnivorous foraging habits may give rise to its broad success. Using stable isotopes we are investigating how the presence of this invasive species interacts with anthropogenic influences to affect macroinvertebrate and fish communities throughout a watershed.