DFC PRocEEDtr\cs - ALPHABETICAL LISTING oF ABsrRAcrs

Year: 1995 (xxvii)

Abstract

Since their virtual extirpation from the Upper Colorado River Basin, very little research has been conducted aimed at understanding the basic ecological requirements of bonytail needed for successful reintroduc[ion. Or:r research has been designed to begin to elucidate such requirements with a specific focus on flow, substrate and food needs and the possible ontogenetic shifts associated with habitat use and competitive interactions with nonnative fish species. These studies are being performed in large, artificial strearns located at the USU/BOR/UDWR Endangered Fish Experiment Station, located on the Utah State University campus. Results of our experiments suggest that physiological responses to flow regime, such as changes in the proportion of white and red musde fibers and their diameters occur very quickly with minimal flow training in young bonytail resulting in individuals that have greatly enhanced swimming abilities. Individualt th.t have uniergone three months of training in intermittent flow (0.07 rr/sj selectively inhabit higher velocities in stream channels and feed exdusively in high flow, high turbulent habitats. These changes result in significant reductions in niche overlap with red shiners. Bonytail that have undergone flolv training spend a large proportion of their time near tlte substrate in high velocity, high turbulent areas, feeding on drifting organisms while red shiners shovv a preference for lower velocity habitats feeding mainly from the mid-water and surface. We discuss these and other ecological considerations that need to be incorporated into reintroduction plans associated with endangered fish species. R^ESL4VTEN A partir de su virtual extirpaci6n de la Upper Colorado River Basin, muy poca investigaci6n se ha conducido para conocer los requerimientos ecol5gicos b4sicos del charalito elegante necesarios para su 30