Cephalopods From Shallow to Deep
By Rachel Plunkett
October 6, 2026
With remarkable senses, complex behaviors, and extraordinary adaptations, cephalopods are some of the ocean’s most fascinating animals. From shallow coral reefs to the darkest reaches of the deep sea, octopuses, squid, cuttlefish, and their relatives have evolved remarkable ways to hunt, hide, communicate, and survive. Cephalopods also play important roles in marine ecosystems. As predators, they feed on fish, crustaceans, mollusks, and other animals, while also serving as an important food source for fish, seabirds, sharks, and marine mammals. Because many cephalopods grow quickly, have short life cycles, and respond to changing ocean conditions, shifts in their abundance and distribution can also provide scientists with clues about broader ecosystem change.
In celebration of Octopus Day on October 8 and Cephalopod Awareness Days from October 8–12, we’re taking a closer look at some of the cephalopods found in and connected to national marine sanctuaries. Along the way, we’ll explore unusual adaptations, cultural connections, scientific discoveries, and memorable encounters—including a rare deep-sea squid recently observed in sanctuary waters.
Bigfin Squid (Magnapinna spp.)
Featured Sanctuary Sightings: Monterey Bay National Marine Sanctuary
Bigfin squid (Magnapinna spp.) are among the most distinctive cephalopods ever observed in the deep sea. Their arms and tentacles extend into extremely long, threadlike filaments and often bend at sharp, elbow-like angles, giving the animals a silhouette unlike that of most other squid. Scientists think the sticky filaments may help capture small prey as the squid hovers above the seafloor, but much about bigfin squid—including what they eat and how they reproduce—remains unknown. They are also among the deepest-dwelling squid ever recorded, with observations from more than 20,000 feet below the ocean surface. The deep-dwelling bigfin squid (Magnapinna spp.) should not be confused with the bigfin reef squid (Sepioteuthis lessoniana), which is found in shallow coastal areas of the Pacific such as in Hawaiian Islands Humpback Whale National Marine Sanctuary.
In August 2026, scientists from the Monterey Bay Aquarium Research Institute and NOAA got an exceptionally rare glimpse of a bigfin squid near Davidson Seamount in Monterey Bay National Marine Sanctuary. While surveying the seafloor with the remotely operated vehicle Doc Ricketts at a depth of about 10,750 feet, the team watched a bigfin squid emerge from the darkness—the first confirmed live observation of the genus in the Northeastern Pacific Ocean and the first confirmed sighting in the sanctuary. Only about 70 bigfin squid have ever been observed or collected worldwide, making every encounter an important opportunity to learn more about one of the deep ocean’s most mysterious cephalopods.
Flapjack Octopus (Opisthoteuthis californiana)
Featured Sanctuary Sightings: Olympic Coast National Marine Sanctuary
Flapjack octopuses are deep-sea cirrate octopods, a group distinguished by the small fins on their heads and rows of tiny, finger-like cirri along their arms. Their short arms are connected by a broad web of skin, and each arm has a single row of suckers flanked by two rows of cirri. When resting on the seafloor, that webbing can spread out around the animal, giving it the flattened appearance that inspired the “flapjack” name. Although they resemble the better-known dumbo octopuses, flapjack octopuses belong to a different genus.
They are not especially powerful swimmers. Instead, flapjack octopuses can pulse their bodies and webbed arms to move through the water, steer with their fins, and then spread their webbing to drift back toward the bottom while conserving energy. On the seafloor, they feed on worms and other small invertebrates, using their cirri and suckers to probe soft sediment for hidden prey. Scientists have also observed pale structures near the eyes that may help concentrate the limited light available in the deep sea, although their exact function remains unknown.
Olympic Coast National Marine Sanctuary staff have encountered flapjack octopuses while reviewing deep-sea ROV footage from sanctuary waters. The species has also been documented during NOAA Ocean Exploration expeditions off the Washington coast. During the 2023 Shakedown + EXPRESS West Coast Exploration aboard NOAA Ship Okeanos Explorer, scientists observed two flapjack octopuses resting on the seafloor during a dive in Nitinat Canyon at about 2,671 feet (814 meters). The expedition recorded numerous octopod sightings overall, giving researchers additional opportunities to observe deep-sea cephalopods in habitats that are difficult to study directly.
Day Octopus (Octopus cyanea)
Featured Sanctuary Sightings: Hawaiian Islands Humpback Whale National Marine Sanctuary, Papahānaumokuākea National Marine Sanctuary, and National Marine Sanctuary of American Samoa
Day octopuses inhabit shallow tropical reefs, where they search coral heads and rocky crevices for crabs, mollusks, and other prey. Unlike many octopus species that are more active at night, Octopus cyanea is frequently seen foraging during the day. They often carry prey back to a den to eat, leaving behind piles of discarded shells called middens. The paired dark spots below their eyes can help distinguish the species. Besides the Giant Pacific octopuses, this is one of the largest octopus species, sometimes reaching over 3 feet (1 meter).
