Laserfiche WebLink
<br />C) <br />C.) <br />~ <br />co <br />.- <br />c;, <br /> <br />In addition to blocking upstream movement, the diversion dams also may reduce native fish recruitment by <br />entraining larvae, hence reducing the suitability of the area above RM 142 for native fish. Colorado <br />pikeminnowand razorback sucker larvae are known to drift downstream from spawning areas, as are the <br />larvae of other native species. In 1996 and 1997, Tranunell and Archer (2000) studied the potential <br />entrainment ofYOY Colorado pikeminnow stocked at the Cudei Diversion, approximately 3 miles below <br />Shiprock, New Mexico, Y oung-of-the-year Colorado pikeminnow were found in the diversion canal both <br />years, showing that even larger fish capable of swimming in the current were entrained in this canal. But <br />the effect of this entrainment to the overall population is unclear; the stocking of YOY Colorado <br />pikeminnow was considered to be successful since retention in the river was good (Trammell and Archer <br />2000). Populations of the other native species, especially flanneImouth sucker, bluehead sucker, and <br />speckled dace, were high in the areas with the diversions, suggesting that entrainment of their young in the <br />diversions does not effect overall population size. The potential limiting factor of entrainment will need to <br />be studied in more detail after adult populations of the two endangered fish are established in and <br />above the diversion reach. <br /> <br />Management Implications <br />The potential limiting nature of water temperature was not fully studied. Additional research is needed to <br />confirm that water temperature may be a limiting factor to Colorado pikeminnow and other species in the <br />San Juan River above Shiprock, New Mexico. That study needs to examine historical and present water <br />temperatures under similar flow conditions to determine to what degree water temperature is affected by <br />cold releases from Navajo Dam, As seen during the 7-year research period, river temperature below the <br />mouth of the Animas River reached 200 C every year by late July, and therefore may not limit spawning of <br />Colorado pikeminnow, but rather delay it a week or two. This delay may affect the survival of young if <br />spawning occurred above RM 150; therefore, it needs to be evaluated in more detail, <br /> <br />The diversion dams, especially the PNM and APS weirs, are much more likely limiting expansion of <br />Colorado pikeminnow into the upper river near Farmington, New Mexico, than is water temperature. <br />Stocking fish above the diversions may negate this factor initially, but as young are produced and drift <br />downstream to nursery areas, they would have no unobstructed route back to the upper river. The Biology <br />Committee, wanting to expand the range of Colorado pikeminnow and perhaps razorback sucker into the <br />upper river, evaluated the five diversion dams and concluded that fish passage should be considered at each <br />of the major dams. During 1999, the Biology Committee reviewed BIA plans to combine the Hogback <br />and Cudei diversions at the Hogback site and to provide nonselective fish passage at the new Hogback <br />Diversion, The Biology Committee also determined that a selective fish-passage structure should be added <br />to the PNM Diversion so nonnative fishes can be removed from the river. Once complete, native and <br />nonnative fish passage through these structures should be monitored to determine whether similar stmctures <br />are needed at the other diversions, <br /> <br />September 2000 <br /> <br />3-43 <br /> <br />Program Evaluation Report <br />