In recent
years, a small commercial recreational and fishery has developed
for stone crabs in high-salinity bays across Louisiana. Stone
crabs began to attract attention in the 1980s, when more of
them began appearing in blue crab traps in coastal lakes and
bays. In early 1985, LSU biologists conducted a study into
the possibility of developing a fishery for them. Before that
could occur, however, the great Christmas freeze of 1989 severely
reduced the number of stone crabs in Louisiana’s coastal
waters. Since then, stone crab numbers have increased to more
than before 1989. Modest numbers are landed in some parts
of the state for sale in the wholesale trade or for retail
sales directly to the public. In some areas, numbers are high
enough for recreational crabbers to target.
The stone
crab found in Louisiana is officially known as the Gulf stone
crab, Menippe adina. It is very closely related to the Florida
stone crab, Menippe mercenaria, but smaller, with some color
differences. The Gulf stone crab has a dark brown body, compared
to the tan or gray color of the Florida stone crab, and it
doesn’t have bands or stripes around its legs like the
Florida stone crab. The ranges of the two species overlap
in the area of Apalachee Bay, Florida, where they hybridize.
Gulf
stone crabs seem to prefer slightly higher salinities than
blue crabs, from full strength sea water at 35 parts per thousand
(ppt) down to 10 ppt. They seem to prefer areas near or on
oyster reefs, rock jetties or debris-cluttered bottoms, where
they burrow in the mud for shelter, cold weather refuge and
when molting their shell. During cold months, they seem to
show a preference for deeper channels and passes. Research
indicates that Gulf stone crabs can survive very low oxygen
levels, at least for a day or so. Females seem to outnumber
males, especially in deeper waters.
Mating
is similar to that in the blue crab, taking place while the
female is in the soft-shell stage, with the male cradling
the female beneath him. A male will begin “guarding”
a female before she molts and will continue to do so until
her shell hardens. Mating seems to take place in the fall.
After
mating, a female will deposit fertilized eggs on the “hairs”
under her belly apron in a large mass called a “sponge”.
Hatching occurs in 7-18 days, depending on water temperature.
Females may spawn several times between March and September
with peak spawning occurring from May through July. After
hatching, Gulf stone crab larvae go through seven stages before
they resemble the adults. During most of this time, they are
planktonic, meaning that they are free-floating, at the mercy
of the currents and tides.
Once
they settle to the bottom, the young stone crabs have a wide
diet of oysters, mussels, barnacles, snails, clams, worms,
jellyfish, blue crabs, hermit crabs and plant matter. Shellfish
of all kinds are staple foods of adults, with oysters being
a major food item. Feeding is highest on spat and small oysters,
but larger Gulf stone crabs eat oysters of all sizes. It has
been estimated that they consume an average 219 oysters per
year and they may be more destructive to both spat and adult
oysters than the oyster drill (conch).
Growth
is fairly slow. Some females are mature enough to spawn by
age two, and by age three, only 30% are mature. By seven years
old, almost all the females are mature. Only the claws on
stone crabs are harvested, but claw removal does slow their
growth rate. Stone crabs have a large crusher claw and a smaller
pincher claw. Both can be harvested if they meet the minimum
propodus (claw) size limit of 2 3/4 inches. Claws on males
are more slender and longer than females and will produce
legal claws at a smaller size than on females.
Louisiana
law provides that only legal stone crab claws can be set on
shore from a vessel and that whole stone crabs cannot be landed,
except for a tolerance of one stone crab per crate of blue
crabs. Since stone crab claws cannot be iced or refrigerated
before boiling, fishermen often hold the stone crabs alive
until near the end of their run before declawing them. Chilling
stone crab claws before boiling will result in the meat sticking
to the shell. Stone crabs may be boiled with traditional Louisiana
seasonings, but are at their best when boiled in lightly salted
water and served with melted butter.
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