HANAN: BLUEFIN TUNA FISHERY 



1963 LWA 

 N = 1,533 



Ih-Mj ' I 



1— 



120 140 



160 



180 



60 



80 



100 



120 



140 



160 



180 



60 



80 



100 



120 



140 



160 



180 



O 4 



100 



120 140 



160 180 



FORK LENGTH (cm) 



4 - 



1965 LWA 

 N = 1,380 



120 140 160 180 



FORK LENGTH (cm) 



FIGURE 13.— Bluefin tuna percent length frequencies, 1963-65. Graphs to the left are based on length-frequency samples only, 



whereas those to the right are based on length-weight-age frequency samples. 



TAGGING DATA ANALYSIS 



From 1953 to 1958, 186 bluefin were tagged 

 and released by CFG and IATTC in the eastern 

 North Pacific incidental to tagging other spe- 

 cies. From 1962 to 1968 a tagging cooperative 

 of CFG, U.S. Bureau of Commercial Fisheries 

 (NMFS), and the Mission Bay Research Founda- 

 tion of San Diego tagged and released 2,836 blue- 

 fin. Of these, 565 (20%) were recaptured in the 

 eastern North Pacific, including 7 by sport fish- 

 ing and 9 in the western Pacific (Clemens and 

 Flittner 1969). Bluefin for tagging were caught 

 by purse seine and tagged with spaghetti-loop 



tags prior to 1960 and with spaghetti-dart tags 

 since then. 



Bluefin are caught within about 200 mi of the 

 coast, thus spatial analysis of tag returns is ex- 

 pressed only by latitude. Of the 565 tagged blue- 

 fin caught in the eastern North Pacific, recovery 

 latitude information is available for 540 returns. 

 Data from tagged fish recovered during the sea- 

 son in which they were released (62%) show a 

 general movement northward (Table 8); how- 

 ever, many were caught near the release point 

 and to the south (Table 9). Tagged fish recaptured 

 during the second and third fishing seasons after 

 tagging were well dispersed throughout the fish- 



115 



