🦀 A Brief Introduction to Crabs

With over 6,700 species in 93 families in the animal kingdom, these crustaceans have been roaming our waters for millions and millions of years. Usually covered in a thick exoskeleton and armed with a pair of claws, they could be found all over the world, most in the oceans while others in bodies of fresh waters. Their size varies from the extremely small pea crab, which measures .75 centimetres, to the extremely large, record holding, Japanese spider crab, which is all of 4 metres.

They are known as decapods because of the fact that they have ten appendages, from the Greek words, deka which means ten and poda which means leg. They have identical halves on each side except when one of their chelae or pincers is larger than the other. These claws serve many functions, for instance capturing food, digging holes, defending from predators, and communication with other crabs to mark territory and to attract the opposite sex.

Anatomy

Their bodies are completely covered with an exoskeleton which also serves as a suit of armour. Every so often, the decapod would need to shed it in order for it to grow bigger. The process of replenishing a new exoskeleton only takes a few hours. Sexuality can be determined just by looking at their abdomens. The male species would have a narrower region than that of the female.

Crabs, generally, walk sideways because of the articulation of the legs. Some, however, are capable of walking forwards and backwards. Being omnivores, they feed on anything from algae to molluscs, fungi, bacteria, worms and even other crustaceans.

Every year we consume an estimated 1.5 million tonnes of crabs which make up about 20 percent of all the crustaceans which are consumed. Of this amount, 300,000 tons are made up of the Japanese Blue Crab or the Horse Crab which is the most consumed around the world and is indigenous to the coasts of China.

Harvesting Crabs

Crabbers are the people who specialise in capturing decapods in various bodies of water. They use a cage-like device with a one-way door which allows the creatures to go in but not out. People who do it for recreational purposes, on the other hand, use a piece of bait which is tied to a string and tossed in the water. The fisherman simply pulls the line in when they start taking the bait. Of course, there are other methods for capturing these animals.

One thing you have to be aware of before you go out and fish for crabs is that there are laws regulating this activity. Check for your local fish and game department for more details

Molting

Molting (also known as Ecdysis) is the process whereby a crab outgrows its old shell and form a new, larger one. As their body grows the shell does not which causes the molting to take place.

Once free of the old shell, they are vulnerable to attack by many other creatures including other crabs. The shedding process is repeated up to 25 times during the life span, which seldom exceeds two to three years. Small crabs will shed about every 4 weeks, larger males will shed every 7 to 8 weeks.

The molting process goes through many different stages. A hard shell crab may stay as a hard shell for 2 to 8 weeks. A ‘white sign’ develops around the edges of our paddles about 14 days prior to molting. In a week a ‘pink sign’ can be seen which gets progressively more red the closer to molting it becomes.

Albino Crabs

Identifying the types of crabs you see is important. Some of the most rare blue crabs are albino crabs which have almost no color other than white. If you intend to catch crabs you will need to be able to recognize the types of blue crabs pictured above. Some are illegal for you to keep!

Although rare, many species of albino cousins and other shellfish such as lobsters are occasionally found in different parts of the world. Crabs are classified as albino when they exhibit deficient pigmentation that is usually milky or has translucent skin, white or colorless hair, and eyes with pink or blue iris and a deep-red pupil.

Common Crabbing Terms

There are a variety of terms used by crabbers to describe certain crab processes. Below is a glossary table so you can better help understand crabbing jargon:

