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40 Recovery of the humpback chub, Gila cypha, and observations on that species, 1977-1978 by C. O. Minckley Biology Department Museum of Northern Arizona, Flagstaff, Arizona ABSTRACT: During 1978, twenty adult humpback chubs were placed at Willow Beach National Fish Hatchery, for propagation purposes. The fish were collected from the Little Colorado River, in the vicinity of its mouth, flown to the south rim of the Grand Canyon, and transported to Willow Beach. All fish arrived in good condition and were in the hatchery raceways within five hours of lift-off from the Little Colorado River. During 1978, 555 humpback chubs were collected. Of these fish, 21.5% (196) were juveniles, and 78.5% (359) were adults. Distribution of this species within the mainstream Colorado River was extended to river mile 194, based on a report from a commercial river runner. General distribution within the system reflects the size of fish, with larger adults preferring water over two meters in depth. Juvenile fish occurred in water less than two meters in depth. Both size groups were usually found in moderate to slow current over silt-sand bottom in the Little Colorado River. Schooling was observed both in adult and juvenile humpback chubs, as was feeding behavior. Schooling fish were observed feeding both on the bottom substrate and the surface film. Adult chubs were observed to take Cladophora sp. as well as food from commercial river parties. The stomachs of three young-of-the-year humpback chubs were found by direct examination to contain dipteran Families of Chironomidae, Ceratopogonidae and Dolichopodidae. Reproduction appeared to have occurred in early June based on the small size of the fish collected by seining (x T. L. = 19 mm). It is suspected that spawning commences in early spring (March) and continues through early summer, as observed. Estimated numbers of humpback chubs, based on seining collections, ranged from 122 fish/hectare in May up to 1527 fish/hectare in June. Tagging operations, were also implemented in July of 1978 using 3/8" x 1/8" fingerling tags. To date, 120 humpback chubs have been tagged and none have been recaptured. Major problems faced by this population of humpback chubs are human impact, water fluctuations, and a newly discovered infestation of the anchorworm parasite Learnea sp. During October, 54% of the chubs collected were infested. This research was supported by grants to the Biology Department, Museum of Northern Arizona from the National Park Service, Grand Canyon, U. S. Bureau of Reclamation, Boulder City, and the Office of Endangered Species, Region II, Albuquerque.