Abundance began to decline in about 1960 and 

 continued to do so until 1964-1965 when it reached 

 about 0.8 fish/1, 000 hooks. By 1966. abundance had 

 dropped to about 0.5 fish/1,000 hooks and has fluc- 

 tuated about that level since. 



Since about 1963 the fishery has not exhibited the 

 marked seasonal pattern which it had prior to that 

 time. 



An examination of the catch statistics in terms of 

 numbers of blue marlin (Fig. 6) shows the catch 

 increasing to approximately 75,000 in 1963 in pro- 

 portion to an increasing effort. By 1966, catches 

 decreased to about 22,000 fish and have continued 

 to fluctuate about that level. 



From the earlier analysis (p. 317-318) it seems 

 likely that blue marlin of the eastern Pacific repre- 

 sent the eastern portion of a much larger popula- 

 tion whose center lies west of long. 130°W. There- 

 fore it would not be valid to attempt to explain catch- 

 es and catch rates in the eastern Pacific in terms of 

 effort generated in the eastern Pacific only. 



SAILFISH AND 

 SHORTBILL SPEARFISH 



19GE 63 



AREAS 5,6 a 9 



Figure 17. — Quarterly hook rate of sailfish expressed as 

 number of fish per 1,000 hooks. Upper panel area 6, 

 lower panel areas 5, 6, and 9 pooled. 



Black Marlin 



Catches of black marlin are so low in the eastern 

 Pacific that it is of little value to analyze indices of 

 abundance for this species. Catches increased from 

 about 500 fish in 1956-1958 to about 4,000 fish in 

 1963 (Fig. 6). Since that time, catches have fluc- 

 tuated around 4,000 fish, the highest being 4,200 

 fish in 1969. 



Sailfish 



It has been mentioned previously that sailfish and 

 shortbill spearfish are not differentiated in the catch 

 statistics of the Japanese longline fishery. Data are 

 available, however, from selected cruises which 

 can be utilized to show the relative distribution of 

 the two species (Fig. 12). It can be noted from Fig- 

 ure 12 and Figure 1 that in areas 5, 6, and 9, short- 

 bill spearfish are not taken, only sailfish. Therefore 

 areas 5, 6, and 9 can be used to represent changes in 

 the indices of abundance. In fact, of the total catch 

 of sailfish and shortbill spearfish, about 80% is 

 comprised of sailfish from areas 5, 6, and 9. 



In Figure 17, the catch of sailfish per 1,000 hooks 

 is shown in two groupings. In the lower panel, quar- 

 terly catch rates are pooled for areas 5, 6, and 9, 

 where most of the sailfish from the eastern Pacific 

 are caught. In the upper panel, catch rates for area 

 6, the center of highest sailfish abundance, are 

 shown separately. 



In the pooled area substantial effort was not gen- 

 erated on the sailfish grounds until about 1964. By 

 the first quarter of 1965 the catch rate was at the 

 highest observed level, about 83 fish/1,000 hooks. 

 The annual average abundance for 1965 was also 

 the highest observed for the series 'of years shown, 

 about 32 fish/1,000 hooks. This decreased to about 

 20 fish/1,000 hooks during 1966-1968, and during 

 1969 and 1970 dropped to about 1 1 fish/1,000 hooks. 

 This latter is about one-third the highest value at the 

 outset of the fishery. 



The trends in apparent abundance of sailfish in 

 area 6 (upper panel, Figure 17) are similar to the 

 trends for the pooled areas; however, the decline in 

 abundance in recent years has not been as great in 

 area 6. When the fishery first developed on a sub- 

 stantial scale in area 6. the annual catch rate was 

 about 95 fish/ 1,000 hooks. This decreased rapidly 

 until by 1967 it was about 58 fish/1,000 hooks. Since 

 1968 it has fluctuated around 53 fish/ 1,000 hooks. 



The total catch in numbers of sailfish and short- 

 bill spearfish combined is shown in Figure 6. The 



327 



