is much branched. The branches extend between 

 the layers of the germinal epithelium. 



Stage B. — From late September to early Novem- 

 ber the ovary contains a greater proportion of 

 oocytes in Stage 3 than earlier in the season. 

 Some oocytes of Stage 4 are also present. 



Stage C. — During winter and early spring the 

 ovary contains some oocytes in Stage 5, a great 

 many in Stage 4, and decreasing numbers in the 

 earlier stages. 



Stage D. — In April, May, and early June the 

 ovary has oocytes mostly in Stages 5 and 6; 

 those in Stage 6 become more and more pre- 

 dominant toward the close of this period. Some 

 oocytes in Stages 1 and 2 also are present. Those 

 in Stages 3 and 4 are rare. The central cavity of 

 the ovary is obliterated by the dense packing of 

 the large oocytes. 



Stage E. — In June, the eggs in the ovary are 

 in a stage subsequent to the last stage shown in 

 figure 11 — some are ready to be spawned. That 

 others have left the ovary is apparent from the 

 empty spaces and the follicular remnants. Oocytes 

 in Stages 1 and 2 are present — a few in Stages 5 

 and 6 may still be found. 



Stage F. — Immediately after spawning and 

 perhaps for a week or two later the ovary contains 

 remnants of the old follicular layers. The oocytes 

 present are mostly in Stages 1 and 2, but some 

 have already reached Stage 3. 



The seasonal progression of ovarian change by 

 no means proceeds at the same rate in all gizzard 

 shad. The figures represent the situation for 

 most shad in western Lake Erie. In some of the 







O .D^fe* 1 



Figure 12. — Unspawned eggs being absorbed while new 

 eggs are developing (I-group gizzard shad, December 16, 

 1953). 



fish the stages are months in advance of those 

 given in the figure; in others, they are months 

 tardy. Nevertheless, differences among indi- 

 viduals decrease as the spawning season ap- 

 proaches. Fish with advanced rates exhibit 

 slower development just prior to the spawning 

 season, but development proceeds rapidly in 

 fish with retarded rates. 



Fecundity 



The number of eggs per individual varied 

 considerably (table 18). Although the number 

 of counts is meager, the averages for the age 

 groups definitely show low egg production among 

 the precocious I-group shad, a maximum pro- 

 duction by the II-group fish, and slowly declining 

 numbers among successively older age groups. 



Table 18 — Number of eggs per individual gizzard shad of different sizes and ages 



