Macchi et a\: Seasonal egg production of Micropogonias furnieri 



337 





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Figure 5 



Degeneration of postovulatory follicles of M. furnieri at different times after spawn- 

 ing; (A and B) 0-6 h after spawning (no evidences of degeneration); (C) 12 h after 

 spawning (with signs of degradation); (D) 24 h after spawning (with advanced signs 

 of degeneration). T = thecal layer; G = granulosa layer; Lu = lumen; P = postovula- 

 tory follicle. Magnification is shown in (D). 



Daily cycle of spawning 



Percentages of females with hydrated oocytes and with 

 POFs collected at difTerent times during the spawning peak 

 in November 1995 can be observed in Figure 6. Hydrated 

 ovaries were observed mainly in the morning and in the 

 afternoon. At dusk, females with hydrated oocytes were 

 not observed, and ovaries showing age-O-h POFs increased 

 sharply to about 40%, declining to about 59/ at midnight. 

 Postovulatory follicles older than 6 hours (POF stages 1 

 and 2) were observed at different times during the day 

 and night. These observations indicate that some spawning 

 of whitemouth croaker apparently took place early in the 

 afternoon, when many females had hydrated oocytes. How- 



ever, the vast majority of spawning occurred at dusk (near 

 20:00 h), when the frequency of hydrated oocytes decreased 

 to 0% and the incidence of females with new postovulatory 

 follicles reached a maximum. 



Fecundity 



Batch fecundity estimates for females sampled during 

 1995-96 revealed significant differences (P<0.01) between 

 the spawning peak and the end of the reproductive 

 season, being significantly greater in November (216,700 

 ±151,700 oocytes) than in February (96,900 ±52,000 

 oocytes). During 1997-98, females with hydrated eggs 

 were scarce, but fecundity values obtained in March were 



