With bright blue claws, sweet white meat, and powerful swimming legs, the blue crab is completely deserving of its scientific name Callinectes sapidus, which translates to “beautiful savory swimmer.” Enthusiastically pursued by both young and old anglers alike, the blue crab is a favorite dish at the local summertime clambake.
Having an extensive range, the blue crab can be found living in shallow coastal bays of the Western Atlantic Ocean from Cape Cod to Uruguay. Here on the North Fork, they are common in many of the small back bays, creeks, and harbors throughout the Peconic. In recent years, I have even been finding them in greater numbers in the harbors along the Sound as well.
Crabs are often thought of as scavengers, feeding only on dead organisms they come across on the sea floor. Although that is true for many species, the blue crab is far better equipped than the average crab. They are armed with sharp, powerful claws that are not only used to tear flesh, but can crush through the shells of armored prey such as clams, mussels, oysters, snails, and even other blue crabs. Their paddle-like rear legs enable them to chase down fast moving prey, such as fish, with ease.
In addition to their strong claws and great speed, they are well camouflaged for both hunting prey as well as eluding predators in the murky backwaters of the bay. Their olive colored carapace (topside) allows them to go unnoticed while they lurk along the dark colored seafloor. Being that they spend a lot of time swimming in the water column, their white colored abdomen (underside) helps them baffle predators prowling below as the light color blends well with the bright sky above. This type of camouflage (dark dorsal and light abdomen) is known as countershading and is exhibited in many of the ocean’s inhabitants.
Blue crabs are sexually dimorphic, meaning they possess external characteristics that enable the sexes to be easily distinguished from one another. Male blue crabs are often referred to as Jimmies, while immature females are called Sallies and mature females are known as Sooks. There are three traits that can be used to differentiate between males and females.
The first and probably most notable way to tell the difference between a Jimmy, Sally and a Sook is to look at the abdomen of the crab. The underside of a male has a pattern that looks like a rocket. Female crabs, depending on their maturity, will have one of two patterns. A triangle will be found on Sallies, while Sooks have a dome shape that will also be much darker in color than the surrounding abdomen.
A second way to distinguish between the sexes is to look at the color of their claws. Jimmies have claws that are almost entirely bright blue in color with only a small amount of dark red at the tips. Sallies and Sooks on the other hand appear to have “painted their nails” as their pincers are red in color.
The shape of the carapace (shell) also varies between the sexes. Although males can grow much larger (up to nine inches), the carapace of a female is wider in proportion to its length when compared to that of a male. This allows the female to carry a much larger egg mass when pregnant.
Blue crab mating takes place from late spring to early autumn. It begins with a male searching for a Sally for a suitable mate. Upon finding his mate, he will literally sweep her off her feet by cradling her underneath his shell with his walking legs. He will carry her for several days until she is ready to molt (shed) her shell. This molt is known as a terminal molt and it is at this point when she will develop the dome shape on her abdomen. Mating will commence immediately after molting and the male will then continue to hold her until her shell hardens. This is the only time in that female’s life that she will mate. The male on the other hand, will mate with several additional females over the next couple of months. Although she will only mate once, this one event has given the female the potential of several spawns, each containing on average two million eggs. Even though that sounds like a lot of future offspring, only a few will survive to adulthood.
After mating, females will store sperm until they reach an area that is suitable for spawning. The length of time between mating and spawning varies from a couple of months to over-wintering and spawning the following season. Once the eggs are fertilized, they are held within the apron (the dome shaped flap) and look like a bright orange sponge. Over the next two weeks, the embryos will develop and the mass will darken in color. Upon hatching, the female will fan the larvae into the water, never to see them again. These larvae will drift for several weeks, going through several metamorphoses before settling on the bottom and taking on the typical crab stage we are familiar with.
August is the perfect time is to head down to your local dock and search out one of Long Island’s most beautiful, savory swimmers.
Be a Citizen Scientist and help the New York State Department of Environmental Conservation monitor blue crab catches by clicking here.