REACTIONS OF FISHES TO ATMOSPHERIC GASES 



223 



2. EFFECT OF A DEFICIENCY OF OXYGEN 



Duncan and Hoppe. Seyler ('95, p. 165) found that the Euro- 

 pean cyprinid (Tinea vulgaris) is not affected by a prolonged 

 exposure to oxygen reduced to 3 to 4 cc. per liter, but that when 

 the oxygen supply is reduced below 1 cc. per liter they come to 

 the surface and breathe heavily, \'iolence of respiration increasing 

 as the oxygen decreases. They were able to keep these fish 

 alive, in a total absence of oxygen, for twenty-four hours. Trout 

 were strongly affected by 1.7 to 0.8 cc. per liter in two or three 

 hours. Reuss ('10) found that an increase of oxygen decreased 

 breathing frequency. For further experiments and observations 

 concerning the relation of fishes to gases, see Knauthe ('98, p. 

 785, '07, p. 148); Konig ('99, p. 32) and Marsh ('07, p. 346). 



Several experiments were performed to determine the oxygen 

 minimum for the different species. Table 5 represents our 

 experience in this matter, together with current preferences 

 which may roughly represent oxygen content of the natural 

 environment. 



The different rates of flow represent the following conditions: 

 Swift water is high oxygen content; the category Variable' may 

 be construed as representing a condition in which stagnation 

 occurs at times and accordingly represents conditions which 



TABLE 5 



Showing the relative time of succumbing to low oxygen content; and the current 

 preferences of the same species after Forbes and Richardson i'08) 



Micropterus 



Ambloplites 



Ambloplites, average.. 



Hybopsis 



Ambloplites 



Notropis 



Abramis 



Ameiurus 



LENGTH 

 IN CM. 



12 



6 



10 



4 

 10 

 10 



TURNING 

 TIMEl 

 IN MIN. 



20 

 320 

 340 

 355 

 360 

 376 

 400 

 1080 



CURRENT PREFERENCES 



Sluggish Sluggish Variable 

 to swift to stagnant ^^.naDie 



55 



55 

 53 



45 

 32 

 37 



18 



15 

 24 



36 

 57 

 53 



27 



30 

 23 



19 

 11 

 10 



1 The 'turning time' is the time before the fishes turned ventral side up 



