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Habitat preference and taxonomy of Gila spp. • Gila spp. (including the humpback chub,. Gila cypha, and bonytail chub, Gila elegans) were extremely rare in collections made the first year of study. Therefore, a special sampling effort for collection of Gila spp. was undertaken in Gray Canyon of the Green River Septem- ber 27, 1980, and April 23, June 6, July 10, and September 27, 1981, with major emphasis on collection of bonytail chub. This site was selected after several Gila spp. previously collected here were tentatively identified as humpback and bonytail chub. Based on all other areas sampled, it was judged to be the best location for humpback and bonytail chubs in the Green River system. Objectives of these collections were to obtain habitat information and also to provide bonytail chub for possible hatchery propagation. Fish were collected with 150-foot (45-meter) multifilament trammel nets, multifilament gill nets, and seines. Sampling was conducted within a 0.1 mile (0.2 kilometer) river reach over a 4-day duration. However, because of manpower limitations, continuous 24-hour sampling over the 4 days was impossible and a sampling design was initiated. A 24-hour period was divided into three subperiods, 2400-0800, 0800-1600, and 1600-2400. Sampling alternated between subperiods. For example, sampling was conducted for a 8-hour subperiod with a subse- quent 8-hour nonsampling subperiod followed by another 8-hour sampling subperiod and so on. This allowed every subperiod to be sampled at least • twice over the 4 days. The first subperiod to be sampled was determined when the sampling team arrived at the sampling site. Seven sites encompassing three habitat types (eddy, run, and back- water) were selected for seining. Five sites, all eddy habitats, were selected for trammel and gill netting. All sampling sites were repli- cated during the period sampled. Trammel and gill nets were checked once every 2 to 3 hours. Seining was conducted twice during a subperiod but was terminated after the first day because of a manpower shortage. Prior collections indicated that field indentification of Gila spp. was difficult. Therefore, specimens collected at Coal Creek were transported to Vernal for use in evaluating all known methods of species identification. Different morphological counts and measurements presented by various authors (Smith et al., 1979; Minckley, 1973) were made on live and preserved specimens. Taxonomists and knowledgeable field workers were also contacted during the interpretation of the results of this work. In addition, selected specimens were sent to noted authorities for identification. Although all specimens were not sacrificed, a square centimeter grid board was utilized for photographing all Gila spp. for future study. During one field trip, fin tissue was taken from all col- lected Gila spp. and shipped to Arizona State University for electro- phoretic analysis. Sacrificed specimens were subjected to a taxonomic study. Specimens were X-rayed and vertebral counts were made. Eight meristic characters and gross morphological Ishape were used to segregate species. Characters 17