KEOKUK DAM AND THE FISHERIES OF THE UPPER 
MISSISSIPPI RIVER 1 
Bv ROBERT E. COKER, Ph. D. 
Professor of Zoology, University of North Carolina 
CONTENTS 
Page 
Introduction 87 
Keokuk Dam as a possible obstruction to 
fish 91 
The dam proper 92 
Power house 96 
Lock 97 
Intervals of free passage 98 
Extent of fish movements during 
intervals of free passage 99 
Capture of fish on the upper gate- 101 
Conclusions regarding the dam as a 
barrier 104 
Significance of the barrier 105 
Types of migratory movements. 105 
Evidence of migration 106 
Alleged diversion of fish up the Des 
Moines River 107 
Injuring and destruction of fish 109 
Extent and character of injury 109 
Structures considered 110 
Experiments 111 
Discussion of evidence and con- 
clusion 112 
Effects of the dam upon conditions in the 
river below 112 
Bottom conditions 112 
Page 
Effects of the dam, etc. — Continued. 
Ice 113 
Oxygen content 113 
Fluctuation of river stage 113 
Lake Keokuk 115 
Creation of a river lake 115 
Area 116 
Depth 116 
Turbidity and temperature 117 
Velocity of current 118 
Bottom material 118 
Plankton of the lake in 1914 118 
Entomostraca 119 
Other plankton animals 120 
Phytoplankton 120 
Fish food 121 
Spawning grounds 125 
Abundance of fish 126 
Summary of observations 127 
Deductions from the commercial fisheries 
of Lake Keokuk and Lake Pepin 127 
Notes of A. S. Pearse on changes in fish 
fauna of Lake Pepin 133 
Conclusions 134 
Bibliography 137 
INTRODUCTION 
With the development of the country there have ensued noteworthy changes in 
the condition of our streams. Deforestation, clearing of lands, drainage, all have the 
effect of passing the surface waters quickly into the rivers. The reclamation of swamp 
lands, leveeing of river banks, and dredging and straightening of river channels make 
it possible for the water to flow more rapidly through the rivers to the sea. The 
general effect, therefore, of the natural accompaniments of agriculture and industrial 
development is to produce extreme flood stages, both high and low, and to shorten the 
periods of change from one extreme to the other. 
1 Submitted for publication Sept. 28, 1928. 
Prepared at the same time and based on observations and collections made during the period covered by this report is a com- 
panion paper entitled “Studies of Common Fishes of the Mississippi River at Keokuk” (to appear in the bulletin of the Bureau of 
Fisheries), in which are presented the known facts of the natural history of the fishes of that region. Such information forms the 
background of the present study, and the two papers should be consulted together by those interested. 
87 
