On Exhibit: Giant Pacific Octopus
clams, cockles, crabs, abalone, scallops, fish, fish eggs, octopuses
often 50 pounds and 15 feet across; sometimes larger
Japan to Alaska to Baja California
Masters of disguise
The giant Pacific octopus is an amazing creature—brainy and beautiful. The Aquarium's specimens are about six feet across, tentacle to tentacle—but that's a modest size for this species. Full-grown giant Pacific octopus often top 50 pounds, and the record was a creature weighing 200 pounds and measuring nearly 20 feet across.
They're usually reddish-pink with a delicate, veinlike pattern when you see them up close, fading to white on the underside of the tentacles. Its eight arms are covered with suction cups—2,240 of them in females, about 100 fewer in males—which give the octopus an iron grip as well as exquisite powers of taste and smell.
In our exhibit, you may have to look closely to find the octopus, as these animals can change their skin color to blend in with the rocks around them, and even this species, the largest octopus in the world, can squeeze itself into tiny, out-of-the-way spaces.
A mollusk without its shell
Octopuses are mollusks—boneless invertebrates related to clams. But they are no shell-bound mussel that lives in the mud. They're agile, smart and sneaky, armed with eight sinuous tentacles that are studded with suction cups.
An octopus is a little like a normal mollusk turned inside-out. It has a soft body, and its shell has been reduced to two small plates where its head muscles anchor, plus a powerful, parrot-like beak. Lacking a shell, octopuses protect themselves with one of the most sophisticated camouflage systems in the animal world.
Smart and solitary
Giant Pacific octopus spend most of their lives alone. They live in chilly (60 degrees Fahrenheit or colder) Pacific waters from Korea and Japan north to Alaska and south to Southern California. They live in fairly shallow, coastal waters down to depths of 330 feet or more. If you're lucky and extremely sharp-eyed you may find one in a tide pool.
Octopuses are very intelligent animals that can learn to open jars, play with toys, and interact with their handlers. Scientists long thought that animals were unlikely to evolve intelligence unless they were social (like us), so the octopus's clever, lonely life is something of a mystery.
The early days: life as a tiny octopus
The largest octopus in the world hatches from an egg the size of a rice grain. The tiny hatchlings are just over a quarter-inch long and weigh 22 milligrams (less than a thousandth of an ounce). On day one, their eight little arms already have about 14 tiny suckers each.
They drift in the surface waters eating plankton for up to three months, then settle to the seafloor weighing five grams. It takes another year for a young octopus to grow to about two pounds; a year after that it may weigh around 20 pounds and be ready to breed. Until they grow larger than about 10 pounds, life is very dangerous. Predators include lingcod, seals and sea otters—as well as mink, diving birds and other octopuses.
An octopus's garden
Adult giant Pacific octopus are stealthy hunters that eat a wide assortment of seafood, most commonly crabs, clams and other mussels. They catch their prey by surprise, using camouflage, jet propulsion and the sure grip that comes with having eight arms. With a quick bite from its hard beak, the octopus injects compounds that paralyze its prey and begin to digest its flesh. Then the octopus can return to its rocky den and settle down for a leisurely meal.
Using a hard, rough tongue called a radula, the octopus scrapes a neat hole in its prey's shell and extracts the contents. After picking it clean, the octopus discards the shell into a rubbish pile, called a midden, just outside its den. Scientists study these piles to learn about octopus diets.
Now you see me, now you don't
Like other octopuses, the giant Pacific octopus is a master of disguise due to a complex system of pigment cells, muscle fibers and nerves. Millions of elastic cells under the skin contain colored pigments. By stretching these open or squeezing them shut from moment to moment, the octopus adjusts its skin color. It can flash a warning signal or melt into the background, using its sharp eyes to match the patterns and colors of its background nearly perfectly. Experiments have shown that octopuses are color-blind, making these feats that much more mystifying.
Octopuses typically live alone, saving up energy for their one chance at mating near the end of their roughly three-year lives. Then a female chooses a male—typically one much larger than herself—and together they head for a den in deeper water (40 to 170 feet deep). A month or more after mating, the female lays 18,000 to 74,000 eggs (occasionally more), hanging them from the roof of a deep-water den in hundreds of strands of around 250 eggs each.
The mother octopus lives in the cave for up to seven months as the curtain of eggs develops, fanning the eggs with her arms or contracting her body to shoot streams of oxygen- and nutrient-rich water over them. She doesn't eat during this time and usually dies shortly after the young hatch.
Giant Pacific octopus have fairly short lives and produce lots of eggs, so their populations are naturally resilient. And even though they're popular in Asian and Mediterranean cuisine, they're not nearly as heavily fished as other seafood. So, happily, giant Pacific octopus populations are in pretty good shape.
They are commercially fished in both North America and Japan, both for food and as bait for species like Pacific halibut. An octopus has the advantage (unfortunately for the octopus) of being reusable as bait—a big savings for commercial fishermen who cast thousands of hooks into the water.
Because giant Pacific octopus are so large, they're a popular species to use. Records show up to 3,500 tons have been caught per year in North America.