relationship between the albacore and this 

 oceanographic feature. 



The data from the three fishing cruises 

 covered by this report give evidence that the 

 transition zone undergoes seasonal meridional 

 shifts, south in the winter and north in the fall. 

 If the tuna are associated with this feature, they 

 may be expected to show a similar seasonal shift 

 in occurrence. In figure 5 the vertical tempera- 

 ture sections and the longline albacore catches 

 along 160 W. longitude are shown for the three 

 survey periods. During the winter of 1953-54 

 (fig. 5A) the transition zone was located approxi- 

 mately between 31 and 36 N. latitude, with the 



o 

 surface temperature varying between 58 and 



64°F. During the fall of 1954 (fig. 5B) the trans- 

 ition zone had been displaced northward to between 

 41 and 46 N. latitude. The surface tennperature 

 in the transition zone during this period ranged 

 from about 59 to 68 F. During the subsequent 

 winter (1954-55) the transition zone again moved 

 south to between 31 and 36 N. latitude, with the 



o / *^ 

 surface temperature varying from 58 to 69 F. 



(fig. 5C). The troll-catches of albacore, as 

 shown in figures 4A-4C, show that the albacore 

 were taken farther north in the fall thcin in the 

 winter. The histograms in figures 5A-5C8how 

 a similar meridional shift in the location of the 

 longline-caught albacore with season. Thus, 

 the albacore appears to make seasonal meri- 

 dional movements similar to the movement of 

 the transition zone. 



Table 6 shows the surface temperatures 

 at which albacore were taken by trolling. 

 Catches were most frequently made in tem- 

 peratures between 59 and 61 F. These tem- 

 peratures fall within the range which generally 

 delineates the transition zone at the surface. 



However, it should be pointed out that 

 surface tennperature alone cannot always be 

 relied upon to indicate the presence of either 

 albacore or the transition zone. This is clearly 

 shown in the case of the high catch of 25 albacore 



NORTH LATITUDE 



Figure 5B. --Vertical tennperature sections and longline catch of albacore 

 (catch/ 100 hooks) along 160 W. longitude during the three survey periods. 

 Manning cruise 22, September -November 1954. 



11 



