FISHERY BULLETIN: VOL. 75, NO. 2 



1(76 5) 



"Large Yellow" 8/24/73 N = 77l 4specimens 



Large Yellow" 10/21/74 N = I495 4specimens 



"Embryos" 3/7/74 N=379 Ispecimen 



"Resting" 3/22/74 NM894 4 specimens 



-i 1 1 1 1 1 1 1 1 1 1 1 1 1 1 



2 03 04 05 06 07 08 09 10 II 12 13 14 15 16 17 18 



Diameter (mm) 



FIGURE 21. — Size composition of oocytes, ova, and larvae within 

 Pacific ocean perch ovaries at different stages of the reproductive 

 cycle. Maturity stage of the gonads these data were collected 

 from is shown above each size frequency curve. Numbers in 

 parentheses indicate the percentage of oocytes that are 0.15 mm 

 or smaller. 



son 1974) indicate that most embryos are released 

 during a single spawning peak that lasts only 2 or 

 3 wk. 



In view of the oocyte measurement results and 

 the fact that studies on the fecundity of Sebastes 

 marinus have suggested a strong element of fail- 

 ure in oocyte fertilization (Raitt and Hall 1967), it 

 seems that current estimates of fecundity must be 

 regarded as somewhat tentative. Complex 

 changes in fecundity probably occur after the first 

 brood of oocytes has been fertilized and detailed 

 morphological work will be required to determine 

 their significance. 



For purposes of this study, fecundity was esti- 

 mated from the number of mature oocytes present 

 prior to fertilization. All oocytes less than 0.30 mm 

 in diameter were classified as immature on the 

 basis of preliminary comparisons of oocyte size 

 frequencies for juvenile and adult specimens. The 

 data in Figure 21 suggest that this cutoff point was 

 somewhat high, however, and that many of the 

 oocytes in the 0.25- to 0.30-mm size class eventu- 

 ally mature. Even if all oocytes that were in the 

 0.249- to 0.293-mm size class during the collection 

 period were actually maturing, the error gener- 

 ated by calling them immature would be less than 

 about 10%. 



Counting the Oocytes 



passed the fertilization stage. There was no single 

 dominant mode of mature eggs or larvae in any of 

 the fertilized specimens that were examined (Ta- 

 ble 15). 



Despite the wide range of egg size and develop- 

 ment within fertilized specimens, most of their 

 progeny will probably hatch and be released at 

 about the same time. Field observations (Gunder- 



TABLE 15. — Oocyte size frequencies for individual specimens of 

 "fertilized" Pacific ocean perch females. 



Oocyte size 

 class (mm) 



Number observed 



Oocyte size 

 class (mm) 



Number observed 



159 

 0.159-0.203 

 0.204-0.248 

 0.249-0.293 

 0.294-0.338 

 0.339-0.383 

 0384-0.428 

 0.429-0.473 

 0.474-0.518 

 0.519-0.563 

 0.564-0.608 

 06090 653 

 0.654-0.698 

 0699-0.743 

 0.744-0.788 



262 



30 



13 



5 



19 



6 



1 



7 



1 



3 



1 



2 

 2 



15 



237 



30 

 10 

 6 

 5 

 1 

 1 

 2 



240 



26 



7 



4 

 3 



1 



227 



54 

 10 



7 

 1 



0.789-0.833 

 0.834-0.878 

 0879-0.923 

 0.924-0.968 

 0.969-1.013 

 1.014-1.058 

 1.059-1.103 

 1.104-1 148 

 1.149-1.193 

 1.194-1.238 

 1.239-1.283 

 1.284-1.328 

 1 .329-1 .373 



Total 



11 

 4 

 4 

 2 

 2 

 1 



1 



2 

 1 

 10 

 4 

 5 

 2 

 6 

 1 



— 2 1 — 

 395 321 317 324 



Fecundity was estimated through subsampling 

 by volume. The ovarian contents from each fish 

 were removed from the storage solution, passed 

 through a 1.17-mm screen to remove large parti- 

 cles of ovarian tissue that remained, and placed in 

 a large beaker; water was then added until 2,000 

 ml of oocytes and water had been obtained. The 

 mixture was stirred magnetically until all oocytes 

 were distributed throughout the water column 

 and a 5-ml subsample withdrawn with a pipette. 

 Care was taken to sample all parts of the water 

 column with the pipette. Four to six subsamples 

 were taken in this manner, the exact number de- 

 pending on the standard deviation of the first four 

 subsamples. 



The oocytes in each subsample were then 

 counted, using a binocular microscope. Two or 

 three replicate counts of each subsample were 

 made by two different observers during the early 

 phases of the study. The number of replicate 

 counts was gradually reduced, however, as it be- 

 came clear that there was little variation between 

 them. Throughout the study, all counts for a given 



392 



