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Upper Colorado River stock and returned to the system when pedigreed family lots have been developed from them. Colorado Squawfish - Upper Colorado River Stock. Seventeen family lots of Colorado squawfish were developed in 1991 using a di-allele 5 X 5 breeding matrix. The progeny are being maintained at the Horsethief State Wildlife Area as future broodstock for future production to be used in reintroduction stocking of the Upper Colorado and Gunnison rivers above the present barrier dams. The development of a broodstock using a breeding matrix of 25 paired coatings is "on hold" because available propagation facilities are in use developing the two razorback sucker broodstocks that are considered by the Biology Committee to be of higher priority. D. Humpback Chub - Black Rocks Canyon. The Biology Committee approved the capture of adult humpback chubs from Black Rocks Canyon on the Colorado River in 1995 for holding in a refuge at the Horsethief State Wildlife Area. This action is a precaution to prevent the potential catastrophic loss of that stock because of the close proximity of a railroad right-of-way through the canyon. Fifteen adult humpback chub were collected from Black Rocks Canyon in September, 1995 and are being maintained at the Horsethief ponds. This will allow Recovery Program participants to become familiar with handling the humpback chub before the additional 15 adults are collected and placed into refuge ponds. If the adult humpback chubs survive the stress of capture, transport, and handling well, another 15 fish will be collected from Black Rocks Canyon in September, 1996. The Gila complex (bonytail, humpback chub, and roundtail chub) in the Upper Colorado River Basin has posed some concern about potential hybridization based on the results of the morphometric analyses by Michael Douglas, Arizona State University and allozyme analyses by Wayne Starnes, Smithsonian Institution. Although hybridization between the three species was possible in a hatchery (Hamman 1981), it is not known if these species will spawn together in the wild. Since all three species overlap temporally during their spawning seasons, one recommendation was to conduct a laboratory or controlled field experiment to determine if spatial or behavioral isolation exists between the Gila species. The adult humpback chub from Black Rocks could be used in this experiment. Another recommendation was to determine if F1 fish produce viable gametes and if these hybrids may be indiscriminate in spawning behavior. Adult fish in the refuge could be spawned to produce F1 hybrids and these progeny could be spawned to determine the viability of their gametes and potential to produce F2 hybrids. No mortality should be encountered through use of the fish in either study. E. Humpback Chub - Westwater Canyon. The collection of adult humpback chubs from Westwater Canyon will be postponed since there is no 7