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December 2008 Bestgen et al.-Ecology of Gila eleg-anJ 493 in downstream areas (Bestgen et al., 2007) has revealed only a few bony tails, so that hypothesis is unlikely. Reasons for slightly higher survival of smaller bony tails in the lower Colorado and Green rivers (P. V. Badame and]. M. Hudson, in Iitt.) are unknown. Their release sites were in mostly lower-gradient, alluvial areas, which may offer more suitable habitat. Predaceous fishes such as smallmouth bass also were absent from those stocking areas. Based in part upon these results, means to increase survival of stocked bony tails have been initiated by managers for the Upper Colorado River Endangered Fish Recovery Program. Newly implemented How and temperature recommen- dations from Flaming Gorge Dam, which at- tempt to restore aspects of a more natural How regime, may improve habitat for bony tails (R. T. Muth et aI., in Iitt.). Evaluation of additional stocking areas, including alluvial-valley river reaches and their associated Hood-plain wet- lands, also has been initiated. Analysis of effects of size at stocking on survival also is ongoing. Additional techniques to improve post-stocking sunival may include different acclimation tech- niques than those already attempted (T. E. Chart and]. S. Cranney, in litt.), and providing exercise or exposure to predators prior to release to increase avoidance behaviors. A new threat that has emerged since \\iId bony tails have declined is proliferation of many large-bodied and small-bodied piscivores (Muel- ler, 2005; Bestgen et aI., 2006). Although species such as channel catfish Ictalurus punctatus were widespread and abundant even when bony tails were more common, species such as the north- ern pike, smallmouth bass, and small-bodied red shiner Cyprinella lutrensis have expanded dramat- ically since the early 1970s and are now common in the Green River Basin in a wide variety of habitat types (Holden and Stalnaker, 1975a, 1975b; Mueller, 2005; Bestgen et aI., 20(6). Ongoing actions to reduce abundance of non- native predators in the Upper Colorado River Basin, particularly large-bodied species, may increase short-term survival of stocked bony tails. In addition to potential negative effects of disease and parasites that we observed, behavior- al, genetic, or physiological traits of hatchery- reared bony tails produced from a limited paren- tal stock may also be responsible for their poor survival in the wild (White et al., 1995). Maladaptive traits that might pre-dispose bony- tails to poor sunival in the wild include high rates of dispersal and, perhaps, occupancy of atypical habitat (e.g., rimes). Such behaviors are energetically inefficient and may increase susceptibility to predation. Optimal river con- ditions and release techniques to enhance survival of stocked bony tails also should be investiga ted. Effects of stocked bony tails on resident native fishes also should be considered (White et aI., 1995). Introduction of disease or parasites, competition with resident chubs for food or space, and hybridization with roundtail and humpback chubs are among the potential negative effects associated with stocking large numbers of hatchery fish in a small area (Ham- man, 1981; 'White et al., 1995). A better understanding of effects of environmental con- ditions on health, condition, and sunivaI of bonytails, and potential for negative interactions with extant populations of congeneric wild chubs, would assist managers attempting to recover bony tails and other populations of Gila in the Green River. This study was funded by the Recovery Implementa- tion Program for Endangered Fish Species in the Upper Colorado River Basin. The Recovery Program is a joint errort of the United States Fish and Wildlife Service, United States Bureau of Reclamation, Westem Area Power Administration, states of Colorado, Utah, and Wyoming, Upper Basin water users, environmental organizations, and the Colorado River Energy Distrib- utors Association, Funding for this research was administered by the United States Bureau of Reclama- tion under cooperative agreements "ith Colorado Stare University and the Larval Fish Laboratory. Administra- tion was facilitated by L. Crist, T. Chart, D, Speas, J. Nusbaum, V. Romero, R. 'Bell, and C. Morales. Laboratory, field, or administrative assistance was provided by D. ll'oing, F. Pfeifer, L. Crist, D, Speas, T. Modde, M, Caldwell, D. Beers, R. Remington, C. Huffacker, C. Smith, M. Trammel, C. Kitcheyan, M. Fuller, S. Finney, J. Pfannenstein, C. Walford, C. \Vilcox, and T. Sorensen; we are sure there are others that have escaped memory who also deserve thanks. C. J.\kAda, United States Fish and Wildlife Service, Grand Junction, provided an electrofishing raft for one trip. Boating and collecting permits from the states of Colorado and Utah, the United States Fish and Wildlife Sel'ooice, the National Park Service-Dinosaur Natiimal Monument, and Bro'Nns Park National Wildlife Refuge were appreciated. T, Czapla and J. Logan provided unpublished data. Re\oiews by L. Crist., D. Propst, D. Speas, G. Garrett, and p, Holden improved this manuscript.