  TermMeaning
AntennaLong appendages found behind the eye stalks.
AntennuleUsed to small and taste, found below eyes.
AppendagesFive pairs of legs.
ApronAbdominal covering on the bottom side of the crab.
Atlantic blue crabScientific name - Callinectes sapidus
Back finThe swimming or paddle fin. Also the term used for the lump white crab meat.
BalliesSponge crab.
Bare pottingAn unbaited trap is placed in deep water where there is no grass or any other hiding place. Crabs enter the traps tp hide and shed. Only done for a couple of weeks in the Spring.
BuckramSoft crab just past the paper shell stage.
Buckshot diseaseSame as salt and pepper disease.
Buffalo crabSoft crab with the claws or legs missing.
Busted sookSponge crab
BustingCrab emerging from its shell.
Callinectes sapidusScientific name of the Atlantic blue crab. Callinectes is Greek for beautiful swimmer and sapidus is Latin for tasty or savory.
CarapaceTop part of the shell or hard covering of the blue crab.
CartridgeWraps around muscles that help with movement.
ChannelerLarge male crab that remains in the deeper channels of the bay or river.
ChelipedFirst pair of legs carrying the claws.
Chicken neckerA regional term (sometimes derogatory) denoting someone who fishes for crabs using chicken necks for bait, also used to describe non-resident weekend crabbers.
Crab floatA flotation device used to indicate the placement of a crab trap.
Cradle carryingDoubler
CrustaceaClass of invertebrates to which the Atlantic blue crab belongs.
Dead man's fingersThe gills of the crab.
DoublerA large male crab carrying a sexually mature female; a pair of mating crabs; buck and rider or carrier. The female crab could most likely be a soft crab.
Dwarf femaleA small but sexually mature female blue crab.
Ebb tideOutgoing tide.
EcdysisMolting. The act of shedding the old shell when it is outgrown. Will result in a crab about one-third larger in size, with a soft shell which takes two to three days to harden.
EelgrassA submerged long-leafed monocotyledonous marine plant (Zostera marina) of the eelgrass family that is abundant along the Atlantic coast.
Fat crabCrab that is nearing the end of its intermolt cycle.
Flood tideIncoming tide.
GillsEight on each side of crab body used for breathing.
Green crabCrab between molts; non-peeler crab.
Hard crabCrab with a fully hardened shell, usually within four days after molting.
HepatopancreasStores and absorbs digested food.
JennyA female crab.
JimmyA male blue crab.
Jimmy pottingMale crab is attached to a line inside a trap and allowed to swim in hopes of attracting and catching a female
KeeperA hard crab with a minimum legal length.
Lateral spinesLargest points on either side of the carapace.
LengthWhat most people would call the width. It is measured across the top shell between the two outermost spines of the crab's body section.
LickTerm used to describe dredging for crabs; a dredge is drawn across the bottom to catch wintering crabs or summer soft crabs.
LumpLargest pieces of meat. Found near the backfin.
MoltSee ecdysis.
MegalopaFinal larval stage, between zoea and crab stage.
MustardThe yellowish substance found under the carapace of a cooked crab. Contrary to popular belief, the "mustard" is not fat, rather it's the crab's organ responsible for filtering impurities from the crab's blood. Do not eat this since many chemical contaminants concentrate in this organ.
Neap tideA neap tide is of medium range and occurs during the first and third quarters of the moon.
Number onesThe largest crabs.
Painted fingernailsFemale crab's red claws.
Paper shellSoft crab about 9 to 12 hours after molting. Shell is slightly stiff.
PeelerShedding crabs caught by soft-shell fishermen.
Pepper spot diseaseSee salt and pepper disease.
PickingEating a steamed crab by picking out the meat.
Pink SignDot which appears on a crab's back fin prior to molting.
PrimeReady for the market.
Sally crabYoung, immature, female crab. Has a V-shaped apron; she-crab.
Salt and pepper diseaseA crab which has been infected with parasites which appear as small dark specks throughout its meat. See. Also called buckshot disease, pepper spot disease, or pepper crabs.
ScappingUsing a dip net to catch soft crabs in shallow grassbeds by hand.
ScarpingAlso called Jenkins Creekers and bar cats. Illegal method of crabbing where a large net pulled behind a workboat scrapes up crabs and everything else from the bottom.
ScrapeA small trawl used for illegally scraping peelers from grass beds.
She-crabMature female crab.
SlabsThe biggest soft crabs.
Soft crab or soft shelled crabCrab which has shed its shell.
SookSexually mature female crab.
Sponge crabFemale crab which is carrying eggs under her apron.
Spring tideGreater than average range between high and low tide that occurs twice each synodic period around the times of a new and full moon when tidal actions of the Sun and moon are nearly in the same direction.
SwimmeretsUnder female apron where eggs are carried.
Terminal moltThe last molt.
TestesPart of male reproductive system found on top of hepatopancreas.
Tinker bellsCrab boots worn by commercial crabbers. Sometimes called Crisfield prom shoes.
ZoëThe larva that hatches from the egg.