Humboldt Squid

## About

A Humboldt squid at the water's surface at night.

## Background Information

### Alternate Name(s)

Red devil, Red devil squid, Killer squid, Jumbo squid, Flying jumbo squid, Pota, Jibia

## Classification

### Species

D. gigas

The Humboldt squid ***(Dosidicus gigas)*** is a relatively large squid species native to the eastern Pacific ocean. Humboldt squid are red or dark orange in colour and have conical mantles and large fins. They possess ten tentacles, each with 100-200 hooked suckers or suction cups, with two of these tentacles being longer and modified for feeding. Possessing chromatophores, Humboldt squid have the ability to change their physical appearance through changing their colour, using this ability to communicate with fellow squids (discussed further in Behaviour). The mantle of a Humboldt squid can reach 1.5-2m (4.9-6.6ft) and can weigh as much as 50kg (110lbs) though this is in the heavier range.

## Diet

Humboldt squid are carnivorous predators hunting a variety of marine life. As juveniles, Humboldt squid hunt copepods and pelagic shrimp however, as they age, they begin to hunt various fish species (including small sharks), crustaceans, plankton and even other squid species, including juvenile Humboldt squid. When hunting, a Humboldt squid will latch onto the prey with the use of their hooked suckers, reeling the prey towards them with their larger two tentacles and tearing it apart with their parrot-like beaks and radula (most often compared to a tongue). They may also drag their prey deep underwater, causing it to fall unconscious before doing this. Humboldt squid most commonly hunt at night, rising to the water's surface, when they feed mostly on pelagic fish and lanternfish ***(Myctophidae)*** in particular. Interestingly, Humboldt squid commonly feed in groups of thousands and when in these large groups, target larger prey.

## Conservation Status

According to the IUCN, the species being the single most targeted species of invertebrate fisheries in the world, is incredibly threatened by commercial fishing. The Humboldt squid is most popular within the Eurasian market, being commonly sold in France, Spain, Ireland, Russia, China, Japan and also southeast Asia. The species is also becoming readily popular in the American markets. Humboldt squid are most often caught through the method of handline jigging or squid jigging, where squids are lured to the surface through the act of using bait to imitate prey at the water's surface. This is done by having the boat's lamps shine against bait, or "jigger". This produces a reflective effect, which attracts the squid's attention. The method gets its name from the constant jittering of the jigger, through means of pulling the rod up and down in the water. Up to twelve jiggers are placed on one handline at a time. Mechanical jigging is also prominent in the industry. Unfortunately, the discover of this method has led to the mass capture and hunting of the species, to the point where the species made up 95% of all catches in Mexico in 2009 and has been fished in thousands of tonnes across its range in South America. Unfortunately, there is still not enough quantifiable data to determine the species' conservation status and so the Humboldt squid is classed as data deficient.

## Range and Population

Humboldt squid occur in the eastern Pacific, along the eastern coasts of North and South America. An incredibly widespread species, the Humboldt squid's range extends from the west coast of Canada to the southern coasts of Chile and Argentina. Humboldt squid can also be found further out to sea in the open ocean, in an equatorial region known as the Doldrums. The species itself is named after the Humboldt current, a strong Antarctic current that ranges from the coasts of southern to central South America. Humboldt squids inhabit areas between 200-700m (660-2,300ft) deep, according to American Oceans. In terms of population, it is unknown how many individuals exist or whether the population is suffering a noticeable decline in numbers.

## Behaviour

Humboldt squid are incredibly sociable animals and can be found in large schools throughout their lives. Juvenile Humboldt squid are very active and energetic, gathering in groups of up to 20-40 individuals only 20-50m (66-164ft) bellow the surface, often even breaching. Subadult squid congregate in hunting schools of anywhere between 20-1,500 individuals however, they have also been known to hunt solitarily or in smaller schools of 200, according to the Animal Diversity Web. Adults are the least sociable individuals, typically only being found in schools of 2-12. This is likely because adult Humboldt squid are aggressive and territorial, also potentially practicing semi-regular cannibalism. Humboldt squid have interestingly been examined hunting alongside purpleback flying squid ***(Sthenoteuthis oualaniensis)***, a squid which they also directly compete with for food. Quite fascinatingly, Humboldt squid have devised a complex language of chromatophore-controlled sequences, of which they use to communicate with one another during hunting. Because the species is bioluminescent, these colour flashing sequences are used in great effect in deep waters. There have been an entire array of colour-coded communications that have been identified in Monterey Bay, California alone, varying from pale white colourations, to vibrant reds, all correlating with specific communicatory ques. The morphology of the squid's photoreceptors -which control the green-yellow bioluminescent glow of the squid- suggest that these communicatory signals may appear differently underwater. To elaborate, these photoreceptors are located underneath the squid's skin, while the chromatophores -which change the squid's colour- are located on the skin itself. This suggests that the patterns mask the bioluminescent glow of the squid, making them superficially appear different in appearance and size to other species. Unfortunately, this behaviour cannot be fully examined or concluded, as technology is currently too limited. When mating, two squids will lock tentacles and mate in a head-to-head position. The male will insert his spermatophores into the buccal (or oral) membrane of the female squid. Humboldt squid mate once annually and due to the mating taking place around 250m (820ft) below the surface, the species' courtship details are unknown. After mating, gravid females will produce jelly-covered floating masses of eggs and apparently have the ability to create anywhere between 3-20 of these masses. One mass examined in the wild contained 0.6-2 million eggs. The young are thought to hatch throughout the year however, an abundance of young can be found in January and October.

### Relationship with Humans

Humboldt squid are the most commercial extracted invertebrate in the world and so human-squid interaction is common. The squid is also frequently hunted recreationally. Beyond fishing, the species also directly competes with humans for food, as it commonly hunts valuable fishery species, leading the squid to possibly threaten northern-Pacific fisheries in the future. Humboldt squid are also significant in climate change research, as the distribution of the species is directly correlated with climate change. When caught by humans, Humboldt squid will turn bright red, earning them the name; "red devil squid" among fishermen and the media. They are also known to bite divers and become aggressive when disturbed by humans.

## In Captivity

No Humboldt squids can be found in captivity.

## Sources

* IUCN Red List of Threatened Species - https://www.iucnredlist.org/species/162959/958088
* Humboldt Squid | Wikipedia - https://en.wikipedia.org/wiki/Humboldt\_squid
* Humboldt Squid | Animal Diversity Web, University of Michigan Museum of Zoology - https://animaldiversity.org/accounts/Dosidicus\_gigas/
* Humboldt Squid | American Oceans - https://www.americanoceans.org/species/humboldt-squid/
* Deciphering the visual language of Humboldt squid | MBARI - https://www.mbari.org/news/deciphering-the-visual-language-of-humboldt-squid/