Contaminants Lower Reproductive Health of Gila River Fish

Downstream of Phoenix, southern Arizona’s Gila River is primarily recharged by irrigation return water, storm water, and wastewater treatment plant effluent, and fish and aquatic invertebrate habitats are degraded. Largemouth bass, common carp and channel catfish from the Gila had elevated levels of organochlorine pesticides, many of which have been associated with estrogen-like effects in fish. Reproductive biomarkers, including gonad size and hormone concentrations, were notably different in fish from the Gila River when compared to fish from the Colorado River, indicating that organochlorine contaminants may be affecting the reproductive health of fish populations in the Gila River downstream of Phoenix. For more information, contact Jo Ellen Hinck at jhink@usgs.gov or 573-876-1808.