Death From Lack of Free Qxygerr 



Since the sardine belongs to the class of comparatively active 

 swimmers, the amount of oxygen it uses must be great, as is clear from 

 the study of Halloo For this reason when the bait fish arc- being trans- 

 ported^ and a great number of them are confined in a small bait tank 

 aboard the boat, in a tank like the ones used heretofore, where the only 

 water circulation is that resulting from the movements of the hull, and 

 even in the new bait tank described above, where the water is circulated 

 by a pump, the danger that the bait fish may use up the limited free 

 oxygen in the sea-water, breathe abnormally, and then finally die of 

 suffocation is an item that should naturally be taken into consideration „ 

 In actual fact, it not infrequently happens that while the bait fish are 

 being transported, an oxygen deficiency develops in the bait tank and 

 almost all of the precious bait dies off in a brief space of time leaving 

 the fishermen dumbfounded,, 



Accordingly, the basis for counter-measures must be formed by 

 experimenting to determine how much free oxygen the bait fish consume 

 under any particular conditions and what is the lethal level of free 

 oxygen „ 



a) Abnormal Respiration of Bait FishJ^ 



Abnormal respiration is the respiration which takes place in sea- 

 water that does not circulate, or in sea-water in which, because of in- 

 sufficient circulation, the supply of oxygen is inadequate,, A suitable 

 example of this is the respiration of bait fish confined in a bait wello 



The author experimented on this point early in September, 1932, a 4- 

 the Kanagawa Prefecture Misaki Marine Laboratory, using a tank for 

 physiological experiments on fish, described below, of his own design ,*U 



This tank was made of wood and was 4,95 shaku long and 1,65 shaku 

 in both width and height (internal dimensions) £_ 1 shaku s 0.994 foot 'Jf m 

 It was divided into three equal compartments by partitions which could be 

 freely opened or closed from the outside, according to the object of the 

 experiment o Each compartment had a glass observation window with a door, 

 a tap for sampling the water, a thermometer, and other instruments. 



I 9 Various valuable advice was received from Mr„ Nobunari Kawamoto „ 



lie There is an interesting study by Kawamoto on abnormal respiration of 

 fishes when being transported alive, 



IIIo In planning this tank I received valuable advice from Dr„ Morisaburo" 

 Tauchio In the experiments I was assisted by Mr, Hidematsu Tckunaga, 

 a member of the staff of the Station, The details of the construc- 

 tion of the tank and the method of operating it will be reported at 

 some future time. 



