MANAGEMENT OF WATERS 33 



younger age groups would be relieved and a satisfactory growth rate 

 would probably result. The average fisherman, however, can hardly be 

 expected to follow such a radical procedure. Nor does this method take 

 into consideration the populations of non-game fishes which are little 

 affected by fishermen but should likewise be controlled. 



Another outstanding defect is the presence of carp and other unde- 

 sirable species. Finally, one of the most "serious problems is the lower- 

 ing of lake levels through drought and drainage developments. The 

 lowering of lake levels creates oxygen deficiencies in winter and reduces 

 game-fish lakes to bullhead types or even makes them entirely unsuit- 

 able for any fish. The extent of these problems is indicated by lake 

 surveys, which thus provide a basis for the management of lakes for 

 fish production. 



