Smelt -- Delta Actions Team Real-time Assessments

Weekly Assessment for Delta Operations on ESA and CESA-listed Osmerids

Final: Tuesday, February 17, 2026 at 3 PM

Executive Summary

• Entrainment management is currently active.
• Adult Delta smelt action no longer active.
• Delta smelt were recently detected at Suisun Marsh.
• No Delta smelt or longfin smelt salvage has been observed this water year.
• Turbidity in the central/south Delta is low.

Operational and Regulatory Conditions

• See current Weekly Fish and Water Operations Outlook document.
• Additional information also available on the SacPAS SMT page.

Delta smelt

Biological

• Delta smelt life stages: Adult, Juvenile

• Abundance estimate: 1769 (95% CL: 155 to 7,562) as of the week of February 2–6, 2026

• Releases: A total of 163,349 cultured Delta smelt have been released for WY 2026. The most recent release of 24,606 fish occurred in Sacramento River at Rio Vista on Dec 16, 2025.

• Delta smelt count: 36 adult Delta smelt and 29 juvenile Delta smelt have been detected this water year. See Table 1 for recent detections, Figure 1 for spatial distribution, and Figure 2 for temporal distribution.

• Delta smelt salvage: 0 Delta smelt have been salvaged, and the cumulative seasonal salvage is 0.

Notes

• Since there are few recent detections of Delta smelt, estimation of distribution within the Delta is limited.
• As mentioned in EDSM reporting, fork length ranges reported for Delta smelt and longfin smelt life stages are defined by permit reporting purposes and are not intended to delineate cohorts or distinguish from hatchery or wild origin. See Table 1 caption for fork-length ranges for age groups of Delta smelt.
• See SacPAS SMT Page for additional details on releases and detection in surveys and salvage.
• Historical salvage trends can be found at: SacPAS Salvage Timing

Environmental

First Flush

• Not relevant

Real-time Assessment Thresholds

Adult Delta smelt

• Not relevant

• See Bay-Delta Live for recent Delta-wide turbidity conditions.

Larval/juvenile Delta smelt

Threshold: After the onset of spawning, if JPF < 0 cfs AND turbidity is \(\ge\) 12 FNU in the south Delta AND PTM modeling indicates the action would avoid \(\ge\) 5% entrainment of Delta smelt population after 30 days

• 12-station South Delta Turbidity: The most recent average turbidity was 5.7 FNU as of Feb 11, 2025

Evaluation

Delta smelt:

1. After the start of entrainment management, is JPF < 0 and is daily average turbidity \(\ge\) 12 FNU in the OMR corridor (stations OBI, HOL, and OSJ)?

   The turbidity in the OMR corridor is not likely to be exceeded this week, and JPF is predicted to stay above 0 cfs.

2. Has the average water temperature at Jersey Point or Rio Vista not exceeded 53.6\(^{\circ}\)F (12\(^{\circ}\)C) for 3 consecutive days and/or has this action already been taken during WY 2026?

   Temperature at Jersey Point exceeded the threshold on February 12th, 2025. Jersey Point 3 day average temperature was (12.05�C) on February 10th, (12.09�C) on February 11th and (12.13�C) on February 12th.

3. What is the evidence for the onset of Delta smelt spawning?

   Upstream migration for Delta smelt occurs between September and December and in response to “first flush” conditions (Sommer et al. 2011, Grimaldo et al. 2009). Migration typically ranges one to four weeks after flow and turbidity increases, based on salvage data (Sommer et al. 2011). Historically, detections of ripe Delta smelt began in January and peaked in February and March and the majority of Delta Smelt spawning occurs within a temperature range of 9-18˚C (Damon et al. 2016). Based on historical monitoring data from the past few years, first detection of larvae in the Central and South Delta has typically occurred by mid to late March. Because first flush conditions were met on December 23, 2025, spawning is likely occurring, consistent with the typical one- to four-week response window following increased flow and turbidity. Survey captures at Chipps Island and the Sacramento Deep Water Ship Channel are consistent with an upstream spawning migration into tidal freshwater habitats.

4. After the onset of spawning, have the following conditions occurred: \(\ge\) 5% entrainment of the Delta smelt population at facilities after 30 days?

   Although spawning may occur during the current assessment period, JPF is above 0 cfs and average turbidity in the South Delta is low; therefore, the conditions required to trigger larval and juvenile Delta smelt entrainment management are not met.

Longfin smelt

Biological

• Longfin smelt life stages: Juvenile, Adult

• Longfin smelt count: 354 adult, 683 juvenile, and 1300 larval longfin smelt have been detected this water year. See Table 3 for recent detections, Figure 3 for spatial distribution, and Figure 4 for temporal distribution.

• Longfin smelt salvage: 0 longfin smelt have been salvaged, and the cumulative seasonal salvage is 0.

Real-time Assessment Thresholds

Start of Entrainment Management (Adult Longfin Smelt)

• Not relevant

Adult longfin smelt

• Threshold: JPF < 0 cfs, annual loss is on a trajectory to exceed 5% of the adult population abundance, and reduced exports will reduce entrainment in the south Delta
  • Daily average JPF: 3,167 cfs as of Feb 16, 2026
  • Adult abundance (Age 1+ LFS index): 2479.2 fish
    • 5% of abundance + 1: 125.0
  • Water year total adult longfin smelt salvage = 0

Larval/juvenile longfin smelt

• Threshold: JPF < 0 cfs AND population model demonstrates need to reduce entrainment to avoid population decline
  • Daily average JPF: 3,167 cfs as of Feb 16, 2026

Evaluation

Longfin smelt:

1. If JPF < 0, what is the trajectory of annual loss of adult longfin smelt and is it likely to exceed 5% of the adult population estimate? Is South Delta entrainment expected to decrease due to a reduction in export pumping?

   JPF is > 0 cfs and no adult longfin smelt have been detected in salvage.

2. For larval and juvenile longfin smelt, if JPF < 0 cfs, do particle tracking models show a moderate to high difference in particle fates across different OMRI scenarios? Does Zone of Influence modeling show moderate to high changes in hydrodynamic footprint across different OMRI scenarios? Are these effects anticipated to cause a population decline?

   JPF is not less than 0 cfs and is not predicted to go below 0 cfs this week. The Zone of Influence modeling indicates moderate differences in hydrodynamic footprint across OMRI scenarios, with no change between current and forecasted conditions.

3. Is there additional information or other analyses that should be considered in this evaluation?

   Additional information may be discussed if needed at the DAT call.

End of smelt Entrainment Management

• Not relevant

References

Damon, L. J., Slater, S. B., Baxter, R. D., & Fujimura, R. W. (2016). Fecundity and reproductive potential of wild female delta smelt in the upper san francisco estuary, california. California Fish and Game, 102(4), 188–210.

Grimaldo, L. F., Sommer, T., Van Ark, N., Jones, G., Holland, E., Moyle, P. B., Herbold, B., & Smith, P. (2009). Factors affecting fish entrainment into massive water diversions in a tidal freshwater estuary: Can fish losses be managed? North American Journal of Fisheries Management, 29(5), 1253–1270.

Sommer, T., Mejia, F. H., Nobriga, M. L., Feyrer, F., & Grimaldo, L. (2011). The spawning migration of delta smelt in the upper san francisco estuary. San Francisco Estuary and Watershed Science, 9(2).