Blue Crab moult7/7 – Cornwall Landing, HRM 57: It was two days after the full moon and blue crab moults were strewn in the shallows and up to the strand line of high tide. Blue crabs tend to favor the spring tides around full and new moon for moulting when stronger and higher tides provide greater access to shoreline niches.
Blue crab empty moultAs a crustacean, blue crabs (Callinectes sapidus) have an exoskeleton (their skeleton is on the outside) and must moult (shed) periodically as they grow to accommodate their increasing interior body size. A shed exoskeleton, or moult, is a nearly exact replica of the crab except that it is empty. Moults frequently inspire e-mails and phone calls of “dead crabs on the beach!” My response is always, “Look inside.” A peek inside the moult will reveal that no one is home.
The shed crab is now a softshell. Their new shell is somewhat larger and has the elasticity of a balloon. They take in water to stretch the new shell and, once the shell hardens–a process that can take up to twenty-four-hours depending on water temperature, they expel the water creating roomier accommodations. While they are in a softshell stage, they are extremely vulnerable to predation as they are unable to use their crushing claws.
Blue crabs have several colloquial names known mainly to crabbers. Blue crab emergent soft-shell crabAdult males are called "Jimmys," mature females are called "Sooks," and immature females are known as "Sallys." Today’s catch included both hard-shell and softshell crabs. One of them was a palm-sized Sally crab (83 mm carapace width) and her moult (80 mm), side-by-side in the net. The river was 79 degrees Fahrenheit (F) and the salinity had fallen a bit to 3.25 ppt. (Tom Lake photos)
- Tom Lake, Phyllis Lake
