American lobster
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| Homarus americanus H. Milne-Edwards, 1837 |
The American lobster, Homarus americanus, is a species of lobster found on the Atlantic coast of North America. Within North America, it is also known as the northern lobster, Atlantic lobster or Maine lobster. It thrives in cold, shallow waters where there are many rocks and other places to hide from predators and is both solitary and nocturnal.
The American lobster is found as far south as North Carolina, and are famously associated with the colder waters around the Canadian Maritimes, Newfoundland and Labrador, Massachusetts, and Maine. They commonly range from 20 cm to 60 cm in length and ½ kg to 4 kg in weight, but have been known to reach lengths of well over 1 m and weigh as much as 20 kg or more, making this the heaviest marine crustacean in the world [1]. An average adult is about 230 mm (9 inches) long and weighs 700 to 900 g (1½ to 2 pounds).
The adult American lobster's main natural predator is the codfish, but other enemies include haddock, flounder, and other lobsters. Overfishing of cod in the early 20th century has allowed the lobster population to grow enormously. Shipwrecks have been related to being an oasis in the middle of a barren desert of sand. American lobsters make their home in and around northeast shipwrecks. In fact, lobster diving is the main attraction for many wreck divers.
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[edit] Molting and mating
American lobsters molt (shed their shells) 2–3 times per year while juvenile, but only once a year or less often when fully mature, about 4 to 7 years old. When the lobster gets near its next shedding period, it will start to grow a new shell underneath the current one. The outer shell will become very hard and darken, becoming covered with black marks that look like scratches. (at this point they are known as hardshells.) The line that runs along the back of the lobster's carapace will begin to split, and the two halves of the shell will fall away. Claws and tail will be pulled out from the old outer shell, as the inner shell is very malleable. The old shell is often eaten for calcium recovery and the leftovers are sometimes buried.
Females usually mate right after molting, but mating in between molts, known as intermolt mating, can occur. Larger females can store sperm for several batches of eggs from a single coupling. All females store the sperm to fertilize eggs later, not at the time of copulation. While getting ready to molt the female will find the den of a suitable male and visit it several times. When finally ready to molt the female will do so in that den. After the molt the male will wait for the shell to start to harden, gently stroking the paper thin new shell with his large antennae. After several minutes male will raise himself on his claws and tail, then use his legs to flip over the female and get on top. The male has a pair of hardened swimmerets, or fins on the bottom, that match a pair of swimmerets on the female which have an opening between them. The sperm, contained in a gelatinous blob called a spermatophore slides down notches in the male's swimmerets into the female. The outside end of the spermatophore hardens to block the hole. The receptacle on the female is part of her shell so she will need to use the sperm before her next molt or lose it. The male dismounts and then may eat the female's shell. The female will then stay in the den for several days while her shell hardens more. Lobsters do not mate for life, contrary to some myths. The female seeks the most alpha male she can find, and the male will mate with as many females as he can.
In the first two weeks after molting, lobsters are very vulnerable, as their shells are so soft they can neither move very fast nor defend themselves with their claws. (At this point, they are often referred to as "turds" in the industry.) They will often fall prey to other lobsters, especially egg-bearing females, who become very defensive when carrying their eggs.
Because lobsters molt, it is extremely difficult to determine a lobster's age. However, many lobsters live up to 50 years.
[edit] Anatomical features
[edit] Antennae
The long antennae are used to feel the area around a lobster, and appear to be more useful than the eyes.
[edit] Antennules
The shorter antennules provide a sense of smell. By having a pair of olfactory organs, a lobster can locate the direction a smell comes from, much the same way we can hear the direction a sound comes from. In addition to sensing smells, the antennules can judge water speed to improve direction finding.
[edit] Eyes
The eyes of these lobsters are different from almost all other animals. Rather than using lenses to focus light on sensitive cells, narrow tapered channels lined with a crystalline material reflect the light onto the retinal cells. This same design is proving useful for focusing x-rays and other hard to refract light — as in the namesake Lobster-ISS x-ray telescope.
[edit] Mouth
The lobster's mouth is used for more than eating. For burrowing it can be shaped into a wedge and used to push gravel and sand, and used to carry small rocks away. A lobster can even pull itself around by its mouth, if it has lost both claws and all legs by fighting.
A lobster actually chews its food in its stomach, rather than its mouth. Food is chewed between three teeth-like grinders in what is called the gastric mill.
[edit] Legs and claws
The first pair of a lobster's ten legs are called the claws and are usually used for hunting and fighting, not locomotion. The other eight legs are used for walking.
At first the claws of a lobster are identical, but with use the lobster will start to favor one over the other. The favored claw will get bigger and be filled with primarily slow-acting muscle tissue which cannot react quickly, but does not tire quickly. This is the crusher claw. The other claw, the pincher, will develop fast-acting muscle tissue useful for grabbing prey quickly. During lobster to lobster fights, one typical move is claw lock where the two lobsters will grab each other's crusher claw and have a showdown of muscle and shell strength.
