Pelagic Organism Decline Overview
In the last few years, the abundance indices calculated by the Interagency Ecological Program (IEP) Fall Midwater Trawl survey (FMWT) and Summer Townet Survey (TNS) show marked declines in numerous pelagic fishes in the upper San Francisco Estuary (the Delta and Suisun Bay) (IEP 2005). The abundance indices for 2002-2004 include record lows for delta smelt and age-0 striped bass and near-record lows for longfin smelt and threadfin shad.
In contrast, the San Francisco Bay Study did not show significant declines in its catches of marine/lower estuary species. Based on these findings, the problem appears to be limited to fish dependent on the upper estuary. In response to these changes, the IEP formed a Pelagic Organism Decline ("POD") work team to evaluate the potential causes.
CALFED Science Program POD Support
POD 2006-07 Workplan Overview
"The overall approach for 2006-7 is intended to evaluate and refine the evidence for the conceptual models. To address the matrix models, the study design is based on temporal, spatial and species contrasts for selected fish and zooplankton. For each contrast, the variables to be evaluated include: abundance, growth rate and fecundity; and feeding success, condition factor, parasite load and histopathology (fish only). To the extent possible, these data will be collected simultaneously to help evaluate the relative importance of different stressors. The narrative models, on the other hand, posit linkages among different stressors and their possible pathways to produce the observed declines of more than one species. The workplan elements that are based on the two narrative models, therefore, emphasize analyses of the proposed linkages among stressors."
For a more detailed look at the 2006 Workplan Proposal, please read the full document: