7998

• UCREFRP Catalog Number: 7998
• Author: Desert Fishes Council, G. a. S., ed.)‎.
• Title: Proceedings of the Desert Fishes Council Volume XXVII, 1995 Annual Symposium.
• USFW Year: 1996.
• USFW - Doc Type: November, 16-19.
• Copyright Material: NO

PROCEEDINGS OF THE DESERT FISHES COUNCIL, 1995 SYMFosium V0IUIEXXV11-PUI$ISIM 1996
updating environmental legislation. The proposals have been abundant, especially at the extremes: from
stronger rules and enforcement, a position of ecologists and citizens, to an easement of rules, and
suppression of all ecological requirements in view of the economic crisis and social needs, supported by
industrialists and non-biologists. The social clash will be strong when the new legislative proposal is
processed in late 1995, or early 1996.
RESUMEN
La sequfa permanente reciente en el Noreste de Mexico ha tenido un fuerte impacto sobre los peces
del Desierto Chihuahuense. Varias localidades en Chihuahua han sido monitoreados desde 1963 hasta
finales de 198Us, reportando reducciones de comunidades de peces promediando 57.7%. Varias localidades
en Chihuahua y Durango fueron visitadas en mayo de 1995, encontrando los dos completamente secos:
Estaci6n Sauz, Rfo Florido en Jimenez, Rio Nazas cerca de Torre6n, Rfo Carmen cerca de Ahumada. Otras
localidades han sido convertidas en canales de denagties y no presentan peces, tales como el Rfo Chuviscar
en Chihuahua, y en Aldama.
El Gobierno Federal de Mexico organiz6 una serie de audiendas p6blicas como una base para actualizar
la legislad6n ambiental. Las propuestas han sido abundantes, especialmente en los extremos: desde reglas
fuertes y vigilancia, una posici6n de ecologistas y ciudadanos, hasta una debilidad de reglas, y una supresi6n
de todos los requerimientos ecol6gicos en vista de la crisis econ6mica y necesidades sociales, apoyado por
industriales y no-bi6logos. El conflicto social sera mas fuerte cuando la nueva propuesta legislativa sea
implementada a finales de 1995, o inicios de 1996.
CONVERSE, Y. K.*; HAWKINS, C. P.; VALDEz, R. (YKC and CFH - Department of Fisheries and WiirDife, Utah State UnWcnity, Logan tar;
RV - BidWest Im. Logm UT)
The effects of Interim Flow Management on subadult humpback chub habitat in the Colorado River
through Grand Canyon
KEYWORDS: humpback chub; subadult; geomorphology; shoreline; habitat; discharge; base flow;
Grand Canyon
ABSTRACT
We examined subadult (less than 200 mm TL) humpback chub Gila gpha densities along 15 miles of
the Colorado River in Grand Canyon to identify relationships between geomorphology, habitat use and
Glen Canyon Dam flow operations. We categorized shoreline habitat based on geomorphology. We then
measured physical habitat parameters of velocity, depth and cover along all shoreline types over the range
of Interim Flow Operations (8,000 to 20,000 cfs) to determine if habitat changes with discharge.
Although cover, depth and velocity were significantly related to subadult humpback chub presence,
they explained very little of the overall variation in subadult humpback chub densities. This variance may
be partially explained by a significant relationship of discharge with habitat quality. We found that cover
decreased with increasing discharge, whereas depth and velocity increased. These results suggest that
habitat quality decreases with increasing discharge.
Historically, base flows ranged from 1,000 to 5,000 cfs. Both preferred alternatives of the Glen Canyon
Dam Environmental Impact Statement require base flows ranging between 8,000 and 20,000, nearly an
order of magnitude higher than pre-dam base flows. Impacts from the reduction of peak flows have been
thoroughly assessed in regulated rivers; however, according to our results, artificially high base flows may
actually limit habitat quality in Grand Canyon. [HUBBS STUDENT PAPER COMPETITOR]
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