Figure 3. — The electrode array of the DC leading device as installed 

 in the Little Ocqueoc River, Presque Isle County, Michigan. 



The procedure was then repeated with the cams which produced 

 duty cycles of 0.10, 0.25, and 0.66 respectively. White suckers 

 (Catostomus c. commersoni ) and brook trout ( Salvelinus f. fontinalis ) 

 used in these initial experiments were held in various facilities 

 available at the Hammond Bay Laboratory. Reasonable precautions were 

 exercised in maintaining and handling the test animals. At all times 

 water temperature in the test tank was held within 3° F. or less of that 

 of the holding tanks and pens. 



The advisability of allowing the test animals to become accli- 

 mated to conditions in the test tank was considered. Ho^rever, no visi- 

 ble difference could be observed in the results obtained vfith brook 

 trout subjected to a test immediately after being placed in the tank and 

 those tested after being in the tank from 2 to US hours. This result 

 was perhaps to be expected inasmuch as the desired reaction was a stimu- 

 lated movement not consciously controllable by the fish. 



Originally it was planned to employ 6 fish for each test; how- 

 ever, it became obvious that unless the test animals x-xere used several 

 times an excessively large number of fish would be required. A small 



