Abstract
The desert pupfish, Cyprinodon macularius, and its allies were formerly <br /><br />common in sloughs and backwaters of the Gila River in Arizona, and the lower <br /><br />Colorado River in the United States and Mexico. They also were common in <br /><br />shoreline pools and irrigation drains of the Salton Sea in California. In spite of <br /><br />their remarkable tolerance for environmental extremes and high reproductive <br /><br />rate, details of which are summarized herein, the species has undergone a serious <br /><br />decline in numbers. Since the late 1 800s fish have disappeared in association with <br /><br />activities of humans such as dam building, diversions of water, ground-water <br /><br />pumping, and pesticides. They have been further threatened by encroachment of <br /><br />non-native vegetation such as tamarisk, Tamarix spp. The most rapid decline <br /><br />has occurred in recent years in association with introduced fishes. Through pre- <br /><br />dation, aggression, and various behavioral activities that interfere with repro- <br /><br />duction, introduced species have driven pupfish to the brink of extinction. A <br /><br />natural population of reasonable size occurs today only at Quitobaquito Spring <br /><br />in Organ Pipe Cactus National Monument in Arizona. Populations of insecure <br /><br />status, subject to wide fluctuations in density, occur south of Quitobaquito in Rio <br /><br />Sonoyta, Sonora, Mexico, and in San Sebastian Marsh and Salt Creek near the <br /><br />Salton Sea in California. On 31 March 1986 a final rule was published in the <br /><br />Federal Register listing Cyprinodon macularis as an endangered species. Desig- <br /><br />nated critical habitat at San Sebastian Marsh, Imperial County, California at best <br /><br />contains an unstable population of desert pupfish.
