Northern Prairie Wildlife Research Center
Federally Listed Endangered, Threatened, and Candidate Species 1995
Plains Minnow (Hybognathus placitus)
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- Status: Former Candidate (Note: As of February 28, 1996, this species is no longer listed as a Candidate species. However, it remains a species of management concern.)
- Historical Status:
- The plains minnow is found from Louisiana to North Dakota. The plains minnow is more abundant in the upper Missouri River watershed but undergoes a gradual decline in abundance downstream. It is uncommon in the lower Mississippi, reaching the downstream limit of its distribution near the mouth of the Ohio River.
- Present Status:
- Plains minnows are most often collected in small streams in western North Dakota. They still inhabit some unchannelized and channelized portions of the Missouri and Mississippi Rivers. Typically they are collected from the Little Missouri, Yellowstone, Cannonball, and Heart rivers and Cedar and Beaver (Golden Valley County) Creeks. The plains minnow is also found in lakes Sakakawea, Oahe, and Bowman-Haley.
- Although the plains and western silvery minnow occur at the same localities, they tend to be segregated ecologically; the plains minnow predominates in the river channel where there is a sandy bottom and some current, whereas the western silvery minnow is more abundant in protected areas with little current and a silt bottom.
- Life History:
- Plains minnows live in schools near the bottom of large prairie streams, often in association with western silvery minnows. In North Dakota the plains minnow spawns from May through August. Detailed food studies have not been conducted but the food typically consists of microscopic plant and animal material found on stream
bottoms. The plains minnow constitute important forage for the young of game species inhabiting the same habitat.
- Aid to identification:
- Very similar to the central silvery minnow but differing in these respects: eye smaller, its diameter going 4.4 to 4.9 times into head length; diameter of eye much less than width of mouth opening; basioccipital process (a backward extension of bone at lower rear margin of skull) narrow and peg-like, its back margin nearly straight; greatest width of basioccipital process going 2.4 to 4 times into its greatest length; muscles of pharyngeal arches nearly touching at point of attachment to basioccipital process. The plains minnow is typically 3 to 6 inches long.
- Reasons for decline:
- The greatest threats to the plains minnow are nonpoint source pollution, and mainstem impoundments impacting natural flow regimes. Other threats across its range include dewatering of rivers from irrigation and degradation of riparian areas.
- Original references to the western and central silvery minnows in North Dakota were probably plains minnows.
- Freshwater fishes of Canada, by W. B.
Scott and E. J. Crossman, 1973. Fisheries Research Board of Canada. Bulletin 184.
The Fishes of Missouri, by W. L. Pflieger, 1975. Published by the Missouri Department of Conservation.
Northern Fishes, by S. Eddy and T. Surber. 1943. University of Minnesota Press.
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