9383 - Laserfiche WebLink

Home Browse Search

I I I I I I I I I I I I I I I I I I I Table 2. Proportion of phenotypic intergrades in six populations of humpback chub, based on ifFP ,ogy of adult specimens. '~:"-'~ Population or Years Total Percent of Total Number Source Habitat Sampled Number G. cypha G. robusta G. elegans Gila spp. (N) Black Rocks 1979-81 552 29 70 0 1 Valdez et al. 1982 1983-85 569 47 44 <1 9 Kaeding et al. 1990 1988 91 58 39 0 3 McAda et al. 1994 1991 127 58 25 0 17 McAda et al. 1994 Westwater Canyon 1979-81 226 19 77 0 4 Valdez et al. 1982 1986 126 36 31 0 33 McAda et al. 1994 1988 143 72 27 0 1 McAda et al. 1994 1991 247 47 45 0 8 McAda et al. 1994 Grand Canyon 1980-81 433 100 0 0 0 Kaeding and -- Little Colorado Zimmennan 1983 River Grand Canyon 1990-93 1791 100 0 0 0 Valdez and Ryel1995 --Colorado River Yampa Canyon 1986-89 922 14 86 0 0 Karp and Tyus 1990 Desolation-Gray Canyons Cataract Canvon 1979-81 48 46 23 13 18 Valdez 1990 Proposed releases of bonytail in or near habitat occupied by humpback chub could increase the likelihood of hybridization among the three Gila species if numbers of hatchery releases greatly outnumber wild individuals and the hatchery fish become active spawners and contributors to the wild genetic pool. Such hybridization co amp" the existing genetic pool, disproportionately affecting the genetic diversity of h Use of hatchery fish (progeny of cultured broodstock to expand or augment existing populations of humpback chub is also not recommended. Existing genetic makeup of wild fish could be compromised by selectively bred hatchery products. Use of hatchery fish is not considered a necessary component of recovery for this species since wild, self-sustaining populations exist. The use of hatchery fish for other endangered species, such as razorback sucker and bonytail is justified because of low numbers of wild individuals and the n augment those declined populations. Provisions and recommendations of the Geneti 21