Science activity

The Smelt Larva Survey (SLS), initiated in January 2009, provides near real-time distribution data for Longfin Smelt larvae in the Delta, Suisun Bay and Suisun Marsh for the protection of larval and juvenile Longfin Smelt from December through March.

Project Need

The data obtained from SLS are used by agency managers to assess vulnerability of Longfin Smelt and Delta Smelt larvae to entrainment in south Delta export pumps. This larval fish survey is designed to provide a more comprehensive coverage of distribution and abundance of larval Longfin Smelt and Delta Smelt in the upper estuary, and augment other sources of data used in the decision-making process for water operations, including the existing IEP 20-mm Survey field operations when the two programs overlap temporally. This survey is also a requirement of Section 5.2 of Incidental Take Permit No. 2081-2019-066-003 for the State Water Project, issued by CDFW under the authority of the California Endangered Species Act and pursuant to Fish and Game Code sections 2081(b) and 2081(c), and California Code of Regulations, Title 14. Export and flow management are guided through distribution and catch criteria based on this study.

Project Objectives

• Determine the larval Longfin Smelt and Delta Smelt abundance, temporal and spatial distribution in near real time.
• Determine whether the temporal and spatial distribution and abundance of larval and post-larval Longfin Smelt and Delta Smelt are determinate factors on the level of entrainment losses.

Schedule of Milestones

• Every two weeks from December to March field surveys will be conducted and field and laboratory results will be reported weekly to the Smelt Monitoring Team (SMT) and the WOMT team starting 5 days after the field sampling are concluded. Shortly afterwards, raw and calculated data will be uploaded to the Region 3’s SLS Survey web page.
• By the end of the calendar year a draft survey summary article will be submitted to the Editor of the IEP newsletter for publication.