National Geographic —
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 tying fishing lines to their truck bumpers. The lower Colorado has the highest ratio of endemic fish in North America—meaning that six of its eight native species exist nowhere else on Earth.
The best-studied member of the river’s distinctive ecosystem is the humpback chub, a creature as bizarre as fish come. Gila cypha is a silvery, foot-long member of the minnow family that has big orange fins and a fleshy, ridge-like protuberance along its back—its mysterious hump. If you crossed a carp with a bison, the humpback chub is what you’d get.