Like most southwest native fish, species of chub (Gila sp.) have been devastated by a combination of non-native fish introductions and habitat destruction related to livestock grazing, water withdrawal, dams, roads and urban and agricultural development. Nine chub species are native to the southwest, including the roundtail, headwater, bonytail, Virgin River, Gila and humpback chubs, all native to the Colorado River basin, and Sonora, Yaqui, and Chihuahua chubs native to drainages in Mexico. Of these, all are listed or proposed for listing as threatened or endangered under the Endangered Species Act (ESA), except the roundtail and headwater chubs. Soon all chub species may be protected under the ESA. The Center for Biological Diversity along with Sky Island Alliance filed a petition on 4-1-2003 to list these last two species as endangered.

Minnows with slender, silver bodies and forked tails, roundtail and headwater chubs have declined to near extinction. In the lower Colorado River basin, the roundtail chub occupies less than 20% of its historic range in only 19 small tributaries to the Gila, Verde, Salt, Bill Williams and Little Colorado Rivers. Likewise, the headwater chub occupies less than 40% of its already small historic range in 13 tributaries to Tonto Creek and the Verde and Gila Rivers.

In the last century, aquatic ecosystems in the southwest have been devastated by the often synergistic effects of habitat degradation and non-native species. Livestock grazing, water withdrawal, dams, roads and urban and agricultural development have reduced stream-flows, polluted streams with sediment, altered flooding patterns and caused stream downcutting across the southwest, all to the detriment of native aquatic species.

Adding insult to injury, numerous species of non-native fish species have been introduced to southwest rivers and streams. The Colorado River, for example, harbors at least 67 non-native fishes. These non-natives compete with and prey on native species, often leading to their complete elimination. Recent research on the roundtail chub and other native fish species demonstrates non-natives are more likely to dominate streams impacted by habitat degradation or where dams have eliminated natural flooding. On the upper Verde River in Arizona, native fish species only dominate in pristine upper sections. Lower sections of the river that have been impacted by a burgeoning human population, dams and overgrazing primarily support non-natives. These results highlight the value of native fish as indicators of ecosystem health and the need to protect habitat if we are to save native fish, such as roundtail and headwater chubs.

You can help save the roundtail and headwater chubs by writing to Steve Spangle, Field Supervisor, Ecological Services Arizona Field Office, U.S. Fish and Wildlife Service, 2321 W. Palm Road, Suite 103, Phoenix, Arizona 85021-4951, to let them know you support listing the roundtail and headwater chubs as endangered species.

graphic Andrew Rodman ©2002
June 9, 2003
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