FISHERY BULLETIN: VOL. 73, NO. 2 



Om 



50 m 



100 m 



150 m 



200 m 



250 m - 



6°N S-N I0°N I2°N I4°N I6°N 



I8°N 20°^ 



Figure 29.-Temperature (°C) sections from lat. 8°05'S to 5°21'N along long. 117° to 120°W, and from lat. 5°45'N, long. 120°14'W to lat. 



21°03'N, long. 157° 14'W, cruise Gilbert 116, 19 October-7 November 1969. 



Table 14.-Tota] fishing effort Cruise Gilbert 116, October 1969. 



Table 15.-Relative abundance (catch /line-hour) of troll-caught 

 skipjack and other tuna in the study area. Cruise Gilbert 116, 

 October 1969. YF and BE mean yellowfin and bigeye. * means 

 <501ine-h. 



Zone 

 latitude 



Current 

 system 



Skipjack catch/ 

 line-hour 



Other tuna 

 catch/line-hour 



0.240 



0.342 



0* 



0.065 



0* 



0.087 



0* 



0.095 



0* 



0* 



0* 



0* 







0.097 



0.017 



0.017 





 

 











0.138 (YF) 



























0.093 (YF or BE) 















correlation between catch/line-hour and 

 schools/hour was significant at the 1% level (r = 

 0.908, data of Tables 15 and 16), as on the cruises 

 made in 1970 and 1971. The covariance analysis in 

 Table 17 shows that the regressions of 

 schools/hour on catch/line-hour for the three 

 cruises did not differ significantly in slope, but 

 differed in elevation. 



Table 16.-Relative abundance (schools/hour) of skipjack in the 

 study area. Cruise Gilbert 116, October 1969. *means < 9 h of 

 observations 



Schools/hour 



Zone 



latitude 



Current 

 system 



Based on 

 troll catch 



Based on total catch 

 (troll plus pole-and-line) 



0.42 



0.50 



0* 



0.31 



0* 



0.21 



0* 



0.34 



0* 



0* 



0* 



0* 







0.15 



0.05 



0.08 



0.42 



0.50 



0* 



0.39 



0* 



0.26 



0* 



0.34 







0* 



0* 



0* 



0.22 



0.15 



0.05 



0.08 



Table 16 shows the maximum at lat. 6° to 

 8°10'N, as in Table 15. Inclusion of the pole-and- 

 hne data increases the indices in other zones, i.e. 

 lat. 4° to 5°N, 2° to 3°N, and 4° to 5°S. The range of 

 the indices for schools /hour is about the same as 

 for the other cruises. 



Considerable catches of skipjack and other tuna 

 were made on passage to and from the area. Data 

 on relative abundance (catch/line-hour) are given 

 in Table 18. Results should be used with care as 

 fishing effort never exceeded 50 line-hours per 

 day. There were moderate to high catch rates 

 between lat. 4°45' and 8°30'N (long. 148° to 

 138°W), with indices at about the same level as at 

 lat. 6° to 8°10'N in the study area (Table 15). Catch 

 indices for other tuna were low. 



404 



