BAGLIN. JR.: REPRODUCTIVE BIOLOGY OF WESTERN ATLANTIC BLUEEIN TUNA 



Figure 6.— Ovarian tissue from a giant bluefin tuna (250 cm) 

 collected off the Gulf of Mexico during March 1978. Early 

 stage 4 oocytes (upper arrow), stage 2 oocytes (middle arrow), 

 and stage 3 oocytes (lower arrow) are present. 



Figure 7.— Ovarian tissue from a giant bluefin tuna (205 cm) 

 collected off the Gulf of Mexico during May 1978. Late stage 4 

 oocytes (upper arrow), stage 2 oocytes (middle arrow), and 

 stage 3 oocytes (lower arrow) are present. 



Frade and Manacas (1933), who speculated that 

 the rapid degeneration of the follicles could be 

 caused by pressure exerted by neighboring 

 oocytes. My findings also confirm that western 

 Atlantic bluefin tuna released eggs intermit- 

 tently during April, May, and June, the majority 

 during May. 



Fecundity Estimates 



Fecundity estimates were obtained for 28 

 western Atlantic bluefin tuna, which were 



collected from the Gulf of Mexico and Florida 

 Straits during April, May, and June of 1967, 

 1968, 1974, 1975, 1976, and 1978 (Table 4). The 

 reliability of the dry gravimetric method was 

 tested by estimating the fecundity of an 

 individual fish by counting and weighing eggs 

 from four subsamples. Based on these four 

 estimates, the average number of eggs >0.46 mm 

 in diameter was 41.6 million with a range from 

 40.0 to 43.0 million and a standard error of the 

 mean (SE) of 0.76. The average number of eggs 

 >0.32 mm in diameter was 76.0 million with 

 a range from 72.5 to 82.5 million and SE = 

 2.2. 



I am presenting two estimates of potential 

 fecundity, and the estimate based on eggs >0.32 

 mm in diameter essentially coincides with the 

 size of 0.33 mm used by Rodriguez-Roda (1967) 

 for eastern Atlantic bluefin tuna. This would be 

 the potential number of eggs that could be 

 spawned, assuming there was no degeneration or 

 absorption of advanced unovulated eggs. My 

 histological examinations of bluefin ovaries, 





Figure 8.— Ovarian tissue from a giant bluefin tuna (256 cm, 268 kg) collected off the northeast coast of the 

 United States during August 1975. Stage 2 oocytes are present, as indicated by arrow. 



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