FISHERY BULLETIN: VOL. 80. NO. 1 



FIGURE 9.— Ovarian tissue from a giant bluefin tuna (264 cm, 297 kg) collected off the northeast coast of the 

 United States during July 1975. Brown bodies are present, as indicated by arrows. 



however, revealed the presence of atretic bodies. 

 It was impossible to quantify the number of eggs 

 constituting these atretic bodies, although I 

 assume that absorption would occur principally 

 with the smaller vitellogenic ova. Therefore, I 

 have also estimated the number of eggs >0.46 

 mm in the most advanced size mode that could 

 potentially be spawned during one spawning 

 season. For bluefin tuna 205-269 cm FL and 156- 

 324 kg round weight, the average number of 

 eggs 0.33 mm in diameter and larger was 

 estimated as 60.3 million (SE = 4.04) and the 

 average number of eggs 0.47 mm in diameter 

 and larger was estimated as 34.2 million (SE = 

 2.15). No apparent relationship was found for 

 fecundity as a function of length or estimated 

 weight for the size range of bluefin tuna I 

 studied. MacGregor (1968) said that the 

 relationships of length and weight to egg 

 production are masked in many species of fish, 

 because egg production occurs over a relatively 

 short range in size, and because variation in 

 number of eggs produced at each length is great. 



Bailey (1964) found no obvious relationship 

 between fecundity and fish size for American 

 smelt, Osmerus mordax. Schenck and Whiteside 

 (1977) and Loesch and Lund (1977) found a great 

 amount of variability in fecundity for a given fish 

 size for the fountain darter, Etheostoma 

 fonticola, and blueback herring, Alosa aestivalis. 

 Since histological examinations of ovaries and 

 estimated GSI showed that the bluefin tuna are 

 multiple spawners, it is possible that some of the 

 fish selected for fecundity estimates had 

 previously shed eggs. Also the rate of absorption 

 of vitellogenic ova could have varied for the fish 

 selected for fecundity estimates. I found, 

 however, that the dry weight of eggs could be 

 used for estimating fecundity. The following 

 relationships were found: 



F= 5.2895 + 0.0167 W (F? = 0.64), 



where F is the number of ova >0.46 mm in 

 diameter and W is the dry weight of all eggs 

 separated from the ovarian connective tissue. 



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