TUNA FISHING METHODS AND THEIR APPLICATION 



by 

 Vernon E. Brock ±/ 



The relative importance of different methods of fishing tuna are demonstrated by 

 their contributions to the catch. The limitations and advantages of the various methods 

 are a function of the distribution and behavior of the several species in relation to 

 certain features of the environment. Such differences are described, particularly for 

 the Japanese fisheries, which are the largest and most diversified in the world. 



In brief, the more important methods 

 of fishing are: 



(1) gillnetting - chiefly of importance 

 for the bonito in Peru; 



(2) traps - used in both Japan and 

 Europe for bluefin; 



(3) trolling - important here and in 

 Europe for albacorej 



(U) purse seining - used in the U.S. 

 chiefly for bluefin, but takes 

 also substantial quantities of 

 yellowfin and skipjack; used in 

 Japan for bluefin tuna. 



(5) live-bait fishing - important here 

 for skipjack, yellowfin and in 

 Japan, for skipjack and albacorej 



(6) longline fishing - important chiefly 

 in the expanding Japanese high-seas 

 fishery for all species except skip- 

 jack, and in fact the method by 

 which the largest quantity of tuna 

 is taken by the Japanese; it con- 

 stitutes the basis of the expansion 

 of their tuna fisheries and is the 

 only method presently available 

 which appears to take such fish as 

 the larger tunas in areas of the 

 tropics where the mixed layer is 

 deep. 



JAPANESE TUNA CATCH BY SPECIES AND GEAR 



Data for 1952 and 1957 are graphi- 

 cally presented in figure 1. In 1952 the 

 live-bait method produced 60.6 percent of 

 the total tuna catch (including yellowfin, 



bigeye, black tuna, albacore and skipjack), 

 followed by longline which took 31.3 per- 

 cent. In 1957 the picture has changed 

 considerably with long line becoming the 

 principal gear for tuna production. 



1952 1957 



JAPANESE TUNA CATCH BY SEAK TYPE 



1952 1957 



JAPANESE TUNA CATCH BY SPECIES 



l/ Area Director, Hawaii, Bureau of 



Commercial Fisheries, Honolulu, Hawaii. 



Figure 1. — Japanese tuna catch by gear 

 type and species. 



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