7780

• UCREFRP Catalog Number: 7780
• Author: Brooks, J. E., et al.
• Title: San Juan River Seven Year Research Program Summary Report 1992.
• USFW Year: 1992.
• USFW - Doc Type: \
• Copyright Material: NO

sucker, followed, in descending order, by common carp (Cyprinus
carpio), channel catfish (Ictalurus punctatus), and bluehead
sucker. In 1992 the most abundant species was flannelmouth sucker,
followed by bluehead sucker, channel catfish, and common carp.
Fish community composition did not change significantly between the
two years. Common carp and channel catfish accounted for 20°s of
the total catch in the first two years, while all other introduced
species composed only 3~ of the total catch. Native species,
mostly flannelmouth sucker and bluehead sucker, composed 77g of all
fish collected in 1991 and 1992. Colorado squawfish and roundtail
chub combined composed less than 1% of the total catch in the first
two years. Electrofishing capture rates were highest for
flannelmouth sucker, bluehead sucker and speckled dace (Rhinichthvs
osculus) in the reach of river from Hogback Diversion, New Mexico
(RM 158.6) to Four Corners Bridge (RM 119.2). Catch rates for most
species showed a downward trend as sampling proceeded downriver
from Hogback Diversion.
Twelve Colorado squawfish and five roundtail chub were collected in
two years. No razorback sucker were collected. All Colorado
squawfish were captured between RM 142.0 and 117.0. Four of five
roundtail chub captures occurred between RM 147.9 and 135.3.
Nine individuals of Colorado squawfish were surgically implanted
with radio tags and tracked year-round from the air and ground.
One hundred and thirteen radio contacts were made with these fish
between June 1991 and January 1993. All radio contacts occurred
between RM 142.0 and 117.0. During pre-spawn periods, May and
early June, Colorado squawfish demonstrated an affinity for the
section of river in and around the Mancos River confluence (RM
122.6). During estimated spawning periods, 79 percent of radio
contacts with Colorado squawfish were made within the "Mixer" area
(RM 133.4 to 129.8). The highest percentage of ground contacts
(34.38) were made with Colorado squawfish using run habitat. Mean
maximum displacement (7.4 miles) and mean final displacement (3.99
miles) were very close to that of Colorado squawfish in the "15-
mile reach" of the Colorado River near Grand Junction, Colorado.
Total longitudinal movement averaged 8.94 miles.
Information to date is insufficient to assess the impacts of
existing instream water diversion structures on rare fish movement.
Two roundtail chub were collected above Cudei Diversion (RM 142.0),
but below Hogback Diversion (RM 158.6). One Colorado squawfish was
also sighted in this river reach.
All of the above information, suggests that the river reach between
Hogback Diversion (RM 158.6) and Four Corners Bridge (RM 119.2) is
important to the native fish community of the San Juan River.
Two sampling trips were conducted in April and May, 1993. These
trips concentrated on RM 136.6 to 119.2 for the purpose of
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