Effects of Suction-Dredge Gold Mining on Benthic Invertebrates in a Northern California Stream

Abstract

Abstract The effects on benthic invertebrates of mining with two suction dredges were investigated in 1983 by using artificial-substrate samplers in Big East Fork Creek, a tributary to Canyon Creek in northern California. The samplers were placed in Big East Fork Creek above and below the dredge site and in Canyon Creek above and below the confluence of Big East Fork Creek. The effects of dredging on invertebrates varied with taxa and were site-specific at the level of dredging during the study. Total numbers of invertebrates that colonized samplers and their diversity indices did not differ significantly between Big East Fork and Canyon creeks or above and below dredges in either creek. Numbers of invertebrates peaked earlier in samplers below the dredges. In Big East Fork Creek, shredders were more abundant above than below dredges, whereas gatherers were more abundant below dredges. Filterers rapidly colonized samplers below dredges and were later displaced by siltation. Shredders were more abundant ab...