1966. Catch rates of swordfish taken by the mod- 

 ified gear at night are generally different from the 

 catch rates resulting from standard gear; the reader 

 is referred to Kume and Joseph (1969a) for a discus- 

 sion of this difference. In this report no distinction 

 is made between day and night fishing. 



Data on the longline catches of the Republics of 

 Korea and of China are from the official reports of 

 the respective fisheries agencies of these countries 

 (Anonymous 1968a, 1969a, 1970a, 1971a). These 

 data have not been included in the charts and 

 graphs presented in this report because the amount 

 that they represent of the total catch is extremely 

 low and highly variable. During 1969 the Korean 

 and Chinese catch of billfish in terms of weight 

 amounted to less than 5% of the total longline catch 

 of billfish from the Pacific Ocean. 



OVERALL TRENDS IN CATCH 

 AND EFFORT 



When Japanese longline vessels first began fish- 

 ing in the eastern Pacific in 1956, effort was re- 

 stricted to a narrow region on either side of the 

 equator extending eastward only as far as about 

 long. 120°W (Fig. 1). Effort increased rapidly be- 

 tween lat. 10°N and 10°S of the equator, and by 

 1961 fishing extended eastward to long. 90°W (Suda 

 and Schaefer, 1965). By the end of 1963 it had 

 reached the mainland of South America (Kume and 

 Schaefer, 1966). It then began to expand rapidly 

 poleward and by 1966 fishing was conducted in al- 

 most the entire region bounded by long. 130°W and 

 the continents and lat. 35°N and 40°S (Kume and 

 Joseph, 1969a). Since 1968 the distribution of effort 

 has remained relatively constant. 



The first fishing effort by the Republic of China 

 east of long. 130°W occurred in the mid-1960's. It 

 has remained rather restricted to the area east of 

 long. 1I5°W and lat. 5°N and 30°S. Korean vessels 

 fish primarily between long. 130°W-110°W and lat. 

 5°S-40°S. 



In order to examine trends in catch rates within 

 areas for which there is a continuous time series of 

 catch and effort statistics, we have divided the east- 

 em Pacific into the 18 areas defined by Kume and 

 Joseph (1969a). These areas represent expansions 

 in the distribution of effort generated throughout 

 the fishery (Fig. 1). 



Annual estimates of total effort for the Japanese 

 longline fishery are shown in Figure 2. These esti- 

 mates, expressed in millions of hooks set per year 



within the eastern Pacific Ocean east of long. 

 130°W, have been adjusted to represent complete 

 coverage. From a low level of about 3.5 million 

 hooks set prior to 1960, effort increased rapidly to 

 more than 60 million hooks by 1964. Since 1964, 

 effort has varied around 50 million hooks set per 

 year. Although the number of hooks set is propor- 

 tional to the total fishing effort exerted in the east- 

 ern Pacific it is not proportional to the actual 

 number of longline sets made because there has 

 been an increasing trend in the average number of 

 hooks utilized per set (Fig. 3). Whereas in the 

 mid-1950's about 1,900 hooks were used per set, in 

 recent years about 2,200 hooks per set have been 

 used. For this reason, in the subsequent analysis, 

 catch per hook will be used as an index of apparent 

 abundance rather than catch per set. For such 

 analysis it is assumed that the spacing of hooks on 



Figure 1. — Expansion of the Japanese longline fishery 

 into the eastern Pacific Ocean and designation of areas 

 for analytical purposes. 



312 



