WSP12063

• File Number: 8240.300.31.J
• Description: San Juan River - Environmental Studies
• Basin: San Juan/Dolores
• Water Division: 7
• Date: 2/1/2000
• Title: Non-Native Species Interactions: Management Implications to Aid in Recovery of the Colorado Pikeminnow and Razorback Sucker in the San Juan River
• Water Supply Pro - Doc Type: Report/Study

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Hill's Crossing, Utah. With the rise in surface elevation during spring 1995, this barrier was
inundated and allowed the movement oflacustrine species out of Lake Powell into the San Juan
River. Striped bass and walleye were collected in medium velocity runs with depths> I m and
in eddy and pool habitats along rocky points primarily downstrean1 of Mexican Hat, Utah.

White sucker Ca(ostomus commersoni was infrequently collected in the San Juan River
downstream ofthe Hogback Diversion, New Mexico and included hybrids with both
flannelmouth and bluehead suckers. While white sucker and associated hybrids were low in
abundance (< 0.0 I % of all fishes sampled), Miller and Rees (1999) reported this species as
common in tributaries of the upper San Juan River. A single grass carp Ctenopharyngodon
idella (517 nun TL, 420 nun SL, 1500 g) was collected from a shoreline, medium velocity nm
with a depth of
1,5 m and the specimen was retained at University of New Mexico (MSB 14885). Bullhead
Ameiurus sp. was an infrequently collected ictalurid (< 0,01% of all fishes sampled) and was
identified to species as black (A. melas), brown (A, nebulosus), and yellow (A. natalis) during
1991-1993 sampling, but specimens of brown and yellow bullheads were not retained. The only
confirmed species identification for Ameiurus is of black. bullheads (specimens at University of
New Mexico, MSB) and is considered here to be the only resident bullhead in the San Juan River
study area.

Non-native speCies generally increased in proportional abundance of all fishes collected during
main channel electrofishing sampling efforts, 1994-1997 (Figure 3). Prior to 1994, the pattern of
non-native species relative abundance was declining, However, simple linear regression analysis
of the 1987-1997 relative abundance values in Figure 3 did not demonstrate a significant change
(R2 = 0.412). CPUE for both channel catfish and common carp sampled during main channel
electrofishing mirrored the increase in non-native species relative abundance (Figure 4). For
channel catfish, overall CPUE increased but individuals:> 300 mm TL declined in 1997 after a
steady increase during 1994 - 1996 (Figure 5), Results differed for common carp, with the
pattern in CPUE increasing throughout the 1994 - 1997 period for all size classes. Longitudinal
patterns in the abundance of channel catfish, and, to a lesser extent common carp, are discussed
further in Chapter IV, Mechanical Removal, as a response to suppression efforts,

During the 1992-1997 e1ectrofishing surveys of main channel and secondary channel habitats, a
total of3,878 channel catfish and 3,034 common carp were tagged and released (Table 3),
Channel catfish recapture rates ranged from 0.7% (n=26) to 2,2% (n=53) and conunon carp
recapture rates ranged from 1.4% (n=42) to 4,7% (n=79), Recapture rates for both channel
catfish and common carp were highest in 1993 and lowest in 1997. Recapture rates overall were
5.8% for channel catfish and 10.8% for common carp.

Movement by channel catfish and common carp recaptured during 1992-1997 showed both
upstream and downstream movement (Figure 6). Average distance moved (calculated using
absolute distance from last capture regardless of direction moved) by channel catfish was higher
than for common carp (Table 4). Channel catfish were recaptured an average distance of 12.9
river miles from the original or last capture location between 1992 and 1997: maximum distance

San Juan River Non-native Species [nteractions, Final Report, I February 2000

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