Blue crabs belong to a large group of
organisms known as arthropods. Arthropods
are organisms that possess jointed
appendages. When you look at the external
features of the blue crab, you can see
that it is adapted for living in an
aquatic environment. The carapace is
narrow and streamlined. It has two
pincers used for defense and capturing
food items, three pairs of walking legs
and a pair of paddle-shaped rear
swimming legs that make it a very
efficient swimmer. You can distinguish
male blue crabs from female blue crabs
by looking at the shape of their abdomen,
or apron. Mature male blue crabs, or
Jimmies, have a strongly tapered apron
that resembles an inverted T, whereas
mature females, or sooks, have a broad,
rounded apron. Immature females, also
known as She-Crabs or Sallies, have a
triangular-shaped apron. Sponge crabs, or
egg-bearing females, possess a mass of
orange or black eggs on their underside
and are illegal to keep. This image shows
the movement of blue crabs throughout
their lifecycle. Females migrate to
higher salinity waters to spawn. The eggs
hatch into larvae, referred to as zoea
larvae, and undergo a series of molts
using the tides and currents. Blue crab
larvae move from deeper open ocean
waters into shallow waters of the
estuary where they continue to molt.
The estuary serves as an important area
for developing juvenile blue crabs. With
a life expectancy of about three to four
years, blue crabs will spend a large
portion of their time in estuaries and
sounds foraging on clams, oysters, mussels
and other organisms. They are an
ecologically important species that
serve both as predator of benthic
communities and prey for many fish
species, like red drum, croaker, striped
bass and other blue crabs. Economically,
blue crabs are one of Georgia's most
valuable commercial fisheries. Commercial
landings in Georgia produce millions in
dockside value every year.
For more information visit the Marine
Extension and Georgia Sea Grant website.
