Interactions Between Physical Processes and Suspended Sediment Quality in Relation to Spawning Migrations of Delta Smelt

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The proposed study is designed to better establish relationships between patterns of delta smelt abundance and properties of suspended particles as measured by optical and acoustical techniques.

Map showing existing flow stations.

Map showing existing flow stations.

Researchers and ecosystem managers in the Sacramento-San Joaquin Delta have suggested that turbidity is a potentially important trigger for delta smelt migration and as a mechanism for prevention of predation during migration. The occurrence of delta smelt has been associated with low salinity and high turbidity waters (Feyrer et al. 2007). However, although turbidity and salinity are clearly important explanatory predictors of delta smelt occurrence, variation in these simple parameters explain only ~25% of the variability in delta smelt population distribution, suggesting additional parameters related to delta smelt behavior and ecology are also important. We suggest here that the source and quality of the suspended material causing the turbidity as well as the associated dissolved material may also be important explanatory variables because they significantly alter the local environment in ways not captured by turbidity measurements.

Objectives: The proposed study is designed to better establish relationships between patterns of delta smelt abundance and properties of suspended particles as measured by optical and acoustical techniques. The purpose is to identify monitoring parameters that may be incorporated into existing monitoring and data analysis efforts to better predict conditions favorable to delta smelt occurrence. To accomplish these purposes, we propose to address the following questions:

  1. How are measured optical and acoustic properties of particles related to the abundance and distribution of delta smelt during the period of migration?
  2. How are measured optical and acoustic properties of particles related to the abundance and distribution of zooplankton during the period of delta smelt migration?
  3. What is the vertical (through the water column) and lateral (across channel) variability in the properties of suspended particulate material associated with the occurrence of delta smelt and their prey?
  4. How are measured particle properties related to physical dynamics such as flow and turbulence?

This project will be conducted in conjunction with the Interagency Ecological Program Smelt-Turbidity study. Field operations will be conducted during the same period the IEP study is sampling fish. The data developed as part of this study will be related to the patterns of occurrence of Delta smelt to identify habitat indicators that improve the prediction of Delta smelt abundance and distribution as well as the cue for spawning migrations.

This project is to develop fundamental tools to assist in the USGS priority of "Understanding Ecosystems and Predicting Ecosystem Change" by developing relationships between sediment quality indicators and endangered fish abundance and distribution.