104 



BULLETIN OF THE BUREAU OF FISHERIES 



are summarized in Table 2. These data siiow conclusively, as one would expect, 

 that the duration of application of the potential has a decided effect upon the mortality 

 of the fish when voltage gradients above the paralysis value are applied. A voltage 

 gradient of 1.48 volts per inch, used in test No. 19, paralyzed 26 of the 30 fish in one 

 minute but did not kill any of them. Essentially the same voltage gradient, 1.46 volts 

 per inch, used in test No. 27, paralyzed all of the fish, and after a 5-minute application 

 69 per cent of the fish did not recover. The duration of the period of complete 

 paralysis or suspended animation appeared in every case to be the greatest factor in 

 determining recovery from electric shock. Vntually, without exception, it was ob- 

 served that when a group of fish was paralyzed the recovery was in the inverse order 

 of the paralysis — that is, the fish paralyzed first were last to recover and those para- 

 lyzed last were first to recover. 



Table 2. — Influence of voltage gradient and duration of application on mortality of chinook-salmon 

 fingerlings 3.1 inches long when subjected to a uniform electric field in ivater having a resistivity of 

 10,000 ohms per inch cube and at a temperature of 63° F. Electrode plates, 21^ square inches area, 

 spaced 12 inches apart 



OBSERVATIONS DURING PARALYSIS AND RECOVERY 



Some interesting observations were made of the characteristic behavior of fish 

 during the application of potential and during the recovery from an electric shock. 

 These will be given here. When the electrode voltage is increased gradually from a 

 very small value the fish begin to show signs of feeling the potential at from 10 to 20 

 per cent of the value for paralysis. This is indicated by short, quick, caudal (tail) 

 fin movements and slight shifts in position. At from 50 to 80 per cent of the paralysis 

 voltage they become quite active, swimming about in all directions, seeking to avoid 

 the uncomfortable electric field. Just before reaching the paralysis voltage, the fish 

 are extremely active, dashing about trying to escape the field. Then they become 

 paralyzed, the pectoral fins stand motionless and virtually at right angles with the 

 body; the fish then turns belly up and sinks to the bottom, where it lies on one side. 

 In some instances the gill action apparently stops entirely, while in others it con- 

 thiues feebly. The entire fish turns perceptibly lighter in color while paralyzed. 

 The change in color is due to changes m the distribution of the pigment in the chro- 

 matophores of the skin (Kuntz, 1917). These chromatophores are probably under 



