Humboldt squid

## Description

The Humboldt squid (Dosidicus gigas ), also known as jumbo squid or jumbo flying squid (EN), and Pota in Peru or Jibia in Chile (ES) is a large, predatory squid living in the eastern Pacific Ocean. It is the only known species of the genus Dosidicus of the subfamily Ommastrephinae, family Ommastrephidae.

Humboldt squid typically reach a mantle length of 1.5 m (4 ft 11 in), making the species the largest member of its family. They are the most important squid worldwide for commercial fisheries, with the catch predominantly landed in Mexico, Peru and Chile. Like other members of the subfamily Ommastrephinae, they possess chromatophores which enable them to quickly change body coloration, known as 'metachrosis’ which is the rapid flash of their skin from red to white. They have a relatively short lifespan of just 1–2 years. They have a reputation for aggression toward humans, although this behavior may only occur during feeding times.

They are most commonly found at depths of 200 to 700 m (660 to 2,300 ft), from Tierra del Fuego to California. This species is spreading north into the waters of the Pacific Northwest, in Oregon, Washington, British Columbia, and Alaska.

### Animal name origin

This species is most often known as jumbo squid in English, but has also been called jumbo flying squid or Humboldt squid, with the last name most popular in naturalist sources. The name Humboldt refers to the Humboldt Current, off the southwestern coast of South America, where it was first collected.

A general name for this species in Spanish in Latin America is calamar gigante. Local names for it are jibia in Chile or pota in Peru. They notably rapidly flash red and white when captured, earning them the nickname diablo rojo (meaning 'red devil') among local fishermen in Baja California, Mexico.

## Appearance

The Humboldt squid is the largest of the Ommastrephid squids, as some individuals may grow to 1.5 m (4 ft 11 in) in mantle length and weigh up to 50 kg (110 lb). They appear to be sexually dimorphic, on average the females mature at larger sizes than the males. Generally, the mantle (or body) constitutes about 56–62% of the animal's mass (which includes the fins or wings), the arms and tentacles about 11–15%, the head (including eyes and beak) about 10–13%, the outer skin (cuticle) 2.5–5.0%, the liver 4.2–5.6%, with the rest made up of the other inner organs. The gonads consist of 1.5–15.0% of the total mass. The gladius (the single inner 'bone') is 0.7–1.0%. Precise ratios depend on the age, sex and sizes of the individual squid.

They are propelled by water ejected through a hyponome (siphon) and by two triangular fins. Their two tentacles bear 100–200 suckers, each lined with razor-sharp teeth, with which they grasp prey and drag it toward a large, sharp beak.

## Distribution

The Humboldt squid lives at depths of 200 to 700 m (660 to 2,300 ft) in the eastern Pacific (Notably in Chile and Peru), ranging from Tierra del Fuego north to California. Recently, the squid have been appearing farther north, as far as British Columbia. They have also ventured into Puget Sound.

Though they usually prefer deep water, between 1,000 and 1,500 squid washed up on the Long Beach Peninsula in southwest Washington in late 2004 and red algae were a speculated cause for the late 2012 beaching of an unspecified number of juvenile squid (average length 50 cm ) at Monterey Bay over a 2-month period.

Humboldt squid are generally found in the warm Pacific waters off the Mexican coast; studies published in the early 2000s indicated an increase in northern migration. The large 1997–1998 El Niño event triggered the first sightings of Humboldt squid in Monterey Bay. Then, during the minor El Niño event of 2002, they returned to Monterey Bay in higher numbers and have been seen there year-round since then. Similar trends have been shown off the coasts of Washington, Oregon, and even Alaska, although no year-round Humboldt squid populations are in these locations. This change in migration is suggested to be due to warming waters during El Niño events, but other factors, such as a decrease in upper trophic level predators that would compete with the squid for food, could be impacting the migration shift, as well.

