20-mm Survey [Delta Smelt distribution monitoring]

Science activity #49954, updated 11 March 2026

20-mm Survey [Delta Smelt distribution monitoring]

Description / purpose

California Department of Fish and Wildlife (CDFW) conducts the 20-mm Survey annually to monitor the distribution and relative abundance of larval and juvenile Delta Smelt (Hypomesus transpacificus) in the upper San Francisco Bay Estuary. The survey began in 1995 and supplies near real-time catch data to water and fisheries managers as part of an adaptive management strategy to limit the risk of Delta Smelt entrainment during water exports Data collected: temperature, electro-conductivity, water transparency, turbidity, water volume, tidal stage, fish, and zooplankton.

Linked science activities

None specified

Collaborators

None specified

Activity status

1 Awarded / Initiating (2000)
2 In progress / Ongoing (2000 - 2026)
3 Complete

Funding summary

Total allocated funding: $0

Location

Subbasins

Delta regions

Geographic tags

None specified

Products and outputs

Title	Description	Views
20-mm Survey Sampling Sites	Online map of sampling stations for the 20-mm Surv	4
20-mm IEP Fact Sheet	Factsheets are concise documents that explain p	7
Survey Data	Survey data available for download	1

Type and context

Science action area

Unspecified

Management themes

Native species management

Science themes

Environmental conditions , Species

Types

Core monitoring

Science functions

None specified

Management actions

Habitat protection / enhancement / restoration , Population enhancement of listed species

Science Topics

Benthos , Chinook Salmon , Delta Smelt , Green sturgeon , Longfin Smelt , Other zooplankton , Sacramento Splittail , Stage , Steelhead Trout , Tides , Turbidity , Water temperature , White Sturgeon

Lead implementing organization

California Department of Fish and Wildlife [CDFW] , Interagency Ecological Program [IEP]

Partner implementing organizations

U.S. Bureau of Reclamation [USBR] , California Department of Water Resource [DWR]

Funding organizations

None specified

Funding programs

None specified

Funding sources

None specified