7836

• UCREFRP Catalog Number: 7836
• Author: Hamman, R. L.
• Title: Induced Spawning and Culture of Bonytail Chub
• USFW Year: 1982
• USFW - Doc Type: The Progressive Fish-Culturist
• Copyright Material: YES

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Induced Spawning and Culture of Ronytail Chub

Roger L. Hamman

U.S. Fish and Wildlife Service, Willow Beach National Fish Hatchery
P.O. Box 757, Boulder City, Nevada 89005

ABSTRACf: During 1981, bonytail chub (Gila elegans) were spawned and cultured at Willow Beach (Arizona)
National Fish Hatchery.This species is listed as endangered by the U.S. Fish and Wildlife Service. Five females
ovulated 18 to 20 h after intraperitoneal injections of 4 mg acetone-dried carp pituitary per kilogram of body
weight. Eggs were manually stripped and artificially fertilized; mean fecundity was 25,090. Incubation periods
were 99 to 174 h at water temperatures of 20-21 .C, 170 to 269 h at 16-17 .C, and 334 to 498 h at 12-13 "C. Survival
of eggs was 90070 at 20-21 "C, 550/0 at 16-17"C, and 4070 at 12-13 "C. At hatching, total length and weight of fry
averaged 6.8 mm and 2.8 mg. Survival of swim-up fry was 98070 at 20-21 "C, 96070 at 16-17"C, and 25070 at
12-13 .C. Fry placed in raceways doubled in length by 28 days, and fingerlings were 42.9 to 54.3 mm in total
length and weighed 714.1 to 1,326.8 mg 70 days after hatching.

Little is known about the biology of the bonytail chub
(Gila elegans), a species of cyprinid endemic to the Colorado
River basin. Once abundant throughout the upper and lower
basins (Cope and Yarrow 1875), this species has experienced
the most abrupt decline of any fIsh native to the mainstreams.
In the upper basin, the only bonytail chubs reported in
recent years were from the Green River in Utah (Behnke and
Bellson 1980). Although the species is occasionally found in
the reservoir areas of lakes Havasu and Mohave in the lower
basin (Minckley 1973), it is considered in danger of extinc-
tion. The bonytail chub is listed as an endangered species by
the States of Arizona, California, Nevada, Utah, and
Wyoming (Deacon et al. 1979) and by the U.S. Department
of the Interior (1980).
The purpose of the present study was to develop techniques
for the spawning and culture of bonytail chub. Data regard-
ing the fIrst successful spawning of wild brood stock in
captivity and culture of their progeny during 1981 at Willow
Beach (Arizona) National Fish Hatchery are presented.

Methods

The brood stock consisted of six wild females and fIve wild
males collected from Lake Mohave, near Cottonwood Cove,
30 April to I May 1979, 29 April to 3 May 1980, and 11-12
March 1981. Total lengths and weights of the females were
487-564 mm and 956-1,500 g; males were 454-480 mm long
and weighed 728-870 g.
Ovulation was induced with injections of carp pituitary
(Ball and Bacon 1954; Oemens and Sneed i962). Acetone-
dried carp pituitary (40 mg) was nrlxedwith a Solution of
oxytetracycline hydrochloride (10 mL) and injected at the rate
of 4 mg/kg body weight at 24-h intervals (Hamman 1981).
FISh were anesthe~ with. tricaine methaR.eSU1ronate at
50-100 mg.IL (Leitritz 1960) before intraperitoneal injections,
and then placed in a holding tank (6.0 . X 0.75 X 0.75 m) until

Prog. FISh-Cult. 44(4), October 1982

they were manually stripped. Wann water (20-21 ~C) flowed
through the tank at the rate of 23 L/min. Natural spawning
of bonytail chubs is believed to ocCur when the water
temperature reaches 180C (Vanicek and Kramer 1969; U.S.
Fish and Wildlife Service 1919).
When eggs could be expelled with slight pressure, a female
was anesthetized and wiped dry before the eggs were stripped
into a plastic pan. Milt from one male was added to the eggs,
sperm diluent (Billard 1977) at 12,000 mg/L was added to
activate the sperm, and eggs were stirred and washed for
45 min to prevent clumping. After water hardening (about
50 min), eggs were poured on screen trays (53 X 53 cm)
covered with lA-nun-mesh hai-dware cloth and placed in four
aluminum troughs(3.5 X 0.55 X 0.3 m) and slanted at a 300
angle into the incoming water. To determine incubation
periods at different water temperatures,. warm water
(20-21 oc) entered two troughs, cool water (16-17 "C) entered
one trough, and cold water (12-130C) entered the fourth
trough, all at 7.5 Umin.
The day after the fry emerged, they were transferred to an
outside recirculating system consisting of two concrete
raceways (30.5 X 204 X 1.2 m) that were designed as BI and
B2. Water was pumped to the upper end of raceway BI from
the adjacent raceway (82) by a 'h-hp fresh-flo pump at
0.01 m'/s, flowed to the lower end, and returned to B2 by
gravity. The raceways were filled 1 week before spawning to
obtain wanner water temperatures; small amounts of
inorganic (ammonium phosphate) and organic (commercial
trout starter) fertilizers were .added to produce a plankton
bloom. Ten days after the fertilizerS were added, zooplankton
(predominately cladocerans) began apPeMmg. .

Results

Males and females had fme tubercles on the head, oper-
cu1ars, and pectoral and pelvic fIDS when spawning began (4

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