Interagency Ecological Program San Francisco Estuary Larval Entrainment Study (LES)

Sampling began in 2022 using 10-minute stepped oblique tows of a Smelt Larval Survey (SLS) sled mounted with a 500 μm net. Tows were conducted in West Canal, outside Clifton Court Forebay (CCF), where the risk of entrainment is highest. Sampling was conducted five days a week in 2022 and three days a week in the following years..

Beginning in mid-January 2023, a 940 μm mesh net with the same dimensions as the SLS net was added, with sampling alternating between the two. This provided an intermediate gear between SLS (500 μm) and 20mm (1600 μm) nets. In 2024 we expanded to sample a transect of sites within the Old and Middle River (OMR) corridor.

This provides broader spatial resolution and improves our ability to detect Osmerids within the South Delta. Sampling alternated between a high priority day (with intensive sampling in the lower San Joaquin River, SLS stations 809 & 812) and a longer transect day that ran the length of the OMR corridor( at SLS stations 809, 812, 902, 915 & 918). We also began to sample using a bongo sled, which allows two nets to sample side by side.

This data also includes our special studies; a day/night comparison conducted in 2022, a gear comparison in 2023, and a second day/night comparison study in 2024. ## About This Federated Record This CNRA Open Data Platform record is based on metadata federated from the Environmental Data Initiative (EDI) Data Portal. Its purpose is to improve the discoverability of the data package through the CNRA Open Data Platform. The EDI Data Portal is the repository of record for this data package.

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