Mines

They're not spectacular like marlins, but trout are among the most legendary—think A River Runs Through It—and lucrative fish of mountain rivers and lakes. Across the western United States alone, trout fishing generates hundreds of millions of dollars annually. But trout habitat will likely be cut in half by 2080 due to warming rivers and altered patterns of flooding, according to a large study published today. "It's fairly shocking to us, as biologists," says co-author Kurt Fausch of Colorado State University, Fort Collins.

The study, published online today in the Proceedings of the National Academy of Sciences, is the first to tease apart the probable impacts of climate change on common trout species. This is not a case of winners and losers; the four species examined by the team are all likely to decline to varying degrees. The good news for fans of fly-fishing is that the rainbow trout, beloved for its large size, will suffer the smallest impact. On the other hand, the results will further alarm conservationists concerned about the plight of native cutthroat trout.

By running several climate models and plugging in data on habitat characteristics and fish present at 9890 locations in the Rocky Mountains and Great Basin, the team of scientists created predictions for trout habitat across more than 1 million square kilometers of the western United States. They factored physical aspects of habitat—water temperature, patterns of flooding—as well as competition among species. Here's what the study concludes about the future of trout:

Rainbow trout (Oncorhynchus mykiss): Introduced beginning in the 1800s for fishing, these trout live in larger rivers than do the other species. They typically grow up to 110 centimeters long and are relatively easy to catch.Increases in water temperature will restrict their range, but rainbow trout dodge a bullet. Climate change will mean more frequent and intense winter floods, which can scour away eggs laid in the fall, but...