9586

• UCREFRP Catalog Number: 9586
• Author: Desert Fishes Council.
• Title: Proceedings of the Desert Fishes Council Volume XXVI 1994 Annual Symposium.
• USFW Year: 1994.
• USFW - Doc Type: Furnace Creek, CA.
• Copyright Material: NO

PROCEEDINGS OF THE DESERT FISHES COUNCIL., 1994 SYMPOSIUM VOLUME XXVI - published 1995
HORN,MICHAEL J. (Arizona State University; U. S. Bureau of Reclamation)
Use of storage lipids as an indicator of nutritional status of individual larvae
of the razorback sucker (Xyrauchen texanus)
El use de los lipidos almacenados como un indicador del estatus nutricional
de larvas individuales del matalote jorobado (Xyrauchen texanus)
KEYWORDS: critical period; Lake Mohave; larval fish; nutrition; razorback sucker
ABSTRACT
Razorback sucker (Xyrauchen texanus) populations have all but disappeared throughout most of their historic
range. Lake Mohave, Arizona-Nevada, contains the largest remnant population of this fish in existence. This
population is composed of aged fish and is declining rapidly. Recruitment of new fish to the adult population
appears to be the limiting factor in Lake Mohave. Substantial numbers of larvae are present in the lake each spring
following spawning, but survivorship is too low to detect. Several hypothesis exist to explain lack of recruitment
in the razorback sucker population of Lake Mohave, Arizona-Nevada. One such hypothesis explaining an apparent
complete failure of each year class may be the presence of a critical period during the larval phase related to
nutrition. Previous studies have indicated all larvae consistently disappear at the same size, about 10-12mm, the
size at which their yolk reserves are used up. In this study fat stores of larval razorback suckers were measured
using a gravimetric, di-ethyl ether extraction. To determine a base-line for comparison, a series of larvae were
raised in the laboratory at known concentrations of food ranging from starvation to ad-libitum. By comparing lipid
levels of wild caught larvae with laboratory it should be possible to assess the condition of wild larvae to determine
if nutrition is influencing early survivorship.
CLAVES: periodo crftico; Iago Mohave; larva de pez; nutricon; matalote jorobado
RESUMEN
Las poblaciones del matalote jorobado (Xyrauchen texanus), estdn todas por desaparecer en la mayor parte
de su rango hist6rico. El Lago Mohave, Arizona-Nevada, contiene la poblaci6n remanente mds grande existente
de estos peces. Esta poblaci6n estd compuesta de peces viejos y estd declinando rdpidamente. El reclutamiento de
nuevos peces a la poblaci6n de adultos, parece ser el factor limitante en el Lago Mohave. Un numero substancial
de larvas estdn presentes en el lago cada primavera, siguientes a la temporada de desove, sin embargo los
sobrevivientes estdn en nfuneros muy pequehos para ser detectados. Existen varias hip6tesis para explicar la perdida
de reclutamiento en el Lago Mohave, Arizona-Nevada. Una de tales hip6tesis que explica una aparente y completa
falta de cada clase del aho, puede ser la presencia de un perfodo crftico durante la fase larval relacionada a la
nutrici6n. Estudios previos han indicado que todas las larvas consistentemente desaparecen a una misma talla
(10-12 mm), tamano al cual las reservas del saco vitelino son agotadas. En este estudio se midieron las reservas
de grasas almacenadas de las larvas del matalote jorobado usando un metodo gravimetrico y extracci6n con titer
dietil. Para establecer una lfnea base de comparaci6n, una serie de larvas fueron llevadas en el laboratorio a
concentraciones conocidas de comida que variaron desde la inanici6n hasta ad-libitum. Mediante la comparaci6n
de los niveles de lipidos de larvas silvestres cautivas en el laboratorio, podrfa ser posible evaluar la condici6n de
las larvas silvestres para determinar si la nutrici6n esta influenciando sobre los estudios tempranos de los
sobrevivientes.
BURlmi . (Bureau of Reclamation, PO Box 61470, Boulder City, NV 89005)
Rearing wild razorback sucker larvae in lake-side backwaters, Lake Mohave, Arizona/Nevada
Crianza de larvas silvestres de matalote jorobado, en bahias aisladas del Lago Mohave, Arizona/Nevada
KEYWORDS: razorback sucker; Lake Mohave; rearing; reservoirs
ABSTRACT
The Native Fish Work Group captured over 10,000 wild razorback sucker larvae, reared them in lakeside
ponds and released them to the reservoir during the past year. Spawning aggregations of adult suckers were located
using monthly helicopter surveys. Field teams were dispatched to these sites each week. Biologists worked at night
capturing larvae attracted to white lights submerged one meter below the surface. Larvae were brought into
laboratory, fed brine shrimp and held for three weeks to allow full development of paired fins and to verify species.
Young were then transferred to predator-free ponds around Lake Mohave and monitored with trapnets throughout
the summer. Fish were harvested during September and October. Survival varied among ponds, ranging from 0 to
60%. Maximum growth exceeded 30 centimeters in nine months. Growth and survival statistics will be presented.
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