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Barnegat Bay is home to several species of crabs, but the Blue crab is the most common and sought after.

Crabs


Crabs

 

Blue Crab

 

Blue Crab Molting

 

Fiddler Crabs

 

  Crabs                    Crustaceans

Crabs are classified in the phylum Arthropoda.  This is the same phylum as insects and spiders, however crabs are in the subphylum Crustacea (crustaceans) along with shrimp, lobsters and prawn.

They are called "decapods", meaning they have 10 legs. The front pair is modified with strong claws and in some species the rear pair is modified for swimming.
 

Blue Crab                     Callinectes sapidus

Blue crabs are one of the most important commercial and recreational species in New Jersey.

Blue Crabs are found from Nova Scotia to northern Argentina, but are most abundant from Massachusetts on down and around the coast to Texas.

The blue crab's abundance, beautiful coloration (a brilliant blend of olive-green, blue and red), aggressive temperament and delicious flavor make it a favorite of recreational crabbers in New Jersey

Although most small boats are ideal for reaching crabbing areas, almost any bank, bulkhead, bridge or pier bordering tidal waters can provide excellent crabbing.

<click here to learn more about blue crabs>

Black-Fingered Mud Crab     Panoeius herbstii

Photo by K. Hill, courtesy of Smithsonian Marine Station at Ft. PierceThough little known, the black-fingered mud crab is the most numerous of the non-swimming crabs in the bay. These crab grow to be about an inch and a half across its head.

The black-fingered mud crab is a tiny, grayish-brown crab with powerful, black-tipped claws, one bigger than the other.

The larger claw, called the major claw, has a large tooth on the movable "finger" of the claw.

The mud crab's carapace, or shell, is wider than it is long, with five "teeth." 

Like all crabs, they breathe oxygen through gills. These crabs live completely under water, unlike other species of semi-terrestrial crabs such as the fiddler crab.

Mud crabs range from the salty mouth of the Bay up to moderately brackish waters.

These mud crabs are found on and around rocks, mud flats, pilings, oyster reefs, grass beds and sponge colonies near the shore. They sometimes create burrows under shells and stones.

They primarily feed on other small invertebrates, such as worms, clams and other crabs.  They use their strong claws to crush the shells of young clams and oysters, barnacles, periwinkles and other shellfish. They will also feed on hermit crabs by seizing a hermit crab's protruding legs and pulling it from its shell.       <click here for more images>

Fun Fact - Black-fingered mud crabs are commonly found living inside cans, bottles, and other trash discarded by humans. The debris offers the little crabs protection.

  This is a reflection of how animals have learned to adapt to an ever-increasing human impact

Green Crab                    Carcinus maenas

Green crabs have dark green coloration on their carapace with numerous darker blotches. They possess flattened -walking legs on the last set of segments, and not paddles (like the blue crab).

They have more compact claws for crushing their prey.

Mature male crabs sometimes are yellow on their underside, while mature females are reddish-orange.

Green crabs are an introduced species to the area. They generally inhabit the colder waters within the intertidal zones of New England and south to New Jersey.

Green crabs are found in nearshore and estuarine waters. They tend to prefer higher salinity waters, usually near inlets by salt marshes.

The mature males grow to about 3 inches and females to 5 inches. They feed on small invertebrates, including snails.  <click on image to enlarge>      

<click here for more images>

Lady Crab                      Ovalipes ocellatus

 

Common Spider Crab                  Libinia emarginata

The common spider crab is also called the Atlantic spider crab or portly spider crab.  The shell (carapace) is spiny and covered with short hairs.  The shell grows to 4 inches in diameter with a leg-span of twelve inches. 

Like most other crabs , they are decapods.

Spider Crabs  appear fearsome-looking but they are actually slow moving and harmless to humans.

Not particularly aggressive, the spider crab's main defense against predators is camouflage.  The hook-like hairs on the crab's shell  hold algae and other small debris in place.  They can also burrow in soft sediment.

Spider crabs are omnivorous scavengers with diet consisting mainly algae and mollusks but almost anything else available on the bay floor including  fish, sea stars, shrimp, and other crustaceans.

Fun Fact - different from most walking crabs, spider crab usually walk forward, although they are also capable of sidelong movement.

Lady Crab               Ovalipes ocellatus

The common spider crab is also called the Atlantic spider crab or portly spider crab.  The shell (carapace) is spiny and covered with short hairs.  The shell grows to 4 inches in diameter with a leg-span of twelve inches. 

 

Chinese Mitten Crab      Eriocheir sinensis   

The Chinese mitten crab is a burrowing crab whose native distribution is the coastal rivers and estuaries of the Yellow Sea in Korea and China.

The main identifying features of the mitten crab are the dense patches of hairs on the white-tipped claws of larger juveniles and adults, hence the name mitten crab.

The claws are equal in size, the shell (carapace) has four spines on either side, and reaches a width of approximately 3 inches.

The Chinese Mitten Crab occurs in both freshwater and saltwater. Young crabs spend two to five years in freshwater tributaries and can extend many miles upstream of bays and estuaries. Mature male and female crabs migrate downstream to mate and spawn in saltwater estuaries. They burrow into banks along estuaries and are able to leave the water to walk around obstacles while migrating.

The New Jersey Division of Fish and Wildlife is asking the Public to report any sightings of a Chinese Mitten Crab.   Information is at the following websites:

http://www.state.nj.us/dep/fgw/news/2009/mittencrab09.htm

http://www.state.nj.us/dep/fgw/pdf/mitten_crab.pdf

<click here for more information about Chinese Mitten Crabs>

Marsh Fiddler Crab              Uca pugnax

The American marsh fiddler crab is the smallest fiddler crab in the Bay. Its carapace (shell) grows to less than an inch wide and its major claw grows to 1.5 inches long.

