Geochemistry | Fish Ecology | Archaeology

I am a Postdoc at UC Santa Cruz in the Institute of Marine Sciences and National Marine Fisheries Service, Southwest Fisheries Science Center.

At the core of my research is the development and application of novel geochemical tracers and quantitative statistical methods to answer fundamental questions in fish ecology. My current focus is on reconstructing the life history of modern and historic Chinook Salmon populations in California and contrasting their responses to long-term climatic and landscape scale changes.

Over the last 5 years, I have studied several endangered and threatened fish in California, including Chinook Salmon, Delta and Longfin Smelt, and White Sturgeon. For these projects I applied a combination of microstructure and geochemical analyses (trace elements, strontium, oxygen, sulfur isotopes) to otoliths and other fish hard parts (scales, spines, fin rays) to better understand fish life histories, movement patterns, habitat use, and environmental exposure.

I collaborate with research groups at UC Santa Cruz (IMS, NOAA), UC Davis (WFCB, CWS, EPS), and ANU (RSES). In addition I work directly with many state and federal agencies to translate our scientific findings into management actions.


Research Projects


Data and Tools

IRHUM Database

The IRHUM (Isotopic Reconstruction of Human Migration) database is a web platform to access, explore and map strontium isotope data.

IsoFishR

Data reduction and analysis tool for laser-ablation strontium isotope data in R. Available on GitHub and published in PLOSONE.

OGFLtools

R package written by Christian Denney with utility functions used in the OGFishlab at UC Davis. Available on GitHub.


Delta Science Fellowship 2017-2019

In search of refuge: Investigating the thermal life history of Delta Smelt through in-situ oxygen isotope ratio analysis of otoliths

The Delta Smelt (Hypomesus transpacificus) is a small pelagic fish and rapidly approaching extinction. It is endemic to the Sacramento-San Joaquin Bay-Delta which is an important link in California’s water supply. This estuary is managed for human use as well as for several species of threatened and endangered fish and the Delta Smelt is at the center of conflict between human and environmental uses of the limited water resources.

Here we used strontium (87Sr/86Sr) and oxygen (δ18O) isotope tracers from archived Delta Smelt otoliths to reconstruct life history and thermal resilience at fine temporal scales. 87Sr/86Sr ratios from otoliths can be used to reconstruct salinity habitats, while δ18O reflects the water temperature a fish has experienced.

The combination of these two isotopic tracers will allow us to investigate the relationship between Delta Smelt abundance, freshwater outflow and water temperature. Understanding this relationship can give new insights into resilience and habitat utilization of Delta Smelt in the face of warming water temperatures during prolonged drought periods and long-term climate change.