Pelagic Organisms Decline Studies

Project Chief: Larry Brown, Dave Schoellhamer, and Cathy Ruhl

In the last several years (2002-2004), abundance indices calculated by the Interagency Ecological Program (IEP) have been at record lows for delta smelt Hypomesus transpacificus and age-0 striped bass Morone saxatilis and near-record lows for longfin smelt Spirinchus thaleichthys and threadfin shad Dorosoma petenense. While several of these declining species have shown evidence of long-term declines, there appears to have been a precipitous "step-change" to very low abundance by at least 2002-2004 even though flow conditions were moderate. Similar flow conditions have supported modest production of these species in the past. These changes are particularly important to managers because the delta smelt is a federal and state endangered species.

In response to these changes, the IEP formed a Pelagic Organism Decline ("POD") work team ("POD-WT") to evaluate the potential causes for the declines. This initial work has identified a number of potential new studies for future work and has also created a flood of new data that needs to be evaluated and synthesized in relation to the pelagic organisms decline.

The POD-WT has identified many more new studies than existing IEP personnel have the time or expertise to address. Thus, the POD is fostering collaboration with other agencies and partners to accomplish these studies. In response to the flood of new data, the POD-WT is attempting to initiate new data integration and synthesis efforts involving the National Center for Ecological Analysis and Synthesis at the University of California at Santa Barbara.

Contact Information

Larry Brown, Dave Schoellhamer, and Cathy Ruhl
Office phone: 916-278-3000

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