The giant Pacific octopus is the largest species of octopus in the world. Maximum radial width is documented at 9.8 m (32 ft) and weigh as much as 136 kg (300 lb). (Guinness World Records, 2008)
The giant Pacific octopus (GPO) is an octopod having 8 arms (or legs) but it does not have tentacles. Like other cephalopods, this species is a total carnivore and is known to be cannibalistic. The paralarvae (hatchlings) spend about 10 months in the plankton layer. As they are too heavy to float or remain neutral in the water they must support themselves by turning upside down and clinging to the underside of the surface tension. They drop off the surface to feed and then return to rest until they are too large for the surface tension to support. At that time they drop to the bottom and become benthic (bottom dwellers) for the rest of their lives. In general, a GPO will double its weight every 100 days. Female GPO's live to be about 4 years of age while males die a little sooner. Females seldom exceed 25 kg (55 lb) while males will reach 40 kg (88 lb) GPOs over 45 kg (100 lb) are very rare with all the largest animals having been reported in the 1800's and early 1900's.
The octopus is a solitary animal that lives in a den most of the time. They have a range of about 230 square meters (760 ft) but an overlap with other GPOs of up to 94% (Mather et. al., 1985). Locomotion is normally a crawl using the rear pairs of arms to push the octopus forward. The front pair of arms are usually raised with the suckers in contact with the water. Octopus suckers are chemotactic meaning they can taste what they touch including odors in the water.
As a paralarvae the octopus feeds on zooplankton such as copepods, euphausids and mysids. Once the octopus becomes benthic it will progress through a variety of sizes of food as it grows. Food will include small shrimp, small crabs and any fresh carrion it happens upon. As adults their food is most commonly crabs and clams or cockles.
Roughly the same number of males and female are hatched from a single nest. They grow at roughly the same rate depending on the amount of food they get and reach sexual maturity at about 30 months with a weight of approximatley 16 kg (35 lb). Mating normally occurs in the winter (Nov. & Dec.) with a secondary peak in April but mating can occur at any time of year. Once mated the female will select a den, wall off all the exits using available rocks in the area and crawl into the den, pulling the rest of the rocks to her to seal off the den from most predators. After this time the female will not feed again. She spends 28 - 42 days laying her nest of approximatley 68,000 eggs. Each single egg is woven into a string of about 175 eggs and then the string is glued to the roof of the dens. Once the egg laying is complete the female will spend her time grooming and cleaning the eggs and blowing clean water over them. The rate of development of the eggs is temperature dependent but normally is 7 to 10 months. If the female dies before the eggs hatch then the eggs will not hatch properly. If the female is alive, then vertually all the eggs will hatch and the paralarvae will swim to the surface (Cosgrove, 1993). Males continue to feed and increase in weight but will become senescent and die of old age at approximately 36 months. In colder waters, such as Alaska , the GPO may live longer and have longer brooding periods.
While the paralarvae are in the plankton layer they are food for all of the planktonic predators and that will include everything from the baleen whales to jellyfish including many species of fish. When the paralarvae settle to the bottom then the range of predators switches to mostly fish. As the GPO gets larger so do the predators until, as an adult, the major predators are seals and sea lions or very large fish such as halibut and lingcod.
The paralarvae are planktonic for about 10 months. Upon settling and becoming benthic they tend to live in rocky areas where they can find suitable dens. They will make use of human objects such as tin cans, old car tires, etc. if no other den is available (Cosgrove, unpublished data).
The giant Pacific octopus in found from central California and east through the north Pacific to Japan and Korea. It is found in waters from the intertidal to waters as deep as 2,000 m (6,600 ft) (Cosgrove and McDaniel, 2009).
Distribution in British Columbia
The giant Pacific octopus is found in all clean ocean waters of B.C. from intertidal waters to depths of 2,000 m (6,600 ft). Brackish waters or waters with low oxygen contents will not support the GPO.
The giant Pacific octopus has been identified by 7 different names over the years (for a list see pg 21 in Super Suckers by Cosgrove and McDaniel, 2009). There is the suggestion (Pickford, 1964) that there are 3 subspecies of E. dofleini. This is unconfirmed by any DNA or enzymatic work and remains work to be done.
This octopus is a large, powerful and facinating animal to study. It is intelligent and a constant challenge to researchers and aquarists (Anderson, 2005, Mather and Anderson, 2000). It is one of the features of any large aquarium as people love to watch it.
Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2019. E-Fauna BC:
Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab
for Advanced Spatial Analysis, Department of Geography, University of British
Columbia, Vancouver. [Accessed:
2020-08-03 10:51:06 AM]
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