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<br />t <br />1 <br />fl <br />1 <br /> <br /> <br />f <br />1 <br />t <br />1 <br /> <br /> <br />1 <br /> <br />1 <br />The initial study was to be conducted in a controlled setting, with field studies to <br />follow. This was considered the most desirable option because we would have more <br />control over the study, complete observation of the fish could be maintained, and all of <br />the study objectives could be accomplished. Hotchkiss National Fish Hatchery (NFH), <br />Colorado, was identified as the site to conduct studies for roundtail chub and juvenile <br />Colorado squawfish and razorback sucker. Dexter NFH, New Mexico, has been <br />designated the principal endangered fish hatchery for Colorado River endangered fishes. <br />Here, brood fish for Colorado squawfish and razorback sucker are maintained. <br />Therefore, we anticipated PIT tagging some of these brood fish at Dexter to accomplish <br />this phase of the study. <br />One objective in 1987 was to gain experience with implanting PIT tags. Roundtail <br />chub were selected because they were readily available in the river. Also, because <br />roundtail chub are a member of the genus Gila, they could be used as a surrogate for <br />humpback chub. However, a series of culture-related problems unrelated to the PIT-tag <br />treatment developed at Hotchkiss NFH. Two replicate lots of approximately 100 adult <br />roundtail chub were lost because we were unable to control the external parasite, <br />Ichthyophthirius multifillis. Consequently, PIT-tag studies with adult roundtail chub at <br />Hotchkiss NFH were discontinued. <br />Several adjustments were made in 1988 to the general study design after the <br />unsuccessful attempts to culture fish at Hotchkiss NFH. Because no other nearby <br />comparable facilities suitable to conduct these controlled studies were available, the <br />study design was modified to utilize other sites. The study was expanded to include <br />5 <br />