138 Theories and Techniques of Management 



shallow and have a water hardness of 25 or more parts per million 

 (Figure 6.2). If the hardness is less than 25 ppm, the effective field of 

 the electrodes is too small for the shocker to function efficiently. A boat 

 shocker is often much more effective in taking fish at night, when fish 

 are in the shallows, than in the daytime. A lighting system presents no 

 problem because lights may be powered from the generator.'^^ 



Figure 6.2. An electric fish shocker mounted on an aluminum work boat. 

 Biologist standing in front of boat controls a 220-volt generator, keeps elec- 

 trodes in position, and picks up stunned fish. Biologist in rear runs outboard 

 motor and cares for stunned fish which are placed in the tank amidship. 



The boat shocker is selective in that it may stun fish attempting to 

 hide in vegetation or on the shallow bottom; whereas fish swimming ahead 

 of the advancing edge of the electrical field may escape unless they are 

 cornered at the end of a bay or channel and forced to swim through the 

 field. In general, bass tend to swim ahead of the shocker boat while odier 

 smaller centrarchids often try to hide in vegetation. Catfish and bullheads 

 are seldom taken with an alternating current shocker because they are 

 stunned on the lake or pond bottom where they are difficult to see and 