In Hawaiʻi, the day octopus is known as heʻe mauli. The species also has strong cultural significance across the Pacific. In Hawaiʻi, heʻe can be a kinolau, or physical manifestation, of Kanaloa, the god of the ocean, deep-sea voyaging, and healing through seawater. Heʻe mauli may also serve as a family’s ʻaumakua, or ancestral guardian.
The species can be found in shallow coastal areas of Hawaiian Islands Humpback Whale National Marine Sanctuary, and day octopuses have also been observed in Papahānaumokuākea National Marine Sanctuary. In July 2023, sanctuary staff documented one at about 50 feet deep on the forereef of Kuaihelani, moving in and out of rocky crevices and rapidly changing its skin color and texture as it tried to stay hidden. Another day octopus was spotted during a 2025 maritime heritage expedition in sanctuary waters.
In Samoa, octopus are known as feʻe. In American Samoa, traditional knowledge and fishing practices involving feʻe are tied to stories about the relationship between the octopus and the rat, reflecting the long-standing connection between people and reef octopuses in Samoan culture.
Graneledone boreopacifica
Featured Sanctuary Sightings: Cordell Bank, Chumash Heritage, and Monterey Bay national marine sanctuaries
Graneledone boreopacifica is a deep-sea octopus with large blue eyes found in all of the world's ocean basins, where it lives on cold, rocky seafloor habitats. It has been documented from roughly 2,300 to 9,800 feet (700 to 3,000 meters) deep. Its most remarkable trait is its extraordinary reproductive care.
In Monterey Canyon, researchers from the Monterey Bay Aquarium Research Institute (MBARI) documented a female G. boreopacifica brooding about 160 eggs for four and a half years—the longest brooding period ever recorded for any animal. Scientists returned to the site 18 times between 2007 and 2011 and repeatedly found the same female guarding her eggs on a rocky ledge about 4,600 feet below the surface. During those visits, researchers never observed her leaving the eggs or feeding.
The species has also been documented during deep-sea exploration in other national marine sanctuaries offshore California. Scientists aboard E/V Nautilus in 2017 observed G. boreopacifica in Bodega Canyon within Cordell Bank National Marine Sanctuary, noting that it was one of the most common cephalopods seen during the expedition. Farther south, MBARI documented the species at a depth of 2,900 feet at Rodriguez Seamount, now protected within Chumash Heritage National Marine Sanctuary. These encounters add to what scientists know about the distribution of this deep-sea octopus along the California coast.
Graneledone boreopacifica is also an active benthic predator in deep-sea ecosystems. Near a Northeast Pacific hydrothermal vent, it was documented having eaten dozens of gastropods and polychaete worms, including species associated with vent communities. By preying on these species, G. boreopacifica is helping to move energy through deep-sea food webs and contributing to the complex predator-prey relationships that shape these unique communities.
Caribbean Two-Spot Octopus (Octopus filosus)
Featured Sanctuary Sighting: Flower Garden Banks National Marine Sanctuary
The Caribbean two-spot octopus (Octopus filosus) is a small reef-dwelling species found throughout the tropical western Atlantic, from Florida and the Bahamas through the Caribbean to Brazil. Adults have a mantle length of only about 3 inches, and the species is typically associated with coral reefs, shell rubble, and sandy or gravel bottoms from shallow water to about 660 feet (200 meters) deep. Its most distinctive feature is a pair of dark false eyespots, or ocelli, located near the bases of the arms. Each ocellus includes an iridescent blue ring, although the spots may only be obvious when the octopus displays certain color patterns.
At Flower Garden Banks National Marine Sanctuary, the species has produced some memorable observations. Sanctuary video captured a Caribbean two-spot octopus hunting in broad daylight—an unusual sight—while carrying a file clam across the reef. As it moved away from the camera, the octopus repeatedly changed its color and pattern before disappearing into a den. Nearby piles of discarded clam shells, known as middens, offered another clue that an octopus was living there.
A 2012 sanctuary research report featured what was then only the second documented sighting of a Caribbean two-spot octopus in Flower Garden Banks National Marine Sanctuary, and the first at East Flower Garden Bank. Continued observations like these help researchers build a clearer picture of where this small, secretive octopus occurs within sanctuary habitats.
Giant Pacific Octopus (Enteroctopus dofleini)
Featured Sanctuary Sightings: Cordell Bank, Greater Farallones, Channel Islands, and Olympic Coast national marine sanctuaries
The giant Pacific octopus (Enteroctopus dofleini) is the largest octopus species in the world. Adults commonly reach 30 to 50 pounds, though much larger individuals have been recorded, and their arms can span several feet from tip to tip. They inhabit cold waters of the North Pacific, sheltering in rocky dens and feeding opportunistically on crabs, clams, fish, and other marine animals. Giant Pacific octopuses are also relatively long-lived for octopuses, typically surviving about three to five years. Females lay tens of thousands of eggs and spend months guarding, cleaning, and aerating them inside a den, stopping feeding during the brooding period and dying soon after the young hatch.
