7879

• UCREFRP Catalog Number: 7879
• Author: Wydoski, R. S.
• Title: Annual Propagation Operation Plan, 1996.
• USFW Year: 1996.
• USFW - Doc Type: \
• Copyright Material: NO

The Gila complex (bonytail, humpback chub, and roundtail chub) in
the Upper Colorado River Basin has posed some concern about
potential hybridization based on the results of the morphometric
analyses by Michael Douglas, Arizona State University and allozyme
analyses by Wayne Starnes, Smithsonian Institution. Although
hybridization between the three species was possible in a hatchery
(Hamman 1981), it is not known if these species will spawn together
in the wild. Since all three species overlap temporally during
their spawning seasons, one recommendation was to conduct a
laboratory or controlled field experiment to determine if spatial
or behavioral isolation exists between the Gila species. The adult
humpback chub from Black Rocks could be used in this experiment.
Another recommendation was to determine if F, fish produce viable
gametes and if these hybrids may be indiscriminate in spawning
behavior. Adult fish in the refuge could be spawned to produce F,
hybrids and these progeny could-be spawned to determine the
viability of their gametes and potential to produce F2 hybrids. No
mortality should be encountered through use of the wild fish in
either study.
E. Humpback Chub - Westwater Canyon. The collection of adult humpback
chubs from Westwater Canyon will be postponed since there is no
genetic data to indicate that the two stocks are separate. Some
exchange between the two locations has been documented. Three
adult humpback chubs of 43 tagged in Westwater Canyon moved
upstream to Black Rocks Canyon (Valdez et al. 1982). About 1,200
humpback chubs were PIT-tagged by the Utah Division of Wildlife
Resources through 1994 and most recaptures of these fish were close
to the point of release (T. Chart, 1994, Personal Communication).
Several of the fish tagged by Utah in Westwater Canyon were
recaptured by the Colorado Division of Wildlife in Black Rocks
Canyon (B. Elmblad, 1995, Personal Communication).
F. Long-Term Research. Razorback suckers and Colorado squawfish are
being reared at the Ouray Endangered Fish Facility to determine if
these fish species imprint to spawning areas from olfaction cues
(Scholz et al. 1993) based on the strong fidelity to spawning areas
by Colorado squawfish (Tyus 1990) and razorback suckers (Tyus and
Karp 1990).
Some of the male razorback suckers will attain a total length of
400-425 mm (about 16-17 inches) and over 60 were mature in the
spring of 1996. These fish will be tested during 1996 for
preliminary information related to imprinting. Most of the
razorback suckers are expected to mature (at 17 inches TL) in the
spring of 1997 when results should be obtained to make a
comprehensive evaluation as to whether or not razorback suckers
imprint through olfaction cues.
Improved growth of the chemoreception study fish is expected in
1996 when they will be reared at much lower densities in the new
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