more would remain attached to the surface of the body of the fish for as 

 long as 10 minutes or more without dissipating. 



If we collate and examine these facts and the experiment described 

 above, we see that even though the presence of so many small air bubbles 

 may have the advantage of increasing to some extent the free oxygen in 

 the water j, physically the bad effect on the bodies of the fish outweighs 

 thiSo When the air bubbles rise in the water, they not only cause injuries 

 indirectly by disrupting the swimming of the fish, but if they stick to 

 the gill lamellae, which are the breathing apparatus of the fish, they 

 make respiration difficult, and in either case there is plenty of danger 

 of their finally leading the fish to its death. 



Death from Unnatural Feeding 



The natural food of sardines is phytoplankton such as diatoms and 

 zooplankton such as copepods, so even in a net live-pound or in the bait- 

 wells of a boat as long as there is a certain amount of circulation of 

 water the fish will not go completely without food even though they are 

 not fed. However, if the fish are kept for a long time without feeding, 

 they become as shown in Figure 13, with the body lean and only the head 

 large, and not only is their quality as bait lowered but their resistance 

 to all sorts of damage is weakened. Accordingly, when bait fish are to 

 be kept for a long time or transported a long distance they should be 

 properly fed^' **), but if errors are made in the time and amount of 

 feeding the results are sometimes worse than no feeding at all. 



If bait fish are held in captivity and a few days are allowed to 

 pass, then, as described earlier, the school will begin an orderly circling 

 inside the live-pound, and somewhat later they begin to show a condition 

 that the fishermen call "puffing out their cheeks". This term describes 

 the movement in which the opercles are spread as wide as possible, fully 

 opening the gills, the fish swimming for a while in this condition and 

 then closing the opercles. This is the food-seeking action peculiar to 

 these fish, and it is carried on simultaneously with respiration. XIII 

 Since bait fish which show this action are in a good state of health, 

 the fishermen use its presence or absence as a criterion by which to 

 judge the quality of bait. Fish which act in this way may be fed without 

 any trouble, but fish which do not show this type of activity will never 

 take the food that is given to them, and feeding will only result in 

 fouling the water so this is a matter which requires care. Ordinarily 

 it happens only rarely that deaths are caused by mistakes in feeding, 

 but sometimes when bait fish which have been kept for a long time without 

 feeding are being transported and are mistakenly fed the wrong amount, 

 very regrettable results ensue. On July 5, 1931, in the course of an 

 experiment in holding bait aboard the Fuji Maru, the author suddenly 



XIII. The author has experimental proof, but will leave its publication 

 to another time. 



44 