At Cordell Bank National Marine Sanctuary, technical divers with Bay Area Underwater Explorers and the Lee Oceans Foundation encountered multiple giant Pacific octopuses during a 2023 expedition to document the sanctuary’s rocky reef communities. Divers found one octopus occupying a den near the top of the Northern West Ridge and encountered two more around 200 feet deep, including one that approached the divers as they photographed it. An image from that expedition later helped represent the species on Cordell Bank National Marine Sanctuary’s commemorative poster.
The species is also a familiar inhabitant of Olympic Coast National Marine Sanctuary’s cold-water ecosystem. Sanctuary staff recently encountered a giant Pacific octopus during mooring servicing, when one came up with the equipment from below. The species is also featured in the New England Aquarium’s Olympic Coast exhibit, which highlights animals and habitats representative of the sanctuary ecosystem.
Elsewhere along the California coast, NOAA researchers encountered a giant Pacific octopus occupying a mystery shipwreck during a 2014 maritime archaeology expedition in what is now Greater Farallones National Marine Sanctuary. In 2026, Cordell Bank National Marine Sanctuary Advisory Council fishing representative Dick Ogg reported an unusual number of giant Pacific octopuses entering Dungeness crab traps set on sandy continental-shelf habitat—an unexpected sighting for a veteran fisherman more accustomed to associating the species with rocky features.
In Channel Islands National Marine Sanctuary, a NOAA seafloor mapping and exploration mission aboard NOAA Ship Bell M. Shimada documented giant Pacific octopuses during ROV dives, including one about 330 feet deep in Santa Cruz Canyon.
Longfin Squid (Doryteuthis pealeii)
Featured Sanctuary Sightings: Stellwagen Bank and Florida Keys National Marine Sanctuaries
Longfin squid (Doryteuthis pealeii) are fast-growing, short-lived predators found along the western Atlantic from Newfoundland to the Gulf of Venezuela. Adults live over sandy and muddy continental shelf habitats in waters as deep as about 1,300 feet (400 meters) and make daily vertical migrations, staying closer to the seafloor during the day and moving toward the surface at night. Juveniles feed largely on plankton, while adults prey on crustaceans and small fish—and can even consume fish larger than themselves. Longfin squid are also an important food source for marine mammals, seabirds, and predatory fishes, making them an important link in coastal food webs.
They occur in Stellwagen Bank National Marine Sanctuary, part of the highly productive Gulf of Maine ecosystem, and farther south in Florida Keys National Marine Sanctuary. Their abundance in the Keys was highlighted in NOAA’s 2025 Get Into Your Sanctuary photo contest, where a photograph of a longfin squid illuminated at night in sanctuary waters won first place in the Sanctuary Life category.
Because squid are soft-bodied, fast-moving animals that can be difficult to follow underwater, scientists have developed new ways to study what they do when humans are not watching. Researchers at Woods Hole Oceanographic Institution, working with the University of Michigan and Monterey Bay Aquarium Research Institute, developed a high-resolution bio-logging tag called ITAG and have attached it to longfin squid in laboratory and field studies. Sensors in the tags record movement, orientation, and depth, allowing researchers to identify behaviors and investigate questions about habitat use, energy expenditure, daily activity patterns, and interactions with other animals.
Hawaiian Bobtail Squid (Euprymna scolopes)
Featured sanctuary sightings: Hawaiian Islands Humpback Whale National Marine Sanctuary and Papahānaumokuākea National Marine Sanctuary
The Hawaiian bobtail squid (Euprymna scolopes) is a small, nocturnal cephalopod endemic to the Hawaiian Islands with a short lifespan of just 10 months. About the size of a golf ball, it spends much of the day buried in sand and emerges at night to hunt shrimp and other small crustaceans. The species is known in Hawaiʻi as mūheʻe and has been reported from Maui north to Midway Atoll in the Northwestern Hawaiian Islands.
Its most famous adaptation is a partnership with the bioluminescent bacterium Vibrio fischeri, which lives in a specialized light organ inside the squid’s mantle. The bacteria communicate with one another to produce light that the squid can use for counterillumination, matching the downwelling moonlight and starlight so its silhouette is harder for predators below to see. This unusual partnership has made the Hawaiian bobtail squid an important model species for scientists studying symbiosis and how animals and beneficial microbes interact.
Recent research on Hawaiian bobtail squid is also revealing how tightly their biology is linked to their bacterial partners. Scientists at the University of Hawaiʻi have found that the squid’s relationship with Vibrio fischeri influences not just light production, but aspects of the animal’s development, immune function, and daily rhythms.
Rachel Plunkett is the content manager and senior writer-editor for NOAA’s Office of National Marine Sanctuaries
