FISHERY BULLETIN: VOL. 81, NO, 2 



TABLE 4.— Seasonal changes in frequency (7c) of different oocyte developmental stages 

 inyellowtail flounder, n = number of cells examined. Developmental stages and regress- 

 ing type are described in text. 



50 r 



40 - 



>■ 

 o 



3 



O 30 



Ui 



cr 

 u. 



20 



O 



oc 



UJ |0 



a. 



EARLY PERINUCLEOLUS 



00G0NIA 



RESTING 



80 r- 



o 



jan'feb'mar'apr'may' jun 1 jul'aug'sep'oct'nov'dec' 



FIGURE 4.— Seasonal changes in the percent frequencies of oogonia, 

 early perinucleolus, and resting stage oocytes in yellowtail 

 flounder. 



(Table 5; Figs. 6, 7), as did their size-frequency dis- 

 tribution (Fig. 8). 



Oogonia were present year-round in variable per- 

 centages (Table 4), but showed a tendency to be 

 more abundant during the summer and early fall (Fig. 

 4). No significant differences in mean diameter were 

 apparent between months (P>0.05). 



Early perinucleolus oocytes were also present on all 

 sampling dates, but marked seasonal changes in 

 abundance were apparent (Table 4). Relatively few 

 were seen from October through May, but their per- 

 centage increased sharply from June through Sep- 

 tember (Fig. 4). Although their size stayed fairly 

 constant over the year, a significant decrease in mean 

 diameter was noted between September and Oc- 

 tober, and April and May (P<0.05), while a signifi- 

 cant increase (P<0.05) was seen between February 

 and April (Fig. 6). Most early perinucleolus oocytes 

 were from 2 1 to 30 /u.m in diameter in all months ex- 



o 



w 60 

 o 



UJ 



tr 



U. 40 



z 



UJ 



o 



CC 20 

 UJ 



a 



LATE PERINUCLEOLUS 

 EARLY MATURING 

 LATE MATURING 



JAN' 'MAY ' JUN ' JUL 1 AUG 1 SEp'oCT ' NOV ' DEC ' 



FIGURE 5. — Seasonal changes in the percent frequencies of late peri- 

 nucleolus, early maturing, and late maturing stage oocytes in yellow- 

 tail flounder. 



cept June, July, and September when their modal 

 size increased to 31-40 jura (Fig. 8). 



Resting oocytes were present only from October 

 through June (Table 4). From September to October 

 their percentage increased sharply, then fluctuated 

 from about 14 to 32% through the following May 

 when they began a sharp decline in abundance (Fig. 

 4). The percentages of early perinucleolus and rest- 

 ing oocytes were inversely related. As the percentage 

 of early perinucleolus oocytes declined from Sep- 

 tember to October, the percentage of resting oocytes 

 increased. An opposite situation was noted from May 

 to June (Fig. 4). From October through December 

 the mean diameter of resting oocytes increased (Ta- 

 ble 5). It remained fairly constant through April, and 

 then began a gradual decline through June (Fig. 6). 

 The size-frequency distributions of resting oocytes 

 widely overlapped those of early perinucleolus, late 

 perinucleolus, and early maturing oocytes. Modal 

 diameter was relatively small in October, increased 



348 



