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<br />C) <br />(~) <br />...... <br />co <br />...... <br />~ <br /> <br />In sununary, water temperature reduced the potential range for native fishes in the San Juan River and may <br />be a limiting factor in the ability of Colorado pikeminnow to spawn at an appropriate time above RM 150, <br />If a population of this species is established above RM 150, cool water from Navajo Dam may negatively <br />impact recruitment as a result of late spawning times, <br /> <br />Diversion Structures <br />In addition to the habitat lost by filling the two reservoirs, including the effect of reduced sununer <br />temperature, five diversion structures between RM 140.0 and RM 180,0 represent potential barriers to <br />fish movement, especially upstream movement. The diversions include: the Cudei Diversion (RM 142,0); <br />Hogback Diversion (RM 158.6); Arizona Public Service Company (Four Comers Power Plant) Weir <br />(APS Weir) (RM 163.3); Public Service Company of New Mexico (San Juan Generating Station) Weir <br />(PNM Weir) (RM 166.6); and the Fruitland Diversion (RM 178.5). Masslich and Holden (1996) <br />provided a detailed description of each of these structures. Ryden (2000a) showed that Colorado <br />pikeminnow used the portion of river between RM I 15,0 to RM 138.0 extensively (the area below the <br />lowest diversion), but he found no Colorado pikeminnow above RM 138.0, MilIer and Ptacek (2000) <br />noted that one adult radio-tagged Colorado pikeminnow moved up through the Cudei Diversion in 1994 <br />and then back, the furthest upstream any wild Colorado pikeminnow was found, In 1988, Platauia (1990) <br />captured a Colorado pikeminnow about a mile above the Cudei Diversion, the most upstream collection <br />since 1962 (pre-Navajo Dam), <br /> <br />Electrofishing catches from adult monitoring trips (Ryden 2000a) showed that common native species were <br />found above and below the diversions, which is reasonable since they inhabited this area prior to <br />constructionofthe dams. Ryden (2000a) reported that one subadultrazorback sucker stocked just below <br />the Hogback Diversion moved upstream over the diversion and that another stocked fish moved over the <br />Cudei Diversion. Nonnative fish distribution was noticeably affected by the PNM Weir. Channel catfish, <br />common carp, and red shiner were all fairly common below the PNM Weir, but not above. These data <br />suggested the Cudei Diversion, Hogback Diversion, and the APS Weir were all passable by fish at some <br />flows, but that the PNM Weir was a more-substantial barrier, <br /> <br />Because of the lack of endangered fishes in the river reach containiog the five diversions, Ryden (2000a) <br />floy-tagged 2,649 flanneImouth sucker and 1,303 bluehead sucker as surrogates, as well as 3,706 channel <br />catfish and 2,778 common carp, A few of the latter two species were also radio-tagged. During adult <br />monitoring trips, electro fishing was used to recapture the tagged fish and determine movement. Eighteen <br />adult flanneImouth sucker were able to move upstream and downstream over all five stmctures, and eight <br />adult bluehead sucker moved upstream over the APS Weir and Fruitland diversion but not over the PNM <br />Weir. Thirty-five channel catfish and six carp also moved at least one way over a structure. These data <br />suggest passage is possible over each of the weirs, but it is limited, and the diversions undoubtedly make <br />it difficult for fish to traverse upstream in this portion of the river. <br /> <br />September 2000 <br /> <br />3-42 <br /> <br />Program Evaluation Report <br />