34 
Fishery Bulletin 119(1) 
spawning, and males have been observed to guard egg 
clutches and then die when the eggs they were guarding 
complete development or hatch (Orlov, 1994). It is diffi- 
cult, therefore, to determine if lumpsucker species feed 
during their entire life cycles. However, other representa- 
tives of Cyclopteridae, the Atlantic spiny lumpsucker, 
smooth lumpsucker, and lumpfish, can spawn several 
times during their life cycles (Cox and Anderson, 1922; 
Berge and Nahrgang, 2013; Zhukova et al., 2018). 
In this paper, we provide the first comprehensive data 
on the stomach contents, gonadal development, and fecun- 
dity of Fedorov’s lumpsucker and describe the biology and 
reproductive processes of this little known species. 
Materials and methods 
A total of 69 adult specimens of the Fedorov’s lumpsucker 
were caught on the shelf and slope of Simushir Island, 
located near the center of the Kuril Islands in the Sea of 
Okhotsk in the northwest Pacific Ocean, from 19 March 
through 25 March 2017 during tows of the bottom trawl of 
the FV Anatoly Torchinov that targeted greenlings (Plew- 
rogrammus spp.) at depths of 150—230 m. Specimens were 
caught near Simushir Island within the area bounded by 
the following coordinates: 46°46’N and 151°56’E, 46°40’N 
and 151°52’E, and 46°44’N and 151°46’E (Fig. 1). All 69 
specimens were frozen at —20°C immediately after cap- 
ture and then transported to the laboratory at the Russian 
Federal Research Institute of Fisheries and Oceanography 
in Moscow. The Fedorov’s lumpsucker examined 
in this study ranged in total length (TL) from 64 to 
103 mm and weighed from 12.4 to 64.0 g. The 
59 females caught were 64-103 mm TL (mean: 
81.3 mm TL [standard deviation (SD) 1.23]) and 
12.4-64.0 g (mean: 33.22 g [SD 1.36]), and the 
10 males were 73-95 mm TL (mean: 84.7 mm 
TL [SD 2.50]) and 22.9-60.1 g (mean: 41.85 g 
[SD 5.00]). 
After a specimen was thawed, the food items 
were collected from its stomach, separated under 
a MicroMed MC-2' stereomicroscope (CIT Nelian, 
Moscow, Russia), and weighed to the nearest mil- 
ligram with analytical scales (R160P, Sartorius, 
Bohemia, New York). Fish specimens and food 
items were identified with the aid of Tuponogov 
and Kodolov (2014), Oku et al. (2017), and 
Voskoboinikova (2015). 
Gonads of 14 females and 2 males (size: 
64-92 mm TL and 30.1-38.5 g) were fixed in 10% 
formalin, dehydrated, cleared with xylol, embed- 
ded in paraffin, sliced into sections 5 pm thick, 
and stained with hematoxylin and Ehrlich’s 
eosin. An Olympus BX45 microscope (Olympus 
Corp., Tokyo, Japan) equipped with a Leica DC 100 digital 
camera (Leica Microsystems, Buffalo Grove, IL) was used 
for imaging. Diameters of oocytes and intracellular struc- 
tures were measured by using the software ImageJ, vers. 
1.51 (Rasband, 2018). 
The maturity phases of each ovary and testis were clas- 
sified on the basis of the most advanced stage of germ cells 
observed in histological sections, according to the scale 
described by Guzman et al. (2017). Ovaries were divided 
into 5 phases of development: onset of vitellogenesis, early 
vitellogenic, mid-vitellogenic, late vitellogenic, and perio- 
vulatory. Phase of testis maturity was determined on the 
basis of the presence or absence of male germ cells in a 
gonad: early recrudescence (spermatogonia and spermato- 
cytes), mid-recrudescence (spermatogonia, spermatocytes, 
and spermatids), late recrudescence (spermatogonia, sper- 
matocytes, spermatids, and spermatozoa), spermiating 
(spermatozoa prevail), and postspawning (spermatogo- 
nia and residual spermatozoa). Oocyte development was 
determinated by using the following stages and their asso- 
ciated indicators: primary growth (PG, absence of cortical 
alveoli and yolk granules), early developing (Vtg1, cortical 
alveoli and scattered yolk granules along the outer region 
of the cytoplasm), developing (Vtg2, yolk granules partly 
occupy the cytoplasm), fully vitellogenic (Vtg3, cytoplasm 
completely filled with yolk), and maturing (M, yolk globule 
fusion and nucleus migration). 
Absolute and relative fecundity were estimated by using 
the gravimetric method (Murua and Saborido-Rey, 2003) 
for 5 frozen females (size: 74-95 mm TL and 25.4-60.1 g) 
Sea of Okhotsk 
Pacific Ocean 
A 
151°30'E 152°E 
Figure 1 
Map showing the location (outlined with a black circle) where 69 
adult Fedorov’s lumpsucker (Eumicrotremus fedorovi) were caught 
' Mention of trade names or commercial companies is 
for identification purposes only and does not imply 
endorsement by the National Marine Fisheries Service, 
NOAA. 
during 19-25 March 2017 off Simushir Island, located near the 
center of the Kuril Islands in the Sea of Okhotsk in the northwest 
Pacific Ocean. 
