Over 700 freshwater fish species in North America, nearly 40 percent of the total, are considered vulnerable to extinction or worse, according to a new study led by the U.S. Geological Survey. The study, published in the journal Fisheries, is the most comprehensive assessment of North American freshwater fish species since 1989, but the results show little reason for celebration. Of the assessed species, only 11 percent were better off than in 1989, while the list of imperiled species nearly doubled since then and suspected extinctions grew by over 50 percent to a total of 61. Researchers said that pollution, drought, invasive species, the effects of development, and demand for water all contributed to the decline and that climate change may have also played a role. "Fish are indicators of how good the water quality is," said Howard Jelks of the USGS. "As long as you're losing fish, you're also likely losing crayfish, mussels, and other things of that nature. They're kind of the canary in the coal mine."