BIOLOGICAL SURVEYS AND INVESTIGATIONS IN 

 MINNESOTA. 



By Thaddeus Surber 

 Biologist, Minnesota Game and Fish Department, St. Paul, Minn. 



The fact has been long established that certain plants of fish 

 fry and fingerlings, made by both Federal and State departments, 

 end in failure; but the causes underlying the failure are but little 

 understood because of a lack of knowledge of the exact conditions 

 of the waters so planted. The mere fact that a body of water, be it 

 lake or some favorite trout stream, is thought to be all right simply 

 because it was fonnerly good, but had only become fished out, is the 

 argument most frequently used, and the applicant, be it club or 

 individual, proceeds with this idea and procures fish fry and dumps 

 them in, often at considerable expense to himself, and most cer- 

 tainly to the Government. Then, when no results are forthcoming, 

 blame is attached to the Government (State or Federal) that the 

 fry were either too small, or delivered at the wrong season of the 

 year, and were subsequently washed out by floods, etc., when the 

 real fact of the matter is that the fry would not have been planted 

 if some attention had been given to an investigation of the waters, 

 the nature and amount of its food resources, and extent of the 

 pollution. 



The writer, during his boyhood and early manhood, lived near 

 a famous spring, now the site of a Federal hatchery, where brook 

 trout had spawned for untold centuries in great numbers, and 

 probably continue to do so to the present day. Now, this spring 

 and the brook below it for a considerable distance maintained a 

 temperature of 50°to54°F., winter and summer, which is about the 

 average temperature of all Minnesota springs, and the temperature 

 of the water supplied to most trout hatcheries. As we know 

 the temperature of the water controls the development and 

 subsequent hatching, we infer that the period at which 

 the fry emerge from the shell and their subsequent development 

 near the heads of these spring-fed streams coincides very closely 

 with conditions existing at the hatcheries of the present day. At 

 the big spring under consideration and in the brook below it, my 

 observations showed fry in the creek gravel in the early part of 



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