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Science
Volume 40 Issue 8 • June 24-30, 2010
now in our 40th season

The Kraken’s Younger Brother

by Dr. Sarah D. Oktay
Managing Director UMass Boston Nantucket Field Station

I was visiting an island seafood purveyor in early June when the topic of squid came up.  I am a big fan of squid and other less traditional seafood and was wondering if there was viable local market for them and how sustainable the fishery might be.  I knew people locally were into jigging for squid on the docks, but I was curious as to whether they were sold frequently.  The owner told me very few commercial fishermen fish for squid and what catch there is depends on the use of small gauge nets for winter flounder and the ongoing fishing regulations. Mid June, fishermen switch to nets with larger holes that the squid can slip through. Although this practice makes it difficult to stock and sell this seafood in stores, it does help protect the breeding stock. We’ll talk more about the fishery below.

Squid are marine cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two longer tentacles. Tentacles are longer then arms and they usually only have suckers at their tips.  The squid is one of the most highly developed invertebrates, well adapted to its active, carnivorous predatory life. Squids are mollusks of the phylum Mollusca. Their molluscan relatives are snails, clams, and other bivalves.

Squid are members of the class Cephalopoda.  Other members include octopus, cuttlefish, and the ancient nautilus. The word Cephalopoda means literally, "head-foot bearing" and refers to the way the cephalopod arm appear to be attached directly to the head.  The shell of the mollusk has evolved to become a cartilaginous plate shaped like a quill pen and buried under the mantle. The mantle, the chief swimming organ of the animal, is modified into lengthwise fins along the posterior end of the body and projects forward like a collar around the head. As the mantle relaxes and contracts, the squid swims forward, upward, and downward. Water is expelled in jets from the muscular funnel located just below the head, propelling the squid backward in abrupt jetlike motions. The combination of chitin and mantle makes the squid fast and able to withstand great depths and pressure. The arms are used to steer in swimming and the tentacles are used to seize and immobilize prey, which are then cut into pieces by the animal's strong beaklike jaws. The beak is made of chitin, and is indigestible which explains why squid beaks are often found in the stomachs of predators from whales to seals.

The squid breathes through gills, and like its cousin, the octopus, will squirt a cloud of inky material from its ink sac when in danger. The circulatory and nervous systems are highly developed. The eye of the squid is remarkably similar to that of humans—an example of convergent evolution, as there is no common ancestor. Some deep-sea forms have luminescent organs. More squid fun facts: they have three hearts; most squid have a type of chromatophores, which enable the squid to change color to suit its surroundings; and they may have limited hearing (good to know for all the squid whisperers out there). And of course, there is the mythological creature, the Kraken. The Kraken of legend is probably what we know today as the giant squid. While a colossal octopus might also fit the description, the squid is thought to be much more aggressive and more likely to come to the surface.

Squid and octopuses are also highly intelligent for invertebrates. Many of my college friends worked at a squid behavioral center and neurological facility in Galveston at the University of Texas Medical Branch and they would spend their evenings watching hours of tapes of squid and cuttlefish swimming around in big tanks (yes, they got paid for it, college students have to make money somehow). Each night, some wayward squid would tire of the tank and escape to be found the next morning in another tank or sometimes manage to open a door handle and be halfway down the hallway!

The common squid, when not scuttling around in laboratories, is found from Maine to the Carolinas, often moving in shoals. In the United States tons of squid are used for fish bait, particularly by the cod fisheries in New England. Squid is a favorite food in East Asia and in the Mediterranean area. Species range in size from about 2 in. (5 cm) to the proportions of Mesonychoteuthis hamiltoni, the colossal squid, which is the largest of all invertebrates and may attain a mantle length of 13 ft (4 m) and total length of 33–46 ft (10–14 m), and the giant squid, Architeuthis dux, which has a mantle length of 7.4 ft (2.25 m) and is known to reach 43 ft (13 m) in total length. (Accessed June 19, 2010 at http://encyclopedia2.thefreedictionary.com/Teuthida).

