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PACIFIC SCIENCE, Vol. XIX, October 1965 
Observations on living animals were made 
in a 20-gallon aquarium with a sealed top 
aboard the M/V "John N. Cobb” during a 
cruise in January 1962. Motion pictures were 
taken at this time which allowed a more de- 
tailed behavioral analysis to be made on shore. 
OBSERVATIONS 
Geographic Distribution 
Prior to this study the known geographic 
distribution of O. calif orniana was recorded 
from four specimens reported by Berry (1949: 
24; 1952:183; 1954:29; and 1955:219, 223). 
The exact locations for these captures are not 
given, but from Berry’s descriptions they ap- 
parently were confined to a small area off Hum- 
boldt Bay, California (approximately 45° 10'N, 
125°10'W). 
The data in Table 1 extend the geographic 
range northward 2200 miles along the conti- 
nental shelf to off Unimak Island, Alaska — 
that is, from northern California to the Aleu- 
tian Islands, Alaska. 
Bathymetric and Seasonal Distribution 
The known bathymetric range of this spe- 
cies off northern California as recorded by 
Berry (ibid.) is from 188 to 280 fathoms (344- 
512 m). Specimens collected from the Colum- 
bia River trackline were taken at depths from 
250 to 450 fathoms (457-823 m) ; those off 
Washington from 150 and 308 fathoms (274- 
563 m); and those from the Gulf of Alaska 
from 68 to 300 fathoms (124-548 m). The 
above records extend the known bathymetric 
range shoreward to 68 fathoms (124 m) and 
seaward to a depth of 450 fathoms (823 m). 
As has been observed for the western Pacific 
congener (O. depressa ) , O. calif orniana has 
been collected from shallower water at the 
northern end of its range, with the bathymetric 
range being wider to the north despite infre- 
quent trawling in water deeper than 300 fath- 
oms in northern waters. 
The known bathymetric ranges of the other 
species of Opisthoteuthis are not all similar 
(Robson, 1929:167-173). Both O. depressa 
from Japanese waters and O. agasshii from 
the North Atlantic have been reported at greater 
depths (587 and 1058 fathoms [1073 and 
1934 m], respectively) than O. calif orniana. 
The bathymetric ranges of the other four spe- 
cies, O. extensa, persephone, pluto, and medu- 
soides , fall within that of O. calif orniana. 
The temporal distribution of males and fe- 
males by depth along the Columbia River 
trackline is presented in Figure 1. Although 
the number of specimens is small, males appear 
to occupy a greater bathymetric range than 
females. The latter were never captured at 
depths shallower than 375 fathoms (686 m). 
There are, however, three known records of 
females from levels shallower than 375 fath- 
oms (686 m): one off California in 188 fath- 
oms (344m) (Berry, 1949:24), one off Wash- 
ington in 150 fathoms (274 m), and one from 
the Gulf of Alaska in 68 fathoms (124 m). 
On the trackline the data suggest that the 
males may move seasonally, being found at 
shallower depths in the summer. Perhaps mat- 
ing takes place in late winter when the sexes 
occupy similar depth zones, but this is only a 
surmise. 
In cephalopods a separation of the sexes by 
depth has been noted by several authors. Is- 
grove (1909:472) notes a disparity in the sex 
ratio of Eledone. She suggests that the dis- 
parity is caused by the females breeding in 
littoral waters, in which they are more fre- 
quently taken. Robson (1925:1325) presents 
figures for Octopodidae picked at random from 
selected reports, where inside of 200 fathoms 
(366 m) the percentage of females is greater 
and outside the percentage of males is greater. 
Both of the above findings, where the female 
Octopodidae predominate in shallow water, 
are reversals of the situation which has been 
found in this study for Opisthoteuthis, where 
the males predominate in shallow water. 
Of the specimens collected off the north 
Oregon coast for which the sex is known, 18 
males and 10 females are recorded. Since greater 
trawling effort was expended at the depths 
where the males predominate (in the shallow 
part of the range), the above ratio probably 
does not reflect the actual sex ratio. 
Availability 
Catch-per-hour trawling for O. calif orniana 
at various depths is given in Figure 2. The data 
