| Considered
by many to be the most delectable seafood of all, the blue
crab is quite abundant and widespread along Gulf and Atlantic
coastal states. Its scientific name, Callinectes sapidus,
which translates to “beautiful swimmer,” was
more than likely given the blue crab due to its bright colors
of green, blue, red and white and not its swimming grace.
Adult male crabs can be distinguished from females by their
blue claws, while the females’ are tipped with red.
Louisiana is the nation’s top blue crab producing
state at over 52 million pounds landed in 2006, with a dockside
value of $31.7 million dollars.
Female blue crabs become sexually mature immediately following
their pubertal molt and mate only once in their lives (immediately
following this molt). When approaching this pubertal molt,
females release a pheromone in their urine that attracts
males. Male crabs vie for females and will carry and protect
the female until molting occurs. Following this molt, when
the female's shell is soft, the pair will mate. During mating,
the female captures and stores the male's sperm in sac-like
receptacles so that she can fertilize her eggs at a later
time. Once the female's shell has hardened, the male will
release her and she will migrate to higher salinity waters
where as many as 1 million eggs will be spawned. The eggs
are laid in the female’s apron in a large mass called
a sponge. They are carried until mature and hatching begins,
at which time the female shakes them into the tide to be
carried into the estuaries.
The
larval crabs undergo metamorphic changes and at times do
not even resemble a crab. The first larval stage is the
zoeae stage, in which the crab lives a plankton-like existence,
floating near the water’s surface and filter feeding.
After two to four weeks and four to seven molts, the crab
enters the megalop stage and is approximately 1 mm in width.
(A U.S. dime is 1 mm thick.) The megalopae remain in the
higher salinity estuarine areas during this stage, at which
time they become free swimmers. After one to three weeks,
the megalop molts into a first-stage juvenile and looks
like an adult crab for the first time.
During these the larval and juvenile stages, crabs are preyed
upon heavily by fish, birds and other estuarine animals.
Survival rate to adulthood is very low, but like most estuarine-dependent
species, this is overcome by sheer numbers. Crabs spawn
in Louisiana throughout the spring, summer and into the
fall. This protracted spawning period, along with Louisiana’s
vast estuaries and coastal marshes, is the right combination
for crab production.
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