258 
Fishery Bulletin 112(4) 
A 
0.07 
• GSI 
7 
0.06 
oMOL 
• 
6.5 
0.05 
<> 
6 
0.04 
• 
o 
5.5 g 
O 
GSI 
0.03 
O 
• 
5 T 
3 
4.5 3. 
0.02 
• 
4 
0.01 
O 
3.5 
Spring 
Summer 
Fall 
Winter 
O 
B 
P- 
O 
d 
0.06 
0.05 
A 
ISO 
0.04 
I 
* 
0.03 
0.02 
0.01 
0 1 1 ? 1 
Spring Summer Fall Winter 
Figure 4 
(A) Gonadosomatic index (GSI) and maximum ova length 
(MOL) by season for maturing and mature female speci- 
mens of North Pacific giant octopuses ( Enteroctopus dofle- 
ini ) and (B) GSI by season for maturing and mature male 
North Pacific giant octopuses. Specimens were collected 
from the central and western Gulf of Alaska in 2010-2011. 
Error bars indicate standard error of the mean. 
fractions of both small mature males and large imma- 
ture males. Growth and maturity of this species appear 
to be quite variable, and regional differences in size 
at maturity may reflect differences in environmental 
conditions, food availability, or genetic differences be- 
tween stocks. 
Seasonality 
The life history of the North Pacific giant octopus in 
the Gulf of Alaska is similar to that in Japanese and 
Canadian waters of the North Pacific Ocean, but the 
timing of reproductive events is different for mem- 
bers of this species in the Gulf of Alaska. In Japanese 
waters, this species has been reported to mate dur- 
ing summer and early fall (July-October) and to lay 
eggs or spawn during fall and winter (October-Janu- 
ary) with a 2-month lag between mating and spawning 
(Kanamaru, 1964). Another study in Japanese waters 
found that the spawning season occurred in early sum- 
mer (Sano et al., 2011). In the Bering Sea during 
a recent study, female development was most ad- 
vanced in the fall months and male development did 
not show a seasonal pattern (Brewer 3 ). Our study 
indicates that peak spawning in the Gulf of Alaska 
occurs during the winter months (January-March). 
The development of male gonads indicates that mat- 
ing may peak earlier in the spring months. 
Results from our study indicate that mating occurs 
predominately in the spring and summer months but 
may be very protracted and occur throughout the 
year. It is assumed that females of this species are 
capable of storing sperm. This phenomenon has been 
documented in an aquarium study of North Pacific 
giant octopuses in British Columbia (Gabe, 1975) 
and has been observed in several other octopus spe- 
cies (Joll, 1976; Perez et al., 1990). The seasonal dif- 
ferences in the timing of peak GSI values between 
male and female North Pacific giant octopuses indi- 
cate that storage of sperm may occur in octopuses 
in the Gulf of Alaska between spring mating and 
winter spawning. Females of this species appear to 
lay eggs predominately during winter, although the 
presence of mature females throughout the year in- 
dicates that some spawning may occur during other 
periods of the year. 
This species is found throughout the North Pa- 
cific Ocean, but there is little information available 
about its seasonal movements in Alaska waters. It 
is, therefore, difficult to interpret how the habitat 
of these octopuses differs during periods of the year 
when octopuses are mating and spawning. Japanese 
studies indicate that North Pacific giant octopuses 
in waters off of the coast of Hokkaido, Japan, move 
to deeper waters in summer to mate and move into 
shallower waters to spawn (Kanamaru, 1964). How- 
ever, no evidence of a seasonal or directed migration 
for this species has been found in studies of this spe- 
cies in British Columbia (Hartwick et al., 1984) and 
south central Alaska (Scheel and Bisson, 2012). Long- 
term tagging studies are needed to obtain a more com- 
plete understanding of the migratory pattern of this 
species. 
Another complicating factor that may contribute to 
the variability in both size at maturity and seasonality 
of the reproduction of the North Pacific giant octopus 
is the complicated stock structure and phylogenetic re- 
lationships of this species throughout its range. Three 
subspecies have been identified on the basis of large 
geographic ranges and morphological characteristics: 
Enteroctopus dofleini dofleini (far western North Pacific 
Ocean), E. dofleini apollyon (waters near Japan, Bering 
Sea, Gulf of Alaska), and E. dofleini martini (eastern 
part of range [Pickford, 1964]). A recent genetic study 
(Toussaint et al., 2012) indicated the presence of a 
cryptic species of North Pacific giant octopus in Prince 
William Sound, Alaska, and raises additional ques- 
tions about the stock structure of this species. More 
data are needed to define the stock structure of this 
