5. HatltB 



When moving about • the aklpjacks are often grouped into ehoale composed of Be7eral 

 hundred to many thousands of fish. The fish seen to prefer the waters of the Kuroshlo Cur- 

 rent > which are wanner than those closer Inshorei for the offshore schools are larger and 

 more numerous than those In coastal waters. When sklpjaclcs attack a school of fish such as 

 sardines or anchovies, they surround them until a dense spherical mass Is formed. Then, as 

 stragglers become detached from the school of small flsht the slclpjacks prey upon them. 



The earliest study on the feeding habits of the skipjack was made by Okamura and 

 M&rukawa (1909). Analysis of the stomach contents of fish collected by various fisheries 

 experimental stations throughout Japan showed the food of the skipjack to consist mainly of 

 sardines, gaetropod8> and large crustaceans. Succeeding studies have yielded similar re- 

 sults, and Kiehlnonye (1923, p 454), summarizing these works, stated the food to be medium- 

 sized plsmkton (such as amphlpode, larvae of Squilla and other crustaceans, pteropode, heter- 

 pods, calamarles) and Immature or small fish. In all food studies the sardine is listed as 

 the principal food, but it is highly probable that a large part of the food analyred was the. 

 bait used to catch the skipjack. Therefore, it is difficult to evaluate the importance of 

 the sardine as a natural food. 



In a recent study (Suyehlro, 1938, pp 93-101) the etomach contents of 220 individuals 

 taken under various fishing conditions were analyzed. The main foods of the skipjack were 

 shown to be sardines, anchovies, cuttlefish, and pelagic crustaceans. The author also dis- 

 tinguished between the food habits of the resident and the migratory skipjack. The resident 

 populations living in shallow coastal places where abundant food (sardines, mackerel i horse 

 mackerel, shrimp, an^ihipods, crab larvae, etc) is available eat almost argrthing and can al- 

 wnys find food. In contrast, the migratory skipjacks swimming in the open sea or the deeper 

 coastal waters generally subsist on the Crustacea, cuttlefish, flying fish, and the occasion- 

 al schools of sardines found in the open ocnen and appear to be continually hungry. Since 

 the quantity of food present In the open sea is insufficient for the nnmber of fish present, 

 the migratory skipjacks are more easily taken by the fishermen. 



6. Economics 



The skipjack is eaten raw, boiled, or roasted bat Is most valuable when processed 

 Into "katsuobushi'* (dried skipjack stick). The methods utilized in preparing katsuobusbl 

 were probably developed at an early stage in the history of skipjack fishing, since the spe- 

 cies is soft-fleshed and decomposes r^idly during hot weather, which coincides with the 

 period of peak catch. The skipjack stick is prepared as followst 



The flesh is first flleted from the bone and steamed. At this stage it Is known 

 as "naaaribushi" and will remain without spoiling for about a week or 10 days. A large part 

 of the catoh Is distributed in this manner. If processing is continued, however, the nam&ri- 

 buehi is subjected to alternate smoking and diying for a period of about three weeks, and the 

 weight is decreased to 20-30 percent of the original. Sun drying for one day follows, and 

 then the filets are placed in a barrel where normal growths of Asperlglllus (the penicillin- 

 producing mold) form on the surface. In addition to flavoring and dehydrating the fish, the 

 mold aids in removing fat and in breaking down complex amino acids into their slinpler forms. 

 The growth and scraping off of the mold, followed by sun drying, are repeated several times. 

 Mold growth ceases entirely when the flesh is thoroughly dehydrated. The weight has now been 

 reduced to about 17-18 percent of that of the original fresh filet. This finished product 

 in compearance and texture resembles a stick of hardwood, hence the name "dried skipjack 

 stick* Katsuobushi is one of the most appreciated condiments in the Ji^anese diet. The 

 sticks aire shaved and the shavings used to flavor soap and other dishes. 



BLACK (OR BLUSFIH) TUMA 

 Thunnus or 1 entails (Temninck & Schlegel) 

 Kaguro, Kiromaguro, Suroshibl, Mejl (immatare) 



1. fleneral 



The black tana t^proaches the J^anese coast during its seasonal migration and en- 

 ters shallow waters in great nnabers. Thas the Japanese people have long bean able to ase 



18 



P-630T 



