FISHERY BULLETIN: VOL. 81. NO. 1 



60 



80 



100 120 



140 



160 180 



60 80 100 120 140 160 180 



10 



8 - 



Z 6 

 HI 



o 

 a 



LU 4 



1960 

 N = 3.498 



80 



100 120 140 



FORK LENGTH (cm) 



FORK LENGTH (cm) 



FIGURE 12.— Bluefin tuna percent length 

 frequencies. 1958-62. 



1 r 



160 180 



Table 7. — Mean length frequencies 

 of bluefin tuna, north and south of 

 lat. 32°N, 1952-65. 



when overlapping years (1963-65) and composite 

 samples for both data sets are compared (Fig. 

 15). 



Analysis of fish lengths from the first data set 

 shows a decrease in mean length with increasing 

 latitude. These data (1952-65) were also sum- 

 marized by year for areas north and south of the 

 32d parallel (Table 7) for a two-way analysis of 

 variance. The analysis shows significant differ- 

 ences (P<0.01) among years and between areas. 

 These results show that bluefin caught in the 

 north are smaller than those to the south (Fig. 16) 

 and that mean lengths vary considerably, as 

 much as 39.8 cm/yr. 



114 



