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<br />"- <br />Q01588 <br /> <br />water diversion structures in the upper portion of the San Juan River were evaluated as fish <br />movement barriers. Based on fish distribution above and below them, one or two of the structures <br />appeared to impede most species most of the time. Plans for removing one diversion and adding <br />fish passage structures on two of the other diversions were initiated in 1998 and 1999. Cooler <br />water temperatures from Navajo Dam releases created lower temperatures in the San Juan River, <br />at least downstream as far as Shiprock, New Mexico, and may affect Colorado pikeminnow <br />spawning success. Additional studies are needed to clarifY this potential limiting factor. <br /> <br />Several studies focused on nonnative fish interactions, including predation and competition. <br />A.lthough negative effects of nonnative predation or competition documented by these studies were <br />not substantial, partly because the endangered fish populations were too smaIl, the shl:eI:.llumb.ers . <br />of some species, such as channel catfish,_p.2!!!!!l9Jt carn,-1l!lQ J:~d_ shim:r, !)uggt:sj the)'-'l~gatively <br />impact native sI>eci~. In parts of the Colorado River Basin, some nonnative fish densities declined <br />d~ring years with high spring flows, but in the San Juan River during the 7-y~ar~e~e.ll!ch eeriod <br />this occurrence was not documented for nonnative fi.she~i~l?ner~I;.chapneLcatfish and ~omin9n <br />c~ numbers actually increased during thl'.smQ)'.pmQQ. Re~.sl:!in~I:.llumbers did decline in San <br />Juan River secondary channels during high flow years. -.--- -..--. <br /> <br />~y,\? <br />".\:;-I'- <br /> <br />F~h health. water quality, and contaminants were evaluated as potential limiting factors to the <br />native fish communi but none of them roved to .~pJ).rtantJimitinR factoJ:$. For both <br />en angered species, an important factor limiting their ability to increase their population size <br />during the 7-year research period was too few adults in their populations. <br /> <br />~ <br /> <br />1Jle studies showed that native tlannelmouth sucker. bluehead sucker. and speckled dace were <br />abJlndantinJhe over, but roundtail chub was rare. Roundtail chub was also a target species during <br />the 7-year research study since it was rare in several Colorado River Basin areas and may be <br />considered for listing under the Endangered Species Act. During the 7-year research period, <br />flannelmouth sucker populations increased in the upper river but decreased in the lower river. <br />Reasons for the decline in the lower river were not clear, but they will continue to be investigated. <br /> <br />The native fish community's overall good health, the razorback sucker and Colorado pi~innow <br />s.!9.cking success. and reoperating..Na.vajo Dam to provide key habitats.for_the&e.speciesindic.ated <br />that the San Juan ~i~er h,!s_potential for providing demog!:'lI>@c:ally viable I10P_1IIatiol1s of both <br />specieii. th<i.Uvill be iI!lP.QrtaE.t.iIl_ r.ecovery'()(the . species, noLonJ)'. in th~.S.a1Lll!an R!~l?!'JJut <br />thToughout the Colorado River Basiri~-- . ..- <br /> <br />The results obtained during the 7 -year research period will guide future recovery actions. Future <br />actions will focus on expanding the San Juan River razorback sucker, Colorado pikeminnow, and <br />roundtail chub populations. A razorback sucker Augmentation Plan was completed in 1997, and <br />population augmentation is underway. Growout ponds were developed on Navajo Nation property <br />near Farmington, New Mexico, to rear yoUng fish, but problems with obtainillg .young fish ne(:d <br />to oe resolv~4:-A Colorado plkemlnnow AugmeiifatlonPlan Will bedeveloped and implemented <br />to augment the small wild population. Colorado pikeminnow stocking will also occur above <br /> <br />~ <br />,: <br /> <br />September 2000 <br /> <br />5-3 <br /> <br />Program Evaluation Report <br />