192 



Fishery Bulletin 92(1). 1994 



vitellogenesis occurred when oocytes reached a di- 

 ameter of about 150 p. Vacuolization occurred in 

 oocytes ranging from 180 u to 250 p Deposition of 

 yolk in the outer cortex occurred in oocytes ranging 

 in size from 200 p to 430 p, and hydra ted oocytes 

 ranged in size from 375 (i to 550 p. 



We began our investigation of the timing and 

 duration of oocyte maturation by examining the size 

 composition and histological stage of oocytes col- 

 lected from fish sampled between January and No- 

 vember. Ovaries examined from 68 of 72 fish col- 

 lected during winter and spring (January 1987-88 

 and March 1987-88) contained mainly pre- 

 vitellogenic oocytes. The fish examined from the 

 January samples contained previtellogenic oocytes 



only. Four of 22 fish examined 

 from samples collected during 

 the month of March contained 

 vitellogenic oocytes. Three of 

 these (36-40 cm in length) con- 

 tained vitellogenic oocytes that 

 were hydrated and translucent 

 (405-429 p mean diameter). 

 The fourth fish (46 cm in 

 length) contained oocytes that 

 had recently undergone vitello- 

 genesis (mean diameter=230 p). 

 Vitellogenesis for most fish 

 occurred in the early summer. 

 In May 1988, we observed 

 vitellogenic oocytes in six of 

 nine fish examined, ranging 

 from 40 to 49 cm in length. All 

 of these oocytes were in the 

 early stages of development, 

 prior to vacuolization, with 

 mean diameters ranging from 

 174 to 263 p. Smaller fish 

 (length range 33-42 cm) con- 

 tained previtellogenic oocytes 

 only . In June (1987, 1988) vi- 

 tellogenic oocytes, ranging in 

 mean diameter from 178 p to 

 269 p, were present in 23 of 24 

 fish examined (length range 

 36-52 cm). Vitellogenic oocytes 

 in one fish of 52 cm were at an 

 advanced stage of development 

 (mean diameter=252 p), with 

 yolk granules formed in the 

 outer cortex. The relation be- 

 tween mean diameter of vitel- 

 logenic oocytes and fish length 

 was not significant for the 

 months of May ( 1988) and June 

 (1987, 1988) (linear regression, P>0.1 for all three, 

 n=6, 11, 12) 



By August the oocytes in some of the larger fish 

 (45-50 cm) were nearing hydration. Mean diameters 

 for vitellogenic oocytes from fish sampled in August 

 (1987, 1988, 1990) ranged from 226 p to 429 p. 

 There were significant, positive linear relationships 

 between fish length and mean oocyte diameter for all 

 of these samples (Table 2, Fig. 4). 



The size distributions for previtellogenic and 

 vitellogenic oocytes did not differ significantly 

 (Shapiro- Wilk test, P<0.05) from that of the normal 

 distribution for any of the following cases. There was 

 no significant difference in mean diameter of 

 previtellogenic oocytes for the same months across 



