Longline in 1957 took 52.1 percent of the 

 total landings followed by live-bait with 

 Ul. 7 percent. This changeover can be 

 attributed to the increased effort on the 

 part of the Japanese in exploiting tropical 

 waters. Mothership expeditions have con- 

 tinued to increase production, vessels were 

 based in foreign ports (such as Samoa and 

 New Hebrides) and more and more larger 

 vessels have been built which are capable 

 of long voyages independent of motherships 

 or foreign bases. This increase in longline 

 catches (the picture for 1956 is quite sim- 

 ilar to that shown for 1957) came about by 

 the expansion of fishing grounds into the 

 Indian Ocean around 1953 and the Atlantic 

 at the end of 1956. 



In 1952 skipjack dominated the land- 

 ings accounting for UO.l percent of the 

 total tuna landings in Japan. Next in 

 importance was albacore with 28.0 percent. 

 There was a change in 1957 with yellowfin 

 landings increasing tremendously (27.2 per- 

 cent) followed by skipjack with 26.6 percent. 

 This change is also attributable to increas- 

 ed exploitation by the larger longliners in 



YELLOWFIN 

 BLUE FIN 

 GEYE 



1952 



1952 



YELLOWFIN 

 BLUEFIN 

 BIGEYE 



Figure 2. — Species composition of Japanese 

 longline and livebait fisheries. 



the tropical Pacific, Indian and Atlantic 

 oceans. This change is quite apparent in 

 figure 1. 



The longline catch in 1952 con- 

 sisted very heavily of bigeye tuna (U2 per- 

 cent) followed by equal amounts of albacore 

 and yellowfin (26.5 and 26.2 percent). 

 Bluefin (black tuna) and skipjack are 

 rather insignificant in longline catches. 



In 1957, yellowfin dominated long- 

 line landings (50.3 percent). This change- 

 over is again due to increased longlining 

 effort in recent years. Yellowfin landings 

 which amounted to 25,500 tons in 195'2, 

 increased to 109,500 tons in 1957- 



While not indicated in figure 2, in 

 1957, 96 percent of the total skipjack catch 

 was made by the live-bait method. The 

 remainder was taken by longline, trap, purse 

 seine, and other methods. Similarly, 96 

 percent of the yellowfin catch was made by 

 the longline method. 



In the case of the bigeye tuna, 91 

 percent was made by longline and 9 percent 

 by live-bait. Albacore was largely taken 

 by live-bait (6U percent) and longline (36 

 percent) . Forty-two percent of the bluefin 

 (black tuna) was taken by purse seine and 

 Ul percent by longline. About 9 percent 

 was taken by traps (set nets) . 



The live-bait method accounts for 

 about 75 percent of the United States 

 Eastern Pacific tuna catch. However, purse 

 seiners have increased their share of the 

 catch of tropical tunas in the last three 

 years. 



OBSERVATIONS ON GEAR SELECTIVITY 



Shown in the five panels of figure 3 

 are typical examples of albacore sizes taken 

 by the different types of gear. For long- 

 line, we have shown two panels, one for a 

 sample of sizes taken in the winter long- 

 line fishery by the Japanese, and the other 

 from data obtained at the cannery in Samoa. 

 The second represents sizes taken in the 

 tropical South Pacific. 



It may appear strange that the modal 

 size of winter longline albacore in the 

 North Pacific is slightly smaller than that 

 of the Japanese summer live-bait fishery. 

 As discussed in certain Japanese publica- 



13 



