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Report Offers Updated Delta Smelt Findings

May and June 2015
Delta smelt on the rocks

It may take a village to raise a child, but it takes a whole year to make a mature Delta smelt. That’s one of the key findings in an updated conceptual model and recent report of Delta smelt biology by the Interagency Ecological Program’s Management, Analysis, and Synthesis Team (MAST).

The MAST group is comprised of more than a dozen members from federal and State agencies and boards, including former IEP Lead Scientist and Delta Stewardship Council (Council) scientist Anke Mueller-Solger.

The report, “An updated conceptual model of Delta smelt biology: our evolving understanding of an estuarine fish,” was presented to the Council by MAST members Ted Sommer from the Department of Water Resources and Larry Brown from the U.S. Geological Survey on behalf of the Interagency Ecological Program (IEP) earlier this year.

The MAST report updates previous conceptual models for Delta smelt to reflect new data and information since the release of the last synthesis report about the Pelagic Organism Decline (POD) by IEP in 2010. The current report and conceptual model describes habitat conditions and ecosystem drivers affecting Delta smelt throughout its different life stages and across the different seasons.

Conceptual models are formalized versions of mental models that are communicated to others verbally and graphically. A conceptual model gives people an understanding of how things really fit together, “instead of the usual process of picking one favorite factor and trying to look at its individual importance,” Sommer explained.

The main purpose of the report is to provide an up-to-date assessment and conceptual model of factors affecting Delta smelt throughout its annual life cycle and to demonstrate how this conceptual model can be used for scientific and management purposes. The MAST conceptual model, a synthesis of current thinking on the factors affecting vital rates of the Delta smelt population, was used to try and answer the question, why did Delta smelt suddenly do so well in 2011?

“They’d been doing miserably for the past decade; why in 2011, when it was a wet year, did they finally do well?” Sommer asked. “One of the things that we found is compared to another recent year, 2006, they both produced lots of babies in each of those years. But what happened differently in 2006 is we had a very hot summer and we think that undermined a lot of the fish. You can have really good conditions early in the year—those wet conditions—but it can easily change if something happens later in the year.”

The document includes a number of recommendations about how the conceptual model should be used:

  • Address scientific questions important to management
  • Identification of science priorities and gaps
  • Guidance for adaptive management
  • Development of quantitative management

To read the full report please click here.

Coequal goals

The Delta Stewardship Council was created in legislation to achieve the state mandated coequal goals for the Delta. "'Coequal goals' means the two goals of providing a more reliable water supply for California and protecting, restoring, and enhancing the Delta ecosystem. The coequal goals shall be achieved in a manner that protects and enhances the unique cultural, recreational, natural resource, and agricultural values of the Delta as an evolving place." (CA Water Code §85054)