FISHERY BULLETIN: VOL. 85, NO. 2 



mary growth and yolk vesicle phases as defined by 

 Wallace and Selman (1981), 2) vitellogenic growth, 

 and 3) maturation. An additional developmental 

 category— prematuration— may or may not be con- 

 sidered a substage of late vitellogenesis; although 

 oocyte growth appears to level off at this time, we 

 have no direct evidence that the oocyte completely 

 ceases to take up yolk precursors at this time. 



Changes in the LOD (Fig. 3) during the period of 

 seasonal ovarian recrudescence were similar to 

 changes in the GSI. LODs were small in August and 

 early September, representative of still previtello- 

 genic oocytes. LODs then rose sharply in mid- 

 September as vitellogenic oocytes began to appear 

 in females captured in the Inlet. The range of LODs 

 in the population at this time varied considerably, 

 from <0.01 mm in some fish to nearly 0.56 mm in 

 others. LODs continued to rise in one portion of the 

 population through mid-November, before leveling 

 off between 0.60 and 0.72 mm; in other females, 

 LODs remained below 0.18 mm through the end of 

 each study period. Females with high LODs were 

 last collected in mid-December during the 1985-86 

 breeding season and in mid-January during the 

 1984-85 season. 



Body Size at Maturity 



An examination of the LODs as a function of stan- 

 dard length on a month to month basis (Fig. 4) 

 reveals several body size-related trends that bear 

 on the results presented in Figure 3. During August, 

 the first month of the collections, there was little 

 difference between the LODs of different-sized 

 females, all being low and representative of pre- 

 vitellogenic oocytes. Only a few large striped mullet 

 were collected during this month. This changed in 

 September, with larger females over 32 cm SL 

 becoming more prevalent in the Inlet and exhibit- 

 ing a tendency to have higher LODs than smaller 

 females. By October, smaller females (to a lower 

 limit of 28 cm SL) also began to acquire vitellogenic 

 oocytes, although their average LODs were still 

 lower than those of larger females. During Novem- 

 ber, LODs of larger females leveled off at 0.60 to 

 0.72 mm, but a few smaller females (now to a lower 

 limit of 26 cm SL) continued to have intermediate 

 LODs indicative of oocytes in the early stages of 

 vitellogenesis. By December and January, recruit- 

 ment of smaller females into sexual maturity ap- 

 parently ceased because LODs were now uniform- 

 either greater than the 0.60 mm prematurational 

 oocyte size or less than the minimum 0.18 mm vitel- 

 logenic size— in all females regardless of body size. 



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STANDARD LENGTH (cm) 



Figure 4.— Monthly variation in the relationship of the 

 largest oocyte diameter (LOD) to standard length (SL) 

 in female Mugil cephalus during prespawning ovarian 

 recrudescence along the northeast Florida coast. Circles 

 represent data points from prespawning females (open: 

 1984-85; closed 1985-86); squares represent data points 

 from postspawn females (open: 1984-85; closed 1985-86). 

 Open arrows indicate oocyte size at beginning of vitello- 

 genesis; solid arrows indicate minimum prematuration 

 oocyte size. 



192 



