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DFC PROCEEDINGS - ALPHABETICAL LISTING OF ABSTRACTS <br />RESUMEN <br />Exan»namos densidades de subadultos (menos de 200 mm LT) de charalito jorobado Gila gpha a to <br />largo de 15 millas del Colorado River en el Grand Canyon para identificar relaciones entre la geomorfologfa, <br />use de habitat y operaciones de flujo de la Presa Glen Canyon Dam. Categorizamos el habitat de la lfnea <br />de playa basado en la geomorfologfa. Medimos despues parametros ffsicos de habitat de velocidad, <br />profundidad y cobertura a to largo de todos los tipos de lfnea de playa sobre un intervalo de Operaciones <br />de Flujo Interino (8,000 a 20,000 cfs) para determinar si existen cambios con la descarga. <br />Aunque la cobertura, profundidad y velocidad fueron significativamente relacionadas a la presencia de <br />subadultos de charalito jorobado, estos explicaron muy poco de toda la variation general en las densidades <br />de adultos del charalito jorobado. Esta varianza puede ser parcialmente explicada por una significativa <br />relaci6n de descarga con la calidad de habitat. Encontramos que la cobertura decreci6 con el incremento <br />la descarga, en cambio la profundidad y la velocidad incrementaron. Estos resultados sugieren que la <br />calidad de habitat decxece con el incremento en la descarga. <br />Hist6ricamente, los flujos base fueron desde 1,000 a 5,000 cfs. Las dos alternativas preferidas de la <br />Manifestaci6n de Impacto Ambiental de la Presa Glen Canyon Dam requieren de flujos base desde 8,000 <br />y 20,000, cerca del mismo Orden de magnitud mas alto que las descargas base antes de la construcci6n de <br />la presa. Los impactos por la reducci6n de los maximos flujos han sido ampliamente evaluados en rfos <br />regulados; sin embargo. de acuerdo a nuestros resultados, flujos base artificialmente altos pueden <br />actualmente limitar la calidad de habitat en el Grand Canyon. [PAPEL EM-UDUNnL COMPMDORAL PREMIO HUBBSJ <br />CROWL, T. A.*; LENTSCH, L. D.; THOMPSON, P.; CONVERSE, Y. (TAC - Utah state unWenity, Logan, vr; LDL, Pr aid <br />YC - Utah Division of WilAife ResaunQ , Salt Lace City, LTr) <br />Ecological aspects for the reintroduction of bonytail Gila elegans in the upper basin of the Colorado <br />River <br />KEYWORDS: reintroduction; bonytail; Gila elegans; ecology-, physiology; competition <br />ABSTRACT <br />Since their virtual extirpation from the Upper Colorado River Basin, very little research has been <br />conducted aimed at understanding the basic ecological requirements of bonytail needed for successful <br />reintroduction. Our research has been designed to begin to elucidate such requirements with a specific focus <br />on flow, substrate and food needs and the possible ontogenetic shifts associated with habitat use and <br />competitive interactions with nonnative fish species. These studies are being performed in large, artificial <br />streams located at the USU/BOR./UDWR Endangered Fish Experiment Station, located on the Utah State <br />University campus. Results of our experiments suggest that physiological responses to flow regime, such <br />as changes in the proportion of white and red muscle fibers and their diameters occur very quickly with <br />minimal flow training in young bonytail resulting in individuals that have greatly enhanced swimming <br />abilities. Individuals that have undergone three months of training in intermittent flow (0.07 m/s) <br />selectively inhabit higher velocities in stream channels and feed exclusively in high flow, high turbulent <br />habitats. These changes result in significant reductions in niche overlap with red shiners. Bonytail that <br />have undergone flow training spend a large proportion of their time near the substrate in high velocity, high <br />turbulent areas, feeding on drifting organisms while red shiners show a preference for lower velocity habitats <br />feeding mainly from the mid-water and surface. We discuss these and other ecological considerations that <br />need to be incorporated into reintroduction plans associated with endangered fish species. <br />RESUMEN <br />A partir de su virtual extirpacion de la Upper Colorado River Basin, muy poca investigaci6n se ha <br />conductdo para conocer los requerimientos ecol6gicos basicos del charalito elegante necesarios para su <br />30