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North Dakota's

Federally Listed Endangered, Threatened, and Candidate Species – 1995


Sturgeon Chub (Macrhybopsis gelida)

JPG -- species photo gif--species map

Official Status: Candidate

Historical Status:
Sturgeon chub were first collected from the Milk River in Montana during the Pacific Railroad Surveys of 1853-1855. Their historic range included the Missouri and Lower Mississippi Rivers and major tributaries. Thcy have been collected at nearly 200 different locations.

Present Status:
Sturgeon chub have been most recently collected on the Powder River in Wyoming and Montana, the Yellowstone River in Montana and on portions of the Missouri River in Nebraska and Missouri. An extensive survey of historic sturgeon chub collection occurred in 1989-1990 yielded only one specimen from the Yellowstone River and 158 from the Powder River. Sturgeon chub population levels on the Powder River have remained nearly steady over the past decade. The most recent sturgeon chub collections in North Dakota occurred in 1977 on the Little Missouri River.

Habitat:
Sturgeon chub are most commonly collected in gravel and rock rapids. They are also collected in sandy areas as long as some gravel is present. High turbidity and swift currents are vital habitat components. Sturgeon chub are most frequently collected in water less than 3 feet deep.

Life History:
The oldest recorded sturgeon chub have been 4 years of age. However, less than 5% of sturgeon chub even live until age 3. Sturgeon chub mature in their second year and spawning occurs in the spring and early summer at water temperatures of 65-72° F. Fish ready to spawn have been collected from early June until the end of July. Approximately 15-20% of a ripe female's body weight is composed of eggs. Spawning habitat consists of shallow gravel and rock rapids. No detailed sturgeon chub feeding studies have been made, but their stomachs have contained unidentifiable insect parts. Sturgeon chub may be preyed upon by walleye, sauger, pike and burbot (ling).

Aid to identification:
Sturgeon chub are mottled olive green-brown on their back and have a silvery-cream belly. Their most distinguishing features are the small ridges of skin, called keels, found on each scale on their upper body. These keels can be seen without aid of a microscope on larger specimens. They are believed to help the chub maintain position in fast currents. Sturgeon chub have dense concentrations of tiny external taste buds on the lower head, body and fins. They have small eyes and a long fleshy snout which overhangs the mouth. They reach a maximum length of 4 inches. Sturgeon chub are quite similar in appearance to longnose dace. Examining the specimen for keels is the best differentiating characteristic.

Reasons for decline:
The decline in sturgeon chub abundance over much of their range can be attributed to habitat loss. Inundation by reservoirs likely directly eliminated some sturgeon chub habitat, while also preventing migration and repopulation of some tributary streams. Siltation, flow reduction, turbidity reduction, and increased predation and competition may have all contributed to population reduction and elimination in some areas.

Comments:
The Powder River in Wyoming and Montana currently supports the largest known reproducing population of sturgeon chub. Reproduction has occurred each year from 1988-1990 despite drought conditions. Sturgeon chub are minnows and are not related to the much larger, true sturgeons.

References:
The Fishes of Missouri, by W. L. Pflieger, 1975. Published by the Missouri Department of Conservation.
The biology of the sturgeon chub (Hybopsis gelida Girard) in Wyoming D. Stewart, 1981. A M.S. thesis from the University of Wyoming, Laramie, Wyoming. Population status and characteristics of a rare Hybopsis species and two ecologically similar species in the Missouri River Basin by S. Werdon, 1992. A M.S. thesis from South Dakota State University, Brookings, South Dakota.


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