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Show CEA Report Environmental - Ecology Impact on Fish and Wildlife Fragmentation of the Colorado River and Glen Canyon ecosystems by Glen Canyon Dam has separated species, reduced the abilities for natural distribution corridors, and corrupted the ecological processes that historically defined the Colorado River system. Today the remaining species are isolated from their historic genetic distribution patterns with the result eventually leading to species loss. 35 • Prior to the reservoir, 79 species of plants, 155 species of birds and 12 species of mammals lived along the streamsides of Glen Canyon. Flooding of the canyon drowned species not able to relocate and destroyed the natural habitats of others. 36 • The river terraces in Glen Canyon were home to 164 species of plants, 38 species of birds and 22 species of mammals. Like the streamside organisms, the terrace organisms drowned or had their habitats destroyed during the flooding of Glen Canyon. 36 • Habitat destruction is a major threat to native species. As the dam prevents natural flooding, native vegetation such as cottonwood and willow cannot regenerate. Many species rely on this indigenous habitat for their survival and once this becomes altered or destroyed, populations are affected. Once habitats are altered, food sources can be altered. 35 • Glen Canyon provided a nursery area for native fish and bird life, much more so than Grand Canyon. • Several factors have contributed to the decline of amphibian and reptile species diversity and population size. Glen Canyon Dam has created a large impact on the habitat and species that historically utilized the Glen Canyon area. 35 • The increased tourism at Powell reservoir has created impacts from motorboats, jet skis, and garbage. This environmental and noise pollution has the potential to greatly affect the species number and diversity in Glen Canyon. Endangered and Threatened Species • Four native species of fish- the pike minnow ( formerly the Colorado squawfish), the bonytail chub, the humpback chub, and the razorback sucker- are endangered. The pike minnow and the bonytail chub are no longer found in the Grand Canyon. The decline of these species is largely attributed to the impacts of Glen Canyon Dam. In 1994 the u. s. Fish and Wildlife Service designated 3168 kilometers of the Colorado River and its tributaries as critical habitat for the survival of these species. 6 Introduced species, thriving in the cold, clear post- dam waters have increased predation of and competition with native species. 6 The Endangered Species Act requires all federal agencies to use their authorities to help preserve a listed species. Lack of adequate water, nutrients, and sediment reaching the Colorado River Delta and Sea of Cortez has reduced critical habitat, desiccated the delta, and shrunk the wetlands. This was especially severe during the twenty years required to fill Powell reservoir, during which time the delta was essentially destroyed. The green sea turtle, Yuma clapper rail, desert pupfish, vaquita, and totoaba are currently threatened. Their decline is due, in part, to habitat degradation. 6 The Reservoir would have to be drained over a long time period- perhaps 15- 20 years- to avoid detrimental ecological effects to endangered and threatened species. mmmm E99 Incubation Range mmmmm Spawning Range Current Temperature Range NATIVE Humpback Chub Razorback Sucker Ranneimourh Sucker Bluehead Sucker Speckled Dace NON- NATIVE Channel Catfish Common Carp Fathead Minnow Striped Bass Red Shiner Green Sunfish Black Bullhead Rainbow Trout Cutthroat Trout Brown Trout laaai 32 4150596* 778695 Degrees Fahrenheit Figure 6 Spawning and egg incubation temperatures for fish species in Grand Canyon. Shaded region indicates current temperature range. Note current temperature range is too cold for successful spawning and incubation of most native fish species. ( BOR 1996EIS) page 9 |
