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<br />Generally, the investigations of CRFP have included the entire range of the endangered fishes in the
<br />upper basin, except for some regions that are not part of the sampling design or require special
<br />equipment because they are difficult to access and sample. One such area is Cataract Canyon, located
<br />between the confluence of the Colorado and Green Rivers and upper Lake Powell. Cataract Canyon
<br />is a 16-mile reach of whitewater within Canyonlands National Park administered by the National Park
<br />Service.
<br />
<br />Attention was first drawn to this region of the upper basin in April 1980, when 45 adult Colorado
<br />squawfish were captured in upper Lake Powell during a study by the Utah Cooperative Fishery
<br />Research Unit (Persons et aI. 1982, Valdez et a1. 1982). The objective of that investigation was to
<br />assess spawning success of striped bass in that portion of the Colorado River flowing into Lake Powell.
<br />The Colorado squawfish were captured coincidentally in gill nets set for st.riped bass.
<br />
<br />Initial efforts by FWS in 1979-81 in Cataract Canyon (Valdez et a1. 1982) and continued efforts by
<br />Reclamation in 1981 near Gypsum Canyon also encountered Colorado squawfish, but not in the
<br />numbers seen in 1980. From 1982 to 1984, Reclamation equipped adult Colorado squawfish in upper
<br />Lake Powell with radio transmitters in an attempt to locate fish concentrations, monitor movements, and
<br />identify possible spawning areas. Small numbers of adults were found in the Imperial/Gypsum Canyon
<br />areas in July and August of these years, but no spawning sites were identified. Seining in these areas
<br />yielded numerous larval and young-of-the-year (YOY) Colorado squawfish, indicating that reproduction
<br />had occurred in either upper Lake Powell or in the river immediately upstream, within Cataract Canyon.
<br />
<br />In 1985, Reclamation continued st.udies with radiotelemetry in the "Imperial/Gypsum Canyon areas,
<br />and initiated a pilot study in Cataract Canyon (Valdez 1985). Six field trips were conducted from July
<br />through October. These efforts yielded YOY as well as juvenile and adult Colorado squawfish and
<br />humpback chub. Two fish, tentatively identified as bonytail (one adult and one YOY), were also
<br />reported. These findings indicated the need for additional st.udies to locate possible spawning areas
<br />in the canyon and to assess the importance of habitats within Cataract Canyon and upper Lake Powell.
<br />
<br />Field efforts for the current investigation were initiated in Cataract Canyon on July 11, 1986 (Valdez
<br />1987). Six trips were conducted through the canyon between that date and October 6, 1986, with the
<br />objectives as previously st.ated. In 1987, eight sample trips were conducted from April 13 to October
<br />12, and in 1988, nine sample trips were conducted from March 21 to October 12.
<br />
<br />1.3 Administration of the Study
<br />
<br />This investigation was the result of a cooperative effort by several agencies and many individuals
<br />(Figure 1). The st.udy was contracted and administered by the Bureau of Reclamation with the
<br />cooperation of the FWS, NPS, and UDWR. The work was conducted primarily by BIO/WEST, Inc. with
<br />participation in all field efforts by Reclamation biologists. Field work was conducted by one crew,
<br />generally composed of four biologists, and logist.ic support was from Tag-A-Long Tours, a commercial
<br />river company. All larval fish were identified by the Larval Fish Laboratory of Colorado State University.
<br />
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<br />This investigation was conducted on the Colorado River from near Potash (RM 50) downstream to
<br />Imperial Canyon in upper Lake Powell (RM 200, 16.4 miles below the confluence of the Green and
<br />Colorado Rivers), as well as that portion of the Green River from near Mineral Bottom (RM SO)
<br />
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