DEVELOPMENT AND CONSERVATION OF TUNA FISHERIES 157 



part of the long-line catches, as noted above. Occurrence in surface 

 schools is less frequent, so that this species is an incidental and insig- 

 nificant part of the catch where surface fishing, using live bait or by 

 purse seines, is the means of production. 



In the Eastern Pacific fishery along the coasts of the Americas, the 

 few bigeye captured are included with the yellowfin in the catch statis- 

 tics. The exact percentage of bigeye included is not known, but exam- 

 ination of landings on a sampling basis indicates it is not large, probably 

 not over 2 or 3 per cent. 



Skipjack 



As indicated above (pp. 154-155) the skipjack, Katsuwonus pelamis, 

 occurs in surface schools in the region of the Eastern Pacific fishery in 

 the same general localities as the yellowfin. It occurs sometimes in pure 

 schools and sometimes in mixed schools with yellowfin of similar size. 

 It is fished both by live bait and by purse seine, just as is the yellowfin. 



The development of the fishery for yellowfin and skipjack in the 

 Eastern Pacific has already been described. The growth of the skipjack 

 catch is shown with that for yellowfin in Figure 1. Although both species 

 have been fished since the initiation of the fishery, yellowfin has been 

 the preferred species, commanding a higher price and being somewhat 

 easier to preserve, particularly before the days of brine freezing. In 

 consequence, the expansion to distant areas during the 1930's was 

 directed primarily at the yellowfin tuna. The postwar growth of the 

 fishery has, on the other hand, depended on skipjack to an increasing 

 extent. It appears that with the increasing exploitation of the yellowfin 

 stock of the Eastern Pacific, and the inevitable accompanying decrease 

 in catch per unit of effort, the fleet has turned increasingly to skipjack, 

 the catch of which has, in recent years, risen a good deal in relation to 

 that of yellowfin. 



Skipjack is the most important species in the Japanese tuna fishery, 

 the landings at the present time being over 200 million pounds per year. 

 This species of tuna has been an important article in the Japanese diet 

 since ancient times, but its capture was confined to coastal waters until 

 introduction of powered fishing vessels early in this century. The off- 

 shore fishery giew rapidly thereafter, encompassing not only Japanese 

 home waters, but regions to the south to well below the equator, and 

 eastward through the Mandated Islands. The fish are captured almost 

 exclusively by pole and line, using live bait for chum. Negligible 

 quantities are taken incidentally by long-lines. Purse seining is reported 

 to have been tried experimentally in recent years. 



During the 1930's, skipjack fishing in the Caroline, Marshall, and 

 Marianas Islands was rapidly developed, in spite of scarcity of live bait 



