Table 8. — Summary of albacore catch by relative hook depth (continued) 

 b. Gear with 15-fathom float lines 



below as well as above the thermocline in north- 

 ern waters. It may be calculated from table 7 

 that on Manning cruise 22 the average maximum 

 fishing depth of the 5-fathom gear was 405 feet, 

 which was considerably deeper than the average 

 thermocline depth of 124 feet, while on cruise 

 23 the average maximunn depth of fishing (328 

 feet) was approximately at the depth of the ther- 

 mocline (321 feet). On both cruises the 15- 

 fathom gear was well below the thermocline, 

 with an average nnaximum depth of 432 feet on 

 cruise 22 and 410 feet on cruise 23. If it is 

 accepted that the deeper hooks were fishing 

 below the thermocline, the vertical distribution 

 of the albacore catches (table 8) shows that 

 some of them were caught below the thernno- 

 cline. We cannot as yet accept these findings 

 as final in view of the small catch and the pos- 

 sibility that all of the albacore could have been 

 caught at shallower depths during the retriev- 

 ing of the line. This question can only be 

 settled with nnore data than are presently 

 available. 



Size of Albacore 



The size distribution of the albacore 

 taken in the North Pacific during the three sur- 

 vey periods is shown in figure 7 in which 

 catches fronn longline and trolling gear are 

 treated separately. It is seen that the longline- 

 caught albacore had a wider size range than the 

 troll-caught albacore. During the fall, troll 

 catches ranged in size from 52 to 74 cm. (7 to 

 20 pounds) while the longline -caught albacore 

 ranged from 54 to 114 cm. (8 to 68 pounds). 

 This indicates that the trolling gear samples 

 chiefly the smaller albacore, while both small 

 and large fish are taken on the longline. We do 

 not as yet know how efficiently the longline gear 

 samples the snnaller fish, nor whether or not the 

 small fish were chance captures at the surface 

 during the hauling of the line. But if small alba- 

 core were being taken only during hauling, then 

 they should cdl have been alive when landed. 



However, only 1 7 of the 30 small albacore (less 

 than 80 cm. )£' taken were landed alive, while 

 among fish larger than 80 cm. , 62 out of 88 

 were alive (table 9). The implication is that 

 small albacore are not being taken only at the 

 surface during the hauling of the gear. 



Table 9. • 



-Summary of longline-caught albacore 

 landed alive 



A majority of the longline-caught albacore 

 taken during the first winter (January-March 1954) 

 were large, 93 percent of the catch measuring 

 over 80 cm. (25 pounds). During the fall 

 (September -October 1954) the reverse was true, 

 with the catch made up nnostly of small fish and 

 with those larger than 80 cm. constituting only 

 19 percent of the catch. Finally, the results fronn 



2/ 



— All troll-caught albacore measured 



less than 80cm. (fig. 7) therefore it is 

 assumed provisionally that 80 cm. is the approx- 

 imate size at which "small" and "large" fish are 

 separated. 



16 



