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t <br />sucker monitoring program. Other ongoing field studies provide additional information on status and trends <br />of all endangered fish species as well as nonnative fishes. <br />Monitoring the Status and Trends of Endangered Fish Stocks. The status and trends of endangered fish stocks <br />in the Upper Colorado River Basin will be reviewed annually by the Program's Biology Committee using new <br />information on the stocks from the Interagency Standardized Monitoring Program and ongoing studies. <br />Present Status and Trends of Endangered Fishes in the Uoner Colorado River Basin. The status and trends of <br />these endangered fish stocks were reviewed by members of the Program's Biology Committee and other <br />interested persons using the criteria described above and are snmm~ri~ed in Table 2. <br />Razorback Sucker: The interim management objective for adult razorback sucker estimated population-size <br />in the upper Colorado River basin is 5316 (± 804) per stock (Lentsch et al 1998). Current status and trends of <br />the razorback sucker are at critically low levels throughout the Upper Basin (Bestgen 1990; Burdick 1992; <br />Lanigan and Tyus 1989; Maddux et al. 1993; McAda and Wydoski 1980; Tyus and Karp 1990). Old <br />individuals in current presumptive stocks are declining rapidly. <br />Middle Green River <br />The presumptive stock in the middle Green River between the confluence with the Duchesne and <br />Yampa rivers is low, Modde et al. 1993 estimated about 500 adults; but some recruitment occurs in <br />this reach as indicated by the presence of small fish (< 475 mm). However, this recruitment is not <br />sufficient to maintain self-sustaining populations of this species in that river reach. The razorback <br />sucker population was estimated to be 948 fish (95% confidence interval, 758 - 1,138) in 1988 <br />(Lanigan and Tyus 1989). This population declined to between 250 and 550 fish in 1993 (Modde et <br />al. 1993). Statistical analyses of this population, using the same data as Lanigan and Tyus with the <br />addition of data from recent years, indicates that the previous population estimate was high (Modde <br />et al. 1993). <br />Although spawning occurs in the Yampa River, no recruitment has been documented and the number <br />of spawning fish appears low and may be declining. Fourteen ripe razorback suckers were captured <br />in the Yampa spawning site in 1975, but only 32 ripe fish were captured during the of 1975, 1981, <br />1988, and 1989 (Tyus and Karp 1989). <br />An augmentation plan was implemented in 1995 (Wydoski 1996). During 1995, 929 razorback <br />sucker averaging 170 mm in total length along with 21 ranging in 74-125 mm in total length were <br />stocked in the Green River. In 1996, 1,068 razorback sucker ranging in size from 209-308 mm total <br />length were stocked (Tom Pruitt, personal communication). No recaptures offish stocked in 1995 <br />have occurred; this stocking has been considered unsuccessful with little or no survival after two <br />years of observations. To date, 7 of the 1996 stocking event have been recaptured. <br />Lower Green River <br />Yet to be determined, the basinwide monitoring program was unable to collect samples in this <br />portion of the River due to Program cut backs in 1997. The expansion of the ISMP in 1998, includes <br />quantifying the trends of razorback in the lower Green River. <br />Upper Colorado River <br />A dramatic decline in razorback suckers occurred between 1974 and 1991 for the reach of the Upper <br />Colorado River between River Miles 152.8 and 185.1 (Burdick 1992). A high capture of 206 <br />razorback suckers in this reach during 1974 declined and no fish were captured during 1989-1992 <br />(Burdick 1992). During 1993, three adult razorback suckers were captured in this reach of the <br />Colorado River (F. Pfeifer, 1993, Personal Communication). The razorback sucker has been <br />extirpated from the Gunnison River upstream from the Redlands Irrigation Diversion Dam and <br />10 , <br />