The findings are the result of a USGS study to be published in the September issue of Bioscience.
Researchers found that between 1900 and 2010, species of North American freshwater fish went extinct 877 times faster than in the past, and that number is expected to climb in the years to come.
The rate represents an estimate, calculated by comparing old fossil records to modern-day data.
The actual extinction rate could be much higher.
"Estimates of freshwater fish extinctions during the twentieth century are conservative, because it can take 20-50 years to confirm extinction," said Noel Burkhead, the study's author, in a statement.
Researchers aren't sure what is accelerating the rate -- but human activity is a likely cause.
The study found that species of mussels and snails are also experiencing a rapid decline.