A study was made o? the foo'^ habits of the yellowfin tuna taken by tho research 

 v^easol Shonan Waru oi" the Taiwan Government-General Fisheries Experiment Station in 

 the course of exploratory fishing in the Celebes Sea. 



■nie stomachs were removed from the fish Imme'^ lately after they were caught and 

 were preserved in formalin. In order to prevent the loss of any of the stomach con- 

 tents each stomach was olaced separately in a bleached cotton bag. Collections 

 were made at two different times, in February 1933 and from July to September 193^. 

 Stomachs from a total of 57 fish were collected, 34. on the first voyage and 23 on 

 the second. 



The fishing grounds were as shown in Figure 1. It can be seen that, except 

 for a part of the stations, these two exploratory fishing cruises were carried out 

 in exactly the same waters. As a result, although they were not both made in the 

 same year, the study can be regarded as providing an opportunity to compare results 

 from collections made at two diametrically opposite seasons of the year. 



The materials for this study were obtained through the kindness of Mr. Hitoshl 

 Hiratsuka, who was in charge of operations aboard the ship at the time. My pro- 

 found gratitude to him is here expressed. 



In discussing fooci] habits it is thought that there will naturally be some 

 argument about the matter of basing such a study solely on stomach contents, but it 

 is believed that they have much value as data for reference. 



T^e stomachs were cut open and all of their contents emptied out into a dis- 

 secting pan for insriection. The results of that examination are shown in Figure 3. 



The number of times of appearance was counted as the number of stom??chs in 

 which a particular item appeared without any regard to the number of specimens con- 

 tained in the stomach. The number appearing is the total number of specimens of 

 each species which was found in all of the stomachs. Consequently the number of 

 times of appearance and the number appearing are not necessarily the same nor even 

 correlated. 



The reason for the adoption of this distinction is that the items which appear 

 in large numbers may not in some cases necessarily be important foods, and the op- 

 posite case may also be true, while those items which appear both In a large number 

 of cases and with a large number of specimens may be thought to be the Important 

 foods of the yellowfin tuna. 



The greatest difficulty in this work was the frequent appearance of species of 

 fish which, because of the progress of digestion, could not be accurately identified. 

 If we examine the progress of digestion as It applies to fish, it appears that first 

 of all the skin is completely digested and the eyes are lost. The muscles should be 

 next to be digested, but it is interesting that in many cases the head is destroyed 

 and separated from the body while the muscles are still not fully digested. The 

 skeleton and other tissues appear to be broken down separately, and in many cases 

 the skeleton is rolled up in a ball and lodged near the pylorus. It is not known 

 whether this digestive detritus (bones and other undigested material) passes on 

 down through the intestine or whether it is expelled by regurgitation, but at any 

 rate it is interesting thit i". the stomach the skeletal parts undergo this process 

 and end up in a mass in one part of tho stomach. It is not oossible to tell with- 

 out examining the intestines, but it may be that these materials are regurgitated. 



