freed from the connective tissue with dissecting 

 needles. 



Egg diameters were ascertained by using an 

 eye-piece micrometer to measure the axis of 

 the egg as it lay parallel to the micrometer 

 (Clark, 1925). Diameter frequencies were 

 taken for each sample until the lower limit 

 of the most advanced mode was defined. The 

 total number of eggs in this mode was then 

 counted. Fecundity was determined by multi- 

 plying the number of eggs in the most ad- 



vanced mode of the sample by the weight of 

 the two ovaries, and dividing the product by 

 the weight of the sample. I assumed that the 

 number of eggs maturing for the next spawn- 

 ing (fecundity) would be the same as the num- 

 ber of eggs in the most advanced modal group. 

 Frequency distribution of egg diameters, as 

 used for determining the most advanced mode 

 for the first fish in table 3, is shown in figure 

 5. For this fish, only eggs larger than 0.4 mm. 

 in diameter were counted. 



Table 3. --Estimated number of eggs in the largest modal group in ovaries of 

 13 skipjack tuna collected in the western tropical Atlantic, March 26 to 

 April 7, 1966 



Ship, 

 cruise , 

 station 



Date 



Fork length 



Eggs in the 

 largest modal group 



Geronlmo 

 Cruise 7 



133 



Do 



Do 



Undaunted 

 Cruise 2 



129 



103 



Do 



Do 



Do 



Do 



Do 



Do 

 133 



Do 



4/7/66 

 do 

 do 



3/31/66 

 3/26/66 



do 



do 



do 



do 



do 



do 

 4/1/66 



do 



Mm. 



465 

 540 

 540 



580 

 587 

 594 

 604 

 612 

 616 

 631 

 659 

 774 

 809 



No. 



275,000 

 472,000 

 587,000 



482,000 

 465,000 

 262,000 

 877,000 

 389,000 

 689,000 

 653,000 

 857,000 

 1,331,000 

 1,264,000 



13 



