324 



liUcrior Wfxr — Our Li\'iiif; Resounes 



Spav\ning cui-iii. 



For further information: 



G. Gary Scoppettone 

 National Biological Service 

 Reno Field Station 

 46(10 Kietzke Ln. 

 BIdg. C. Rm. 120 

 Reno. NV 89502 



Future Outlook 



The cui-ui has an excellent prognosis for 

 recovery. It has an approved recovery plan and 

 supporting legislation (P.L. 101-616). which 

 provide for acquisition of water and water rights 

 to elevate Pyramid Lake, improve fish passage 

 over the delta, and enhance spawning tlows. 

 Plans to acquire water for Pyramid Lake and 

 cui-ui are being developed. Cui-ui population 

 trends over the past 10 years demonstrate the 

 rebound potential of the species when it is pro- 

 vided with passage and sufficient water for 

 reproduction. Because limited water is a\ailable 

 for acquisition, however, Truckee River flows 

 required for cui-ui recovery need to be precise- 

 ly determined. Our monitoring of the adult cui- 

 ui population is part of a cui-ui population 

 dynamics study aimed at calibrating an existing 

 Truckee River water-management model being 

 used for cui-ui recovery. Monitoring will con- 

 tinue through the 1998 spawning season, at 

 which time sufficient information should have 

 been generated to calibrate the model. 



References 



Scoppettone. G.G. 1988. Growth and longevity of the cui-ui 

 and longevity of other catostoniid.s and cyprinids in west- 

 ern North America. Transactions of the Atiierican 

 Fisheries Society 1 17:301-307. 



Scoppettone. G.G.. M. Coleman, and G.A. Wedemeyer. 

 1986. Life history and status of the endangered cui-ui of 

 Pyramid Lake, Nevada. U.S. Fish and Wildlife Service 

 Fish and Wildlife Res. 1:1-23. 



Scoppettone. G.G.. and G. Vinyard. 1991. Life history and 

 management of four endangered lacustrine suckers. 

 Pages 359-377 in W.L. Minckley and J.E. Deacon, eds. 

 Battle against extinction: native fish management in the 

 American West. The University of Arizona Press, 

 Tucson. 



I I M I I I I I I I I I M I I M I I M I I I I I I I I I I I I I I r 1 I 



45 55 65 75 85 



Year class (year hatched) 



Fig. 2. Year-class structure of adult cui-ui in spring 1983, 

 1991. 1992, and 1993. 



Bonytail and 

 Razorback 

 Sucker in the 

 Colorado 

 River Basin 



by 



Gordon Mueller 



National Biological Service 



Paul Marsh 



Arizona State University 



Bonytail {Gila elegcms) and razorback sucker 

 {Xynutchen texanus) are large river fish 

 found only in western Noilh America's Colorado 

 River basin. The bonytail is nearly extinct and 

 the razorback sucker is becoming rare. 



The bonytail (Fig. 1 ) is a large, streamlined 

 minnow (family Cyprinidae) that may reach 50 

 cm (18 in) in length and weigh up to 0.5 kg ( 1 

 lb). The razorback sucker (Catostomidae; Fig. 

 2) may grow to 75 cm (2.5 ft) in length and 

 weigh up to 5 kg (10 lb). Both species have 

 evolved a unique dorsal keel or hump, a charac- 

 teristic shared by few other fish. Individual life 

 spans approach 50 years. 



Historically, both species were common and 

 were used by Native Americans and early set- 

 tlers as food and fertilizer. Physical and biolog- 

 ical changes to their habitat and direct competi- 

 tion and predation from non-native fishes are 

 responsible for their decline. Young fish no 



longer survive to replace adults as they die of 

 old age. 



Status 



Information about these fish is found in 

 sources ranging from scattered personal jour- 

 nals of early travelers to more recent biological 

 reports and scientific literature. Bonytail and 

 razorback sucker were first described by scien- 

 tists in the late 1850"s. Comprehensive studies 

 were not conducted in the lower Colorado River 

 until 1930, while similar investigations 

 upstream were delayed until the 1960"s because 

 the area is rugged and remote. 



Dill (1941) reported an alarming decline of 

 endemic fish in the lower river; Miller et al. 

 ( 1982) reported similar trends farther upstream. 

 Three years after the 1973 passage of the 

 Endangered Species Act, the Colorado River 



