National Marine Fisheries Service, pers. 

 comm.). 



The ovaries were removed from specimens 

 that had been fixed in 10% Formalin^ and stored 

 in 40% isopropanol. A wedge-shaped sample 

 was taken from each ovary and about 200 eggs, 

 0.25 mm (one micrometer unit) in diameter or 

 greater, were measured, following the method 

 described by Clark (1925). The eggs were se- 

 lected along an edge of the sample correspond- 

 ing to the radius of the ovary. We determined 

 that eggs below 0.25 mm formed most of the 

 egg-stock present in all mature females through- 

 out the year. In some ovaries, eggs about 

 0.25 mm in diameter appeared to be in the early 

 stages of yolk accumulation because they were 

 more opaque than the stock eggs. Each ovary 

 was classified according to the following stages: 



Stage 1. This stage corresponds to stage 1-S 

 described by Schaefer and Orange 

 (1956) : "The gonads are small and 

 ribbon-like. At this stage it is not 

 possible to determine the sex by gross 

 examination. Presumably these are 

 virgin fish that have never yet 

 reached sexual maturity." 



Stage 2. The ovaries contained eggs which 

 formed most of the egg-stock. In 

 some ovaries the larger eggs may 

 have been in the early stages of yolk 

 accumulation but did not form a dis- 

 tinct modal group. 



Stage 3. The ovaries contained one group of 

 eggs distinctly separated from the 

 egg-stock. Modal diameters of this 

 group were from 0.375 to 0.675 mm. 



Stage 4. The ovaries contained two groups of 

 eggs distinctly separated from the 

 egg-stock. Modal diameters of the 

 group formed by the larger eggs 

 were from 0.875 to 0.975 mm. 



Selected egg diameter frequency distributions 

 from stages 2, 3, and 4 are shown in Figure 2. 



Our evidence indicates that Auxis from the 

 tropical Atlantic mature at about 290 mm fork 

 length (Table 1). Fish with ovaries in stages 2, 

 3, or 4 were considered mature; fish which con- 

 tained stage 1 ovaries were considered imma- 

 ture. The smallest mature fish (stage 3) from 

 the eastern Atlantic was 270 mm and the largest 



35- 

 30- 

 25 



20' 

 15' 

 10- 

 5- 



0' 



20- 

 15- 

 10 

 5 

 0' 



STAGE 3 



IS- 

 M- 

 S' 

 0' 



STAGE 4 



r 



05 

 EGG DIAMETER (mm) 



0.75 



Figure 2. — Percent egg diameter frequency distribution 

 from selected ovaries in stages 2, 3, and 4 (smoothed 

 by a moving average of 3). 



Table 1. — Number of mature and immature Auxis ex- 

 amined from the eastern and western tropical Atlantic 

 by 10-mm length intervals. 



^ Reference to trade names does not imply endorse- 

 ment by the National Marine Fisheries Service, NOAA. 



322 



