7339

• UCREFRP Catalog Number: 7339
• Author: Valdez, R. A.
• Title: A Review of the Hatchery Program for Threatened and Endangered Fishes of the Colorado River.
• USFW Year: 1985.
• USFW - Doc Type: Logan, Utah.
• Copyright Material: NO

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3-11

broodstock for that hatchery program.

Since that original attempt to culture the species in a hatchery,
numerous wil d adul ts have been transferred to hatcheri es to produce many
young for use in research, propagation, and release to the wild. Of the
four rare species discussed, hatchery-reared razorback suckers are receiving
the greatest redistribution in the wild, although these stockings are
exclusively in the Lower Colorado River Basin.

3.4.2 Releases To The Wild

The precarious status of the razorback sucker in the wild prompted a
cooperative agreement between the State of Ari zona and the FWS to stock
100,000 fingerlings annually into Arizona waters for 10 years. This
agreement was finalized in May 1981 in lieu of listing the species (Johnson
1984). On June 23, 1981, the first 7,000 five-inch razorback suckers were
released into the Gila, Salt, and Verde Rivers in Arizona (Stuart and
Johnson 1981). An additional 8,064 were released to other tributaries of
the Colorado River in September 1981 (Table 4) for a total release of 15,064
fish in 1981. In 1982, a total of 615,627 razorbacks were released in the
tributaries of the Gila, Verde and Salt Rivers and in Lake Mohave.

In 1983, 2,655,811 razorback were introduced into Arizona waters,
mostly as fry and 3 and 6-inch fingerlings. In 1984, at least 3,129,936 fry
and fingerlings were stocked into Arizona waters. Thus, a total of
6,4l6,438 razorback suckers have been released in the wild.

3.4.3 Culture Techniques

The development in cul ture techni ques for razorback suckers was
initiated in 1981 (Inslee 1981) and became well refined by 1983 (Jensen
1983b). Sexual maturation is reported to be more a function of size than
age. Hatchery-reared males mature as early as 2 years of age and 14 inches
in length while females usually first produce viable eggs at 3 years of age
and 16 inches in length (Jensen 1983b).

Femal es become gravi d at about 500F and are ready to spawn at water
temperatures of about 550F. As the egg mass ripens, the abdomen and
pregeni tal area softens and the genital papi 11 ae enl argens consi derably.
Ripe male razorbacks develop large tubercles on their anal and caudal fins
while females occasionally develop vary few fin tubercles.

Females are injected with human chorionic gonadotropin (HCG) to
finalize maturation of the egg mass and to stimulate ovulation. Best
results are attained from intramuscular injections of 100 IU of the HCG per
pound of body weight at 24 hour intervals. Ovulation usually begins after
36 to 48 hours of treatment with release of eggs after 60 to 96 hours. Male
razorbacks are injected daily with 300 IU of HCG per pound of body weight
for 2 to 3 days, and when milt production decreases (Inslee 1981;
Jensen 1983b).