Delta Smelt (Hvuomesus Transpacificus) Recovery Review And Status Update.pdf

## Hvuomesus transvacificus (Delta Smelt) Recovery Review Summary

This review summarizes the current status and recovery efforts for the delta smelt (Huvomesus transpacificus), a threatened fish species in California and Nevada.

Background:

Recovery Potential: The delta smelt has been assigned a recovery potential of 2 (high), reflecting its ability to rebound from past declines. However, severe droughts and water development pose significant threats to its survival.
Listing History: Listed as threatened under the Endangered Species Act in 1993 with critical habitat designated in 1994.
Recovery Plan: A recovery plan was completed in 1996, setting criteria for delisting. However, these criteria have proven incorrect, and the species has not met delisting benchmarks.

Key Findings:

Declining Population: Delta smelt populations have experienced a tenfold decline over the past 20 years, remaining at extremely low levels despite occasional fluctuations.
Threats: The primary threats to delta smelt include:
Reduced river outflow from the Sacramento and San Joaquin Rivers and their tributaries.
High river outflow during heavy rainfall years.
Entrainment mortality caused by water diversions.
Perturbations to the smelt's food web.
Presence of toxic substances in aquatic habitats.
Loss of genetic integrity due to a reduced population size.
Competition: The introduced Japanese smelt (Hypomesus nipponensis) poses competition for resources and potential displacement of delta smelt.
Future Projections: Numerous proposals for increased water exports, diversions, and changes in Delta inflow threaten the species' future.

Current Status:

The most recent comprehensive analysis (2003) indicates:

Population Status: Declining
Recovery Achieved: Not met
Active Recovery Team: None established

Recommendations:

The review highlights the need for:

Revised recovery criteria: Based on updated scientific information and current threats.
Increased monitoring: To track population trends and assess the effectiveness of recovery efforts.
Water management strategies: That prioritize delta smelt needs, including reduced diversions and increased inflows during critical periods.
Research: Further investigation into habitat requirements, life history, and interactions with other species.