Humboldt squid

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The Humboldt squid (Dosidicus gigas), also known as Jumbo squid, Jumbo flying squid, Pota or Diablo rojo (Spanish for 'Red devil'), is a large, predatory squid living in the waters of the Humboldt Current in the eastern Pacific Ocean. They are most commonly found at depths of 200 to 700 meters (660 to 2,300 ft), from Tierra del Fuego to California. Recent findings suggest the range of this species is spreading north into the waters of Oregon, Washington, British Columbia, and Alaska. Though they usually prefer deep water, between 1,000 and 1,500 squid washed up on the Long Beach Peninsula in southwest Washington in the fall of 2004. They have also ventured into Puget Sound.

Contents

Behavior and general characteristics

Humboldt squid are carnivorous marine invertebrates that move in shoals of up to 1,200 individuals. They swim at speeds of up to 24 kilometers per hour (15 mph/13 kn) propelled by water ejected through a hyponome (siphon) and by two triangular fins. Their tentacles bear suckers lined with sharp teeth with which they grasp prey and drag it towards a large, sharp beak.

Although Humboldt squid have a reputation of being aggressive, there is some disagreement on this subject. Recent research suggests they are only aggressive while feeding; at other times, they are quite passive. Their behavior while feeding often extends to cannibalism and they have been seen to readily attack injured or vulnerable squid of their own shoal. This behavior may account for a large proportion of their rapid growth. Some scientists claim the only reports of aggression towards humans have occurred when reflective diving gear or flashing lights have been present as a provocation. Roger Uzun, a veteran scuba diver and amateur underwater videographer who swam with a swarm of the animals for about 20 minutes, said they seemed to be more curious than aggressive. In circumstances where these animals are not feeding or being hunted, they exhibit curious and intelligent behavior.

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 only about one year, although larger individuals may survive up to two years. They may grow to 1.75 meters (5.7 ft) in mantle length and weigh up to 50 kilograms (100 lb). They can rapidly change their skin color from deep purplish red to white using chromatophores (specialized skin cells) in what some researchers believe is a complex communication system. Experts have also stated the squid hunt for their prey of small fish and krill in a cooperative fashion, which would be the first observation of such behavior in invertebrates. This species is known to hunt near the surface at night, taking advantage of the dark to use its keen vision to feed on more plentiful prey.

Distribution

The Humboldt squid lives at depths of 200 to 700 meters (660 to 2,300 ft) in the eastern Pacific (Chile, Peru), ranging from Tierra del Fuego north to California. It gets its name from the Humboldt Current, in which it lives, off the coast of South America.

Body characteristics

Generally, the tube (or body) constitutes about 40% of the animal's mass, the fin (or wing) about 12%, the tentacles about 14%, the outer skin about 3%, the head (including eyes and beak) about 5%, with the balance (26%) made up of the inner organs.

Behavior

They often approach prey quickly with all ten appendages extended forward in a cone-like shape. Upon reaching striking distance, they will open their eight swimming and grasping arms, and extend two long tentacles covered in sharp 'teeth', grabbing their prey and pulling it back towards a parrot-like beak, which can easily cause serious lacerations to human flesh. The whole process takes place in seconds.

Recent footage of shoals of these animals demonstrates a tendency to meet unfamiliar objects aggressively. Having risen to depths of 130–200 metres (430–660 ft) below the surface to feed (up from their typical 700 meter (2,300 ft) diving depth, beyond the range of human diving), they have attacked deep-sea cameras and rendered them inoperable. Reports of recreational scuba divers being attacked by Humboldt squid have been confirmed. One particular diver, Scott Cassell, who has spent much of his career videotaping this species, has developed body armor to protect against attacks. Each of the squid's suckers is ringed with sharp teeth, and the beak can tear flesh, although it is believed they lack the jaw strength to crack heavy bone.

Ecology

The Humboldt squid feeds primarily on 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. The Humboldt squid is also known to quickly devour larger prey when hunting in groups. Although claims of cooperative hunting have been made for Dosidicus gigas, this behavior is unconfirmed. Until further study reveals otherwise, most researchers believe group attacks by cephalopods on large prey are the result of many individuals attacking simultaneously, but without any coordination.

Scientists suspect the recent expansion of the squid's range north along the west coast of the US is the result of some combination of overfishing of longer-lived apex predators and higher temperatures.

Fisherman catch squid at night. Lights from the fishing boats reflect brightly on the plankton, which lure the squid to the surface to feed. Since the 1990s, the most important areas for landings of Humboldt squid are Mexico and northern Peru.

Humboldt squid are known for their speed in feasting on hooked fish, sharks, and squid, even from their own species and shoal. There are numerous accounts of the squid attacking fishermen and divers in the area. Their colouring and aggressive reputation have earned them the nickname Diablos rojos (Red devils) from fishermen off the coast of Mexico as they flash red and white when struggling with the fishermen.

Humboldt squid and El Niño

Although Humboldt squid are generally found in the warm Pacific waters off of the Mexican coast, recent years have shown an increase in northern migration. The large 1997-98 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 there are no year-round Humboldt squid populations 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.

Humboldt squid and ocean acidification

A study published in the Proceedings of the National Academy of Sciences found that by the end of this century, ocean acidification will lower the Humboldt squid's metabolic rate by 31% and activity levels by 45%. This will lead the squid to have to retreat to shallower waters where it can take up oxygen at higher levels.

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