The Role of Blue Crabs in the Environment

Despite its name, the blue crab is usually grayish or bluish-green in color. Only the crabs' claws are blue, and adult female claws have bright orange tips. Blue crabs play a dual role as predator and prey in their environment and regulate populations of their prey. Moreover, these crabs are harvested by fisheries throughout the world for their sweet, tender meat, according to "National Geographic."

  1. Predators

    • As predators, blue crabs feed on plants, crustaceans, fish, and worms, among other animals. Some of the blue crab's favorite foods are thin-shelled bivalves. Larger crabs also occasionally feed on younger crabs, helping regulate the population. These crabs are typically opportunistic feeders that eat whatever creatures are most available, according to South Carolina Department of Natural Resources. Also, crabs feed on marsh periwinkles, enhancing the salt marshes, according to Chesapeake Bay Program.

    Prey

    • Some bony fish, sharks and rays feed on young and larger crabs. Moreover, the Atlantic Ridley sea turtle also prefers to feed on these crabs, according to the National Aquarium of Baltimore. Other animals that prey on blue crabs include eels and birds. Blue crab larvae are a part of the planktonic community, meaning oysters and bay anchovies feed on crab larvae, according to Chesapeake Bay Program.

    Location

    • As bottom dwellers, blue crabs live in coastal lagoons and estuaries from Nova Scotia through the Gulf of Mexico and reaching as far south as Uruguay. Crabs require both brackish inshore waters and high salinity ocean waters to complete their life cycles, according to South Carolina Department of Natural Resources.

    Harvesting

    • Desired for their sweet, tender meat, blue crabs are among the most heavily harvested creatures on the planet. In fact, their scientific name, Callinectes sapidus, means "savory beautiful swimmer," according to "National Geographic." Louisiana, South Carolina and the Chesapeake Bay have the largest blue crab fisheries, according to South Carolina Department of Natural Resources. Furthermore, one-third of the nation's blue crab harvest originates from the Chesapeake Bay area, according to the Chesapeake Bay Program.

    Physical Characteristics

    • Crabs grow by shedding their shells, a process known as molting. The smallest crabs shed their shells every three to five days, while the crabs three inches or larger shed every 20 to 50 days, according to South Carolina Department of Natural Resources. During molting, crabs take in water to expand and break out of their old shells, and the new soft shell underneath fully hardens in two or three days, according to National Aquarium of Baltimore and South Carolina Department of Natural Resources.

    Conservation

    • Blue crabs are sensitive to environmental changes, and many populations, especially the population living in the Chesapeake Bay area, have experienced declines. Because of their role as both predator and prey in their environment, several states are protecting the blue crab. For example, South Carolina uses money generated from the sales of Marine Recreational Fisheries Licenses, which are required to fish from a private boat, to benefit and protect sea life such as the blue crab, according to South Carolina Department of Resources. Virginia's blue crab sanctuary protects crabs from being harvested because the area is off limits to commercial crabbing, according to Chesapeake Bay Program.