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Fishery Bulletin 11 6(2) 
ing times in different parts of the North Pa¬ 
cific vary but generally occur from February 
through May (Vinogradov, 1950). There are 
no data on the development of the reproduc¬ 
tive system, oogenesis, ovary organization, and 
spawning pattern of this species. 
Our main goal was to provide the first de¬ 
scription of 1) oogenesis, 2) type of fertiliza¬ 
tion, 3) gonadal differentiation and develop¬ 
ment, and 4) an estimation of fecundity in 
female smooth lumpsuckers and to define both 
macroscopic and microscopic maturity phases. 
Macroscopic staging is much quicker and less 
expensive than histological staging; however, 
microscopic analysis provides a more pre¬ 
cise determination of phases and was used to 
evaluate the efficacy of macroscopic maturity 
scales. Understanding the reproductive cycle of 
the smooth lumpsucker will help to elucidate 
the biology of other members of the Cyclopteri- 
dae family. 
Materials and methods 
Sampling for this study was carried out during 
an expedition on board of the research vessel 
Professor Kaganovsky (gross tonnage: 2508) of 
the Pacific Scientific Research Fisheries Center 
(TINRO-Center), Vladivostok, Russia, in the 
spring (16 March-30 May) of 2014. An RT/TM 57/360 
midwater trawl net with 30-mm mesh was used. A total 
of 130 female smooth lumpsuckers were collected for 
analysis from the Sea of Okhotsk and near the south¬ 
ern Kuril Islands (43-60°N, 139-159°E). Total length 
(TL, in millimeters), body weight (BW, in grams), and 
gonad weight (GW, in grams) of each female were mea¬ 
sured. The stomachs of smooth lumpsuckers typically 
were filled with water when the fish were brought on 
board, as is characteristic of this species and other 
Cyclopteridae (Ilynsky and Radchenko, 1992; Orlov, 
1994). In this study, BW was measured after water had 
been expelled from the stomach. To analyze gonadal 
development, photographs were taken of the different 
maturity phases and then examined under magnifica¬ 
tion (Fig. 1). Gonadosomatic index (GSI) was calculat¬ 
ed (Barrett and Munkittrick, 2010; Bahamonde et ah, 
2013) according to the following formula: 
Figure t 
Photographs of ovaries of the smooth lumpsucker (Aptocyclus 
ventricosus) in different phases of gonadal maturation: 1) imma¬ 
ture; 2) early developing; 3) developing; 4) spawning capable; 5) 
actively spawning subphase; 6) regressing; and 7) regenerating. 
The length of the scale bars represents 2 cm. 
GSI = 
GW x 100 
BW 
( 1 ) 
where GW = gonad weight (in grams); and 
BW = fish body weight (in grams). 
Histological analysis was performed on 31 gonads 
that represent the different phases of development: 
3 gonads for the immature phase, 12 gonads for the 
early developing subphase, 6 gonads for the develop¬ 
ing phase, 4 gonads for the spawning-capable phase, 2 
gonads for the regressing phase, and 1 gonad for the 
regenerating phase. Gonads were dissected and fixed 
in a 10% formalin solution in the field. The samples 
were then dehydrated, cleared with xylol, embedded in 
paraffin, sectioned (4 pm thickness), and stained with 
hematoxylin and Ehrlich’s eosin. An Olympus BX45 1 
microscope (Olympus Corp., Tokyo, Japan) and Leica 
DC 100 digital camera (Leica Microsystems,Wetzlar, 
Germany) were used for microscopy and photography. 
The image processing and data analysis program Im¬ 
aged, vers. 1.34e (Schneider et al., 2012) was used 
for measuring the diameters of oocytes and visualiz¬ 
ing their structures. The ovarian phases of each go¬ 
nad were classified on the basis of the most advanced 
oocyte stage observed in the histological sections ac¬ 
cording to the scale described in Brown-Peterson et al. 
(2011) (Table 1). 
Absolute and relative fecundity were estimated by 
using 46 freshly caught females determined to be at the 
spawning-capable phase and at the actively spawning 
subphase by using the gravimetric method of Murua et 
al. (2003). A piece of ovarian tissue was taken from the 
median portion of the gonad from each specimen. The 
subsample of each ovary, representing 1.1-5.5% (about 
10 g) of the GW, was weighed, and all advanced oocytes 
(diameter: 1.6-2.0 mm) in the subsample were counted 
by using an optical microscope MBS-9 (LZOS, Lytka- 
1 Mention of trade names or commercial companies is for iden¬ 
tification purposes only and does not imply endorsement by 
the National Marine Fisheries Service, NOAA. 
