Figure 2. — Annual estimates of total longline effort for 

 the Japanese longline fishery in terms of millions of hooks 

 set in the eastern Pacific during 1956-1970. 



the line does not appreciably affect the catchability 

 of a single hook, although we have not tested this. 

 When the Japanese longliners first began fishing 

 in the eastern Pacific their catches were nearly all 

 tuna (Fig. 4) because very high catch rates of tuna 

 were common in the area in which they operated. 

 As effort increased catch rates of tunas began to 

 decrease rather quickly (Fig. 5). At the same time 

 the demand for billfish (except swordfish) increased 

 as a result of the rapid development of the fish sau- 

 sage and fish ham industry in Japan. The most in- 

 portant ingredients for fish ham and sausage were 

 sailfish and marlin. Another important development 

 related to the billfish fishery took place in about 

 1966; as Ueyanagi (1972) explains, "Raw meat of 

 striped marlin is considered to be the best quality of 

 billfishes and its price equals that paid for the flesh 

 of the more expensive tunas. The meat of billfishes, 



however, did not always command high prices. It is 

 only since about 1966 that the price has increased 

 remarkably. This can be attributed to the advance- 

 ment in freezing techniques; in 1966 rapid deep 

 freezing facilities became a standard part of new 

 fishing vessels. This processing method had a great 

 influence on the demand for the flesh of billfishes in 

 Japan, which almost overnight began to be con- 

 sumed as 'sashimi' (raw fish) just as are the other 

 tunas." In response to the increased demand and 

 higher prices for billfish as well as the decreasing 

 catch rates for tunas, the fishery expanded during 

 the early 1960's rapidly towards the north and 

 northwest where greater concentrations of striped 

 marlin were found. The northward expansion con- 

 tinued through the mid-1960's and increased 

 catches of marlin were made; additionally the 

 fishery expanded shoreward onto the sailfish 

 grounds. From Figure 4 it is clear that after 1965 

 almost half the total catch was comprised of billfish 

 whereas prior to that time most of it was made up of 

 tunas. The catch of tunas decreased from a peak of 

 about 1 .45 million fish to the present average level 

 of about 0.75 million fish. Catch rates for tuna have 

 likewise decreased by about one-half the initial av- 

 erage levels. 



The total catch of billfish, as noted, began to in- 

 crease at about the time catch rates of tunas 

 dropped off in 1962 and has continued to increase to 

 the present average level of about 0.6 million fish 

 per year. 



1.50 





li\ \ 



■A 



1.25 



X 



TUNAS 



l \ 



2 



TUNAS AND 



31LLFISH . / \ 



"" 



BILLFISH 



// \ 





O i.OO 







o 



i .75 





// \ 



A N \ 



* 





// > 





5 -m 





/ / 



.25 



y%^ 



J / 



/ 







/ j. , 



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5657M»60 6iS2« M 6S66 67« 



Figure 3. — Annual average number of hooks per set. 



1956 57 58 59 60 61 62 63 64 65 66 67 68 69 1970 

 YEAR 



Figure 4. — Total annual catch of tuna and billfish, in mil- 

 lions of fish, by Japanese longline vessels in the eastern 

 Pacific. 



313 



