The Bureau of Commercial Fisheries Type IV Electrofishing 

 Shocker--lts Characteristics and Operation 



By 



BENJAMIN G. PATTEN, Fishery Research Biologist, and 

 CHARLES C. GILLASPIE, Electronic Development Technician (Design) 



Bureau of Commercial Fisheries Biological Laboratory 

 Seattle, Washington 



ABSTRACT 



A fish shocker which is effective, dependable, light weight, and economical to 

 purchase and operate is described. The output energy of this shocker is 450 volts 

 direct current at 150 milliamperes, pulsed into square waves at frequencies con- 

 trollable from 20 to 100 per second with a fixed duration of 6 milliseconds. 



This output energy produces a good galvanotaxis reaction in fish in the field. 

 Our experimentation and information from the literature indicates the output energy 

 of the described shocker to be of a favorable range. 



Methods of operation of electric shockers are given. The recommended sizes 

 of the electrodes are about 40 cm. square for the anode and 2.3 m. square for the 

 cathode. The electrodes should be operated close together, especially in resistive 

 waters. In suitable waters a wading technique is used, but a floating electrofishing 

 operation is necessary if waters are deep or swift. 



The effectiveness of a shocker is often reduced by environmental factors, but in 

 most situations little can be done to compensate for this. The effects of water re- 

 sistivity, variations in fish size or species, temperature, and fish mortality factors 

 are discussed in relation to the success of electrofishing operations. 



INTRODUCTION 



In recent years electrical methods of col- 

 lecting fish in fresh-water shallows have been 

 developed because they are more convenient 

 and efficient compared with nets or traps. 

 Little is known, however, of the basic rela- 

 tions between fish and electricity, or how 

 environnnent affects the amount of electrical 

 energy that reaches the fish. Quantitative 

 evaluations and comparisons of electrofishing 

 research by different authors are almost im- 

 possible because varied shocks and shock- 

 producing equipment have been used in waters 

 of varying resistivities on different species and 

 sizes offish. The interrelations of these factors 

 are not commonly known or understood. 



Because it is difficult to evaluate electro- 

 fishing operations, most shockers do not pro- 

 duce the optimum stimulative electrical energy 

 for fish, or the methods of introducing elec- 

 tricity into water may not fully utilize the 

 power potential. As a contribution to knowledge 

 of electrofishing, we describe the design and 

 operations of the Bureau of Commercial Fish- 

 eries Type IV shocker, which has proven tobe 

 effective and dependable for electrofishing. 

 Also, -we attempt to delineate the preferred 

 type of electric shock and the effects of en- 

 vironment on electrical energy gradients in 

 the water. 



THE TYPE IV SHOCKER 



The Type IV shocker is the fourth of a series 

 of shockers constructed by the Bureau of 

 Commercial Fisheries technicians at the 

 Seattle Biological Laboratory for the collec- 

 tion of fish. The Type I shocker produced a 

 wave shape that was relatively ineffective in 

 comparison with the wave shape produced by 



Types II, III, and IV. Shockers of Types I, II, 

 and III require a heavy, cumbersome, port- 

 able generator for power, and the initial cost 

 of these generator-shocker sets is much 

 greater than for Type IV. The Type IV shocker 

 is also more dependable and more economically 

 maintained than its predecessors. 



