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 Services 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 historically collected."
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 are ineffective.
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 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 Morgenweck.
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 Missouri rivers.
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 rivers 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 conditions.
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 Engineers 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 Services web site at http://mountain-prairie.fws.gov/endspp/chubs .
The U.S. Fish and Wildlife Service is the principal Federal agency responsible for conserving, protecting and enhancing fish, wildlife and plants and their habitats for the continuing benefit of the American people. The Service manages the 94-million-acre National Wildlife Refuge System which encompasses more than 530 national wildlife refuges, thousands of small wetlands and other special management areas. It also operates 70 national fish hatcheries, 64 fishery resource offices and 78 ecological services field stations. The agency enforces Federal wildlife laws, administers the Endangered Species Act, manages migratory bird populations, restores nationally significant fisheries, conserves and restores wildlife habitat such as wetlands, and helps foreign governments with their conservation efforts. It also oversees the Federal Aid program that distributes hundreds of millions of dollars in excise taxes on fishing and hunting equipment to state fish and wildlife agencies.
