(Adds reason for USGS study, background, details)
Aug 29 (Reuters) - Hydraulic fracturing fluids that spilled into a Kentucky creek in 2007 likely caused "widespread death or distress" to fish, according to the U.S. Geological Survey (USGS).
Hydraulic fracturing, or "fracking," has revitalized U.S. oil and gas production in recent years but also prompted charges that it damages the environment, causes minor earthquakes and contaminates drinking water.
The USGS and the U.S. Fish and Wildlife Service initiated a study of Acorn Fork, a small Appalachian creek in southeastern Kentucky, following a release of fracking fluids from nearby natural gas wells in 2007 and after a local resident complained that fish had been dying.
"Hydraulic fracturing fluids are believed to be the cause of the widespread death or distress of aquatic species in Kentucky's Acorn Fork ... ," the agency said in a statement dated Aug 28.
The fish in question were the blackside dace, which is on a federal list of threatened species, and the more common creek chub and green sunfish. (Reporting by Sabina Zawadzki; Editing by Gerald E. McCormick and John Wallace)