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

capturing additional adult Colorado squawfish for implantation of
radio tags prior to the 1993 spawning season. July 1993 sampling
will cover the river reach between Farmington, New Mexico and
Hogback Diversion, RM 179.0 to 158.6 (a stretch of river sampled
only once during 1991-1992 adult monitoring trips), and also from
Mexican Hat, Utah to Clay Hills, Utah, RM 53.0 to 2.0, a river
reach previously unsampled for adult fish during our study.
October 1993 sampling will be conducted from Hogback Diversion to
Mexican Hat, Utah.
Early Lifestage - Low-velocity habitats were sampled between the
Hogback Diversion, New Mexico, and Clay Hills Crossing, Utah,
during summer and fall 1991 and spring, summer, and fall 1992 to
determine the early life stage fish community in the San Juan
River. In addition, two larval drift stations were operated in
summer 1991 and three in summer 1992 to determine larval drift
patterns. Fish communities in tributaries to the San Juan River,
Utah, were also surveyed in fall 1992.
Four young-of-the-year sampling trips were made in the San Juan
River in 1991 and five in 1992. Low-velocity habitats targeting
backwaters were sampled using seines. A total of 26,099 native and
96,802 non-native fish specimens were collected in 1991 and 21,911
native and 75,759 non-native specimens were collected in 1992.
Non-native red shiner and fathead minnow were the most abundant
species found in low-velocity habitats during both years. Native
species commonly found were flannelmouth sucker, bluehead sucker,
and speckled dace. Five specimens of roundtail chub were collected
in 1991 and eighteen specimens were collected in 1992. No other
rare fish (Colorado squawfish or razorback sucker) were collected
in low-velocity habitats in 1991 or 1992.
Fish community structure differed temporally and spatially by catch
rate and species composition in 1991 and 1992. Non-native red
shiner and fathead minnow were the most abundant species in late
summer and fall during both years. Native flannelmouth sucker,
bluehead sucker, and speckled dace were most abundant in mid-summer
during both years. In addition, native species were most commonly
found upstream of Chinle Creek.
A total of 716 native and 1,723 non-native fish specimens were
collected at the Four Corners and Mexican Hat larval drift sites in
1991 and 638 native and 432 non-native specimens were collected in
1992. Non-native red shiner was the most abundant species in
larval drift collections at the Four Corners larval drift site in
1991 and native flannelmouth sucker was most abundant in 1992.
Non-native channel catfish was the most abundant species at the
Mexican Hat larval drift site in both 1991 and 1992. Few fish
(N=50), mostly speckled dace and flannelmouth sucker, were
collected at the Mixer larval drift site in 1992. No rare fish
(Colorado squawfish, roundtail chub, or razorback sucker) were
found in larval drift collections in 1991 or 1992.
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