Native and Introduced Stream Fishes of the San Joaquin Valley Floor - Their Relation to Quality of Water and Habitat

Larry R. Brown

In:
American Fisheries Society, 31st Annual Conference, California-Nevada Chapter, Consensus building in resource management, Napa, California, February 3-4, 1995 Program and Abstracts, p. 13.

Abstract:
The San Joaquin-Tulare Basins study unit of the U.S. Geological Survey's National Water Quality Assessment Program includes 28,500 square miles in central California. Sixteen San Joaquin Valley floor sites on the San Joaquin, Stanislaus, Tuolumne, and Merced rivers were sampled for fish during August 1994. Four sites were sampled on each river. Twenty-one introduced species and eight native species of fish were captured.

A cluster analysis of Jaccard similarity coefficients identified six groups of sites. The San Joaquin River sites were characterized by introduced red shiner, fathead minnow, inland silverside, and threadfin shad. The middle and downstreams tributary sites were characterized by introduced basses, sunfishes, and catfishes. The remaining four groups, primarily upstream tributary sites, were characterized by differing combinations of introduced and native species, which included Sacramento squawfish, hardhead, Sacramento sucker, and tule perch.

The abundance of introduced species was positively correlated with increased water temperature, specific conductance, alkalinity, pH, and oxygen concentration. Introduced species were positively correlated with increased stream discharge and width, but negatively correlated with elevation, riparian shading, and instream cover. Native species showed opposite relations to these variables. These data show that fish can be useful indicators of water and habitat quality.