Monitoring wild delta smelt using environmental DNA (eDNA)

For more information contact Ann Holmes:

Background and Significance of Study

The GVL is using environmental DNA (eDNA) to detect delta smelt in the San Francisco Estuary and Delta. Previously, GVL researchers developed a genetic assay that detects delta smelt in predator gut contents (Baerwald et al. 2011, Brandl et al. 2015). Now, we are using this assay to detect the presence of delta smelt in water using trace amounts of DNA left by fish.

The goal of this project is to develop a tool that can be used to augment existing monitoring of delta smelt. eDNA is a promising new tool in conservation and monitoring. Adequate monitoring of endangered species like delta smelt can be challenging. Not only are the fish hard to find, but trawling may harm populations. eDNA, on the other hand, is a non-invasive monitoring method. In addition, eDNA detects fish of any life stage and in habitats that may be inaccessible to traditional trawling. Developing and evaluating eDNA for delta smelt monitoring includes testing water from cultured smelt tanks, field experiments using cultured smelt, and field sampling coordinated with the USFWS Enhanced Delta Smelt Monitoring (EDSM) survey. Our research will optimize eDNA detection of delta smelt and address questions related to interpretation of results (such as the decay rate of DNA in the environment).

Cultured delta smelt from the UC Davis FCCL. Water from this tank was used to test eDNA methods in the field.


Ann Holmes, Mandi Finger, Andrea Schreier, Melinda Baerwald, Tien-Chieh Hung (UC Davis)

Ted Sommer, Brian Schreier, Brian Mahardja (DWR)

Jeff Rodzen (CDFW)