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7/14/2009 5:02:32 PM
Creation date
6/1/2009 12:41:56 PM
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UCREFRP
UCREFRP Catalog Number
8036
Author
Haynes, C. M., R. T. Muth and G. T. Skiba.
Title
Identification of Habitat Requirements and Limiting Factors for Colorado Squawfish and Humpback Chubs (July 1 1982 to June 30 1983).
USFW Year
1983.
USFW - Doc Type
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were collected between 7 and 25 August at 10 sites between km 0.5 to <br />19.6 (stratum 1) in low-velocity habitats, i.e., backwaters (3), embayment <br />(1), pool (2), concavity (1), and 13 in isolated pools. <br />Age at time of capture (using methods described in Haynes and Muth <br />(1982) and Haynes et al., (in press)) was 5-15 days post-spawning for <br />drift collections (27 Jul) and 9-45 days for seine collections in the <br />Colorado River study area. Estimated spawning dates in the Colorado River <br />are 13-23 July for drift-caught animals and 10 July - 15 August for seine <br />specimens. In the Yampa River, spawning is estimated to have occurred <br />from 6 to 28 July 1982. <br />Analysis of YOY squawfish, 1979-82 <br />Since 1979, 102 YOY squawfish have been collected in the Colorado River <br />study area (Table 4), of which 89 were collected in Stratum H and 13 <br />in Stratum K. In the Yampa, only Stratum 3 (Deerlodge Park area) was <br />sampled in 1979 while Cross Mountain Canyon (Stratum 5), Lily Park (Stratum <br />4), and the downstream Dinosaur National Monument reach (Strata 1 and 2) <br />were added in 1980. A total of 89 YOY squawfish has been collected in <br />the Yampa during 1980-82 (Table 4), all of which were collected in the <br />lowermost 30 km of Dinosaur National Monument (Stratum 1). <br />In the Colorado River, estimated spawning dates during 1979-82 based upon <br />maximum and minimum size per collection and estimated growth rate ranged <br />from 18 June (1981) to as late as 26 August (1980) (Fig. 1). In the <br />Yampa, spawning is estimated to have occurred as early as 16 June (1980) <br />and as late as 3 August (1981) (Fig. 2). In 1981, we estimated that <br />spawning occurred in the lower Yampa as early as 25 June, which correlates <br />closely with the dates and locations of ripe radio-marked adults observed <br />over apparent spawning gravels in the same area by Tyus et al. (1981), i.e., <br />26 June - 10 July km 19.6 - 0.2. Comparative data for 1982 are not <br />available. Fish growth-rate is temperature-dependent (De Vlaming 1972), <br />and lower late-August water temperatures can be expected to reduce rate <br />of squawfish growth. Therefore estimated late-summer spawning dates should <br />probably be adjusted forward. Since growth rate-temperature data for <br />young squawfish are lacking, it is not possible, however, to determine to <br />what extent late-season spawning periods should be corrected. <br />Our estimated spawning periods indicate that squawfish spawning occurred <br />as water levels were decreasing and water temperatures were rising <br />(Fig. 1, 2). The possible interrelationships between spawning, flows, <br />and water temperature have been the subject of intense discussion and <br />speculation and has been summarized by Haynes et al. (in press}, <br />At this time, the influence of temperature upon spawning is apparently <br />based upon observations of adult ripeness by Vanicek and Kramer (1969), <br />hatchery observations by Toney (1974) and Hamman (1981), and this report. <br />>_,~ <br />
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