The sharks, striped bass, eels, drum, whiptail stingrays, conose rays, and trout are considered as some of the natural predators of blue crabs. During this time females migrate to the mouths of estuaries so that larvae may be released into high salinity waters. They also store water in their bladder, blood, and specialized pockets throughout their bodies. Blue crabs live in estuaries along the United States' Atlantic and Gulf coasts. It weighs 1 to 2 pounds (0.45 to 0.9 kg) when fully grown. The first pair is modified as pinchers and the last four pairs are walking legs. Seasonal appearance: Early spring to late fall. Land crabs have even more adaptations to prevent drying out. These crabs enter estuaries as juveniles and grow quite quickly, maturing after one year. Adult male crabs live in the low-salinity waters upstream, while adult female crabs live in the higher-salinity waters near the mouth of the estuary. Stowaway blue crabs on ship ballasts have even showed up in the Mediterranean. They are mobile predators whose salinity requirements change at different stages in their lives. It was first seen off Egyptian waters in the 1940s, but reports of blue crab sightings in Italy, Israel, Greece, and Turkey have been made, too. If the crab is flipped over, the shape of the folded surface of the belly (the apron) reveals the animal's approximate age and sex. Size: Up to 9 inches long from point to point, and 4 inches from head to tail. Additional Resources. Blue Crab (Callinectes sapidus)Color: Olive green carapace, with brilliant blue claws. There are many crab behavioral adaptations for survival that this shellfish do since they need to be able to fight their predators and live in their natural habitat. The Blue Swimmer Crab is a popular food in Australia and is targeted and caught in large numbers by professional and recreational fishers. They drink water from dew and the ground, they get it from food, and even from water vapor. Juvenile and adult blue crabs serve as food for fish, birds and even other blue crabs. Blue crab larvae are part of the Bay’s planktonic community, serving as food for menhaden, oysters and other filter feeders. Blue crabs are subject to predation throughout their life cycle and are particularly susceptible when they are soft during the molting process. The scarlet king crab lives even deeper than the golden king crab, and has legs that are much thinner in respect to their length. Description. Females have red-tipped claws. Blue crabs are sexually dimorphic.Males are slightly larger than females and have bright blue claws. Florida Fish and Wildlife Conservation Commission Species Profile Facts about Blue Crabs 8: the natural predators. The blue crab's carapace (or shell) is about 7 inches (17.8 cm) wide and 4 inches (10.2 cm) long. Thinner legs require less oxygen, hence less energy. This may be an adaptation to low oxygen levels, since the scarlet crab lives at 1000 m, near the oxygen minimum zone. This creature itself is actually very unique shellfish and with great taste, this creature has also become one … Females have red-tipped claws. Habitat: Shallow and brackish waters, eelgrass beds, muddy bottoms. Blue crabs have been introduced to various international waters such as in Black Sea, Mediterranean Sea, Baltic See, European Water and Japanese water. The megalopae and juvenile crabs are consumed by various fishes and birds, as well as other blue crabs. Monitoring blue crab population levels and range shifts to gain knowledge on how changing conditions may be impacting crab populations is a useful first-step adaptation strategy for this species. Blue crab larvae have a salinity requirement of at least 20 ppt, and show poor survival below this threshold. The blue crab's incubation time is 14-17 days, which is when the eggs are brooded. 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