vi NORTHERN FISHES 



Leech, Winnibigoshish, and Mille Lacs, all tributary to the Mississippi 

 River. The numerous deep, clear, rocky lakes in Cook, Lake, and St. 

 Louis counties are mostly within the Hudson Bay drainage system. 

 The remainder of the lakes in these counties are within the Great Lakes 

 basin and drain through numerous streams into Lake Superior. 



The conditions of Minnesota waters are changing rapidly, however. 

 Power dams are being built, creating lakes in rivers. Once-drained 

 lakes and swamps arc being restored by dams and diversion ditches, 

 thus adding more waters for fish life. Over a period of years forests 

 have been threatened not merely through the activities of the lumber- 

 man but more seriously by fires, which have likewise affected the lakes 

 within these areas. Happily there is a vast area of untillable land in 

 the northern and northeastern counties, large blocks of which are still 

 heavily forested and are dotted with innumerable lakes and streams in 

 which relatively undisturbed fish hfe can be perpetuated indefinitely. 

 In the central lake region, forest fires have been few and have exerted 

 little infiuence on lake conditions. In the prairie region both streams 

 and lakes have been affected, not only by drainage and intensive culti- 

 vation of surrounding lands but by periodic drought as well. It is in 

 the prairie region that the fisheries have suffered the greatest depletion. 

 Obviously conservation measures must be taken. This book seeks to 

 provide information that will be helpful not only to the sportsman but 

 also to all who are interested in conserving our fish resources. 



The extensive investigations on which this book is based were financed 

 largely by the Minnesota Department of Conservation and the Univer- 

 sity of Minnesota. The authors wish to acknowledge also the many 

 helpful suggestions and criticisms given them by Dr. Carl L. Hubbs of 

 the University of Michigan. They are deeply indebted to Dr. Hubbs. 

 to Dr. Karl F. Lagler, and to the Cranbrook Institute of Science for per- 

 mission to modify and adapt their keys to the minnows and darters 

 of Minnesota. They are under obligation also to Dr. John B. Moyle and 

 Kenneth Carlander for their splendid assistance in the identification 

 of the minnows and darters, and to John Dobie of the Minnesota De- 

 partment of Conservation, who has spent much time in making the 

 photographs of actual specimens with which the volume is illustrated. 

 The colored plates have been prepared by Ruth Delano of the Univer- 

 sity of Minnesota. Much of the statistical work on lake surveys, age 

 determinations, and population studies was done with the assistance of 

 several WPA projects. Most of the egg counts referred to were made by 

 Dr. M. F. Vessel at the University of Minnesota. The authors are grate- 

 fully indebted to Doctors W. A. Riley and D. E. Minnich of the Uni- 

 versity of Minnesota, who read and criticized the manuscript. They 

 acknowledge their obligations also to the many graduate students, 

 game wardens, and others who contributed in various ways. 



S. E. and T. S. 



