690 



Fishery Bulletin 92(4). 1994 



a<0.05). The exceptions were that stage- 1 ovaries 

 were not significantly different from stage- 1' or stage- 

 2' ovaries nor were stage- 1' ovaries significantly dif- 

 ferent from stage-2' ovaries. 



Mean GSI of female cobia was low in both Janu- 

 ary and March (1.1 ± 0.2 for each month) (Fig. 4B). 

 The January fish were caught on the winter grounds 

 in south Florida waters whereas the March fish were 

 early arrivals in Mississippi waters. GSI increased 

 to 5.5 ± 2.9 in April but declined slightly in May to 

 4.7 ± 2.0; the largest number of cobia enter Missis- 



sippi waters during these two months. 1 Mean GSI 

 continued to decline during July (2.9±1.9) and Au- 

 gust(1.7±1.6). Slightly more than half of the pairwise 

 comparisons showed significant differences (Tukey- 

 type multiple comparison test, oc<0.05). The GSI of 

 January and March fish was significantly different 

 from April, May, and July fish; the GSI of April and 

 May fish was significantly different from July, Au- 

 gust, and September fish; and the July and August 

 fish were significantly different from each other. 



B Jt¥ -"ASS 









Figure 2 



(A) Stage-1 cobia, Rachycentron canadum, ovary, previtellogenesis. Early previtellogenesis (EP) with large germi- 

 nal vesicle (GV) developing; middle previtellogenesis (MP) characterized by developing nucleoli (N) which cause 

 evaginations to form in the nuclear envelope; late previtellogenesis (LP) characterized by appearance of lipid vacu- 

 oles. (B) Stage-2 ovary, vitellogenesis. Vitellogenic oocytes (st 2) have increased in size and in number of lipid 

 vacuoles. Note nonsynchronous formation of oocytes; early previtellogenic (EP) and middle previtellogenic (MP) 

 stage-1 oocytes also occur. (C) Stage-3 ovary, final maturation. Oocytes (st 3) enter pre-ovulation stage and become 

 more rounded. Lipid vacuoles concentrate around periphery and cause a clearing. Stage-1 (St 1) and stage-2 (St 2) 

 oocytes are also present. (D) Detail of stage-3 ovary. Lipid vacuoles are aggregated around oocyte periphery. Chro- 

 mosomes (C) condense for initiation of meiosis. Stage-1 (St 1 ) and late stage-2 (St 2) oocytes are also present. Scale 

 bars=250 |im. 