A 2017 Chinese study found that D. gigas is affected by El Niño events in the waters off Peru. The squid populations cluster into groups less, and are thus more dispersed, during El Niño events. Additionally, during warm El Niño conditions and high water temperature the waters off Peru were less favourable for D. gigas.

## Behavior

Humboldt squid are carnivorous marine invertebrates that move in shoals of up to 1,200 individuals. They swim at speeds up to 24 km/h (15 mph; 13 kn).

Electronic tagging has shown Humboldt squid undergo diel vertical migrations, which bring them closer to the surface from dusk to dawn. Humboldt squid are thought to have a lifespan of about a year, although larger individuals may survive up to 2 years.

Crittercams attached to two or three Humboldt squid revealed the species has two modes of colour-generating (chromogenic) behaviour:

The entire body of the squids ‘flash’ between the colours red and white at 2–4  Hz when in the presence of other squid, this is behaviour likely represents intraspecific signalling. This flashing can be modulated in frequency, amplitude and in phase synchronisation with each other. What they are communicating to each other is unknown – it could be an invitation for sex or a warning to not get too close.

The other chromogenic mode is a much slower ‘flickering’ of red and white waves which travel up and down the body, this is thought to be a dynamic type of camouflage which mimics the undulating pattern of sunlight filtering through the water, like sunlight on the bottom of a swimming pool. The squid appear to be able to control this to some degree, pausing or stopping it.

Although these two chromogenic modes are not known in other squid species, other species do have functionally similar behaviours.

## Diet

The Humboldt squid's diet consists mainly of small fish, crustaceans, cephalopods, and copepods. The squid uses its barbed tentacle suckers to grab its prey and slices and tears the victim's flesh with its beak and radula. They often approach prey quickly with all 10 appendages extended forward in a cone-like shape. Upon reaching striking distance, they open their eight swimming and grasping arms, and extend two long tentacles covered in sharp hooks, grabbing their prey and pulling it back toward a parrot-like beak, which can easily cause serious lacerations to human flesh. These two longer tentacles can reach full length, grab prey, and retract so fast that almost the entire event happens in one frame of a normal-speed video camera. Each of the squid's suckers is ringed with sharp teeth, and the beak can tear flesh, although they are believed to lack the jaw strength to crack heavy bone.

Their behavior while feeding often includes cannibalism and they have been seen to readily attack injured or vulnerable squid in their shoal. A quarter of squid stomachs analyzed contained remains of other squid. This behavior may account for a large proportion of their rapid growth. An investigation of the stomach contents of over 2,000 squid caught outside of the Exclusive Economic Zone off the coasts of Chile found that cannibalism was likely the most important source of food. Over half of the squids had the beaks of D. gigas in their stomachs, and D. gigas was the most common prey item. The researchers do note, however, that squids which were jigged in the light field around the survey vessel showed much more cannibalism.

Until recently, claims of cooperative or coordinated hunting in D. gigas were considered unconfirmed and without scientific merit. However, research conducted between 2007 and 2011 indicates this species does engage in cooperative hunting.

The squid are known for their speed at eating; they feast on hooked fish, stripping them to the bone before fishermen can reel them in.

## Reproduction

Female squids lay gelatinous egg masses that are almost entirely transparent and float freely in the water column. The size of the egg mass correlates with the size of the female that laid it; large females can lay egg masses up to 3–4 m in diameter, while smaller females lay egg masses about one meter in diameter. Records of egg masses are extremely sparse because they are rarely encountered by humans, but from the few masses found to date, the egg masses seem to contain anywhere from 5,000 to 4.1 million eggs, depending on size.

## Population

### Conservation

A 2008 study predicted that ocean acidification will lower the Humboldt squid's metabolic rate by 31% and activity levels by 45% by the end of the 21st century. It also predicted that the squid wouldn't be able to spend as much of the day in deeper and colder waters, as a larger proportion of the ocean would fall into the oxygen minimum zone.

A more recent study, however, provided empirical and theoretical evidence that the squid metabolism was unaffected by ocean acidification.