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Other evidence and analyses also supported the notion of an apparently declining <br />population of Colorado pikeminnow in the Green River Basin during the study period. Estimates <br />of X greater than I for most years from 1991 to 2000 suggested an increasing population of <br />Colorado pikeminnow in the Green River Basin. After 2000, 1 was consistently much less than <br />1, which suggested a declining population. The negative rate of population change could be the <br />result of reduced survival or recruitment of Colorado pikeminnow, or some combination of all <br />those factors. <br />Trends in the ISMP catch/effort data were consistent with I and abundance estimates and <br />suggested a post year-2000 decline in abundance of Colorado pikeminnow in every portion of the <br />Green River Basin. If catch/effort indices reflected abundance, the Green River Colorado <br />pikeminnow population may be reduced to levels at or near those present in 1991. Catch/effort <br />data for Colorado pikeminnow for individual rivers showed a positive and reasonably strong <br />relationship with abundance estimates for middle and lower Green river reaches, and moderately <br />strong relationships in the White and Yampa rivers. Osmundson (2002) found poor agreement <br />with abundance estimates and catch/effort indices in the Colorado River, perhaps because of <br />relatively poor precision of abundance estimates. Investigation of the strength of these <br />relationships, and factors that affect those relationships, should continue in the future when more <br />abundance estimates are gathered, because ISMP-like sampling may yet be a useful, less- <br />intensive monitoring tool in the future. <br />Consistency of trends indicated by the less sampling intensive catch/effort and X <br />parameters compared to higher effort abundance estimation sampling suggested less costly <br />options to monitor some demographic parameters for Colorado pikeminnow in the Green River <br />Basin. Recall that data to estimate the I parameters for the years 1991 to 1999 were derived <br />45