38 
Fishery Bulletin 119(1) 
Figure 4 
Images of gonads of Fedorov’s lumpsucker (Humicrotremus fedorovi), caught 
during 19-25 March 2017 around Simushir Island, at various macroscropic 
phases of development: (A) early vitellogenesis, (B) mid-vitellogenesis, (C) late 
vitellogenesis, and (D, E) periovulatory ovaries and (F) a mid-recrudescence 
testis. The histological stages, structures of germ cells, and gonadal elements 
are indicated in the images as follows: primary growth (PG), early developing 
(Vtg1), developing (Vtg2), fully vitellogenic (Vtg3), and maturing (M) oocytes, 
as well as oil droplets (O), zona radiata (ZR), chorion (Ch), follicular layer (F), 
spermatogonia (Sg), spermatocytes (Sc), spermatids (St), Sertoli cells (Se), and 
interstitial tissue (It). The lengths of the scale bars represent 100 pm (panels A, 
B, and E), 200 ym (panel C), 500 pm (panel D), and 50 pm (panel F). 
specimens of other fish species that are releasing demersal 
eggs. Adhesive and demersal eggs have been reported for 
other species of Cyclopteridae (Washington et al., 1984) and 
for representatives of the families Liparidae, Osmeridae, 
Salmonidae, Pleuronectidae, and Clupeidae (Able and 
Musick, 1976; Stehr and Hawkes, 1979). 
The sizes of germ cells at different stages of development 
found in our study were comparable to those reported for 
the smooth lumpsucker (Zhukova et al., 2018). The diam- 
eters of oocytes at the M stage were the same as those in 
lumpfish and a little smaller than those in Atlantic spiny 
lumpsucker and Siberian lumpsucker (Wienerroither 
et al., 2011; Panchenko and Balanov, 2020). 
The F,, of the Fedorov’s lumpsucker 
in our study was significantly lower than 
that reported for other species of Cyclopte- 
ridae. For example, in another study, 
fecundity of lumpfish ranged from 50,000 
to 159,000 eggs (Gregory and Daborn, 
1982). The values of F’,,, of Atlantic spiny 
lumpsucker and smooth lumpsucker 
have been reported to be more than 1000 
eggs (Dolgov’; Hutchings®) and between 
24,240 and 63,756 eggs (Zhukova et al., 
2018), respectively. Such low values of 
F.,,; and low GSI values are due to the 
smaller body size of Fedorov’s lump- 
sucker (size: 74-95 mm TL; GSI: 9-12%) 
compared with the size of lumpfish 
(size: 370-450 mm TL; mean GSI: 18% 
[SD 5.8]) and of smooth lumpsucker (size: 
170-350 mm TL; GSI: 31-56%) (Zhukova 
et al., 2018). Among close relatives of the 
Fedorov’s lumpsucker, only the Atlantic 
spiny lumpsucker had lower GSI values 
in prespawning females with similar body 
length (77.30 mm [SD 15.80]), with GSI 
values of 4.5% according to Hutchings? 
or 1.4-4.8% according to Berge and 
Nahrgang (2013). This circumstance is 
in line with the very weak positive cor- 
relation (linear regression: coefficient of 
multiple determination=0.31) between 
total weight and the GSI, indicating 
equal gonadal development between each 
size class (Berge and Nahrgang, 2013). 
The F,, was 2 times lower in Fedorov’s 
lumpsucker than in smooth lumpsucker 
(Zhukova et al., 2018). In both species, F’,.) 
is also associated with the size of females. 
The structure of the testes and dis- 
tribution of spermatogonia for the 
males examined in our study indicate 
that male gonads were of the unre- 
stricted lobular testis type, as defined 
by Uribe et al. (2014). Similar testis 
types have been recorded for lumpfish 
(Guercini, 2019) and for other teleost 
species of Percidae, Centropomidae, 
Rachycentridae, Cichlidae, Gadidae, Synbranchidae, 
and Erythrinidae (Grier et al., 1980; Taylor et al., 1998; 
Brown-Peterson et al., 2002; Lo Nostro et al., 2003; 
Bizzotto and Godinho, 2007). Therefore, the results of our 
study provide the first data on the diet and reproductive 
features for the rarely caught Fedorov’s lumpsucker. 
? Dolgov, A. V. 1994. Some aspects of biology of non-target fish 
species in the Barents Sea. ICES CM 1994/0:12, 23 p. [Available 
from website.] 
3 Hutchings, J. A. 2002. Ecology and biodiversity of commercially 
unexploited marine fishes in the Northwest Atlantic, 14 p. Final 
report. Dalhousie Univ., Halifax, Canada. 
