REACTIONS OF FISHES TO ATMOSPHERIC GASES 



253 



TABLE 18 



Showing the reactions of fishes to a gradient of boiled water with ammonia added. 

 Data arranged as in preceding tables. Controls in tap water. Gradient between 

 tap and treated water. 



Ameiurus showed some signs of stimulation, such as gulping 

 but gave no movements which tended to bring the fish into 

 better conditions. As in Abramis, no avoiding or regulatory- 

 reactions were given. After going back and forth for twenty- 

 nine minutes, the two fishes came to rest, one in the high ammonia 

 and low oxygen, the other in the low aimnonia and high oxygen. 

 The former was apparently dead at the end of forty minutes 

 though it recovered after a week or more in clear water. The 

 one in the lower ammonia lived and showed no sign of having 

 been affected. 



While these two species probably rarely encounter acid media 

 except carbonic acid, they react to the acid in much the same 

 manner as to carbon dioxide. This result is in accord with 

 much experimental work in animal behavior. 



Fishes must encounter ammonia in very weak concentrations 

 quite often in primeval nature, but the species studied in these 

 preliminary, experiments, appear to be unable to react to the 

 concentration used, at least when it is accompanied by low 

 oxygen content. Low oxygen accompanies ammonia in sewage 

 and if the results obtained with these fishes are the rule, the 

 relation of fishes to ammonia and low oxygen is a life or death 

 matter. 



