264 
suggests diurnal vertical migration of these 
species. 
Some of the cephalopods were uncommon in 
epipelagic waters and are considered to be of 
basically mesopelagic (200-1000 m) distribu- 
tion. Four species were more abundant in deep 
tows than in shallow tows (Table 2 B) . With 
the exception of G. armata, individuals of these 
species were occasionally collected in 0-200 m 
tows after dark at other stations, but they were 
smaller than those from deeper collections. The 
bathymetric distribution of G. armata, sum- 
marized by Sasaki (1929), also suggests that 
it is a deep water species. Vampyroteuthis in- 
fernalis, another deep water species, was taken 
only in tows below 500 m. 
Seasonal Variations 
Seasonal differences in relative abundance 
were striking, though species composition ap- 
parently was not greatly influenced by season. 
The number of animals per tow during the 
summer was about an order of magnitude 
greater than it was during other months. 
PACIFIC SCIENCE, Vol. XIX, April 1965 
TABLE 3 
Seasonal Occurrence of Common 
Cephalopods, 0-200 m Collections, 
All Stations 
SPECIES 
AVERAGE NUMBER PER TOW 
JULY-SEPT. 
(79 tows) 
OCT.-JUNE 
(205 TOWS) 
Gonatus fabricii 
4.9 
0.61 
Gonatus spp. 
1.9 
0.32 
Chiroteuthis veranyi 
0.71 
0.20 
Abraliopsis sp. 
1.9 
0.33 
Catches of G. fabricii were about eight times 
higher during the summer, of Gonatus spp. and 
C. veranyi about six times higher (Table 3). 
Such seasonal differences indicate marked 
changes in the availability of cephalopods due 
to changes in susceptibility to capture or to 
changes in actual abundance. Since the differ- 
ences could be related to the life history of the 
Fig. 2. Size-frequency distributions of Abraliopsis found in midwater trawl samples during the summer 
(July-September) and other seasons of the year (October-June). 
