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ARTIFICIAL SPAWNING OF COLORADO SQUAWFISH AND <br />GROW-OUT POND INVESTIGATIONS <br />Introduction <br />Artificial propagation of fish is a potentially important component of <br />recovery programs for the endangered fishes of the upper Colorado River <br />basin. The decline of Colorado squawfish and razorback sucker in their <br />remaining habitats may necessitate stocking to augment wild subpopulations. <br />In addition, much can be learned about the behavior and habitat requirements <br />of endangered fish by studying hatchery-reared individuals released in <br />nature. <br />During 1982-84, hatchery-reared Colorado squawfish (35-95 mm long) were <br />experimentally stocked into the upper Colorado and lower Gunnison rivers <br />near Grand Junction, Colorado. Although individuals recaptured during <br />subsequent years had growth rates comparable to those of wild fish, the <br />small numbers captured suggested that the rate of survival of the stocked <br />fish might have been low. However, the observation that hatchery-reared <br />fish made up a seemingly large proportion of all 100-200-mm-long Colorado <br />squawfish caught suggested that the early-life survival of wild squawfish <br />too was quite limited in the Colorado River. Concurrent with those <br />preliminary efforts in the upper basin, hatchery-reared Colorado squawfish <br />and razorback sucker were experimentally stocked into unoccupied reaches of <br />former habitat in the lower Colorado River basin. Brooks (1986) found that <br />stocked razorback sucker were heavily preyed on by catfish (Ictaluras spp.). <br />Rearing squawfish to a length of 200-250 mm before stocking may be necessary <br />to insure greater survival of stocked fish. A recent study of growth and <br />30