Science activity

Description
Entrainment into the State Water Project and Central Valley Project (CVP) is a source of mortality for native osmerid species, including Delta Smelt (Hypomesus transpacificus) and Longfin Smelt (Spirinchus thaleichthys). However, these facilities do not quantify larval fishes, leading to a gap of knowledge in understanding larval fish entrainment. The Larval Smelt Entrainment Monitoring study fulfils the 2020 Incidental Take Permit Condition of Approval (COA) 7.6.2, which states, “Permittee shall fund and implement a new Smelt Larval Entrainment Study (LES) to quantify larval DS and LFS entrainment into Clifton Court Forebay (CCF).” This COA has directed an interagency team to complete a pilot study (LEPs 2022-2024) and continuing monitoring into 2025. Further, LES supports multiple reporting and consultation requirements on threatened and endangered native osmerid species.
Project Need
Delta Smelt (Hypomesus transpacificus) and Longfin Smelt (Spirinchus thaleichthys) have been in decline for many decades and are both protected under the State Endangered Species Act. Water exports at the State Water Project (SWP) result in direct and indirect entrainment of fish and are a source of mortality. Only juvenile and adult smelt (>20 mm) loss has been quantified and no quantitative native larval smelt monitoring currently occurs at the salvage facilities. The sensitivity of existing larval smelt monitoring at the salvage facilities is only appropriate for detecting presence. LES is intended to provide quantitative estimates and early detection of native larval osmerids into the south Delta and CCF.
Project Objectives
•    Provide the framework for a final monitoring survey design, through adaptive management, for approval by CDFW during the term of the ITP.
•    Understanding the spatial and temporal variability in larval Longfin and Delta Smelt presence outside of Clifton Court Forebay.
•    Examine the sensitivity of different detection systems (e.g. eDNA, townet sampling) for Native osmerids.
•    Analyze potential biotic and abiotic variables that correlate with native osmerids.
•    Identify strategies to improve sensitivity and quantification of native larval smelt entrainment into Clifton Court Forebay (CCF).