Integrating Chemical, Water Quality, and Habitat Data with Fish Assemblage Data from the San Joaquin River Drainage

Larry R. Brown, Charles R. Kratzer and Neil M. Dubrovsky

In:
Smith, C.S., and Scow, K., eds.,1999, Integrated Assessment of Ecosystem Health: Ann Arbor, Mich., Ann Arbor Press

Abstract:
As part of the National Water Quality Assessment of the U.S. Geological Survey, studies of concentrations of dissolved pesticides and other measures of water quality, stream habitat, and fish assemblages were conducted in the San Joaquin River drainage, California, from 1992 to 1994. Forty-nine pesticide compounds were detected in one or more water samples collected for analysis. The ten most frequently occurring compounds were simazine, diazinon, metoalchlor, chlorpyrifos, DCPA, EPTC, trifluralin, atrazine, diuron, and cyanazine. Detailed studies at four site revealed significant seasonal variability in the number of pesticides detected in individual site samples and in the summed concentrations of all pesticides detected in a site sample. Concentrations of diazinon were related with application patterns to different crop types and to timing of rainfall. Significant correlations were found between water quality, habitat, and fish assemblage data. The correlations, however, were dependent on the number and locations of the sites included in the analysis. There was no clear link between pesticide concentrations and fish assemblages. Our results highlighted difference in the temporal and spatial scales of sampling between water quality and ecological studies. The water quality and pesticide studies emphasized single samples over a large geographic area because of lack of information on the range of possible ecological conditions in the study area.