Exposure of delta smelt to dissolved pesticides in 2000

Delta smelt abundance in San Francisco Estuary has been declining since 1983. The exposure of delta smelt to toxic pesticides during larval and juvenile life stages may be one possible factor of this decline (Bennett and Moyle 1996; Moyle and others 1996). Although pesticides have been detected in the Delta (MacCoy and others 1995; Kuivila and others 1999), minimal data on pesticide concentrations and the duration of occurrence in delta smelt habitat are documented. A three-year study (1998– 2000) was undertaken by the U.S. Geological Survey (USGS) to quantify the exposure of larval and juvenile delta smelt to dissolved pesticides. Moon and others (2000) reported on the exposure of delta smelt to dissolved pesticides in 1998 and 1999, and this article follows up on Moon’s work and reports the results from late spring and summer of 2000.