The squid you most commonly see off of Nantucket is one of the many species in the genus Loligo which is one of the most common and widely distributed squid species. The genus was first described by Jean Baptiste Lamarck in 1798. However, the name had been used earlier than Lamarck and was most likely used by Pliny the Elder, also known as Gaius Plinius Secundus  (circa 23-79), the Roman officer and encyclopedist in book 9 of his 37 volume opus called Naturalis Historia. In the early nineteenth century, this generic name was often used as a grouping for all true squids. Giant squid, which measure 40 feet and longer, and their smaller cousin, the Loligo pealei, have large optic nerves. When people aren’t eating them, squid are also harvested in bulk each spring for research by fishermen for scientists at the Marine Biological Laboratory in Woods Hole and other labs and universities across the country. Squid were long prized by scientists for their huge axons. More than 100 times the size of a human axon, the squid's axon is roughly a millimeter in diameter and the largest nerve fiber on Earth. The enormous size allows scientists to study how signals are sent along the length of the axon to other nerve cells or muscles. Squid research today focuses on everything from evaluating the progression of Alzheimer’s damage in the brain to investigating cures for various eye diseases.

In 1963, the Nobel Prize in Physiology or Medicine was awarded jointly to Sir John Carew Eccles, Alan Lloyd Hodgkin and Andrew Fielding Huxley "for their discoveries concerning the ionic mechanisms involved in excitation and inhibition in the peripheral and central portions of the nerve cell membrane" (http://nobelprize.org/nobel_prizes/medicine/laureates/1963/). In essence, these men used squid to investigate how human neurons worked; essentially doing research on an axon large enough to see with the naked eye. In a serious of groundbreaking experiments that could have come out of the novel “Frankenstein: or, The Modern Prometheus,” they hooked up electrodes and circuitry to the axons to see how electricity, and therefore information, could be transmitted.
The Long-finned inshore squid, Loligo pealei can reach lengths of up to 24 inches. A close relative the Boreal Squid, lllex illecebrosus, also known as the short-finned squid, overlaps Loligo over some of its range. It is generally found farther north. The two squids can be distinguished by the relative lengths of the fins. Several species are commercially exploited, such as Loligo vulgaris and Loligo plei. Many squid species are attracted to lights; they are therefore fished using different light attraction methods (accessed June 10th at http://en.wikipedia.org/wiki/Loligo). Squid will eat small copepods and other zooplankton when they are first born, graduating to fish and shrimp as they get larger.

The Longfin Inshore Squid (Loligo pealeii) is a species of squid of the family Loliginidae. The species is sometimes referred to by only its genus name Loligo. The Longfin Inshore Squid is found in the North Atlantic, schooling in continental shelf and slope waters from Newfoundland to the Gulf of Venezuela. It is commercially exploited, especially in the range from Southern Georges Bank to Cape Hatteras. The Longfin Inshore Squid spawns year-round and most scientists agree that they only live on average for one year, although this conclusion was only recently reached as a result of studies of the animal's statocyst, a calcium carbonate rock in the animal's balance organ that grows in rings that are laid down daily. Individuals hatched in summer generally grow more rapidly than those hatched in winter. The species presents sexual dimorphism, with most males growing faster and reaching larger sizes than females. The dorsal-mantle length of some males can reach 40 cm, although most squids commercially harvested are smaller than 30 cm long.

Reading through riveting copies of the Marine Fisheries Advisor over the past years, we can see that the Division of Marine Fisheries for Massachusetts had changed regulations for trawling for squid.  There is an active on-line forum for squid fishermen at http://www.squidfish.net/ which provides some insight into the evolving regulations for squid fisheries over time, most of which concern extending the season by a week or two, limiting the size of trawlers (especially large trawlers) in some key squid spawning areas, controlling the amount of discarded squid through the process of trawling for other species, and monitoring the size of squid caught. From the April 13, 2005 Marine Fisheries Advisory “Commercial trawling regulations for waters south of Cape Cod and the islands were amended. The commercial squid season when small-mesh trawling is allowed, formerly ending on May 31, was extended through June 9th. The summer-time allowance for the use of 4 1/2" mesh during the June through October period in waters south of Cape Cod and the islands was eliminated (322 CMR 6.22, 8.07, & 8.08). Squid are also a part of the Cape and Islands recreational fishery. Fishing for squid from lighted spots of docks or off boats is a very popular activity on both sides of the Sound.

