WSP02839 - Laserfiche WebLink

Home Browse Search

o o (::J .~ 5 :.::~, achieve the objectives of the Implementation Program as set forth above. en The razorback sucker was listed as endangered on October 23, 1991. Causes for the decline of the sucker have been identified as fragmentation of its habitat by the construction of dams, the manipulation of flows with attendant alterations of temperature and water quality, and the introduction of non-native fishes. Once abundant throughout the mainstem of the Colorado River and its major tributaries, the species now occupies only an estimated 25 percent of its historic range, and where it does occur, its numbers are extremely low. Critical habitat has been designated for the razorback sucker in the San Juan River and its 100- year floodplain from the Hogback Diversion Dam in T.29N., R.16W., section 9 (New Mexico Meridian) to the full pool elevation at the mouth of Neskahai Canyon on the San Juan arm of Lake Powell in T.41 S., R.11 E.. section 26 (Salt Lake Meridian). Information on the historic distribution and abundance of the razorback sucker in the San Juan basin is sparse. The number of fishery surveys that have been conducted in the San Juan River is relatively small compared to the rest of the Colorado River Basin. Anecdotal reports of the species from the Animas River near Durango (1891), and the San Juan River near Farmington (1960) mayor may not have been razorback sucker (Platania 1990). Pre- impoundment piscicide applications in the Navajo Dam area in 1962 killed fish downriver to Farmington, New Mexico; however, no razorback sucker were documented among the fish killed (Olson 1962). The first verifiable record of razorback sucker from the San Juan River basin was in 1976 when two adults were seined from a pond near Bluff, Utah, at approximately river mile 81 (VTN Consolidated Inc., and Museum of Northern Arizona 1978, Platania 1990, Minckley et al 1991). According to local residents, a second pond adjacent to the one where these two fish were caught was drained just weeks before, leaving approximately 100-250 juvenile razorback sucker stranded, resulting in the mortality of all fish at the site. These two ponds were linked to the river via a canal that allowed fish movement to and from the river (VTN Consolidated Inc., and Museum of Northern Arizona 1978, Platania 1990, Minckley et al 1991). Between 1987 and 1989 sixteen adult razorback sucker were collected from the San Juan River arm of Lake Powell, near Piute Farms Marina (Platania 1990). In 1988 one razorback sucker was captured and released in the main channel of the San Juan River near Bluff, Utah, close to the 1976 capture site. No wild razorback sucker have been collected from the San Juan River in Colorado or New Mexico. Neither have spawning or recruitment been documented in the San Juan River. However, the presence of a few large adult fish near Bluff, Utah, suggests that there is a remnant population of old razorback sucker remaining in the river. As has been evidenced by the small number of wild fish captured in the San Juan River, the razorback sucker is the least abundant of the three target species (razorback sucker, Colorado squawfish, and roundtail chub, ili!g robusta) in this river system (Ryden and Pfeifer 1993, Platania 1990). Thus. artificial propagation and release of hatchery-reared razorback sucker is a potentially vital component to recovery of this species. In order to gather basic data concerning the species in the San Juan River, an experimental stocking program with a total of 939 razorback sucker has been conducted by the Service from 1994 through 1996.