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WSP03308
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Last modified
1/26/2010 12:49:41 PM
Creation date
10/11/2006 11:39:11 PM
Metadata
Fields
Template:
Water Supply Protection
File Number
8220.105.I
Description
Colorado River-Water Projects-Navajo-Environmental Studies
State
CO
Basin
Colorado Mainstem
Water Division
5
Date
1/26/2004
Title
Navajo Dam EIS-Draft Bio Opinion-US Fish and Wildlife Service New Mexico Ecological Services Field Office
Water Supply Pro - Doc Type
Report/Study
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<br />.' <br /> <br />, <br /> <br />. <br /> <br />. <br /> <br />Area Manager <br />DRAFT <br /> <br />12 <br /> <br />the particular life stage for the species. The physical habitat includes areas of the Colorado River <br />system that are inhabited or potentially habitable for use in spawning and feeding, as a nursery, <br />Or serve as oorriuurs ut;L-weelllhesc areas. In addition, oxbow"s, backw"atcrs, and oL~er :::reas in tJ.:!e <br />100-year floodplain, which when inundated provide access to spawning, nursery, feeding, and <br />rearing habitats, are included. Food supply, predation, and competition are important elements <br />of the biological environment. <br /> <br />Life History <br /> <br />The life history phases that appear to be most limiting for pikeminnow populations include <br />spawning, egg hatching, development oflarvae, and the first year ofli fe. These phases of <br />pikeminnow development are tied closely to specific habitat requirements. Natural spawning of <br />pikeminnow is initiated on the descending limb of the annual hydrograph as water temperatures <br />approach or exceed 20'C (680F) (Vanicek and Kramer 1969, Hamman 1981, Haynes et al. 1984, <br />Tyus 1990, McAda and Kaeding 1991). Temperature at initiation of spawning varies by river. <br />In the Green River, spawning begins as temperatures exceed 20-23'C (68-730F); in the Yampa <br />River, 16-23T (61-680F) (Bestgen et al. 1998); in the Colorado River, 18-22'C (64-72'F) <br />(McAda and Kaeding 1991); in the San Juan River temperatures were estimated to be 16-220C <br />(61-72'F). Spawning, both in the hatchery and under natural riverine conditions, generally <br />occurs in a 2-month period between late June and late August. However, sustained high flows <br />during wet years may suppress river temperatures and extend spawning into September (McAda <br />and Kaeding ]991). Conversely, during low flow years, when the water wanns earlier, spawning <br />may commence in mid-June. <br /> <br />Temperature also has an effect on egg development and hatching success. In the laboratory, egg <br />development was tested at five temperatures and hatching success was found to be highest at <br />20'C (68'F), and lower at 25'C (7TF), Mortality was 100 percent at 5,10,15, and 30'C (41, 50, <br />59, and 86'F). In addition, larval abnormalities were twice as high at 25"C (77'F) than at 20'C <br />(680F) (Marsh 1985). <br /> <br />Experimental tests of temperature preference of yearling (Black and Bulkley I 985a) and adult <br />(Bulkley et al. 1981) pikeminnow indicated that 25'C (7TF) was the most preferred temperature <br />for both life phases. Additional experiments indicated that optimum growth of yearlings also <br />occurs at temperatures near 250C (7TF) (Black and Bulkley 1985b). Although no such tests <br />were conducted using adults, the tests with yearlings supported the conclusions of Jobling (1981) <br />that the fmal thermal preference of25'C (7TF) provides a good indication of optimum growth <br />temperature for all life phases. <br /> <br />Most information on pikeminnow reproduction was gathered from spawning sites on the lower <br />20 miles (12.2 kilometers) of the Yampa River and in Gray Canyon on the Green River (Tyus <br />and McAda 1984, Tyus 1985, Wick et al. 1985, Tyus 1990). Pikeminnow spawn after peak <br />runoff subsides and spawning is probably triggered by several interacting variables such as <br />daylength, temperature, flow level, and perhaps substrate characteristics. Known spawning sites <br />in the Yampa River are characterized by riffles or shallow runs with well-washed coarse <br />substrate (cobble containing relatively deep interstitial voids (for egg deposition)) in association <br /> <br />O!l{08 <br />
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