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Humpback Chub Gi Za cypha Status Endangered on both federal and Colorado lists. little is known about its biology. Apparently it Distinguishing Features feeds on invertebrate animals and is sometimes caught As the name implies, a prominent hump on the body by fishermen on bait such as grasshoppers or worms. immediately behind the head characterizes this spe- cies. The hump of the humpback chub differs from that of the razorback sucker in being rounded and not sup- ported by internal bone; in the razorback sucker the hump is sharp edged and has a bony structural support. The degree of development of the hump is highly vari- able. The humpback chub has a fleshy snout which pro- trudes over the lower jaw; large, streamlined fins; and a small eye -- smaller than the eye of roundtail or bonytail chubs of similar size. The caudal pedun- cle (the thinnest part of the body, just in front of the tail) is thicker in the humpback chub than in the bonytail chub, but thinner than in the roundtail chub. Hybridization of the humpback chub with both the bony- tail chub and the roundtail chub has been reported. As a result, positive field identification of the humpback chub is not always possible, even for the experienced biologist. In the Little Colorado River of Arizona, humpback chubs have been observed feeding on food scraps thrown into the water by picnickers. The humpback chub may feed on the surface of the water, although the peculiar body shape seems designed to maintain stability on the bottom in turbulent flow. Its body may be designed to facilitate up and down movements, so that it can feed on a variety of foods at dif- ferent depths from the bottom to the surface. The maximum size attained by humpback chubs is about 16 to 18 inches. Young humpback chubs prefer quiet backwater areas similar to those used by young squawfish. No one has yet observed the spawning of this species, but chubs ready to spawn were observed in water of about 650 F, suggesting that they spawn slightly earlier than squawfish. Most of the prime humpback chub habitat in the canyon areas of the basin is now covered by reservoirs. As with the squawfish, adult humpback chubs continued to live in Life History reservoirs, but they became older and fewer until The humpback chub was not known to science until they finally disappeared because they did not repro- 1946, when a specimen from the Grand Canyon was des- duce. cribed as a new species. It was never a common fish because of its habitat restrictions. Humpback chubs Past and Present Distribution occur in river sections that contain swift, deepwater The original distribution of the humpback chub areas, typically in canyons. Because of its rareness, is not known with certainty, but it is assumed to be 16