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BIOCHEMICAL GENETICS OF COLORADO PIKEMINNOW 67 ion and for the tection, staining istorical Dish and on iden- known his spe- tvior as- )smund- vn about analyses genetic Ammer- line sus- 'Veinbetg ese wild TABLE 1.-Year of initiation, number of founders, collection source,. and designation of captive Colorado pikeminnow broodfish populations presently held at the Dexter National Fish Hatchery and Technology Center, New Mexico. The Willow Beach National Fish Hatchery, Arizona, and the Dexter fish technology center were involved in the capture and production of these fish. Various unpublished collecting records were use [o collate this information. Year Number of founders Collection source Broodfish designation 1973 8 fish Yampa River 1974 Progeny of Yampa River fish Yampa DX-F~ (74) (unknown sex ratio and numbers of broodfish) 1978 22 fish Colorado and Green rivets 1979 7 fish Colorado and Green rivers 1981 Progeny of Colorado and Green River fish Colorado-Green DX-Ft (81) (3 females crossed with 10 males from 1978 and 1979 collections) 1987 Progeny of Yampa DX-Ft (74) Yampa DX-FZ (87) (1 female crossed with 5 males) 1991 Progeny of Yampa DX-Ft (74) Yampa DX-Fz (91) (unknown sex ratio and numbers of broodfish) I991 10 fish Colorado River Colorado DX-Fp (91) populations (Ammerman and Morizot 1989) could indicate sampling of multiple mixed populations rather than a single panmictic population. Am- merman and Morizot (1989) examined only age- O fish from wild populations and the offspring of two captive broodfish stocks at Dexter National Fish Hatchery and Technology Center, New Mex- ico. Their results indicated that the captive fish were representative of the two wild poptalations sampled and that mean heterozygosity estimates for wild and captive Colorado pikeminnow pop- ulations were similar to those for other cyprinids. Production of Colorado pikeminnow from cap- tive broodfish at the Dexter fish technology center (Table 1) is being used to supplement populations in tributaries of the Colorado River. Numerous stockings with hatchery fish have been done in the Colorado River basin; these include, but are not limited to, the White River (Kenney Reservoir) in the late 198Os and early 199Os (Trammel et al. 1993) and the Colorado River main stem (Grand Valley) in the early to mid-198Os (Table 2). All stockings through the early 199Os were done with hatchery stocks derived from Yampa River pop- ulations (R. Hamman, Dexter National Fish Hatch- ery and Technology Center, personal communi- cation). Fish derived from mixed Colorado and Green River broodfish were stocked into the San Juan River in 1996, 1997, and 1998 (Hamman, personal communication). The magnitude of these stocking events may have been sufficient to ho- mogenize extant wild populations of the Colorado pikeminnow. Migration, spawning, and recruitment are sub- jects of great interest and debate among manage- ment biologists responsible for recovery efforts. T.astt: 2.-Partial stocking history of hatchery-produced Colorado pikeminnow in the upper Colorado River basin. Kenney Reservoir is an impoundment of the While River in the Green River basin. Date Number of fish stocked Stocking site Broodfish designation 1980 1,500 5-year-old fish. Colorado River Yampa DX-FI (74) 1982 3Q,000 fingerlings . Colorado River Yampa DX-Ft (74) 1983 42,059 fingerlings Colorado River Yampa DX-Ft (74) 1984 25,802 juveniles Colorado River Yampa DX-Ft (74) 1984 30,649 juveniles Colorado River Yampa DX-Ft (74) 1989 30,000 juveniles Kenney Reservoir Yampa DX-Ft (74) 1990 30,000 juveniles Kenney Reservoir Yampa DX-FI (74) 1991 30,000 juveniles Kenney Reservoir Yampa DX-Ft (74) 1996 114,480 fingerlings San Juan River Colorado-Green DX-Ft (81) 1997 116,878 fingerlings San Juan River Colorado-Green DX-Ft (81) 1998 10,571 fingerlings San 7uan River Colorado-Green DX-Ft (81)