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<br />EXECUTIVE SUMMARY
<br />
<br />As part of the San Juan River Basin Recovery Implementation Program (SJRIP), investigations
<br />of non. native fishes were conducted during 1991.1997 to characterize interactions with native
<br />fishes. The impacts of non-native fish species on natives has often been identified as a key
<br />impact, along with habitat alteration, that facilitates loss of native biological diversity, In the San
<br />Juan River, the endangered Colorado pikeminnow Ptychocheilus lucius and razorback sucker
<br />Xyrauchen texanus, as well as the other members of the native fish community, are the focus of
<br />the SJRIP. A major component of native fish recovery efforts in the San Juan River is the
<br />mimicry of the natural hydrograph, and SJRIP studies were designed to assess the response of the
<br />resident fish community to variable flow conditions affected the releases from upstream Navajo
<br />Dam. Section 5.4 of the SJRIP Long Range Plan identified several informational and action
<br />needs regarding non. native fish species: 1) characterize distribution and abundance patters of
<br />non.native fishes, 2) characterize habitats used by non-native fishes, 3) describe the food habits
<br />of non-native fishes. 4) characterize the response of non-native fishes to varying flow regimes, 5)
<br />develop a non-native fish stocking policy, 6) develop regulations to restrict bait-fish species
<br />harvest, 7) develop regulations to control importation of non.native fishes, and 8) monitor and
<br />evaluate non-native fishes control actions implemented as part of the SJRIP. This report presents
<br />results of non. native fishes investigations that address items 1-4 and 8 above.
<br />
<br />The distribution and abundance patterns oflarge.bodied non.native fishes were studied to
<br />determine responses to varying flow regimes, Sampling was primarily by raft.mounted
<br />electrofishing. but also included limited hoop and trammel netting. Main and secondary channel
<br />sampling collected 18 species of non.native fish, Channel catfish !ctalurus punctatus and
<br />common carp Cyprinus carpio were the most abundant and the most widely distributed species,
<br />Seasonal movements of striped bass Marone saxatilis and walleye Stizostedion vitreum out of
<br />Lake Powell and upstream into the San Juan River as far as Shiprock, New Mexico were
<br />documented. Mark and recapture studies of channel catfish and common carp were used to
<br />estimate abundance and to evaluate movement patterns lor the entire reach of the San Juan River
<br />sampled, Farmington, New Mexico downstream to Clay Hills, Utah. Schnabel population
<br />estimates (95% C.L) for channel catfish ranged from 131,768 (72,]43 . 219,393) in 1992 to
<br />274,484 (115,7]2.563,162) in 1995 and for common carp were 26,576 (14,2]3.45,019) in
<br />1992 to 107,268 (61,438 - 172,692) in 1995, The proportional abundance of non-native species
<br />sampled during electro fishing surveys in main and secondary channel habitats increased during .
<br />1994-1997, after initial declines observed during1991.1994. Implementation of high spring
<br />releases from Navajo Dam did not appear to negatively impact non-native species distribution or
<br />abundance,
<br />
<br />Recapture rates for 3,878 channel catfish and 3,034 common carp tagged with numbered Floy
<br />tags were 5,8% and 10.8%, respectively, Neither species exhibited strong movement patterns to
<br />or affinities for specific areas of the San Juan River as has been documented in other river
<br />systems. The mean distance moved between recapture and original or last capture locations was
<br />
<br />San Juan River Non-native Species Interactions. Final Report, I February 2000
<br />
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