Table 2. --Minimum total peak current for satisfactory electrotactic response of aholehole 

 at various "on-fr actions" with a constant frequency of 10 c.p.a. 



0.02, 0.04, 0.06, 0.08, 0.12, and 0.16. For 

 each on-fraction the sanne 4 fish were used in 

 several successive trials at increasing currents 

 of 6, 8, 10, 12, 14, and 16 amp. Table 2 shows 

 the minimum total peak current for satisfactory 

 response. Again it was difficult to distinguish 

 between shades of satisfactory response at some 

 of the higher currents and the results were 

 doubtful in some cases because of the fatigue 

 factor. It was tentatively concluded, hpwever, 

 that the minimum current for satisfactory 

 response (12 amp.) was associated with an on- 

 fraction of 0.06 to 0.08. 



In a third series of tests, each ennploying 

 two fish with the results shown in table 3, an 

 attempt was made to determine the relationship 

 between peak current for satisfactory response 

 and length of fish for a constant on-fraction of 

 0.08 and a frequency of 10 c.p. s. Unfortunately 

 only a small range of fish sizes were available. 

 However, the results plotted in figure 3 indicate 

 that the total peakcurrent requirement decreases 

 with increase in fish length. If we assunne a 

 simple reciprocal relationship I=k/L and if we 

 choose k so this equation fits our data at L = 11 

 cm. and I = 16 amp., the curve shown as a 

 dashed line in figure 3 results. Although the 

 curve does not fit the data well, it is perhaps 

 realistic in that the curve nnust ultimately 

 approach the horizontal. 



In a fourth and final series of tests, at an 

 on-fraction of 0.06, and a frequency of 10 c.p. s., 

 the total peak current was adjusted to the optinnunn 



value according t o the length of the fish. As 

 shown in table 4 all tests resulted in satisfactory 

 response except No. 4, which was made on a 

 school of 29 fish varying in length from 9 to 12 

 cm. When thecurrent was adjusted to the longer 

 fish, there was considerable erratic swimming 

 by the shorter fish which tended to interfere with 

 the electrotactic response of the longer fish. 

 However, the school as a whole moved slowly 

 towards the positive electrode. When the 

 schools were of more nearly uniform size as in 



5 12 



10 II 12 13 



LENGTH OF FISH (CM ) 



Figure 3. --Relationship between total peak 

 current (1) for satisfactory response and 

 length of fish (L). Dashed line expresses 

 the relationship I = 176/L. 



