7768

• UCREFRP Catalog Number: 7768
• Author: Desert Fishes Council, H., Dean A., ed.)‎.
• Title: Proceedings of the Desert Fishes Council Volumes XXII and XXIII, 1990 and 1991 Annual Symposia and Index for Volumes XVI through XXIII.
• USFW Year: 1992.
• USFW - Doc Type: July 1992.
• Copyright Material: NO

and Wisby (1951). They suggested that young salmon imprint to the odor of
their natal tributary, store this information in a long-term olfactory
memory, and later use this memory to relocate the stream during spawning
migrations. In the following 40 years, many other workers have tested and
further refined this hypothesis. It is now recognized that fish imprint to a
"home-site olfactory bouquet" which consists of environmental odors that may
include both a geologic and species-specific component (Hasler and Scholz
1983, Foster 1985). However, our knowledge of the adaptive significance of
migrations and reproductive cycles is poor for all but a few, commercially
important species.
Migration patterns of adult Colorado squawfish are similar year to year.
These movements are presumably an orientation to environmental conditions in
the spawning reaches, and movements of fishes in up- and downstream directions
is suggestive of an olfactory orientation mechanism (Harden-Jones 1968, Hasler
and Scholz 1983). Some behaviors associated with olfactory orientation in
salmonids were exhibited by Colorado squawfish, and the presence of spring-fed
tributaries and other water inputs in spawning reaches may provide piloting
cues. Tributary streams may provide gross cues for long-distance orientation,
while more subtle cues, unique to specific sites, may be used for egg
deposition (Tyus, In press). Reproductive by-products from previously-hatched
young (Foster 1985) may also be included in a home-site olfactory bouquet.
Colorado squawfish larvae may imprint such odors in the areas in which they
develop, and later recognize these odors as migrating adults.
Recaptured and radiotagged adult Colorado squawfish have demonstrated a
fidelity (repeated return) to the same spawning areas (Wick et al. 1983, Tyus
1985, in press). However, it has yet to be shown that these fish return to
natal areas for spawning. The similarity of their behavior to that of many
other fishes makes it probable that they do so, and this could lead to
reproductive isolation and separate genetic stocks. It is noted that the
maintenance of discreet stocks can be developed through spawning site
imprinting and homing (Horrall 1981), and thus, specific migration routes and
positive or negative rheotaxis in homing orientation suggests different
genetic stocks (reviewed by Smith 1985). Some genetic interchange between
stocks may occur from fish that "stray" from one area to another, and could be
important for successful evolution of the species (Baker 1982; Leggett 1984).
It is therefore important that the genetic identity of separate stocks of
Colorado squawfish be identified and protected.
Knowledge of the reproductive ecology of the razorback sucker is poorly
known, principally because successful recruitment is lacking throughout the
Colorado River Basin (Lanigan and Tyus 1989, Marsh and Minckley 1989).
However, razorback sucker migrations have been documented, and there is
compelling evidence that homing behavior occurs as in the white sucker. The
possibility of at least two separate spawning stocks of the razorback sucker
in the Green River basin (Tyus and Karp 1990) suggests that imprinting and
home site selection may be also be important considerations in the recovery of
this fish.
STUDY METHODS AND APPROACH:
Because of the time required to do this work, and the critical need to
demonstrate progress towards recovery of endangered Colorado River fishes, we
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