They live in salt marshes along the bay and construct burrows that are utilized for mating, rest and "hibernation" during the winter.

The burrows also serve as refuge from predators, heat, and incoming tides.

The males are dark olive to almost black in color with a royal blue spot on the center of its carapace.

Females are of similar color as the males, but do not have the blue spot.  Either one of the male's chelae (major claw) may grow until it is half of the crabs body weight, while the claws of the female are the same size.

<learn more about fiddler crabs>

Fun Fact - The common English name “Fiddler Crab” comes from the feeding of the males, where the movement of the small claw from the ground to its mouth resembles the motion of a someone moving a bow across a fiddle (the large claw).

 Mole Crabs and  Sand Crabs                       Family: Albuneidae

Sand crabs and mole crabs, while not common in the bay, are found on Island Beach and Long Beach Island living in the turmoil of breaking waves. They move up and down the tide line to feed in the swash zone. The crabs burrow backward into the sand and face seaward, with only their eyes and first antennae showing.

As a receding wave flows over them, the sand crabs uncoil a second pair of featherlike antennae and sweep them through the water to filter out tiny plankton.

Fun Fact - Sand Crabs are commonly referred to as Mole Crabs, they are also called Sand Fleas, Beach Fleas, Sand Bugs, and Beach Hopper (to name a few).

Atlantic Sand Crab             Emerita talpoida   also called  Atlantic Mole Crab

Mole crabs are among the smallest of the crabs.  Like other crabs they has five pairs of legs, but they do not have pincers and move backwards rather than walking sideways.

They are egg-shaped and pale grayish-tan in color. The carapace (shell) is convex with crosswise-creased line immediately behind the beak and another curved one farther back.  The rear end of carapace is smooth.    see image, top left

The first pair of antennae are hairy while the second pair of antennae are long and feathery, usually concealed under edge of carapace. The eyestalks are long and slender.   see image, center left

The first pair of walking legs are broad and sturdy broad without pincers. The  2nd, 3rd, and 4th pair less sturdy and leaf-like. The fifth pair are very slender.

Shown in the image to the right, the abdomen is broad in front, tapering rapidly with a pair of forked, leaf-like appendages and long, spearhead-shaped tailpiece on the last segment usually bent forward underneath body.

 

   <click on any image to enlarge>

 

Females grow to about one inch, while males grow to about half an inch. 

The lower left image shows a handful of mole crabs with the females being the larger specimens.

 

Ghost Crab     Ocypode quadrata

Ghost crabs belong to the Family Ocypodidae (fiddler crabs and ghost crabs)

Adults are grayish or the color of straw, and about 2 inches wide at maturity. Like fiddler crabs, they are terrestrial and need to return to the water periodically to moisten their gills. Their compound eyes are on stalks and can swivel to give them 360° vision.

Also called sand crabs, they are mostly nocturnal being active from dusk to dawn, scouring the beach looking for anything edible. 

Ghost crabs spend most of the daytime hours in burrows. The golf ball-sized entrance holes may be visible in the dry sand of the upper beach, or in the sand dunes. The burrows extend down 3-4 feet with a "turn-around" chamber at the end.

They also use these burrows to hibernate in winter existing by storing oxygen in specialized sacs near their gills.

Ghost crabs return to the water for a few reasons.  As mentioned above, they need to moisten their gills to breathe.  Females with egg masses need enter the water to keep them moist and to release the young when they hatch.

Running into the water is also a means to escape from a predator if the burrow is not accessible. 

Fun Fact - Ghost crabs are one of the fastest crustaceans capable of running up to 10 MPH and they can run forward, backward and sideways.

Fun Fact - Like fiddler crabs, ghost crabs have one enlarged claw.

Hermit Crabs

Hermit Crabs are not true crabs, but are an intermediate form having a soft shrimp-like tail that is protected inside the snail shell.  (like all crabs, they are decapods)

Unlike other crabs, the hermit crab has no exoskeleton, so for protection, it forces its vulnerable body into the curved chamber of an empty gastropod shell (or similar object) for protection.

The four hind legs that appear to be missing have evolved into grippers that hold the crab inside the shell so strongly that you will tear the animal in half before you can extract it. The claws are usually shaped so that together they will exactly block off the opening when the crab retreats inside.    <click here or on image to enlarge>

Hermit Crabs are always on the lookout for bigger and better shells, and when they find one they like, they quickly switch to see if is the right fit.

Fun Fact - hermit crabs can be classified as marine hermit crabs and land hermit crabs.

Marine crabs breathe through gills using the oxygen dissolved in water.  Land crabs have a modified gill mechanism that absorbs oxygen from the humidity in the air.

Long-Armed Hermit Crab     Pagurus longicarpus

Long-armed hermit crabs are marine crabs that inhabit the shorelines and muddy or sandy bottoms of Barnegat Bay  They live in grass beds, from the low-tide line to the deeper waters of the bay.

Their bodies are greenish-white or gray with pincers that are often gray with light brown stripe. The right pincer is larger than the left and is three times longer than it is wide. The long-clawed hermit lives in the shells of mud snails, oyster drills or periwinkles.  The body grows to about one inch (or less)

The long-armed hermit crab is a scavenger which consuming edible material from the surfaces of sand grains and also a consumes larger pieces of detritus plant and animal material therefore , an omnivore.



Credits

beach mole crab   Rebekah D. Wallace, Bugwood.org

black-fingered mud crab images - Irene H. Stuckey, courtesy of R.I. Natural History Survey

ghost crab images - Joy O'Keefe    www.okeefes.org

ghost crab resources - http://www.answersingenesis.org