Defining habitat quality for young-of-year longfin smelt: Historical otolith-based reconstructions of growth and salinity history in relation to geography, climate, and outflow

Start/End: February, 2018 to January, 2020

The longfin smelt population has collapsed to less than one percent of its pre-1980s abundance. Though several possible factors have been implicated, including freshwater outflow and prey abundance, little is known about the optimal environmental conditions needed by early life stages. Using otolith-based growth and isotope analyses, this study will provide historical chronologies of growth and salinity history for hundreds of archived longfin smelt spanning the previous two decades.

This project will use cutting-edge tools to examine an extensive collection of archived wild longfin smelt specimens. The aims are to:

  1. Provide a better understanding of longfin smelt life history, habitat use, growth, recruitment and population responses to spatiotemporal environmental variability (such as regional and annual variation in temperature and salinity).
  2. Provide tools to support and evaluate habitat restoration.
  3. Facilitate development of a comprehensive plan to recover the threatened species in accordance with the California Water Action Plan.
  4. Improve the understanding of longfin smelt population dynamics in relation to flow, helping California meet the Delta Plan’s co-equal goals of protecting native species and simultaneously providing a reliable water supply for the state of California.

Results from this project will be integrated into the Interagency Ecological Program’s longfin smelt management, analysis, and synthesis report, which will be used to determine federal listing status and inform adaptive management of freshwater flows for fishes in the upper San Francisco Estuary.

Research Mentorn: James Hobbs, University of California Davis
Community Mentor: Randy Baxter, California Department of Fish and Wildlife