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.
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.
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.
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.
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.