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<br />Telemetry Systems (A TS), Incorporated, external antennae transmitters. Model 2 (130 day, II g,
<br />40 pulses per minute) and model 6 (400 day; 30 g, 55 pulses per minute) transmitters with
<br />30-36 em teflon coated antennae were used to implant both size classes, respectively. Surgical
<br />procedures used to implant channel catfish were identical to those used by Ryden and Pfeifer
<br />(1995) to implant Colorado pikeminnow in the San Juan River.
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<br />Movement of radio-tagged channel catfish was monitored monthly for one year using both aerial
<br />and ground tracking. Aerial tracking was used to determine approximate river mile locations one
<br />to five days prior to ground tracking by boat. Radio tracking flights were conducted monthly,
<br />October 1996 through September 1997. During each flight for each implanted channel catfish
<br />contacted, data were recorded for date, time, river mile, latitude and longitude, and general
<br />habitat type. Ground tracking by boat was conducted monthly following each flight and data
<br />recorded during initial contact were date, time, river mile, and habitat typed occupied. Radio
<br />contact with each implanted fish was continued at 15-20 minute intervals for a minimum of four
<br />contacts per fish. During each contact, the location and habitat type occupied were recorded onto
<br />an aerial videography sheet for that reach of the San Juan River. Concurrent with the radio
<br />tracking, the habitat type from 100 m upstream to lOa m downstream of the most frequent
<br />contact location was mapped on each videography sheet to determine habitat availability,
<br />Habitat type classifications followed those defined by Bliesner and Lamarra (1999). We also
<br />collected data for depth, current velocity, substrate type, water physical chemistry (temperature,
<br />salinity, dissolved oxygen, conductivity), proximity to cover, and type of cover available,
<br />Habitat use data were analyzed for average distance moved (up- and downstream), monthly
<br />habitat selection as calculated by the aggregate percent method (Swanson et aL 1974), and mean
<br />habitat complexity (number of habitat types found in the area of the river used by the fish each
<br />month),
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<br />Results
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<br />Distribution, Abundance, and Movement - Non-native fishes, primarily channel catfish and
<br />common carp, were widely distributed within the San Juan River downstream of Farmington,
<br />New Mexico, During electrofishing efforts in main and secondary channels juvenile, sub-adult,
<br />and adult channel catfish were collected from all habitat types sampled. Common carp sampled
<br />were primarily adults and were collected in low velocity, shoreline areas over silt/sand substrate
<br />with depths < I m throughout the reaches sampled. Other non-natives sampled during
<br />electrofishing efforts were primarily centrarchids (largemouth bass Mieropterus salmoides,
<br />small mouth bass Micropterus dolomieu, green sunfish Lepomis cyanellus). Juvenile centrarchids
<br />were usually collected in Reaches 2-4 in low-velocity habitats in association with mouths of dry
<br />arroyos, secondary channels, and canals. Sub-adult and adult centrarchids (almost exclusively
<br />largemouth bass) were collected primarily in Reaches 4-6.
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<br />After spring 1995, adult striped bass Marone saxatilis and walleye Stizostedion vitreum were
<br />frequently collected in the San Juan River downstream in Reaches 1-4, but primarily in I and 2.
<br />Prior to spring 1995, lowered surface reservoir elevation of Lake Powell had resulted in
<br />formation of a barrier to upstream fish movement approximately 3 RM's downstream of Clay
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<br />San Juan River Non-native Species Interactions, Final Report, I February 2000
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