Surface Swarming of Euphausiids — Komaki 
439 
Fig. 4. Annual changes of surface water temperature and salinity at Nyudozaki (a), Kyogasaki ( b ), and 
Okinoshima (c). Locations are shown in Figure la. Measurements were made from 1915 to 1950 with 
interruptions in some years. 
Kuroshio. Such a condition of low and uniform 
temperature as prevails from the surface down 
to 200 m in the vicinity of Kinkazan provides 
no temperature barriers to euphausiids that may 
be dwelling in the depths (Boden and Kampa, 
1958). In other words, euphausiids, during 
their vertical migration, do not encounter the 
temperature difference between day and night 
levels that has been discussed by H. B. Moore 
(1952). 
Annual Variations in Swarming 
The statistics for annual yields of euphausiids 
recorded at the Onagawa fish market (Table 
2) indicate remarkable annual changes in 
euphausiid abundance in the vicinity of Kin- 
kazan. Each value in Table 2 can be inter- 
preted as an index of the standing crop of 
swarming euphausiids in each swarming sea- 
son, because there were no notable changes in 
fishing effort (i.e., the number of fishing boats) 
throughout these seven years, and almost all 
euphausiids fished in the area were landed at 
the Onagawa fish market. 
Similarly, in the nearshore waters of the 
Sea of Japan, it was also observed that the 
extent of swarming fluctuates widely from 
year to year. Although profuse swarming oc- 
curred during the period from 1943 through 
1949 (Uda, 1952), it has been observed only 
rarely since 1953. The relative abundance of 
euphausiid swarming during the period 1945- 
1956 in the nearshore waters of the Sea of 
Japan is shown in Figure 7. Each symbol repre- 
sents an answer from an individual fisherman. 
Figure 7 illustrates that intensive swarming in 
the Sea of Japan took place until 1953 but 
ceased thereafter. Although no numerical data 