[edit] Bladder
Lobsters have not one, but two urinary bladders, located on either side of the head. Lobsters use scents to communicate who and where they are, and those scents are in the urine, as in dogs. But while a dog will just mark places, lobsters have strong muscles to project long (up to 1½ m) plumes of urine in front of them and do so when they detect a rival or a potential mate in the area. Lobsters also urinate continually while at the doors of their hiding places to indicate who is inside.
[edit] Eggs
The eggs are green, and very small, about 1 mm in diameter. They are carried by the female on the underside of the tail for a period of about one month, whereupon they are released over several days and hatch. The number of eggs carried by a single female can range well into the tens of thousands, but the survival rate is very low, speculated at around 0.1%. Older females produce vastly more eggs than younger ones. In one observation (Francis Herrick, in the 1890s) 5-inch (13 cm) females were found to have about 4,000 eggs, while 10 inch (25 cm) ones produced about 50,000 eggs.
Eggs and newly hatched lobsters can by carried very long distances by ocean currents. Within the egg lobsters molt thirty-five times. At the time of hatching, the larva still looks more like a shrimp than a lobster. For several weeks, the larva floats near the surface of the sea, eating and growing. It has small fins that allow some movement, but not real swimming. The final juvenile stage, the postlarva stage, has been called the "superlobster" by some. It is the only time in a lobster's life that it can swim forward, an act which bears some resemblance to Superman flying. At this age the lobster is about 2 cm long. This stage lasts a week or two, during which the lobster will swim during the day, at speeds of up to 20 cm/s — fast enough to cover 10 km per day. The superlobster will seek a rocky bottom with good hiding places. Without anywhere to hide it quickly falls prey to small fish, such as sculpin and cunner.
[edit] Mutations
[edit] Blue lobsters
Around one in one million lobsters is blue. A research study conducted by Professor Ronald Christensen at the University of Connecticut, discovered that a genetic defect causes a blue lobster to produce an excessive amount of protein. The protein, and a red caratenoid molecule known as astaxanthin, combine to form a blue complex known as crustacyanin, giving the lobster its blue color [2].
[edit] Yellow lobsters
On August 1, 2006 a Maine lobsterman named David Percy caught a yellow lobster near Whaleback Island at the mouth of the Kennebec River. The odds of finding a yellow lobster are apparently around 1 in 30 million [3].
[edit] Split-color lobsters
On July 13, 2006 a Maine fisherman named Alan Robinson caught a half-and-half lobster, where the colors are perfectly divided on each side of the shell. He submitted the lobster to the local oceanarium which has only seen three lobsters of this kind in 35 years. The chance of finding one is estimated at 1 in 50 million. Lobster shells are usually a blend of the three primary colors: red, yellow and blue. The colors mix to form the greenish-brown color of most lobsters [4].
[edit] Albino lobsters
It is estimated that only about one in 100 million lobsters is albino — lacking in colored pigments [5].
[edit] Fighting
American lobsters are solitary animals. The only time they peacefully share a burrow or other enclosed area is for mating. At other times, when two lobsters meet, they will size each other up. If one is clearly bigger or stronger, the weaker one will retreat. A well matched pair will move through a ritualized series of aggressive displays until one gives up. These start with whipping antennae at each other, then shoving each other around with their claws, then a claw crushing show of strength called claw lock, and lastly flipping the opponent and trying to kill it. However, at any point before the end a lobster can back-off, admitting defeat, and the victor will usually not progress further. After this the loser lobster will be able to recognize the victor for up to about a week and will immediately back out of a fight.
An exception to this ritual order occurs with egg-bearing females. These lobsters are more solitary than usual, and will skip preliminary steps and go for a kill when possible.
[edit] Lobsters as a food
American lobsters are a popular food, commonly boiled or steamed; for either method, they must be alive until they are cooked to avoid food poisoning. Hardshells (lobsters that are several months past their last molt) can survive out of water for up to two days if kept refrigerated. Softshells (lobsters that have only recently molted) will not survive more than few hours out of water. Because of this requirement, they can often be selected out of the tank in many restaurants, and their cost also can vary seasonally.
Lobster on its own is very low fat but not suitable for low sodium diets. One common way of serving lobster tail is known as surf and turf.
Lobsters have a greenish or brownish organ called the tomalley that performs the functions of the liver and pancreas in a human, i.e. it filters out toxins from the body. Some diners consider it a delicacy, but others avoid it, considering it a toxin source.
Most lobsters before cooking are mottled in appearance, but after cooking, almost all of them are completely red. Caution is advisable, as much of the body will still contain water, which may stay hotter than the outside of the shell, and can scald or startle an inexperienced diner.
A set of nutcrackers and a long, thin tool for pulling meat from inaccessible areas are suggested as basics, although more experienced diners can eat the animal with their bare hands or a simple tool (a fork , knife or rock). Eating a lobster can get messy, and most restaurants will offer a lobster bib (a thin plastic dickey-like item, usually white, usually with a picture of a cooked lobster on it).
