BAGLIN, JR.: REPRODUCTIVE BIOLOGY OF WESTERN ATLANTIC BLUEFIN TUNA 



little development towards maturity was evident 

 in the age 1 through age 7 western Atlantic fish 

 with the exception of one age 7 fish collected in 

 June with a GSI of 1.75. The eastern Atlantic 

 small and medium fish, on the average, have a 

 larger mean GSI than the western Atlantic small 

 and medium fish. The largest GSI (2.2) calcu- 

 lated from the eastern Atlantic small- and 

 medium-sized bluefin tuna was found for a fish 

 captured during May at an estimated age of 8 yr. 

 Body and ovary size, by month, for 403 western 

 and 75 eastern Atlantic female giant bluefin 



tuna are presented in Table 3, with the 

 calculated monthly GSI presented in Figures 1 

 and 2. The average body and ovary size of the 

 female giant fish from the western Atlantic was 

 larger than that of the eastern Atlantic fish for 

 each month. Well-developed ovaries were 

 present in western Atlantic giant bluefin tuna 

 during April and May. These fish were collected 

 from the Gulf of Mexico longline and sport 

 fishery and from the Florida Straits sport 

 fishery. Ovarian development was minimal 

 during October, as indicated by a low mean GSI, 



3.6 

 3.2 





Table 3.— Length, weight, and gonadal data for 403 female giant western Atlantic 

 bluefin tuna collected during 1965-68, 1974-78, and for 75 female giant eastern Atlantic 

 bluefin tuna collected during 1963 by Rodriguez -Rod a (1967). 



3.2-| 



3.0 



2.8 



2.6 



2.4 



2.2- 



2.0 



1.8 



1.6 



1.4 



1.2 



1.0 

 .8 

 .6 

 .4' 

 .2- 

 O 



MAY 

 N = 17 



1UNE 

 N=12 



JULY 

 N=30 



AUG. 



Nil. 



Figure 1. — Seasonal variation in gonosomatic index of 403 

 female giant western Atlantic bluefin tuna collected from 1965 

 through 1968 and 1974 through 1978. The number, mean 

 (horizontal line), range (vertical line), 1 SD on each side of the 

 mean (open box), and 2 SE on each side of the mean (shaded 

 box) are shown. 



Figure 2.— Seasonal variation in gonosomatic index of 75 fe- 

 male giant eastern Atlantic bluefin tuna collected during 1963 

 by Rodriguez-Roda (1967). The number, mean (horizontal line), 

 range (vertical line), 1 SD on each side of the mean (open box), 

 and 2 SE on each of the mean (shaded box) are shown. 



125 



