A Primer for Understanding Aquatic Resource Issues in the Upper San Francisco Estuary

The San Francisco Estuary is the largest estuary on the west coast of the United States.  As with many other estuaries, it has been highly altered by human activity.  Over the past several decades, the ecosystems of the San Francisco estuary and watershed have undergone a substantial series of changes that have been associated with marked declines in some species of pelagic fishes and invertebrates.  Migratory fishes such as salmon, sturgeon, and steelhead trout have also declined.  Efforts to protect declining fish populations have conflicted with increasing demand for fresh water and other ecosystem services such as disposal of treated waste water.  The watershed currently provides all or part of the water supply for 25 million California residents and supports a multi-billion-dollar agricultural industry.  This conflict has led to a resource management crisis of national significance.  The purpose of this presentation is to provide an introduction to the current understanding of environmental and biological conditions and resource issues in the estuary.  The following presentations in the symposium will introduce the major issues and present the latest research addressing some of the causes of the fisheries problems in the upper San Francisco estuary, where the changes in the ecosystem, particularly declines in pelagic organisms, have been most severe.  The presentations will emphasize studies conducted over the past five years as part of an integrated research plan of the Interagency Ecological Program.  These, and other presentations in the symposium, will cover a variety of topics ranging from changes in the food web to the evolution of conceptual models used to organize and understand information.