6 



Theories and Techniques 



of Management 



objectives of management are to produce and maintain a fish popu- 

 lation that will supply a satisfactory sustained return to those with the 

 authority to take an annual crop. Few populations are handled with suf- 

 ficient intensity to keep them producing at peak level, although many 

 provide a fairly adequate sustained yield. Probably, private and public 

 demand for angling would be satisfied if all available waters offered a 

 moderate sustained yield. However, in many regions unproductive ponds 

 and lakes (those that supply little or no fish) predominate. This is par- 

 ticularly true of small artificial lakes and reservoirs located near centers 

 of population. 



Most unproductive lakes or reservoirs contain "problem" fish popula- 

 tions. Obviously, management effort should first be directed to restoring 

 reasonable production to these bodies of water; the application of in- 

 tensive fish management can come later. 



There are two methods of handling a "problem" population in a pond 

 or lake. One is to eliminate the population entirely and start anew with 

 fish from an outside source; the other is to change the problem population, 

 either by direct action upon it or through indirect action, brought about 

 by modifying the fishes' environment. Both of these approaches are in 

 common use. However, before deciding on a management procedure, a 

 rather careful diagnosis, requiring one or several methods of sampling 

 the population, must be made. Following is a dicussion of the uses of 

 fish samples and some common methods of taking them. 



FISH SAMPLING 



The fisherman or fisheries manager can rarely see beneath the water 

 sufficiently to identify and count the fishes in a lake or pond. Conse- 



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