University of Kansas Publications
Museum of Natural History

Volume 13, No. 7, pp. 323-348, pls. 21-24, 2 figs.
February 10, 1961

Geographic Variation
In the North American Cyprinid Fish,
Hybopsis gracilis

BY
LEONARD J. OLUND AND FRANK B. CROSS

University of Kansas
Lawrence
1961

University of Kansas Publications, Museum of Natural History

Editors: E. Raymond Hall, Chairman, Henry S. Fitch,
Robert W. Wilson

Volume 13, No. 7, pp. 323-348, pls. 21-24, 2 figs.
Published February 10, 1961

University of Kansas
Lawrence, Kansas

PRINTED IN
THE STATE PRINTING PLANT
TOPEKA, KANSAS
1961

28-5871

Geographic Variation In the North American Cyprinid Fish, Hybopsis gracilis

BY
LEONARD J. OLUND AND FRANK B. CROSS

CONTENTS

•   PAGE
• Introduction 325
• Methods, Materials, and Acknowledgments 326
• Description of the Species Hybopsis gracilis 327
• Hybopsis gracilis gracilis 328
• Hybopsis gracilis gulonella 330
• Intraspecific Variation 333
• Natural History 334
• Habitat 334
• Associated Species 336
• Food 338
• Spawning Season 338
• Discussion 340
• Literature Cited 343

INTRODUCTION

The flathead chub, Hybopsis gracilis (Richardson), occurs in the Plains Region of Canada and the United States, in four major drainage systems: Mackenzie River, which discharges into the Arctic Ocean; Saskatchewan River, which discharges into Hudson Bay via Nelson River; and Missouri-Mississippi System and Rio Grande, both draining into the Gulf of Mexico. Each of these systems is occupied in part only. In the Mackenzie Basin, H. gracilis has been reported as far north as Fort Good Hope (Walters, 1955:347). Flathead chubs occur in the Saskatchewan Basin from Alberta eastward to Lake Winnipeg, Manitoba, but have not been found in other streams that flow into Lake Winnipeg (Red River, Brokenhead River and Whitemouth River) nor in Nelson River downstream from Lake Winnipeg. In the Missouri Basin the species occurs more or less continuously from the high plains adjacent to the Rocky Mountains in Montana and Wyoming down the mainstream of the Missouri River to its mouth, and down the mainstream of the Mississippi River as far as Barfield, Arkansas, but not to the Gulf. The species probably attains its greatest abundance in the Missouri Basin, but it is scarce or absent in tributaries north and east of the Missouri mainstream, in the South Platte Basin, and in the central part of the