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<br />Chapter 2.0 Description of Alternatives 23 <br /> <br /> <br />01199 <br /> <br />Although the proposal is focused on water years 2003 and 2004, it could take an <br />indeterminate number of years to implement the sediment conservation portion of the <br />Proposed Action due to the necessary sediment input triggering involved. To ensure <br />that development of a program of experimental flows benefits the resources of concern, <br />the Adaptive Management Work Group has directed GCMRC to report back at six- <br />month intervals on progress. <br /> <br />2.2.2 Mechanical Removal of Non-Native Fish <br /> <br />A second key component of the Proposed Action is assisting native fish through <br />mechanical removal of non-native fish. Non-native fish removal is targeted at reducing <br />adult rainbow and brown trout and other non-native fish in the Colorado River near the <br />confluence of the Little Colorado River. The area around the confluence of the Colorado <br />and Little Colorado rivers has the highest abundance of adult and juvenile humpback <br />chub in the Colorado River mainstem (Maddux et al. 1987, Valdez and RyeI1995). To <br />help the humpback chub in this reach, an area located approximately five miles <br />upstream (RM 56.4) to four miles downstream (RM 65.8) from the confluence of the <br />Little Colorado and Colorado rivers has been proposed as the" depletion reach." The <br />proposed depletion effort would be uniformly distributed within this 9.4 mile reach and <br />repeated twice a year in the 2003-2004 water years. <br /> <br />Each year for two years, GCMRC is proposing to conduct three depletion trips from <br />January to March and three depletion trips from July to September. The exact timing of <br />these trips could be adjusted through the adaptive management process to minimize <br />adverse effects to humpback chub. The effort would also yield information regarding <br />abundance of young-of-year humpback chub and complement existing monitoring <br />efforts. <br /> <br />During each 10-day field trip there would be five passes through the reach using <br />four electrofishing boats that concurrently sample the river on opposing sides. <br />Following each trip, the data would be used to construct abundance estimates for <br />rainbow and brown trout present at the beginning of each trip. Comparisons among trip <br />population estimates and trip catchability coefficients would be analyzed in order to <br />evaluate if mechanical removal is an effective means to control undesirable fish species. <br />Additionally, electrofishing results would be used to measure juvenile humpback chub <br />relative abundance and any potential adverse effects on adult HBe. <br /> <br />A fish anesthetic will be used to euthanize the non-native fish. The proposed <br />disposal mechanism for non-native fish would be to transport the fish out of the Grand <br />Canyon. In response to concerns expressed by tribes, a beneficial use would be sought <br />for the fish thus removed. <br /> <br />