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Last modified
7/14/2009 5:02:32 PM
Creation date
5/18/2009 12:33:50 AM
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UCREFRP
UCREFRP Catalog Number
7984
Author
Maddux, H. R., L. A. Fitzpatrick and W. R. Noonan.
Title
Colorado River Endangered Fishes Critical Habitat - Draft, Biological Support Document.
USFW Year
1993.
USFW - Doc Type
Salt Lake City, Utah.
Copyright Material
NO
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STATUS <br />Once very common throughout the Basin, Colorado squawfish populations have declined <br />from historic levels. Its present range is restricted primarily to the Upper Basin; Colorado <br />squawfish have been reintroduced in the Salt and Verde Rivers in Arizona. As with the other <br />three endangered fish, the decline of Colorado squawfish populations is due to various <br />human-initiated physical and biological changes in the Colorado River. <br />HABITAT REQUIREMENTS <br />Spawning Habitat <br />Most of the information about Colorado squawfish reproduction is known from the Yampa <br />and Green Rivers, where the fish spawns in white water canyons. This reproduction was <br />associated with declining flows in June, July, or August, and average water temperatures <br />ranging from 71 ° to 77°F depending on annual hydrology. After spawning, adult Colorado <br />squawfish utilized a variety of riverine habitats, including eddies, backwaters, shorelines, and <br />others (Tyus 1990). Specific spawning sites of Colorado squawfish have not been identified <br />outside of the Green River Basin. In the mainstream Colorado River, McAda and Kaeding <br />(1991) suggested that Colorado squawfish spawning may have been adversely impacted by <br />construction of mainstream dams and a 48 percent reduction in peak discharge. <br />Tyus (1990) reported radiotracking of 57 Colorado squawfish to spawning grounds in the <br />Green and Yampa rivers and capture of an additional 208 ripe fish at these locations from <br />1980 to 1988. Numerous capture locations of ripe fish and behavior of radio-tagged fish <br />suggested that egg deposition and fertilization were concentrated in relatively small river <br />reaches (< 12 miles) where large, deep pools, eddies and submerged bars of cobble, gravel, <br />boulder and sand substrates were associated with the main channel. However, substrates in <br />two spawning reaches were different. Substrates in Yampa Canyon were dominated by <br />imbricated cobbles intermingled with gravel and sand. In the Green River, substrates were <br />boulders, sand and silt. Although high turbidity precluded direct observation of fish or <br />deposited sex products, the signal source of radio-tagged fish indicated that fish rested or <br />staged in pools or eddies (average depth, six feet; average velocity, 1.0 ft/sec) for hours or <br />days, and moved abruptly to nearby cobble or boulder bars (average depth three feet; <br />average velocity, 1.9 ft/sec), where they remained from 30 minutes to three hours and <br />presumably spawned before returning to their former habitats. <br />Colorado squawfish spawn after the peak runoff season from June to mid-August. Spawning <br />begins when water temperature reaches 64° to 77°F, and peak spawning activity occurs <br />between 72° to 77°F (Haynes et al. 1984; Archer et al. 1985; Tyus 1990). During the <br />decline in water level following peak runoff, spawning adult fish move into run-riffle areas <br />and also occupy run, eddy, and pool habitats (Tyus 1990). Spawning migrations were <br />initiated at water temperatures of 57 ° to 68 °F, and spawning occurred at temperatures of <br />72°F (range 59° to 82°F), but migrations and spawning periods varied between years. <br />20
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