The Colorado River has been called the American West’s hardest-working river. Lately, it’s been earning overtime. 

The river supplies water to some of the country’s largest cities, including Los Angeles and Las Vegas, as well as its most fertile swath of farmland, California’s Imperial Valley. Forty million people in seven states rely on the Colorado every day, and each year six million more visit its most magnificent stretch, the Grand Canyon.

But many non-human creatures also depend on the Colorado watershed, most of all the strange, hardy fish that prowl its turbid depths. This is the domain of the bonytail chub, the razorback sucker, and the Colorado pikeminnow, a six-foot-long predator that early anglers caught by