Blue Crabs in Louisiana

More than meets the mouth

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One would be hard pressed to walk into a seafood restaurant in South Louisiana this time of year and not see at least one table filled with happy folks cracking crab shells and sucking claws. Boiled blue crab is certainly fine table fare, but there is so much more to explore about the blue crab beyond its great taste.

The binomial name of the blue crab is Callinectes sapidus (and a more apt nomenclature could hardly be invented). Callinectes means “beautiful swimmer” in Greek and sapidus comes from Latin, meaning “savory.” Blue crabs have two large claws, six thin walking legs, and two paddle-like swimming legs, which propel them through brackish waters. These savory swimmers are crustaceans, sporting a hard shell, typically dark grey, blue, or brownish green in color, and as large as five inches across. They have four frontal teeth, which distinguish them from similar species. 

Males and females are fairly easy to tell apart; just flip them over and take a closer look. The male’s abdominal “flap” is narrow, shaped like an inverted T-shape, while the immature female’s is triangular and the mature female’s is wider and rounded. Claw color is another distinguishing feature. The male’s claws are blue on the inner and outer surfaces and tipped with dark blue. The “fingers” of the female’s claws are dark orange, looking very much like polished nails.

[Also growing this time of year: Muscadine: Fruit of the vine.]

Three years is the typical lifespan of the blue crab, during which time it outgrows its exoskeleton up to twenty-five times. When the exoskeleton, or shell, becomes too small to accommodate its growing body, the crab sheds, or molts, its old shell to reveal a new, very soft, shell that has already formed underneath (hence the term “soft-shell crab”). The crab is very vulnerable during this state and cannot defend itself. A hard-shelled male will take advantage of this vulnerability, mating with a soft-shelled female who cannot fight him off. After mating, and much to her benefit, the male stays atop her, protecting her until her new shell hardens, at which time she can fend for herself again.

Both sexes of blue crab mature at about one year. The female only mates once during her life cycle, during her pubertal or “terminal molt.” Since mating can only take place when the female is in soft-shell state, the male senses the pheromones she releases in her urine when she is close to molting stage. The male will possess her, holding her in the “cradle carry” position and protecting her until she molts, after which he inseminates her. The male deposits a reserve of sperm from which the female later draws to spawn about two times during the next year. During each spawn, she releases about two million fertilized eggs onto her abdomen, forming a “sponge” of dull orange eggs on her underside. This is called the “berry stage.” 

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She carries the eggs with her for about two weeks while she makes her way from brackish inland waters to more saline waters before the eggs hatch. Once hatched, the larval crabs feed on plankton, growing and molting rapidly. Aided by the winds and tides, post-larval crabs migrate back to the shallow, less saline waters of the middle and upper estuaries, which act as a protective nursery for the juvenile blue crabs as they mature to spawning age.  In the estuary, juvenile and adult blue crabs thrive on detritus, plant material, small fish, bivalves, and crustaceans. Even though the topography of a healthy estuary offers protective covering for the crabs, it can’t always protect the crabs from their natural predators: red fish, black drum, turtles, birds, and alligators. Oh, and humans!

The blue crab, with its brilliant colors and interesting mannerisms, is another wonder of the Louisiana estuary systems. Not only are they fun to watch, but they are also fun to catch. You don’t even need a boat—just a nice bank along an inland estuarine waterway, a turkey neck tied to a long string, and a dip net. The sweet white meat of the blue crab is delicious in seafood gumbo, crab stew, crab meat au gratin, pan-fried crab, and, of course, everyone’s favorite boiled crab. For a variety of authentic Louisiana seafood recipes featuring blue crab, visit: http://goo.gl/2Ixwa2.