Proceedings of the Desert Fishes Council 2000

PROCEEDINGS OF THE DESERT FISHES COUNCIL - VOLUME XXX1I (2000 SYMPOSIUM) – PUBLISHED NOVEMBER 13, 2001
numbers had slightly increased from the previous August. Population estimates ranged from 4,920/km to
200/km. Spinedace were found in the upper four of six 25-meter permanent transects.
During a survey in March-April 2000 at the Muddy River, 940 Moapa dace, Moapa coriacea, were counted.
This is similar to numbers in the reaches surveyed in 1999. Muddy Spring, the main stem of the Muddy River,
and Plummer Springs were not surveyed. The management focus on the Muddy River has been the eradication
of blue tilapia. Rotenone treatments have been successful at the Apcar tributary and the refuge springs. A
permanent barrier was constructed in July 2000 to prevent upstream movement of tilapia into these treated
segments. Virgin chub, Gila seminuda, Moapa speckled dace, Rhinichthys osculus moapae, and Moapa White
River springfish, Crenichthys baileyi moapae, have also been negatively impacted by the tilapia.
Virgin River native-fishes monitoring completed in Nevada by the recovery team in October and April found
only four woundfin, Plagopterus argentissimus, and no Virgin chub. Studies using woundfin obtained from
Dexter National Fish Hatchery and Technology Center continued in 2000. In October 1999, a total of 9,275
woundfin were released in Nevada reaches of the Virgin River just below the Arizona border. A portion of these
fish have remained in the system resulting in reproduction and recruitment.
A program to repatriate Virgin spinedace, Lepidomeda mollispinis mollispinis, back into Nevada at Beaver
Dam Wash has been ongoing for several years. Sampling in April and June 2000 again found adult spinedace
but no recruitment.
Bio/West Inc., supported by the Southern Nevada Water Authority, continues to survey for razorback sucker,
Xyrauchen texanus, at Lake Mead. At Lake Mohave, NDOW provided assistance in the collection of 91,000
razorback sucker larvae. A portion of these were reared at the Boulder City Golf Course ponds and the Veterans
Park ponds in cooperation with the Bureau of Reclamation. In 1999, these ponds provided a total of 7,500 fish
for repatriation into Lake Mohave.
NDOW and cooperating agencies continued to intensively survey the population status, habitat selectivity,
movement patterns, and growth rates of Amargosa toad, Bufo nelsoni. To date, over 2,000 adults have been
implanted with PIT tags at 11 survey sites. Recapture rates during the latest surveys were above 50 %. The
objective of this project is to quantify the population of Amargosa toad in Oasis Valley by using mark-recapture
monitoring, and to create a model for potentially suitable habitat.
RESUMEN
Manejo de peces nativos y anfibios en el sur de Nevada
Los conteos del tamaño poblacional del cachorrito de Devils Hole, Cyprinodon diabolis, siguen indicando
una tendencia decreciente. Las cifras recientes son: agosto 1999, 344; octubre 1999, 328; diciembre 1999, 288;
febrero 2000, 240; abril 2000, 190; junio 2000, 223; y agosto 2000, 286. Desde su reactivación en 1998, el
refugio de la Presa Hoover sigue funcionando adecuadamente. Los conteos para este sitio para diciembre 1999,
febrero 2000, mayo 2000 y julio 2000 fueron: 35, 38, 45, y 72, respectivamente.
La División de Vida Silvestre de Nevada (NDOW, por sus siglas en inglés) junto con el Refugio Nacional de
Vida Silvestre de Ash Meadows (AMNWR, por sus siglas en inglés) siguen removiendo las lobinas introducidas
anteriormente a este refugio. La última fase del proceso consistirá en remover las lobinas del Reservorio Crystal.
En 1999, personal del AMNWR y voluntarios removieron 12,470 peces, langostinos y anfibios no nativos. Un
gran incendio que quemó casi 1,500 acres en la porción norte del refugio, eliminó grandes bosques de pino
salado [Tamarix] y el remanente de la comunidad de flora nativa del lugar.
Hacia finales de enero y principios de febrero de 2000 se efectuó la evaluación de invierno de carpa cola
redonda de Paharanagat, Gila robusta jordani; se contaron 133 peces, 33 de los cuales eran juveniles. Esta cifra
es similar a la de años anteriores también en invierno. En el censo de julio 2000 se encontraron 138 carpas (68
juveniles). Esto sigue indicando un descenso importante de las estimaciones de verano en 1998 y 1999. En un
estudio de junio de 1998 se estimaron 2,894 carpas (2,596 juveniles). En junio de 1999 se contaron solo 308
carpas (132 juveniles).
En junio de 2000 se hizo el monitoreo del pez de manantial Hiko del Río White, Crenichthys baileyi
grandis, dentro del Valle Pahranagat en los manantiales Crystal y Hiko. En el Manantial Hiko, mediante
marcado-recaptura, se estimaron 6,277 peces adultos de esta subespecie. En ese sitio estos constituyeron casi el
55% de todos los peces. El resto de las especies encontradas aquí fueron topote del Atlántico, guayacón
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