194 



Fishery Bulletin 92(1). 1994 



January 



n=1001 



10 60 110 160 210 260 310 360 410 460 

 Oocyte diameter (micron*) 



May 



previtellogenic 



vltellogenk; 



10 60 110 160 210 260 310 360 410 460 

 Oocyte diameter (microns) 



June 



prevttellooenlc 



1/ n=676 



^ vttellogenlc 



Ik 



10 60 110 160 210 260 310 360 410 460 

 Oocyte diameter (microns) 



600 

 — 500 

 J.400 

 ?300 



V 



I 200 



"- 100 







August 

 prevttellooenlc 

 1/ 



n= )564 



vltellogenlc 



/ 



10 60 110 160210260310360410460 

 Oocyte diameter (microns) 



October 



(spawning) 



prevttellogenlc 



n=377 

 vttellogenlc 



A 



10 60 110 160 210 260 310 360 410 460 

 Oocyte diameter (microns) 



Figure 3 



Oocyte size composition determined from ovary samples collected from Hecate Strait English sole iPleuronectes 

 vetulus) during January-October in 1988 (samples combined). 



lucent. We then combined all the 

 data on mean egg diameter for 

 spawning fish and there was no 

 relationship between mean egg di- 

 ameter at the time of spawning 

 (hydrated and translucent) and 

 fish length (linear regression, 

 P>0.1, rc = 19). 



Discussion 



Oocyte development 



Dunn and Tyler ( 1969) and Dunn 

 (1970) determined the length of 

 time required for oocyte matura- 

 tion in winter flounder iPleuronectes americanus). 

 They observed two size modes of previtellogenic 

 oocytes at any particular time. They documented the 

 rate of increase in size for these modes for three 

 consecutive years and concluded that the oocyte 

 maturation period for this species was three years. 

 We observed only a single mode for both 

 previtellogenic and vitellogenic oocytes in fish 

 sampled during all the months examined in our 

 study. Johnson et al. ( 1991) reported similar results 

 in their study of Puget Sound English sole. If oocytes 



produced in year i were spawned in year i+1, we 

 would expect to see two size classes of immature 

 oocytes in year i+1, corresponding to those oocytes 

 that were produced in year i (large immatures) to 

 be spawned in year i+1 and those that were pro- 

 duced in year i+1 (small immatures) to be spawned 

 in year i+2. The fact that there were no significant 

 differences in the mean diameter of previtellogenic 

 oocytes for the same months in consecutive years 

 (1987-88) suggests that the oocyte maturation pe- 

 riod for Hecate Strait English sole is probably one year. 



