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<br />. <br /> <br />'t~ <br />0- <br />, <br /> <br />.~, <br />\) <br />'" ~\ <br /> <br />. <br /> <br />. <br /> <br />Table 5.1.' <br /> <br />Flow requirements needed to produce important biological responses and <br />habitats in the San Juan River. <br /> <br /> BIOLOGICAL RESPONSE/HASlT AT FLOW REQUIREMENT <br /> REQUIREMENT <br /> Reproductive success of Colorado squawfish lower in Mimicry of a natural hydrograph. especially during <br /> years with low spring runoff peaks. and higher in years relatively high runoff years. <br /> with high and broad runoff peaks. <br /> Decline in f1annelmouth sucker abundance, increase in Mimicry of natural hydrograph with higher spring flows <br /> bluehead sucker abundance. and increased condition and lower base flows. <br /> factor in both species. <br /> Sluehead sucker reproductive success. Number of days of spring runoff >5,000 and 8.000 cfs. <br /> Speckled dace reproductive success. . Number of days of spring runoff >5.000 and 8,000 cfs. <br /> Success of stocking YOY Colorado squawfish and Mimicry of natural hydrograph has provided suitable <br /> subadutt razorback sucker. habitat for these size classes, <br />J' Eddies, pools. edge pools, other low velocity habitats Mimicry of natural hydrograph has lowered base flows <br /> year round for adult Colorado squawfish and worback to provide more low velocity habitats. Flows> 10,000 <br /> sucker. cfs provide more channel complexity which provides for <br /> more habitat complexity, <br /> Aows to cue razorback sucker and Colorado squawfish Mimicry of natural hydrograph with higher spring flows. <br />'Y for migration and/or spawning. <br />. <br />, Adutt Colorado squawflSh and razorback sucker prefer Flows >10.000 cfs provide more channel complexity <br />oj} complex ri'ler areas. which provides for more habitat complexity. lower base <br /> flows add to amount of low velocity habitats. <br />:t Clean cobple bars for spawning of all native species, Aows >8.000 c;fs for 8 days to construct cobble bars. <br />especially Colorado squawfish. and >2,500 cfs for 10 days to clean cobble bars, during <br /> spring runoff. . <br /> Backwaters and other low velocity habitats are High spring flows create conditions for backwater <br />\~ important nursery habitats for Colorado squawfish and formation. low base flows allow them to appear in late <br />\' other native fIShes. summer and fall. flows >5.000 cis for 3 weeks create <br /> and clean backwaters. <br /> Aooded bottomlands appear to be important nursery Overbank flows (> 8.000 cfs) increase flooded <br /> areas for r.azorback sucker. but other habitats may be vegetation. and backwaters formed in association with <br /> used in the San Juan River. edge features maximize on receding flows of 8,000 to <br /> 4,000 cfs. <br /> Temperatures of 10 to 14 .C at peak runoff for Proposed releases from Navajo Dam are too cool to <br /> razorback sucker spawning and near 18 to 20 . C at replicate pre-dam temperature timing, but <br /> bottom ot descending limb for Colorado squawfish temperatures are above spawning threshold for <br /> spawning. Colorado squawfish during the COrTect period. <br /> Reduction of nonnative fISh abundance. Most nonnative fISh did not decrease during research <br /> period, summer flow spikes reduce numbers of red <br /> shiner in secondary channels in the short-term. <br /> <br />Note: cfs = cUOle teet per second, YOY = young-oHhe--year. <br /> <br />SJRIP Biology Committee <br />16 September 1998 <br /> <br />8-4 <br /> <br />Executive Summary <br />Draft Aow Report <br />