Longfin Smelt Distribution in the Coastal Pacific Ocean

Science Center Objects

Longfin Smelt (Spirinchus thaleichthys) is a pelagic fish species found in waters along the Pacific coast, from Alaska to central California. Its complex life cycle makes it vulnerable to threats in both freshwater and at sea. Longfin Smelt is listed as a threatened species by the state of California.

Longfin smelt captured in San Pablo Bay, November 2018.

Longfin smelt captured in San Pablo Bay, November 2018. Longfin Smelt typically live for two years, with 1 and 2 year old fish represented in this photo. Fish of all sizes have been observed in the marine environment.

Changes to currents and climate in coastal marine habitats may be affecting Longfin Smelt populations along the Pacific coast of North America. One such impact may be the latitudinal and spatial distribution of the species along the coast. Localized ocean conditions near the San Francisco Bay and other estuaries may also be impacting species growth and survival.  

Understanding such conditions affecting the Longfin Smelt is important. In addition to protecting the species, the freshwater habitat the Longfin Smelt uses for spawning and rearing is key to California’s water supply. The goal of this project is to estimate the marine distribution of Longfin Smelt and better understand its sensitivity to oceanographic conditions and processes. Of special concern are the effects of climate variability and global climate change.

Scientific Approach

Task 1 data compilation

A major component of this work will be the compilation of longfin smelt occurrence records.  A variety of data sets will be obtained and examined to generate all possible marine longfin smelt occurrence records. These include marine and estuarine records compiled by entities spanning the entire Pacific coast of North America.

Task 2 species distribution modeling

Researchers will develop species distribution models and integrate them with modeled oceanographic conditions. Distributional modeling will be implemented with a combination of simple spatial interpolations and more complex statistical methods. Longfin smelt occurrence data will likely include a combination of presence-absence and presence only records. 


This research will advance the knowledge of Longfin Smelt Life history and contribute the effective management and conservation of this imperiled species.