Conrath and Conners: Aspects of the reproductive biology of Enteroctopus dofleini in the Gulf of Alaska 
257 
26 28 
Figure 3 
The proportion mature as a function of body weight of male (dia- 
monds) and female (circles) North Pacific giant octopuses ( En- 
teroctopus dofleini) collected from the central and western Gulf 
of Alaska in 2010-11. The vertical lines indicate the weights at 
which 50% of the males (solid line) and females (dotted line) 
were mature. The curved lines are the logistic curves fitted to 
the data for males (dotted line) and females (solid line). 
in GSI values during the fall and winter months in 
comparison with the spring and summer months. The 
number of samples used in this analysis was small, but 
these results provide evidence that reproduction for 
this species is weakly synchronous with a peak in egg 
development in the coldest months of the year. 
A similar pattern is evident in the MOL data, with 
peak egg size occurring in the fall and winter months. 
The seasonal MOL values also were significantly differ- 
ent between seasons (P=0.003), with significant differ- 
ences found between the spring and fall (P= 0 . 002 ) and 
the summer and spring (P=Q.Q33). This evidence indi- 
cates that the majority of females lay eggs in late win- 
ter in this region. Spermatophores or other evidence of 
mating was not found within female octopuses during 
any of the sampling periods. These patterns are not 
found in the males of this species. Male GSI values 
were highest in winter and spring but did not vary as 
much as the female values throughout the year (Fig. 
4B). The seasonal GSI values for males were not found 
to be significantly different between seasons (P=0.452). 
Fecundity 
Estimated fecundity of mature and maturing North Pa- 
cific giant octopuses ranged from 41,600 to 239,000 eggs 
per female and mean fecundity was 106,800 eggs per 
female (n= 33, standard error=7900). There was a posi- 
tive relationship between fecundity and total weight of 
female North Pacific giant octopuses, but there was a 
high amount of individual variability in fecun- 
dity (Fig. 5). Exponential regression of fecun- 
dity on total weight of female octopuses was 
highly significant (P< 0 . 001 ), but the predictive 
value of this relationship was low, as indicated 
by a low coefficient of multiple determination 
(7? 2 =0.471). 
Discussion 
Size at maturity 
We found that North Pacific giant octopuses in 
the Gulf of Alaska mature at a size of about 14 
kg — a finding similar to results from another 
study in Japanese waters, a study in which 
females of this species were estimated to ma- 
ture at 10-15 kg and males at 7-17 kg (Kana- 
maru and Yamashita, 1967). Recent research 
indicated size at maturity of this species is 
smaller within the Bering Sea, with a calcu- 
lated JT 50 of 12.8 kg for females and 10.8 kg 
for males (Brewer 3 ). In British Columbia wa- 
ters, male North Pacific giant octopuses were 
also found to mature at around 12.5 kg and at 
a smaller size than females (Robinson, 1983), 
but that study did not include mature females. 
Although our value for weight at 50% matu- 
rity was larger for males than for females, male size 
at maturity was more variable and there were larger 
3 Brewer, R. 2012. Personal commun. 
banks, Unalaska, AK 99685. 
Univ. Alaska Fair- 
Table 1 
Frequency of maturity stage observed during each sea- 
son of the year for male and female North Pacific giant 
octopuses (Enteroctopus dofleini ) captured in the west- 
ern and central Gulf of Alaska in 2010-11. The spring 
season was from April to June, the summer season was 
from July to September, the fall season was from Octo- 
ber to December, and the winter season was from Janu- 
ary to March. 
Season 
Immature Maturing 
Mature 
Male 
Spring 
Summer 
Fall 
Winter 
Female 
Spring 
Summer 
Fall 
Winter 
2 
8 
1 
3 
8 
10 
2 
7 
2 
3 
11 
14 
4 
7 
4 
2 
13 
9 
5 
12 
2 
4 
11 
9 
