20.0 

 IS.0 

 16.0 

 14.0 

 12.0 

 10.0 



e.o 



6.0 

 4.0 

 2.0 



AREAS 14, 15. 16, 17 



i I i . i I ... 1 



AREAS 3, 5, 6 



i . ■ . i . ■ . I ... i 



AREAS 9, II, 12 



Figure 15. — Quarterly hook rates expressed as number of 

 fish per 1,000 hooks for striped marlin for three major 

 fishing areas in the eastern Pacific Ocean. 



this area is great. In a single year quarterly rates 

 have varied by as much as a factor of 15. This var- 

 iability seems to follow a consistent pattern. Prior 

 to 1969 the first quarter exhibited the lowest abun- 

 dance while the third quarter exhibited the highest. 

 During the last 2 yr, 1969 and 1970, the peak catch 

 rate shifted to the fourth quarter. 



Areas 14, 15, 16, and 17 of Figure 1 are used to 

 represent conditons on the southern striped marlin 

 grounds. The fishery developed during 1962-1963 

 and since that time has supported a significant share 

 of the longline catch of marlin from the eastern 

 Pacific. Peak catch rates were experienced in this 

 area during 1965 when about 5.5 fish/1,000 hooks 

 were taken. The index of abundance has declined 

 steadily since that time to the present level of about 

 1.8 fish/ 1,000 hooks. 



These data suggest that the apparent abundance 

 of marlin on the equatorial and southern grounds 

 has decreased to about one-third of its highest level. 

 Apparent abundance on the northern grounds has 

 remained nearly constant since 1965, perhaps in- 



creasing very slightly. When all areas in the eastern 

 Pacific are pooled, the catch rate of striped marlin 

 reflects no consistent increasing or decreasing 

 trends since about 1965. 



The total catch of this species from the eastern 

 Pacific increased, with increasing effort, to about 

 270,000 fish by 1964 (Fig. 6). It decreased to about 

 225,000 fish during 1965 and remained at that level 

 during 1966 and 1967. In 1968 it increased sharply to 

 an all-time high of about 337,000 fish but decreased 

 thereafter to a level of about 180,000 fish by 1970. 



It is difficult to interpret these catch statistical 

 data in terms of the effect that fishing may be having 

 upon abundance and productivity because the 

 striped marlin of the eastern Pacific most likely 

 form part of a larger stock in waters to the west. In 

 order to make such a meaningful stock assessment 

 analysis for striped marlin, it would be necessary to 

 examine the dynamics of the stocks over a much 

 wider range of the fishery. 



Blue Marlin 



Blue marlin have been taken in the Japanese long- 

 line fishery since it first began operating in the 

 Pacific, east of long. 130°W, in 1956. Catches of this 

 species are primarily centered in the area lying be- 

 tween lat. 10°N and 10°S and west of about long. 

 100°W. To examine trends in apparent abundance, 

 catch rates from areas 7, 10, 11, and 13 have been 

 pooled and are shown by quarters in Figure 16. 

 These areas were chosen because a time series of 

 effort extending back to the early years of the 

 fishery are available, and such data should provide 

 a useful index of relative abundance. 



During the late 1950's, catch rates for blue marlin 

 varied around 3 fish/1 ,000 hooks. Up to about 1963, 

 the fishery was very seasonal; the first quarter 

 showed the highest abundance, reaching 5 

 fish/1,000 hooks at times, and the third quarter 

 showed the lowest abundance dropping to nearly 1 

 fish/1,000 hooks at times. 



BLUE MARLIN 



Figure 16. — Quarterly hook rate of blue marlin expressed 

 as catch in numbers per 1,000 hooks for areas 7. 10. 11. 

 and 13 combined. 



326 



