GREELEY ET AL.: STRIPED MULLET OVARY 



added) and control groups, and then transferred into 

 separate 35 x 10 mm petri dishes containing 3 mL 

 of a 75% L-15 culture medium (Sigma) at pH 7.5. 

 A solution containing 3 i^g of 17a-hydroxy-20/?- 

 dihydroprogesterone in 10 /uL of 95% ethanol was 

 added to each treatment dish (for a final steroid con- 

 centration of 1 ^ig/mL); 10 ^L of 95% ethanol was 

 added to each control dish. Oocytes were incubated 

 at 20°C for 48 hours and then examined for germ- 

 inal vesicle breakdown (GVBD), which was easily 

 noted by the absence of the germinal vesicle (GV) 

 or nucleus in the highly transparent postmaturation 

 oocyte, as an indicator of the resumption of meiotic 

 maturation in response to the hormone. 



Fecundity 



Potential fecundity was estimated for each fish 

 whose oocyte size-frequency profile demonstrated 

 that recruitment of oocytes into vitellogenesis had 

 ceased as potential fecundity = [(number of re- 

 cruited oocytes in ovary piece) x (weight of whole 

 ovary) ]/(piece weight). 



RESULTS 



Gonadosomatic Index (GSI) 



Ovarian recrudescence in the striped mullet occurs 

 during autumn and early winter in coastal waters 

 of northeast Florida, as indicated by seasonal 

 changes in the GSIs of females collected from the 

 Matanzas River Inlet (hereafter referred as Inlet) 

 during the 1984-85 and 1985-86 breeding seasons 

 (Fig. 1). In August of 1985, the earliest month of 

 collections for this study, GSIs were <1 in all sam- 

 pled fish. Ovaries represented by these low GSIs 

 were quite small and were either translucent and 

 colorless (smallest and least developed ovaries) or 

 opaque with a red hue resulting from extensive 

 vascularization (slightly larger and more devel- 

 oped ovaries). Similar low GSIs continued to be 

 found in all females collected through mid- Septem- 

 ber. 



In late September the GSIs of a portion of the col- 

 lected females rose sharply, to nearly 9. The much 

 larger ovaries represented by these high GSIs were 



X 



UJ 

 Q 



O 



I- 

 < 



o 

 o 



Q 

 < 



O 



20 



15- 



10- 



o 1984-1985 

 • 1985-1986 



1. 



o 

 o 



o 

 o 



^ 



t 





•: 



" 



o 

 o 



20 

 AUG 



10 20 

 SEP 



10 20 

 OCT 





10 20 

 NOV 



-T^-V 



10 20 

 DEC 



fV-J 



20 

 JAN 



Figure 1.— Variation in the gonadosomatic index (GSI) of female Mugil cepkalus >20 cm 

 SL during prespawning ovarian recrudescence along the northeast Florida coast. 



189 