Squid biology is explored in text and in videos at
www.mbl.edu/publications/pub_archive/Loligo/squid/index.html. The animal is a migratory creature that comes to Cape waters every spring to spawn. They live off shore in deeper cooler water during the winter. If you have ever seen squid reproduction, you would certainly have not forgotten it. In early spring, squid “dating” starts as the dominant males fight for the opportunity to copulate with the females. The female gather the sperm from one or more partners in the off-shore mating ritual.

hen she arrives inshore, the female pulls a jelly-like matrix of eggs out of her body and holds it her arms and releases the stored sperm to fertilize hundreds of eggs. It has been documented by Dr. Roger Hanlon of the Woods Hole Marine Resources Center that sneaker males may lay in wait for females to deposit their egg sacs and fertilize the eggs at the last second, beating out the older sperm the female collected earlier. Squid hatchling will eat the yolks from their eggs sacs for 4-5 days, then progress to eating copepods and other zooplankton, eventually graduating to fish and shrimp as they get larger. Cannibalism has also been documented for squid. Many creatures like gray seals, stripers, and common dolphins feed on squid. Large groups of squid aggregate both south and north of the island each summer; sometimes bringing squid loving marine mammals in their wake like the pygmy and dwarf sperm whales seen last summer.

From the Status of Fishery Resources off the Northeastern US NEFSC - Resource Evaluation and Assessment Division (accessed on June 21st at http://www.nefsc.noaa.gov/sos/spsyn/iv/lfsquid/), the L. pealeii stock has varied with high catch totals from 1999-2002 and lower catches in 2003-2005 ending in a bit of a rebound to mid 1980’s population levels in the past few years. More frequent sampling data is needed for this annual species whose average catch numbers should be around 20,000 metric tons with a high bycatch mortality substantially effecting the population at times.

Autumnal surveys are ideal, but they tend to miss some of the inshore squid. Squid are managed in federal waters (outside of the 3.0 mile limit) by the Mid-Atlantic Fishery Management Council. The take of long fin squid is managed via a coast-wide quota that varies from 15-45 million pounds of which Massachusetts takes on average 10-15 percent of the total catch. The variances in the quota are reflected in the boom/bust years of the squid. The maintenance of the squid fishery and the total sustainable amounts of squid in Nantucket sound is not the simple story I was hoping it would be, but the good news is that according to reputable sources like the sustainable Ocean Project, squid are a sustainable species for your dinner table (sustainableoceanproject.com).

My obsession with squid started with the idea of having them for dinner. You can eat every part of a squid except for the beak and pen.  On our restaurant plates, squid is known as Calamari, which is the plural form of the Italian word for squid, Calamaro. Also known as Kalamari, Kalamar (Greek/Turkish), Calmar (french), Galama or Calamares (Spanish), the name derives from the Latin word calamarium for "ink pot," after the inky fluid that squid secrete. Calamarium in turn derives from Greek “kalamos” meaning "reed," "tube" or "pen,” referring to the quill “pen” inside of the squid. People use the ink to color food like paella and pasta, but also for writing. Last but not least, to access an audio file of Rogen McGuinn’s folk song about squid jigging go to http://www.ibiblio.org/jimmy/folkden-wp/?p=6986 and click on “Squid Jigging Ground.” You’ll also get a neat tutorial on squid jigging. Don’t say I never offered up some culture with all the science tidbits. For a very comprehensive look at “all things cephalopod,” go to http://www.cephbase.utmb.edu/ or http://www.thecephalopodpage.org/.

 

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