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<br />C) <br /> <br />length, width, bank features, shoreline vegetation, dominant substrate and cover for the <br />habitat type, Other parameters measured included water and ambient air temperature, <br />conductivity, and pH, Discharge was obtained from the nearest USGS gaging station, <br /> <br />01 <br /> <br />~"" <br />~. <br />~ <br />N <br /> <br />Radio telemetry studies on Colorado pikeminnow provided seasonal habitat use, river <br />reach use, and spawning behavior for San Juan River fish, These studies also identified <br />possible spawning areas, The majority of wild Colorado pikeminnow contacts were <br />between RM 120,0 and RM 142,0, Only one fish was located outside of this range, <br />Ryden and Ahlm (1996) also found Colorado pikeminnow to be concentrated within this <br />section of the San Juan River, Three of the stocked Colorado pikeminnow were also <br />found in this area, although all three of the transmitters were eventually recovered, It is <br />unknown whether the fish expelled the transmitters or died, Generally, stocked Colorado <br />pikeminnow did not behave like the wild fish monitored in 1993 and 1994, Only the <br />stocked Colorado pikeminnow 40,051 exhibited behaviors and habitat use similar to a <br />wild fish, <br /> <br />Habitat use during the suspected spawning period is concentrated in areas of very diverse <br />habitats with numerous habitat types present. These areas are located in conjunction with <br />complex bar and island systems that have many different habitat types in a small local <br />area. Main features present at the suspected spawning areas include eddies or pools as <br />resting habitat located in close proximity to chutes or steep riffles with very loose cobble <br />substrate, <br /> <br />Two (RM 131,1 and RM 132,0) potential spawning locations were identified for wild fish <br />and one (RM 168.4) for stocked Colorado pikeminnow. One ofthose locations had a <br />documented visual sighting of two paired Colorado pikeminnow, male and female, that <br />were implanted with radio transmitters, The potential sites at RM 131.1 and RM 132,0 <br />were used during both 1993 and 1994 and were used in the same sequence each year. <br />The uppermost site at RM 132,0 was used first followed by the RM 131.1 site, <br /> <br />The use of various habitat types is related to the flow regime as well as life history traits <br />of the Colorado pikeminnow, The pre-spawn time period is during the ascending limb of <br />runoff, which floods local embayments, tributary mouths and secondary channels that <br />provide Colorado pikeminnow staging habitat. During the descending limb of runoff, the <br />habitat complexes for spawning become available, provided sufficient cleaning is done <br />during the peak runoff. These habitats appear to be used for varying lengths of time <br />depending on the suitability of velocities in chute/riffle habitats and the embeddedness of <br />cobble substrate. <br /> <br />Maintaining habitat richness is an important component of maintaining the potential <br />spawning habitats for the fish. Highest habitat use during the spawning periods was in <br />the area of highest habitat richness, Flows that develop and maintain complex habitats <br />over the long term should provide the physical characteristics necessary to provide the <br />spawning habitat. <br /> <br />Colorado Pikeminnow Habitat Use in the San Juan River, New Mexico and Utah <br />Miller Ecological Consultants, Inc. <br /> <br />Pageii <br />January 31, 2000 <br />