The Colorado pikeminnow (formerly known as the Colorado squawfish), Ptychocheilus lucius, is a large minnow native to the Colorado River system of the western United States and Mexico. Due to flow regulation, habitat loss, migration barriers (such as dams), and the introduction of nonnative fishes, however, the current range and numbers of the Colorado pikeminnow are much reduced, and the species now exists only in the upper Colorado River system. Because of these reductions in population numbers and species distribution, the Colorado pikeminnow is Federally listed as endangered.
Colorado pikeminnows are primarily piscivorous (they eat fish), but smaller individuals also eat insects and other invertebrates. The species spawns during the spring and summer over riffle areas with gravel or cobble substrate. Eggs are randomly broadcast onto the bottom, and usually hatch in less than one week.
Adult Colorado pikeminnows prefer medium to large rivers, where they can be found in habitats ranging from deep turbid rapids to flooded lowlands. Young of the species prefer slow-moving backwaters. Although individual Colorado pikeminnows now rarely reach more than one foot in length, historical accounts of six-foot long Colorado pikeminnows exist, making the species the largest minnow in North America.