312 PHYSIOLOGY OF RESPIRATION OF FISHES 



In order to determine whether or not the death of the fish was due 

 to asphyxiation because of low oxygen tension of the sea water, the 

 first set of experiments was checked by testing the fish where they 

 would not suffer from oxygen want so quickly. Ten to twenty-five 

 fish were placed in a carboy (capacity about 42 liters) of sea water at 

 different hydrogen ion concentrations. The results of these experi- 

 ments conform very markedly to the mean curve, although the time 

 until death of the fish in the carboy was from 24 to 48 hours as com- 

 pared with 1 hour and 23 minutes to 2 hours and 40 minutes when 

 five fish were tested in the 2 quart Mason jars (Fig. 3). This shows 

 that the fish died from asphyxiation due to low oxygen tension in the 

 sea water and not to other causes. 



The experiments performed at Friday Harbor corroborate in every 

 way those done at Woods Hole. The results of these experiments 

 conform strikingly with the behavior experiments and field observa- 

 tions made by the writer on the same fish during the summers of 1918 

 aitd 1919. The lowest tension at which the herring, Clupea pallasii, 

 can extract oxygen from the sea water is when the hydrogen ion con- 

 centration is ±7.68 pH. This fish reacts positive to sea water 

 having a pH of from 7.68 to 7.73 and was found most abundantly in 

 the sea water in the vicinity of the Puget Sound Biological Station 

 that had a pH of about 7.73 to 7.76 (Powers, 1921). 



DISCUSSION. 



Workers on fish respiration have found that fishes are able to 

 survive at rather low oxygen tension without any apparent ill effect 

 (Powers, 1921, citations). Gaarder (1918) found that the actual 

 oxygen consumption of an anesthetized carp was reduced only 

 slightly, 0.62 cc. per kg. per minute, until the oxygen in solution in 

 the water had been reduced from 15.4 cc. per liter to about 1.13 

 cc. per liter when the gills were artificially bathed with water at a 

 constant rate. It is not known whether or not this slight falling 

 off of oxygen consumption could have been corrected had the 

 respiratory mechanism of the fish been free to respond normally. 

 Packard (1905) showed that Fundulus heteroclitus injected with 5/16 

 M sodium carbonate were able to live longer in a liter flask of sea water 