Meat is generally contained in the larger claws and tails, and stay warm quite a while after being served. There is some meat in the legs and in the arms that connect the large claws to the body. There is also some small amount of meat just below the carapace around the thorax and in the smaller legs. The meat is generally sweet and tender. Dipping chunks of the meat into melted butter can enhance its taste.
[edit] The American lobster industry
Most lobsters come from the north-eastern coast of North America with the Canadian Maritimes and the US state of Maine being the largest producers. They are caught primarily using lobster traps, although lobsters are also harvested as bycatch by bottom trawlers and fishermen using gillnets.
Lobster traps are rectangular shaped cages made of vinyl-coated galvanized steel mesh with woven mesh entrances (wooden traps, now largely obsolete, were originally used). These are baited and lowered to the sea floor. They allow a lobster to enter, but make it difficult for the larger specimens to turn around and exit. This allows the creatures to be captured alive. The traps, sometimes referred to as "pots", have a buoy floating on the surface and lobstermen check their traps anywhere between one to seven days later. Studies have shown that the inefficiency of the trapping system has inadvertently prevented the lobster population from being overfished. Lobsters can easily escape the trap, and will defend the trap against other lobsters because it is a source of food. The study, conducted at the University of New Hampshire, estimates that only 10% of lobsters that encounter a trap will enter and that only 6% of those will actually be caught [6].
In the United States, the lobster industry is regulated by law. This is done to protect the lobster industry for future generations. Every lobsterman is required to carry a lobster gauge. This is a measuring device that gauges the distance from the lobster's eye socket to the end of its carapace. If the lobster is less than 3¼ inches (83 mm) long, it is too young to be sold and must be released back to the sea. Dishonest lobstermen could try to sell these "shorts." There is also a legal maximum size of 5 inches (127 mm) in Maine, meant to ensure the survival of a healthy breeding stock of adult males, but in parts of some states, such as Massachusetts, there is none. Also, traps must contain an escape hole or "vent", which allows juvenile lobsters and by-catch species to escape. Law in Maine and other states dictates that a second large escape hole or "ghost panel" must be installed. This hole is held shut through use of biodegradable clips made of ferrous metal. Should the trap become lost, the trap will eventually open allowing the catch to escape [7].
To protect known breeding females, lobsters that are caught carrying eggs are to be notched on a tail flipper (second from the right, if the lobster is right-side up and the tail is fully extended). Following this, the female cannot be kept or sold, and is commonly referred to as a "punch-tail" or as "v-notched". These egg-bearing females are also known as "scrubs", since an unscrupulous lobsterman may scrub the eggs off the underside of the tail with a stiff brush and attempt to sell the lobster as an honest catch. The United States Coast Guard often boards the boats of lobstermen to ensure that they are not carrying "shorts" or "scrubs". While the vast majority of lobstermen are honest, the few dishonest lobstermen will try to throw their illegal catch overboard at the first sight of a USCG boarding party.
The commercial lobstering industry is largely self-regulated. There have been well-documented examples of 'ocean justice' where dishonest lobstermen have lost their boats, homes and vehicles to vandalism by other lobstermen in retaliation for illegal acts such as scrubbing, selling shorts or hauling another lobsterman's pots. In the past, many lobstermen would keep firearms aboard their vessels to threaten any boaters or other lobstermen who were seen hauling their pots. This practice continues in many parts of New England. The laws of Massachusetts and several other states permit lobstermen to use force to protect their pots.
Lobster management policy in the US is made by committees called LCMT's or Lobster Conservation Management Committees. These groups are made up of local fishermen, policy managers and scientists. The LCMT's report to the Atlantic States Marine Fisheries Commission, an interstate fisheries organization. Lobstermen are unique in the US in that they are able to create their own conservation policy, as set under specific guidelines by scientists and political management.
Lobster boats range from small rowboats to the larger 80+ ft offshore boats that fish the US EEZ from Maine to North Carolina. The average inshore lobster boat is anywhere from 25 to 42 feet long. These inshore boats haul anywhere from 200-500 traps each day.
An inshore lobster boat costs anywhere from US$30,000 to $400,000, depending upon the size of the boat and engine. Lobster traps cost anywhere from $50-80 each, and most lobstermen fish 400-800 traps (800 is the maximum number of traps allowed lobstermen in the inshore Gulf of Maine). In addition, the rope and buoys used are also very expensive.
[edit] References
- ^ Heaviest marine crustacean. Guinness World Records. Retrieved on August 3, 2006.
- ^ Dennis Hoey. "Professor finds key to rare lobster color", MaineToday.com, 2005-05-04.
- ^ "Man finds rare yellow lobster", local6.com, 2006-08-02.
- ^ Blake de Pastino. "Photo in the News: Lobster Caught "Half Cooked" in Maine", National Geographic News, 2006-07-20.
- ^ Doug Fraser. "Albino lobster pulled from sea", Cape Cod Times, 2005-05-06.
- ^ "Lobster Trap Video", University of New Hampshire.
- ^ "Noncommercial Lobster/Crab Harvesters", Maine Department of Marine Resources.
