The U.S. Geological Survey and the Fish and Wildlife Service, in a joint study, said it observed a "significant" number of fish deaths in Acorn Fork, a small creek in Kentucky, following a spill from nearby natural gas well sites. Fish affected by the release included the Blackside dace, a federally threatened species.
The chemical release occurred in 2007. The government in its announcement of the report didn't indicate the source of the spill but said hydraulic fracturing is the most common method of natural gas development in Kentucky.
The report found fish in the affected area develop gill lesions, an affliction consistent with exposure to acidic water and high concentrations of heavy metals.
The report said samples taken from the Acorn Fork creek "clearly showed" the spilled hydraulic fracturing fluid degraded water quality.
"This is an example of how the smallest creatures can act as a canary in a coal mine," Fish and Wildlife Service ecology and co-author Tony Velasco said in a statement Wednesday.