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<br />o <br />C.' <br />i'~ <br /> <br />:.Il <br /> <br />r\) <br />-..J <br /> <br />Introduction <br />The distribution, abundance, and movement patterns of main channel non-native species, <br />particularly channel catfish and common carp, were the focus of this study segment. Essential to <br />the development of resource management strategies designed to minimize interactions between <br />native and non-native fishes in the San Juan River is the characterization of the spatial and <br />temporal population dynamics of the resident non-native fishes. Data presented and discussed in <br />this chapter emphasize the population dynamics of channel catfish and common carp in main <br />channel and larger secondary channel habitats, Other large-bodied non-natives that inhabit the <br />San Juan River are not as abundant or widely distributed. For lacustrine species that periodically <br />enter the San Juan River, such as striped bass and walleye, interactions with native fishes are <br />temporary and/or occur in restricted reaches of the study area, but may affect native species <br />through predation impacts (see Chapter III, Food Habits). <br /> <br />We hypothesized that the response of non-native species, primarily channel catfish and common <br />carp, to the different flow regimes encountered during 1991-1997 would be negative. <br />Specifically, it was believed that high spring flows would displace adult non-native species and <br />would minimize reproductive success and recruitment of juvenile non-natives. Re-operation of <br />Navajo Dam to mimic a natural hydrograph to allow the San Juan River to function more <br />naturally, particularly for provision of high spring flows, was considered necessary in order to <br />provide for recovery of native fishes (see discussions by McBain and Trush 1997 and Poff et a1. <br />1998), Data analyses for the response of distribution, abundance, and movement patterns of non- <br />native fishes in the San Juan River to flow manipulations by Navajo Dam releases are presented <br />here. <br /> <br />Objectives for this study segment were: <br /> <br />1. Characterize the distribution and abundance patterns of non-native species in main <br />channel habitats, <br />2. Determine the effects of high spring flows on the abundance of non-native species in <br />succeeding years. <br />3, Characterize the movement patterns of channel catfish and common carp to identify <br />significant temporal and spatial movement patterns. <br />4. Characterize the habitat use patterns of channel catfish as a response to habitat <br />availability and flow patterns, <br /> <br />Study Area <br />The study area for characterization of the distribution and abundance of the non-native fish <br />community encompassed the main and all secondary channels accessible by raft from the <br />confluence of the Animas River downstream to Clay Hills, Utah. The determination of the <br />movement patterns of channel catfish and common carp from mark and recapture data, was <br />conducted in the San Juan River from the weir at Fruitland, New Mexico downstream to Clay <br />Hills, Utah. Radio telemetry studies of channel catfish were conducted in the San Juan River <br />the weir at Fruitland, New Mexico downstream to near the Four Corners area. <br /> <br />San Juan River Non-native Species Interactions, Final Repon, I February 2000 <br /> <br />12 <br />