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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 />Y <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. <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. Individuals recaptured during subsequent <br />years had growth rates comparable to those of wild fish; however, the small <br />numbers captured suggested that the rate of survival of the stocked fish may <br />have been low. Concurrent with those efforts, hatchery-reared Colorado <br />squawfish and razorback sucker were experimentally stocked into unoccupied <br />reaches of former habitat in the lower Colorado River basin. Researchers <br />there found that stocked razorback sucker were heavily preyed on by catfish <br />(Brooks 1986). <br />Rearing squawfish to a length of 200-250 mm before stocking may be <br />necessary to insure greater survival of stocked fish. A recent study of <br />growth and survival of Colorado squawfish stocked in gravel-pit ponds near <br />Grand Junction, Colorado, demonstrated that growth rate in a pond <br />environment (warm water; abundant forage fish) can be twice that of fish in <br />either river or hatchery environments (Osmundson 1986). Rearing squawfish <br />17