438 
PACIFIC SCIENCE, Vol. XXI, October 1967 
ZONE 
RANGE (°N) 
OCT 
NOV 
DEC 
JAN 
FEB 
MAR 
APR 
MAY 
JUN 
JUL 
AUG 
SEP 
OCT 
NOV 
ZD 
X 
CD 
2 
o 
X 
3 
X 
CO 
ZD 
1 
2 
3 
4 
5 
6 
7 
8 
9 
10 
I I 
12 
13 
14 
15 
16 
17 
18 
19 
20 
21 
22 
23 
24 
25 
26 
27 
41.0 - 40.5 
40 . 5 - 40.0 
40 . 0 - 39.5 
39 . 5 - 39.0 
39 . 0 - 38.5 
38 . 5 - 38.0 
38 . 0 - 37.5 
38 . 0 - 37.5 
37 . 5 - 37.0 
37 . 0 - 36.5 
37.5 - 37.0 
37.5 - 37.0 
37 . 0 - 36.5 
36 . 5 - 36.0 
36 . 0 - 35.5 
36 . 0 - 35.5 
36 . 0 - 35.5 
36 . 0 - 35.5 
35 . 5 - 35.0 
35 . 0 - 34.5 
36 . 5 - 36.0 
34 . 5 - 34.0 
34 . 5 - 34.0 
34 . 5 - 34.0 
34 . 0 - 33.5 
33 . 5 - 33.0 
33 . 0 - 32.5 
Fig. 3. Swarming season of Euphausia pac/fica in the coastal areas of the Sea of Japan (see text). Zones 
are shown in Figure la. 
temperature during the swarming season ranges 
between 7° and 16°C. 
Figure 5 a shows the average change of sur- 
face water temperature during the first six 
months at Enoshima, a tiny island located in 
the middle of the fishing ground for euphau- 
siids around Kinkazan (Fig. lb). Daily hydro- 
meterological observations have been made at 
this island since 1910, with an interruption 
during the period from 1945 to 1953. In this 
Pacific coastal region, swarming starts with the 
minimum surface water temperature (in Feb- 
ruary and March), continues as the temperature 
rises, and ends when it reaches about 12°C, 
thus demonstrating again a relationship between 
swarming and low temperature. 
The vertical distribution of temperature and 
its annual change was also examined for the 
Kinkazan waters. Figure 6 shows the mean 
annual changes of temperature profiles down 
to 200 m at two points 10 miles off Ozaki ( a ) 
and Shioyazaki (b ) , respectively. It was not 
possible to learn the results of long-term oceano- 
graphic observations carried out at a definite 
station adequately close to Kinkazan, which 
would have been an ideal station. Therefore 
these two stations were substituted. Monthly 
observations have been made along the west- 
east lines, including the above two stations as 
the nearest ones to the coast, for 20 years off 
Ozaki and for 24 years off Shioyazaki. Figure 6 
shows that sea water is completely mixed from 
the top down to a depth of 200 m, and that a i 
low temperature prevails during the months 
corresponding to the swarming season of [ 
euphausiids. 
It seems probable that the water temperature ' 
profile in the euphausiid fishing ground near 
Kinkazan is more nearly similar to that off j 
Ozaki than to that off Shioyazaki, which is 
located in the south where the sea conditions 
are more directly influenced by the warm 
