156 
Fishery Bulletin 116(2) 
Figure 2 
Photographs of ovaries of the smooth lumpsucker (Aptocyclus ventricosus) 
showing the microscopic characteristics of different gonadal phases: (A) im¬ 
mature; (B) early developing subphase; (C) developing; (D) spawning capable; 
(E) actively spawning subphase; and (F) regenerating. Microscopic characteris¬ 
tics include chromatin nucleolar (CN), perinucleolar (PN), cortical alveoli (CA), 
primary (Vtgl), secondary (Vtg2), tertiary vitellogenic (Vtg3), germinal vesicle 
breakdown oocytes (GVBD), postovulatory follicles (POF), atretic eggs (A), and 
oil droplets (arrow). The lengths of the scale bars represent (A-C) 50 pm, (D 
and F) 100 pm, and (E) 600 pm. 
mean GSI of 28.9% (SD 7.6). The most advanced germ 
cells in this phase were primary and secondary vitel¬ 
logenic oocytes, which increased in diameter because of 
increased yolk in the cytoplasm. Oocytes were from 360 
to 448 pm, and the number of oil droplets increased 
during the later stages. In cortical alveoli oocytes, 
the zona radiata became thicker (7-9 pm), and deli¬ 
cate striations appeared. The process of yolk filling the 
cytoplasm began at the periphery and progressed to¬ 
ward the central areas of the oocytes, whose diameters 
ranged from 447 to 512 pm (Fig. 2C). 
Females with ovaries at the spawning-capable phase 
had a mean TL of 263 mm (SD 45.9), a mean BW of 
944 g (SD 186.4), a mean GW of 330 g (SD 131), and 
a mean GSI of 36% (SD 7.4). In the ovaries of these 
females, vitellogenic oocytes (diameter varied from 525 
to 960 pm) had developed simultaneously (Fig. 2D). 
Only minor asynchrony was visible in the development 
of the advanced cohort of oocytes. The degree of oocyte 
cytoplasm filled with yolk was slightly different. How¬ 
ever, these deviations disappeared by the completion of 
vitellogenesis. The zona radiata became thicker (13-17 
pm), and radial striations appeared. 
Females with gonads at the actively spawning sub¬ 
phase had a mean TL of 297.4 mm (SD 31.6), a mean 
BW of 1284.8 g (SD 313.2), a mean GW of 590.7 g (SD 
149.3), and a mean GSI of 45% (SD 7.2). In gonads 
of these females, the stage of “germinal vesicle break- 
