7787

• UCREFRP Catalog Number: 7787
• Author: Desert Fishes Council.
• Title: Proceedings of the Desert Fishes Council Volume XXV, 1993 Annual Symposium.
• USFW Year: 1993.
• USFW - Doc Type: D. A. Hendrickson, ed. November, 10 -14.
• Copyright Material: NO

PROCEEDINGS OF THE DESERT FISHES COUNCIL 1993 - VOLUME XXV
collected in 1978-1979 from the Provo river drainage in central Utah. Information on age and growth patterns was
obtained from chubs collected during Spring/Summer 1993 from the Provo river and Spanish Fork river drainages.
Age and growth patterns were determined by counting annuli on thin-sections of otoliths and back-calculating to
obtain size-at-age. Based on gonado-somatic indices, peak spawning occurs during May. Average number of ova
per female was 1813 (N=9), and number of ova increased with length of the female. Maximum age observed in
the 1993 collection was 9 years. Age of reproductive adults varied from 2-9 years (median = 6), and standard
lengths of adults varied from 65-107 mm. Chubs smaller than 65 mm standard length were nonreproductive. Growth
was rapid in the first year followed by about equal annual gains in length until age 5. These data suggest that
leatherside chubs may be more long-lived than previously thought.
RESUMEN
Los charalitos costados de Cuero Gila copei, son nativos de la parte sur y este de la Cuenca de Bonneville,
donde ocurren en recodos tranquilos de arroyos y rfos frfos. A pesar de que estos charalitos pueden ser abundantes,
se conoce poeo de su comportamiento reproductivo o de sus patrones de edad y crecimiento. Obtuvimos infonnaci6n
del tiempo de reproducci6n a partir de una serie de charalitos colectados entre 1978-1979 en el drenaje del Rfo
Provo en Utah central. La information sobre patrones de edad y crecimiento se obtuvo de charalitos colectados
durante la Primavera/verano de 1993 en los drenajes del Rfo Provo y del Rio Spanish Fork. Los patrones de edad
y crecimiento se determinaron contando anillos en seeciones delgadas de otolitos, y por retrocalculo se obtuvieron
las tallas a diferentes edades. Con base en indices gonadosomaticos se determin6 que el pico de desoves ocurre
durance mayo. El numero promedio de ovocitos por hembra fue de 1813 (N=9), y este numero se increment6 con
]as tallas de ]as hembras. La edad maxima observada en la colecta de 1993 fue de 9 aiios. La edad de los adultos
reproductores vari6 entre los 2 y 9 aiios (mediana=6), y la longitudpatr6n de los adultos vari6 entre 65 y 107 mm.
Los charalitos menores de 65 mm de longitud patr6n estaban inmaduros. El crecimiento fue rapido en el primer ano
seguido de incrementos anuales semejantes en longitud hasta la edad S. Estos datos sugieren que estos charalitos
pueden ser mas longevos de to que se pensaba.
MARSH, P.C. Arizona State University, Center for Environmental Studies, Tempe, AZ
Abundance, movements, and status of adult razorback sucker,
Xyrauchen texanus, in Lake Mohave, Arizona and Nevada
Abundancia, movimientos y estado actual de los adultos del matalote,jorobado,
Xyrauchen texanus, en el Lago Mohave, Arizona y Nevada
KEYWORDS: Razorback sucker; population abundance; movements; Lake Mohave; PIT tag; mark-recapture; staves; Arizona; Nevada;
abundance
CLAVES: Matalote jorobado; abundancia de la poblaci6n; movimientos; Lago Mohave; marca PIT; marcado y recapture; estado actual; Arizona;
Nevada
ABSTRACT
Adult razorback suckers in Lake Mohave have been objects of standardized sampling since 1974 and tagging
since 1980. Objectives of this multi-agency effort include: (1) reliable population estimation, (2) evaluation of
movement patterns and spawning area fidelity, if any, and (3) acquisition of stock status information. About 3,000
Floy and 600 Carlin (1980-1990) and more than 4,000 PIT (Passive Integrated Transponder; 1.991-1993) tags have
been deployed. Total captures during the 14 years exceeded 12,000 and total recaptures numbered more than 1,000
fish; about 40% of the latter were long-term (>30 d). Sequential, long-term recaptures indicated that most fish
returned to the same of three general areas of concentration, but the return interval was irregular and exceeded a
year. Annual abundance estimates are near 20,000, which supports an hypothesis that only about one-third spawns
and is available to capture each year. Time-integrated, multiple mark-recapture population estimates (n=14 years
of data in 1993) indicated 73,500 individuals were present 1980-1993; 59,500 fish in 1988-1993; and the most-recent
3-year estimate had declined to only 23,300 fish in 1991-1993. Seasonal trammel net catches (catch per unit effort
and proportion of total) were unchanged from 1974 to 1984 for one area of the lake (Cottonwood East); however,
both statistics were progressively and significantly lower since 1985. Given the agreement of two independent lines
of evidence, it is virtually certain that a population decline is indicated, despite large inter-annual variance. Most
fish exceed 40-years of age (produced in the early 1950s), natural recruitment has been undetected, and a population
crash may be anticipated. Without replacement, razorback suckers will disappear from Lake Mohave.
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