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. CJ Cl 1-' ca -J 0: . . length, width, bank features, shoreline vegetation, dominant substrate and cover for the habitat type. Other parameters measured included water and ambient air temperature, conductivity, and pH. Discharge was obtained from the nearest USGS gaging station. ~ " ~ <. ~ ~ , ~ c. c. Co ~ " .. Radio telemetry studies on Colorado pikeminnow provided seasonal habitat use, river reach use, and spawning behavior for San Juan River fish. These studies also identified possible spawning areas. The majority of wild Colorado pikeminnow contacts were between RM 120.0 and RM 142.0. Only one fish was located outside of this range. Ryden and Ahlm (1996) also found Colorado pikeminnow to be concentrated within this section of the San Juan River. Three of the stocked Colorado pikeminnow were also found in this area, although all three of the transmitters were eventually recovered. It is unknown whether the fish expelled the transmitters or died. Generally, stocked Colorado pike minnow did not behave like the wild fish monitored in 1993 and 1994. Only the stocked Colorado pikeminnow 40.051 exhibited behaviors and habitat use similar to a wild fish. ~ '" Habitat use during the suspected spawning period is concentrated in areas of very diverse habitats with numerous habitat types present. These areas are located in conjunction with complex bar and island systems that have many different habitat types in a small local area. Main features present at the suspected spawning areas include eddies or pools as resting habitat located in close proximity to chutes or steep riffles with very loose cobble substrate. ". 4 ,. '" to t t ~ ~ t;, Two (RM 131.1 and RM 132.0) potential spawning locations were identified for wild fish and one (RM 168.4) for stocked Colorado pikeminnow. One of those locations had a documented visual sighting of two paired Colorado pikeminnow, male and female, that were implanted with radio transmitters. The potential sites at RM 131.1 and RM 132.0 were used during both 1993 and 1994 and were used in the same sequence each year. The uppermost site at RM 132.0 was used first followed by the RM 131.1 site. ,.. ~. ,.. .... f" .... The use of various habitat types is related to the flow regime as well as life history traits of the Colorado pikeminnow. The pre-spawn time period is during the ascending limb of runoff, which floods local embayments, tributary mouths and secondary channels that provide Colorado pikeminnow staging habitat. During the descending limb ofnmoff, the habitat complexes for spawning become available, provided sufficient cleaning is done during the peak runoff These habitats appear to be used for varying lengths of time depending on the suitability of velocities in chute/riffle habitats and the embeddedness of cobble substrate. e t e e e e ":: Maintaining habitat riclmess is an important component of maintaining the potential spawning habitats for the fish. Highest habitat use during the spawning periods was in the area of highest habitat richness. Flows that develop and maintain complex habitats over the long term should provide the physical characteristics necessary to provide the spawning habitat. ~ ~. e e e ~ e ~ tt' ~ Colorado Pikeminnow Habitat Use in the San Juan River, New Mexico and Utah Miller Ecological Consultants, Inc. Pageii January 31, 2000