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Oocyte diameter (11m) 
Fishery Bulletin 119(1) 
Oocyte frequency (%) 
DS DOH OO LO OL OL 
IPT PLS L we S Ky 
Oocyte diameter (11m) 
Figure 2 
Frequency of occurrence of oocytes in Fedorov’s lumpsucker (Eumicrotremus fedorovi) caught during 19-25 
March 2017 off Simushir Island, by oocyte size and macroscopic phase of ovarian maturity: (A) onset of vitel- 
logenesis, (B) early vitellogenesis, (C) mid-vitellogenesis, (D) late vitellogenesis, and (E) periovulatory. The 
vertical dashed lines indicate approximate boundaries between the sizes of oocytes at different histological 
stages of development: primary growth (1), early developing (2), developing (3), fully vitellogenic (4), and 
maturing (5). 
such ovaries were at the Vtg3 stage. In Vtg3 oocytes, which 
had a mean @ of 1106 pm (SD 83), the cytoplasm was com- 
pletely filled with yolk globules (Fig. 4C). Periovulatory 
gonads were voluminous and contained oocytes with © of 
about 2 mm and clearly visible oil droplets in germ cell 
cytoplasm. Most of the oocytes were at the M and PG 
stages (Fig. 2E). In M oocytes, which had a mean @ of 
2036 pm (SD 321), there were elongated masses of yolk 
globules with large oil droplets. Cytoplasm was sur- 
rounded by a zona radiata and a large chorion that was 
28-30 pm thick (Fig. 4, D and E). 
Absolute fecundity ranged from 297 eggs in the small- 
est female (size: 74 mm TL and 25.4 g; GSI: 9%) to 494 
eggs in the largest female (size: 95 mm TL and 60.0 g; 
GSI: 12%), and mean F,,,. was 409 eggs (SD 87.9). Rel- 
ative fecundity ranged from 7 to 12 eggs/gram of body 
weight, and mean F,,, was 9 eggs/gram of body weight 
(SD 1.9). The only reliable correlation between body 
characteristics and fecundity is the negative correlation 
between body length and F,,, (r=—0.92, P<0.05; p=—0.97, 
P<0.05; df=3). The correlations between body length and 
weight and F’,,,, are generally positive but with low sup- 
port (P>0.05). 
The testes of both males for which gonads were exam- 
ined were classified as at the mid-recrudescence phase. The 
most advanced germ cells were spermatids; spermatogonia 
and spermatocytes were also present. Such composition of 
male germ cells indicates that active spermatogenesis was 
ongoing but that spermiogenesis had not yet begun. Germ 
cells were organized within cysts, surrounded by Sertoli 
cells and the interstitial compartment. The germinal com- 
partment, consisting of male germ cells and Sertoli cells, 
was lobed, with spermatogonia distributed throughout the 
length of the lobes (Fig. 4F). 
Discussion 
The presence of benthic, benthopelagic, and pelagic spe- 
cies in guts of Fedorov’s lumpsucker indicates that this 
species makes regular and significant vertical migra- 
tions; therefore, this species may be considered a 
