Wnen the temperature first rises sharply, the movement of the fish 

 generally becomes more rapid and the respiration increases (as the water 

 temperature rises the amount of saturation of free oxygen decreases, 

 and the situation therefore gradually becomes disadvantageous to the bait,, 

 When bait fish which were carried in the old-fashioned bait tank with 

 its poor water circulation encountered a zone of high water temperatures, 

 they could hardly escape the bad effects of oxygen deficiency) , As the 

 temperature rises and the amount of respiration increases, the amount of 

 combustion within the body also increases „ At this time^, if the water 

 temperature goes to a lethal level, the bait fish immediately begin to 

 run about wildly, and some bend the middle portion of their bodies 

 strongly from time to time, while others are seen to project their noses 

 above the water and others leap clear out of the water,. Finally they 

 begin to die off, the least resistant ones first,, This type of death 

 from high water temperatures is probably, as Mayerl^) says, the result of 

 the accumulation of H2CO5 in the tissues „ There have not yet been any 

 cases of heat rigor at the experimental temperatures mentioned above. 



If the water temperature drops sharply, the bait generally begins 

 to swim slowly and the amount of respiration decreases „ If the temperature 

 falls to a lethal level at this time, the fish gradually become quieter, 

 some begin to lie on their sides from time to time, and finally they 

 begin to die, the least resistant ones first. However, the cause of death 

 in this case is not as clearly apparent as with the high temperatures, 

 and it is probably paralysis of the sinus venosus of the heart*, 20) 



Death from Wounds 



In the foregoing sections I have dealt with mortality due to lack of 

 free oxygen and mortality resulting from sudden rises and falls in the 

 water temperature, both of which become lethal in an extremely short 

 space of time,, In this section I will deal with mortality due to wounds, 

 that is, the type of mortality that results from injuries received at the 

 time of capture, at the time the fish were placed in the bait tank, or 

 thereafter, whicn in many cases causes death and becomes apparent only 

 after the passage of a long period of time, a type of mortality which can 

 occur most easily and whicn is rather difficult to diagnose,, 



When, as has been done hitherto, bait fish which have been kept for 

 some time in a holding net in sheltered waters were loaded into the bait 

 tank, this type of mortality had already been liquidated in the holding 

 net and so it never became much of a problem, but when, as at present, 

 bait that has just been captured, that is, wild bait, is immediately 

 transported in the boats, a good deal of economic loss can result if 

 sufficient attention is not paid to this type of mortality,, There are, 

 however, absolutely no reports of studies designed to deal with this 

 problem, and therefore the author nas attempted the following investiga- 

 tions concerning tne mortality resulting from wounds to bait fish, copying 

 the method of classification used for wounds to human beings«IX 



VIII„ Csic] According to the teachings and writings (21,22) of Professor 

 Sadanori Mita. 



32 



