Yoneda et al Reproductive cycle, fecundity, and seasonal distributions of Lophius litulon 
357 
varies seasonally: in summer it is found mainly in 
the Yellow Sea, and during winter and spring it ex- 
tends its range into the East China Sea. Our study 
was initiated to examine the role of reproductive 
biology during the seasonal change in anglerfish 
distribution and to provide scientific background 
for a national management policy for the angler- 
fish fishery. 
35° N 
Materials and methods 
A total of 989 specimens (males=549, females=412, 
unknown sex=28), caught between March 1991 and 
July 1997, were examined (Fig. 1). Of these, 529 
specimens were obtained from five trawl surveys 
conducted by the Seikai National Fisheries Research 
Institute (SNFRI). A further 425 specimens were 
bought in fish markets at Shimonoseki, Fukuoka, 
and Nagasaki, where there are commercial landing 
sites. The locations and date of capture of these 30 N 
fish were obtained from fishermen. The remainder 
(72=35) were caught during a benthic trawl survey 
conducted by Nagasaki University. 
Five SNFRI benthic trawl surveys between Janu- 
ary and February in 1991, 1995, 1996, and 1997, 
and in September 1993 were conducted in the East 
China and Yellow seas, between latitudes 27° and 
37°30'N, west of 128°E longitude. The sampling ar- 
ea was divided into five regions by using lines of 
latitude and longitude, and further divided into 30' 
x 30' (minutes) sampling stations (Fig. 1). Eighty 
and sixty-nine trawl stations were established in 
the sampling area in 1991 and 1993, respectively, 
at depths between 35 and 150 m. In 1995, 1996, 
and 1997, respective totals of 65, 123, and 78 trawl 
stations were established in the sampling area at 
depths between 50 and 200 m. All SNFRI surveys were 
conducted with the RV Kaiho Maru , a 466-ton stern trawl- 
er. At each station, a bottom trawl, with a 66-mm codend 
mesh, was towed for 30 minutes at approximately 3 knots. 
The net mouth was approximately 20 m wide and 5 m 
high. Nagasaki University conducted a trawl survey in the 
East China Sea between 29°and 32°N latitude and 126° 
and 127°30'E longitude, at depths between 70 and 120 m 
in May 1995 with the training ship Nagasaki Maru , an 
842-ton stern trawler. Seventeen sampling stations were 
established. A bottom trawl net, with a 62-mm codend 
mesh, was towed for 60 minutes at approximately 3 knots. 
The net mouth was approximately 17 m wide and 10 m 
high. Most specimens captured by the commercial fishery 
were obtained in winter and spring because the fishing 
areas of commercial vessels vary seasonally owing to sea- 
sonal changes in the target fishes. Winter and spring spec- 
imens were available from the southern Yellow Sea to the 
northern East China Sea, between latitudes of approxi- 
mately 30° and 35°N, west of 128°30'N, at depths between 
35 and 200 m, and were supplemented with specimens 
from the coastal waters of northern Kyushu Island, Japan. 
Summer and fall specimens were taken from the East Chi- 
120°E 
125°E 
1 30° E 
Figure 1 
Geographical distribution of specimens of Lophius litulon collected 
in the East China and Yellow seas. Roman numeral (I-V) repre- 
sents each sampling area. Arabic numeral represents the sam- 
pling station number, n = total number offish examined. 
na Sea, roughly between latitudes 28° and 33°N, west of 
128°30'N, at depths between 35 and 200 m. 
The total length (TL) of all specimens was measured 
to the nearest millimeter. Body weight (BW) and visceral 
weight ( VW) were determined to the nearest gram, and go- 
nadal weight (GW) and liver weight (LW) were measured 
to the nearest 0.1 g. From 989 specimens measured during 
this study, 367 testes and 267 ovaries were collected. For 
histological examination, the middle portion of the left tes- 
ticular lobe was excised, as well as three different parts of 
the ovary (the center of the anterior, middle, and posterior 
portions of the left ovarian lobe). These tissue samples were 
fixed in Bonin’s fluid for 24 hours and preserved in 707 
ethanol. The remainder of each ovary was preserved in 107- 
formalin to measure oocyte size (diameter, size-frequency 
distribution, and batch fecundity) because oocytes shrink 
when fixed in Bonin's fluid. 
After dehydration in ethanol, the gonadal tissues were 
embedded in paraffin wax or methacrylate polymer resin 
(Technovit, Kulzer). Paraffin sections, 5-10 pm thick, were 
stained with Mayer's haematoxylin-eosin. Methacrylate 
polymer resin sections, 2-3 pm thick, were stained with 
a V/r solution of toluidine blue. Paraffin serial sections 
