7163

• UCREFRP Catalog Number: 7163
• Author: Haynes, C. M. and J. R. Bennett.
• Title: Relationship between the Preservation of Wilderness Values and Endangered Species
• USFW Year: 1985.
• USFW - Doc Type: A Case-Study from the Upper Colorado River Basin, U.S.A.
• Copyright Material: YES

August, 1980 by DOW and followed by CRFP in 1981.
Field work has continued to present. DOW efforts
were oriented largely toward the collection of
early life history information as was done in
1979-80 on the mainstem Colorado River (Mesa
County). CRFP efforts were an extension on upper
Green River (Utah) studies and were initiated
following the collection of squawfish larvae by
DOW researchers during the initial 1980 trip.
CRFP studies were designed to evaluate adult
movements within the Yampa River and between the
Green and Yampa Rivers via radiotelemetry and to
identify spawning sites. CRFP field methods have
been described by Archer and others (1980) and
Tyus and McAda (1984) and need not be reiterated
here. Similarly, DOW methods have been pre-
viously described by Haynes and Muth (1983,
1984), Wick and others (1981, 1983), and Haynes
and others (1984).

RADIOTELEMETRY FINDINGS

Spawning migrations had long been hypothesized
for the Colorado squawfish but never documented.
Long distance movements between Utah's Green and
White River had been observed by CRFP (Tyus and
others 1981) in 1980, but the relationship of
this movement to spawning was unclear. In the
spring of 1981, .adio transmitters were implanted
in mature squawfish in the upper Yampa River
(above Dinosaur National Monument) and in the
Green River in Utah. Continuous tracking
revealed that seven of the implanted Yampa River
fish moved downstream 50 to 100 mi. to the lower
Yampa and that one Green River fish moved approx-
imately 96 mi upstream to approximately the same
site. Radio-tagged fish remained in the lower
Yampa from late June to early July and sub-
sequently returned to their premigratory loca-
tions. At the same time, squawfish to which
small plastic tags had been attached as early as
1978 elsewhere were found in association with
radio-tagged individuals in the lower Yampa (Tyus
and McAda 1984). Observations were continued in
1982 by Wick and others (1983) working under the
authority of the National Park Service and DOW
with similar results except that transmitter
implants were restricted to Yampa River fish.
Results were confirmed with continued studies by
Tyus in 1983. In all years, ripe squawfish
appeared to congregate on cobble bars 20 mi
above the Green River confluence (fig. 3).
Trammel net collections made near these bars when
radio-implanted fish were present revealed a
large number of ripe fish. As was the case in
1981, radio-tagged squawfish in 1983 returned to
premigratory locations following their presumed
spawning (Tyus 1985).

Long distance potamodromous migrations are
unusual in N. A. freshwater fishes, and obser-
vations by the above researchers yielded several
notable facts. Many of the observed movements
covered substantial distances and involved as
many as three rivers. .For example, Wick and
others (1983) captured a fish at a cobble bar (RM
16.4) which had been tagged with a small plastic
Carlin smolt tag in Colorado's White River the

Figure 3.--Early May, 1983, view of spawning area
at river mile 16.4, Yampa Canyon, Dinosaur National
Monument. The cobble bar is approximately 900 ft
long and 300 ft wide.

previous year over 250 mi away. This individual
migrated from the White River in Colorado to the
Green River in Utah upriver to the Yampa, again
entering Colorado. Migrations occurred within
one drainage basin in both upstream and down-
stream directions. Movement appears to begin
during spring runoff with water temperatures as
low as 16 C and convergence at spawning areas
occurs during the descending limb of the hydro-
graph at temperatures of 18-22 C. Fidelity to a
single site in the lower Yampa River is notable.
Although ripe fish were captured by the above
researchers at several lower Yampa locations, the
majority of ripe fish congregated eventually at
cobble bars at RM 16-20. Tyus (1985) has
hypothesized that limestone seeps at this and
another site subsequently discovered in the lower
Green River in Gray Canyon, Utah (this second
site appears to support a second unrelated
spawning migration),constitute an olfactory basis
for homing in Colorado squawfish comparable with
that long known for salmonids.

EARLY LIFE HISTORY STUDIES

Forty-six larval squawfish were captured in the
lowermost 9 wi of Yampa Canyon in 1980 and 23 the
following year (table l)(Haynes and others 1984).
Larvae were collected over a wider area in the
second year and extended to RM 18. Over 200
individual fine-mesh seine (1/16- and 1/32-in.
square mesh) and dip net (1/32-in. square mesh)
samples were required to collect 1981 specimens,
but more than 500 discrete samples collected
during the spring-late summer were required to
collect half as many larvae the following year.
Studies were continued in 1982 and only 20 larval
squawfish were collected from 300 samples. In
all cases, larvae were restricted to shallow
shoreline embayments and backwaters, frequently
isolated from the main channel by rapidly falling
water levels.

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