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<br />679 Razorback sucker <br /> <br />680 The razorback is endemic to the Colorado River Basin with a wide historical distribution. Historically <br />681 the razorhack occurred in the San Juan and Animas Rivers but little is known about population <br />682 abundance (Holden, 1999). Throughout its range the species is now very rare with low to nonexistent <br />683 recruitment. Small concentrations ofrazorback suckers have been reported in the inflow area in the <br />684 San Juan arm of Lake Powell. Ryden (2000) reports that no wild razorback suckers have been <br />685 collected in the San Juan River since 1988, when one individual was collected near Bluff (Holden, <br />686 1999). Overall this species is extremely rare in the San Juan River. <br /> <br />687 The lower San Juan River is designated as critical habitat for the razorback as follows: <br /> <br />688 New Mexico, San Juan County, and Utah, San Juan County. The San Juan River and its 100- <br />689 year flood plain from the Hogback Diversion in T,29N.,R.16W., section 9 (New Mexico <br />690 Meridian) to the full pool elevation at the mouth ofNeskahai Canyon on the San Juan arm of <br />69\ Lake Powell in TAl S., R. ~ I E., section 26 (Salt Lake Meridian). <br /> <br />692 Experimental stocking began in 1994 and these stocked tish have been observed in spawning <br />693 condition. Ponds have been developed to raise fish for stocking in the river. Spawning activity of <br />694 stocked fish has been recorded at a specific area near RM :00 (SJRBRIP, 200Ib). Larval fish were <br />695 collected between Bluff and Montezuma Creek (Service, 2000a). The razorback's current distribution <br />696 in the San Juan, counting introduced fish, is from Lake Powell to near the Hogback Diversion (RM <br />697 158). Twenty one of the stocked razorbacks were recaptured during a May 2001 monitoring trip <br />698 (SJRBRlP,200Ib). <br /> <br />699 Razorbacks spawn on the ascending limb of the hydrograph, thus they spawn earlier than the <br />700 pikeminnow. Razorbacks use backwaters or flooded bottomlands prior to spawning; they generally <br />70 I spawn in runs over gravel or cobble. Backwaters and flooded bottomlands are important to complete <br />702 the specie's life cycle; drifting larva enter backwaters where food sources can be abundant. <br /> <br />703 The razorback decline has probably occurred for similar reasons as the pikeminnow's decline. <br />704 Loss of backwaters and predation by non-natives in remaining backwaters is a major problem as are <br />705 migration barriers. <br /> <br />706 Overall, the proposed action should benefit this species and its critical habitat by improvmg riverine <br />707 and backwater habitat conditions; and, as with the pikeminnow, periodic lower flows may adversely <br />708 affect water quality in the razorback's habitat. <br /> <br />709 Bonvtail and humpback chub <br /> <br />710 These endangered fish do not occur in the San Juan River and would not be affected by the operation <br />711 changes of the proposed plan. Historical presence or absence is unclear; however, there is evidence <br />712 that the bonytail occurred in the river prior to the 20'h Century (Service, 200 I d). If introductions are <br /> <br />24 <br /> <br />00665 <br />