CHANGING FOOD CONDITIONS OF THE TROUT FAMILY. 



By James Nevin, 

 Wisconsin Conservation Commission, Division of Fisheries. 



FISH AND GAME WITHIN THE STATE ARE THE PROPERTY OF 

 THE PEOPLE. 



The degree of success achieved in planting fish is determined 

 by the conditions of the water in which they are planted. Some 

 lakes and streams are more productive of fish and the life upon 

 which the fish feed than others. The problem with which we are 

 confronted is, how can those conditions be maintained? The 

 farmer who sows and reaps without returning anything to the 

 soil soon has a barren field. We have been planting fish in 

 streams for years and the time has arrived when many of our 

 streams cannot support greater numbers of game fish and the 

 question to be solved is, what can be done to restore these streams 

 to their former pristine conditions so they can be stocked to meet 

 the increased demand? 



The principal food of large and small trout and which is in 

 most all spring water fed streams, is the caddis or the May-fly larva. 

 The May -fly larva lives under water and adheres to the stones on 

 the bed of the stream till ready to emerge in the adult state. 

 The caddis larva is a wormlike creature and looks as if it 

 might be encased in bark from the tree or an alder bush. Then 

 again, in most all of our spring water holes, where water-cress will 

 grow, there will be found vast numbers of fresh water shrimp all 

 along the stream clinging to roots, logs or stones as they drift 

 along down the stream. These the fish feed upon. 



Brook trout prefer streams that contain hiding places and 

 clear spring water with a maximum temperature of about 60°. 

 In many of the counties of the state intensive farming has caused 

 the removal of brush and trees from the banks of streams, destroy- 

 ing the conditions that provided natural haunts for the fish. 

 Many farmers set aside for pasture that portion of their farms 

 through which the stream flows. Cattle and hogs wade and 

 wallow in the stream, making it unfit for trout, with the con- 

 sequence that the fish are driven away or die. After a heavy 



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