Release the Kraken!

In the movie, Clash of the Titans, Zeus unleashes his ultimate weapon when he commands, “Release the Kraken!” What is this monster (pronounced krak-en)? This week, Anjani Ganase, marine biologist, tells us about the oceanic giant squid that has been invoked in other films such as Pirates of the Caribbean. Although none as immense as those described by fishermen of a thousand years ago have yet been seen, who can say what lies in the unexplored deep seas that encircle our world. 

This feature was first published in the Tobago Newsday on Thursday, November 17, 2016

Follow Anjani on twitter @AnjGanase

The Norse legend of the Kraken tells about the mythical sea creature that lived off the coasts of Norway and Greenland.  It is a giant squid that rises up from the deep to crush vessels and pull fishing boats to a watery grave. Some of these stories recounted since the 1200s were documented by the Danish naturalist, Bishop Erik Pontoppidan, as part of his written works on the natural history of Norway (1752-1753). In his tales of the marine environment, he included many accounts of encounters by fishermen with this sea monster, the Kraken. He tells of fisherman who would row far out to fish: out to sea, they would find waters teeming in fish at the surface; and in these locations, they knew that below lay the kraken. The fishermen would harvest as much fish as quickly as possible, and seemed to know that more fish in shallow water near the surface would indicate when it was time to move, for the kraken would be  making its way to the surface feasting on the schools of fish above it.

“… they find that the Kraken is raising himself near the surface and then it is not time for them to stay any longer; they immediately leave off, fishermen take to their oars and get way as fast as they can. When they have reached the usual depth of the place and find themselves out of danger, they lie upon their oars, and in a few minutes after they see this enormous monster come up to the surface of the water, he there shows himself sufficiently...” - Pontoppidan

Hetzel edition of 20000 thousand leagues under the sea. Jules Verne (Public Domain)

In his book, the descriptions of the Kraken by the fisherman closely resemble the giant sea squids except for the sheer size of the creature:

 “…though his whole body does not appear, which in all likelihood no human eye ever beheld, its beak or upper part, which seems to be in appearance about an English mile and a half circumference, looks at first like a number of small islands, surrounded with something that floats and fluctuates like seaweeds. Here and there, a larger rising is observed like sand banks, on which various kinds of small fishes are seen continually leaping about till they roll off into the water from the side of it; at last several bright points or horns appear, which grow thicker and thicker the higher they rise above the surface of the water and sometimes they stand up, as high and as large as the masts of middle sized vessels.”

Today, it is commonly accepted that the giant squid is the kraken that the fishermen described in Pontoppidan’s book. Most of the research is carried out on deceased specimens that have been stranded, from deep sea trawling, from the stomach content of their predators, and from other related species. They can be found in the deep waters of most oceans, feeding on other fish and squid. Their only predators include most famously the sperm whales, known to have bite marks from the giant squid. Other predators include the toothed whales, sharks and swordfish; and it now appears that these creatures are not the top predators of the sea as we imagined previously.

“This animal has another strange property, known by the experience of a great many old fishermen. They observed, that for some months the kraken or Krabben is continually eating and in other months he always voids excrements. During this evacuation the surface of the water is coloured with the excrement and appears quite thick and turbid. This muddiness is said to be so very agreeable to the smell or taste of other fishes, or to both, that they gather together from all parts to it, and keep for that purpose directly over the kraken; he then opens his arms, or horns, seizes and swallows his welcome guests and converts them after the due time by digestion, into a bait for other fish of the same kind.” - Pontoppidan

Today research on these so called sea monsters have slowly turned fiction into fact. The excrement that the fishermen describe may actually be the ink that squid releases, which is a thick mucous fluid composed of melanin. Often considered a smoke screen for a quick getaway from predators, the inky exudate darkens the water and blurs their vision. They can even emit an even thicker and darker cloud of mucus that retains its shape, resembling the squid itself, providing a decoy while the squid swims away. What the fishermen may have thought was a tactic for luring prey was more likely an attempt to make a quick getaway from other threats, including the fishermen themselves.

Giant Squid surfacing to feed on baited squid near the Ogasawara Islands, south of Tokyo, Photo by Tsunemi Kubodera, a researcher with Japan's National Science Museum

To date we still don’t know the global population of giant squids, and it has only been estimated by the sperm whales that feed on them. Not much is known about their hunting and feeding habits. They are considered to be strong swimmers and active hunters, even thought to have organs on their tentacles that emit light to lure in prey. Only one confirmed live encounter showed a giant squid feeding at 900 m depth on smaller squid; this was still some 1300m above the bottom. Their stomach contents also show that they do feed on crustaceans prevalent in the deep-sea bottom, indicating that they are capable of roaming at great depths. The age of these creatures is most uncertain; they are considered fast growing,  and many of the specimens caught might be merely teenagers. Finally, and most controversial of all, is the size of the giant squid. Old records suggest lengths of up to 60 m long, however there has never been any recent record of this. Recent studies have suggested a maximal length of 15m with most observed averaging about 11m; much different to the legends that speak of miles in length.

Ninety percent of our oceans are open-water environments remote from coastal environments. We know so little about the creatures that dwell there and much less about how we may be impacting them. Even these giant squids that are deep ocean dwellers aren’t immune from human activities. More strandings have been associated with exceptionally warm water, as well as from acoustic seismic soundings for petroleum. With the projections of warming waters, we can definitely expect more of these strandings to occur. The surfacing of giant squids may also be indicators of changing pelagic ecosystems under future climate scenarios– ocean acidification and warming temperature. Although they do not have calcium carbonate skeletons, their receptors for movement are calcium carbonate based and can be affected by lower pH levels. Warmer waters would limit the squids’ ability to extract oxygen out of the water column and could cause suffocation. With further science and growing education, it is hoped that we might also conserve these sea monsters of the past as living icons of the deep sea, symbols of ocean conservation and awareness.

References:

Roper, Clyde F. E. and Shea, Elizabeth K. 2013. Unanswered Questions About the Giant Squid Architeuthis (Architeuthidae) Illustrate Our Incomplete Knowledge of Coleoid Cephalopods*. American Malacological Bulletin, 31(1): 109-122.

Guerraa, A., Gonzáleza, A. F., Pascuala, S., Daweb, E. G. (2011). The giant squid Architeuthis: An emblematic invertebrate that can represent concern for the conservation of marine biodiversity. Biological Conservation 144(7):1989-1997

Pontoppidan, E. (1755) The Natural History of Norway

The following images were published in James B. Sweeney's A Pictorial History of Sea Monsters and other Dangerous Marine Life, 1972, Bonanza Books. The kraken are identified as giant squid, and alternately called octopus, calamari, or cuttlefish.