Laserfiche WebLink
<br />6 <br /> <br />1 <br />1 <br />1 <br />t <br /> <br /> <br />1 <br />1 <br /> <br />1 <br />u <br />F1 <br /> <br />Li <br />Introduction <br />The Colorado pikeminnow Ptvchocheilus lucius is indigenous within the Colorado River basin of <br />the southwestern United States (Holden and Wick 1982). It is a large river cyprinid listed as endangered by <br />the U. S. Fish and Wildlife Service in 1967 (U. S. Office of the Federal Register, 32;43[1967]:40001). <br />Declines in fish numbers and range have been associated with habitat fragmentation and blocked passage, <br />water diversions, lost spawning and nursery habitat, dewatering, contaminants, and introductions of non- <br />native fishes (Minckley and Deacon 1991)(Figure 1.). More complete historical information on the <br />Colorado pikeminnow can be found in Vanicek and Kramer (1969), Holden and Wick (1982), U. S. Fish <br />and Wildlife Service (1987a), and Tyus (1991). <br />The Endangered Species Act (1973) recovery goals for Colorado pikeminnow, in general, call for <br />protection, maintenance, and establishment of self-sustaining populations throughout the historical range of <br />the Colorado River basin (U. S. Fish and Wildlife Service 1990). However, population identification and <br />status determination is difficult because very little is known of the genetic structure and demographic <br />characteristics, particularly fish movement and behavior associated with reproduction (Tyus 1986). The <br />reason this study was conducted was to try and determine such genetic structure. <br />Biochemical genetic analyses of two wild populations provided some basic genetic information on <br />Colorado pikeminnow (Ammerman and Morizot 1989), but did not address suspected adult spawning <br />populations. Hardy-Weinburg disequilibrium at two loci in wild young-of-the-year populations, as found <br />by Ammerman and Morizot (1989), could indicate sampling multiple, mixed, populations rather than a <br />single panmictic population. However, Ammerman and Morizot (1989) examined only young-of-the-year <br />(YOY) fish from the wild populations; adult or spawning populations have not been directly examined. <br />Offspring of two captive Colorado pikeminnow populations, presently maintained at Dexter National Fish <br />Hatchery and Technology Center (Dexter NFH&TC) as broodfish populations, were also characterized for <br />44 presumptive genetic locus products (Ammerman and Morizot 1989). These data indicate that the <br />captive fish were representative of the two wild populations examined. Estimates of genetic identity among <br />the four populations examined were similar to those observed among populations of other cyprinid species <br />(Ammerman and Morizot 1989). Mean heterozygosity values for wild and captive Colorado pikeminnow <br />populations also were similar to other cyprinids, and were maintained throughout the geographical range <br />examined (Ammerman and Morizot 1989). <br />Plans to use production from the Dexter NFH&TC fish to augment tributaries of the Colorado <br />River are ongoing. Numerous re-introductions of Colorado pikeminnow have been made into the Colorado <br />River basin (Appendix 1; Table 1) and include, but are not limited to, the Green River tributary, White <br />River (Kenney Reservoir) in the late 1980s and early 1990s (Trammel et al. 1993) and the Colorado River <br />mainstem (Grand Valley) in the early- to mid- 1980s. All re-introductions that date were made with fish <br />derived from the Yampa River (Roger Hamman, Dexter NFH&TC, personal communication). Fish were <br />stocked into the San Juan River in 1996, 1997, and 1998. These fish were progeny of mixed Colorado <br />River and Green River broodfish (Roger Hamman, Dexter NFH&TC, personal communication). However, <br />prior to further stocking of fish into areas that may contain additional populations of Colorado <br />pikeminnow, characterization of wild populations is necessary to prevent any further, or potential, co- <br />mingling of populations. <br />Migration, spawning and recruitment are subjects of great interest and debate among management <br />biologists responsible for recovery efforts. Tyus (1986) suggested that Colorado pikeminnow tend to <br />migrate to natal spawning areas and that such behavior is characteristic of the species. If true, genetic <br />differentiation among populations associated with different spawning areas could be, and has been, <br />predicted (Tyus 1991). Such genetic differentiation among populations could impact recovery efforts <br />utilizing fish produced by captive propagation as well as maintenance of refuge populations and broodfish <br />development. <br />The purpose and objectives of the Colorado pikeminnow "genetics study" were outlined in a Scope <br />of Work entitled "Genetic Survey of Colorado Pikeminnow", 6/21/93 (FY93, #23). That proposed work <br />was to initiate and conduct a PCR-based assay or assessment of Mendelian polymorphisms from <br />