NCEAS Project 12198

Potential role of contaminants in declines of pelagic organisms in the Upper San Francisco Estuary, California

  • Erica Fleishman

ActivityDatesFurther Information
Working Group21st—25th January 2008Participant List  
Meeting19th—19th June 2008Participant List  
Working Group2nd—5th September 2008Participant List  
Working Group2nd—5th February 2009Participant List  
Working Group8th—11th September 2009Participant List  

In late 2004, scientists noted that abundance indices of several pelagic fishes in the upper San Francisco Estuary (delta smelt, age-0 striped bass, longfin smelt, and threadfin shad) had remained unusually low since 2001. Delta smelt is an endemic species listed as threatened under both the California and U.S. Endangered Species Acts. Protection of delta smelt often determines water management actions in the estuary, which supplies drinking water to more than 22 million people and supports a multi-billion dollar agricultural industry. The abundance of longfin smelt, another native species, has a strong positive relationship to freshwater outflow. Striped bass and threadfin shad are both introduced species that contribute substantially to the total biomass of pelagic fishes in the ecosystem and support valuable recreational fisheries. NCEAS and the Interagency Ecological Program are collaborating to convene several working groups on issues related to decline of pelagic organisms. We hope not only to gain a better understanding of the specific causes of the organism declines in the San Francisco Estuary, but to place these declines in the broader context of estuarine assessment and management in other geographic regions. This working group seeks to investigate the potential influence on observed declines of contaminants such as pyrethroid use, changes in wastewater discharge as California's human population increases, and changes in use of pesticides. Contaminants may be having chronic effects or effects on the food web rather than acute effects detectable by traditional bioassays. Wastewater includes steroids and other pharmaceuticals that can affect the endocrine and immune systems. There also may be maternal effects on eggs and larvae.

TypeProducts of NCEAS Research
Journal Article Brooks, Marjorie L.; Fleishman, Erica; Brown, Larry R.; Lehman, Peggy W.; Werner, Inge; Scholz, Nathaniel L.; Mitchelmore, Carys L.; Lovvorn, James R.; Johnson, Michael L.; Schlenk, Daniel; van Drunick, Suzanne; Drever, James I.; Stoms, David M.; Parker, Alex E.; Dugdale, Richard. 2012. Life histories, salinity zones, and sublethal contributions of contaminants to pelagic fish declines illustrated with a case study of San Francisco Estuary, California, USA. Estuaries and Coasts. Vol: 35. Pages 603-621. (Online version)
Data Set Johnson, Michael L. 2010. POD!_National Pollution Discharge Elimination System_Delta Discharge_1999-2007. (Online version)
Journal Article Scholz, Nathaniel L.; Fleishman, Erica; Brown, Larry R.; Werner, Inge; Johnson, Michael L.; Brooks, Marjorie L.; Mitchelmore, Carys L.; Schlenk, Daniel. 2012. A perspective on modern pesticides, pelagic fish declines, and unknown ecological resilience in highly managed ecosystems. BioOne. Vol: 62(4). Pages 428-434. (Online version)