The sicklefin chub and sturgeon chub, two minnow species native to the Missouri
River basin and Mississippi River, do not warrant listing as threatened or
endangered species under the Endangered Species Act, the U.S. Fish and Wildlife
Service announced today.
The Service made the finding in response to a petition to list the species as
endangered from American Rivers, Environmental Defense Fund, Mini Sose
Intertribal Water Rights Coalition, National Audubon Society, and Nebraska
Audubon Council. The petitioners cited impacts associated with the construction
and continuing operation of Missouri River main stem dams and channelization as
the principal threats affecting these species and their habitats.
In response to the petition, Service biologists conducted a status review of the
two species that indicates populations are more abundant and better distributed
throughout their range than previously believed.
"While the historic range of the sicklefin and sturgeon chub has been reduced,
we have concluded that stable, self-sustaining populations remain widely
distributed throughout their range," said Ralph Morgenweck, the Servicešs
regional director for the Mountain-Prairie Region. "We estimate that the
sicklefin chub currently occupies 54 percent of its historic range in the
Missouri River basin and the sturgeon chub occupies 55 percent of its historic
range in the Missouri River. The sturgeon chub also is found in 11 of the 30
tributaries of the Yellowstone and Missouri Rivers where they have been
The sicklefin and sturgeon chub are members of the Cyprinidae or minnow family.
The sicklefin chub is 1.4 to 4 inches long with usually yellowish or tan
coloring on the back and silvery-white on the belly. The sturgeon chub is 1.5 to
3.8 inches long with tan to pale green on the back and cream to white on the
belly. A few black speckles occasionally are present on the sides and back. Both
species only inhabit free flowing rivers with relatively high turbidity.
The Service traditionally sampled chub populations using seines to collect fish
in shallow water, but in 1994 biologists started conducting studies using
benthic trawls to sample fish populations in deep water habitats where seines
Studies conducted in Montana, North Dakota, and Missouri using benthic trawls
indicate that sicklefin and sturgeon chub comprise a significant portion of the
fish population in segments of the Yellowstone and Missouri rivers. Also, recent
studies conducted by the Missouri Department of Conservation documented viable
populations of both sicklefin and sturgeon chub in the middle Mississippi River
and in the Wolf Island area of the lower Mississippi River.
"The Service is still very much concerned about sicklefin and sturgeon chub
populations and the health of the Missouri River ecosystem. Because the chub
populations do not warrant listing as either threatened or endangered at this
time does not mean that they have not suffered serious decline. We will continue
to closely monitor the chub populations and will revisit possible listing if new
information regarding the status of the chubs becomes available," said
Under the Act, a species is listed as endangered when it is in danger of
extinction throughout all or a significant portion of its range. Threatened
means a species is likely to become endangered within the foreseeable future.
Historically, the sicklefin chub has been collected from the lower Yellowstone
River, Missouri River, and the Mississippi River downstream from St. Louis. Its
range extended from Montana to Mississippi, including waters in or bordering 13
States. The sturgeon chub historically has been collected in the same locations
as the sicklefin plus an additional 30 tributaries of the Yellowstone and
The Service concurs with the petitioners that the primary factor affecting
sicklefin and sturgeon chub populations is the construction and continued
operation of the six main stem dams built on the Missouri River as part of the
Pick Sloan Plan. The dams have altered the riveršs form, seasonal flows, water
temperature, sediment transport, turbidity, and nutrient input. However, the
impacts associated with the dams have been in place for more than 35 years and
the sicklefin and sturgeon chub remain present in substantial numbers where
turbidity levels and flow regimes in the rivers still provide needed habitat
When determining whether a species warrants listing, the Service assesses both
detrimental and beneficial actions that will likely occur in the foreseeable
future. The most significant action affecting chub habitat is the U.S. Army
Corps of Engineersš system of dams on the main stem. The Corps of Engineers is
currently undertaking an evaluation of their master water control manual through
an Environmental Impact Statement planning effort.
As part of this planning effort, the Service completed the Missouri River
Biological Opinion in November 2000. The Biological Opinion provides
conservation measures and alternatives to avoid jeopardizing the continued
existence of the endangered pallid sturgeon and least tern, and the threatened
piping plover. When implemented, these conservation measures are expected to
benefit sicklefin and sturgeon chub through habitat restoration and creation
projects, improved water temperature, and flow modifications designed to mimic
the natural flows of the river.
Biologists note that the two chub species are not as vulnerable to manmade
changes to the rivers as the endangered pallid sturgeon. For example, the chubs
have short reproduction cycles and do not require long, unblocked stretches of
river habitat to spawn successfully as pallid sturgeons do.
For more information about the sicklefin and sturgeon chubs, visit the Servicešs
web site at http://mountain-prairie.fws.gov/endspp/chubs
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