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<br />,.1 o;I,f~ <br />lJ? <br />ro <br />t""'f <br />'-) <br />C; <br /> <br />water diversion structures in the upper portion of the San Juan River were evaluated as fish movement <br />barriers. Based on fish distribution above and below them, one or two of the structures appeared to <br />impede most species most of the time. Plans for removing one diversion and adding fish passage structures <br />on two of the other diversions were initiated in 1998 and 1999. Cooler water temperatures from Navajo <br />Dam releases created lower temperatures in the San Juan River, at least downstream as far as Shiprock, <br />New Mexico, and may affect Colorado pikenllnnow spawning success. Additional studies are needed to <br />clarifY this potential limiting factor. <br /> <br />Several studies focused on nonnative fish interactions, including predation and competition. Although <br />negative effects of nonnative predation or competition documented by these studies were not substantial, <br />partly because the endangered fish populations were too small, the sheer numbers of some species, such <br />as channel catfish, common carp, and red shiner, suggest they negatively impact native species. In parts <br />of the Colorado River Basin, some nonnative fish densities declined during years with high spring flows, but <br />in the San Juan River during the 7 -year research period this occurrence was not documented for nonnative <br />fishes in general; channel catfish and common carp numbers actually increased during the study period. <br />Red shiner numbers did decline in San Juan River secondary channels during high flow years. <br /> <br />Fish health, water quality, and contaminants were evaluated as potential limiting factors to the native fish <br />community, but none of them proved to be important limiting factors. For both endangered species, an <br />important tactor limiting their ability to increase their population size during the 7 -year research period was <br />too few adults in their populations. <br /> <br />The studies showed that native flannelmouth sucker, bluehead sucker, and speckled dace were abundant <br />in the river, but roundtail chub was rare. Roundtail chub was also a target species during the 7-year <br />research study since it was rare in several Colorado River Basin areas and may be considered for listing <br />under the Endangered Species Act. During the 7-year research period, flannelmouth sucker populations <br />increased in the upper river but decreased in the lower river. Reasons for the decline in the lower river <br />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 pikenllnnow stocking <br />success, and reoperating Navajo Dam to provide key habitats for these species indicated that the San Juan <br />River has potential for providing demographically viable populations of both species that will be important <br />in recove!)' of the species, not only in the San Juan River, but throughout the Colorado River Basin. <br /> <br />The results obtained during the 7-year research period will guide future recove!)' actions. Future <br />actions will focus on expanding the San Juan River razorback sucker, Colorado pikenllnnow, and <br />roundtail chub populations. A razorback sucker Augmentation Plan was completed in 1997, <br />and population augmentation is undeIWay. Growout ponds were developed on Navajo Nation <br />property near Fannington, New Mexico, to rear young fish, but problems with obtaining young fish need <br />to be resolved. A Colorado pikeminnow Augmentation Plan will be developed and implemented to <br />augment the small wild population. Colorado pikenllnnow stocking will also occur above Shiprock, <br /> <br />September 2000 <br /> <br />8-3 <br /> <br />Program Evaluation Report <br />