The movement patterns of endangered delta smelt in the SAN francisco estuary are largely unknown

The U.S. Fish and Wildlife Service, Department of the Interior, awarded a $223,551 Cooperative Agreement to the University of California, Davis on October 1, 2025, under the Central Valley Project Improvement Act (CVPIA), CFDA 15.648, to advance acoustic telemetry methodologies for tracking endangered Delta smelt in the San Francisco Estuary. Over a two-year project period concluding January 2, 2028, UC Davis will conduct field-based experiments to test the detectability and feasibility of newly miniaturized JavaScript Telemetry System (JSATS) tags implanted in Delta smelt. The research encompasses three primary deliverables: testing the detection efficiency of reduced-power JSATS tags (142 decibels output) with both existing receiver arrays in the San Francisco Estuary and at potential new Delta smelt-specific receiver locations; designing and deploying a three-dimensional positioning array to evaluate performance in upper San Francisco Estuary habitats; and conducting small-scale releases of tagged Delta smelt to assess the JSATS receiver array's capacity to detect and position live fish in the field.

This feasibility research directly supports CVPIA's Science Integration Team Fish Information Needs goal of reducing key scientific uncertainties to guide restoration strategies. By resolving critical gaps in Delta smelt movement dynamics and telemetry deployment feasibility, the project will facilitate improved water operations management, optimize stocking efforts for wild population supplementation, and inform habitat restoration decisions for this endangered species.

Activities

First, we will test the detectability of the new jsats tag, by both the existing jsats array within the SAN francisco estuary and at potential locations for new delta smeltspecific receivers. Secondly, we will design and deploy a 3D positioning array to test performance of such an array in upper SAN francisco estuary habitats. Finally, we will conduct several small releases of delta smelt implanted with the new smaller telemetry tag to assess the capacity of the jsats receiver arrays to detect and position live fish.

Expected outcomes

This feasibility study will lay the groundwork for the development of a receiver array and post-detection signal processing algorithm to detect delta smelt tagged with this smaller and lower power tag in later phases of the project. If a jsats array can successfully monitor the dispersal of delta smelt throughout the delta, models developed from this telemetry data may contribute to ongoing management efforts. Spawning-related movement behavior and entrainment of delta smelt into the south delta will resolve critical information gaps in the delta smelt life cycle model. The effect of important water operations variables on delta smelt dispersal can be modeled, providing critical information for operational guidance. Telemetric tracks of individual fish will allow identification of important habitat areas for delta smelt, which may be optimal regions for supplementation. Finally, acoustic detection records could improve delta smelt abundance estimates through the estimation of gear efficiency, leading to absolute, rather than relative, estimates of delta smelt abundance.