AZ - Backwater Manipulations for Endangered Fishes: Management Implications of Selenium on National Wildlife Refuges of the Lower Colorado River : Final Report
Carrie Marr Anthony L. Velasco
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Many studies have evaluated selenium in the lower Colorado River, but none have reviewed selenium levels after river water has been directed into previously isolated backwaters. Radtke et al. (1988) hypothesized that the source of selenium was the upper Colorado River Basin and that backwater lakes along the river were sinks for selenium contamination. Subsequent research has reported that backwater lakes could become selenium sinks when lower Colorado River water is introduced into isolated backwater lakes originally fed by groundwater and where low exchange rates increase retention time. Backwaters created as isolated native fish habitats in partial fulfillment of the Reasonable and Prudent Alternatives of the Service’s Biological Opinion on the Bureau of Reclamation’s operation of the lower Colorado River allow the fish to grow in a predator-free environment, but also may be contributing to selenium bioaccumulation along the lower Colorado River.
Our goals in this study were to conduct a pre- and post-backwater manipulation investigation of created backwaters. To assess selenium accumulation in backwaters, we sampled water, sediment, and macroinvertebrates in 2001 and 2004. We also collected fish tissues in 2001-2004 for a baseline analysis on native fish stock in constructed, isolated backwaters. Project ID: 22410-1261-2N37
http://www.fws.gov/southwest/es/arizona/Documents/ECReports/Final%20CORRECTED%20EDC%20Report%202007.pdf, 2 MB
U.S. Fish and Wildlife Service - Arizona Ecological Services Field Office