The megalopae and juvenile crabs are consumed by various fishes and birds, as well as other blue crabs. These crabs enter estuaries as juveniles and grow quite quickly, maturing after one year. The first pair is modified as pinchers and the last four pairs are walking legs. Facts about Blue Crabs 8: the natural predators. As larvae, they are vulnerable to fishes, jellyfish and other planktivores. The sharks, striped bass, eels, drum, whiptail stingrays, conose rays, and trout are considered as some of the natural predators of blue crabs. Blue crabs are sexually dimorphic.Males are slightly larger than females and have bright blue claws. Description. 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 also store water in their bladder, blood, and specialized pockets throughout their bodies. There, however, the crab is invasive. Size: Up to 9 inches long from point to point, and 4 inches from head to tail. 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. Crabs are crustaceans with five pairs of legs. They are mobile predators whose salinity requirements change at different stages in their lives. 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. Females have red-tipped claws. The scarlet king crab lives even deeper than the golden king crab, and has legs that are much thinner in respect to their length. Blue crab larvae have a salinity requirement of at least 20 ppt, and show poor survival below this threshold. Striped bass, red drum, catfish and some sharks depend on blue crabs as part of their diet. During this time females migrate to the mouths of estuaries so that larvae may be released into high salinity waters. Blue crabs have been introduced to various international waters such as in Black Sea, Mediterranean Sea, Baltic See, European Water and Japanese water. Thinner legs require less oxygen, hence less energy. 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. They drink water from dew and the ground, they get it from food, and even from water vapor. Habitat: Shallow and brackish waters, eelgrass beds, muddy bottoms. Juvenile and adult blue crabs serve as food for fish, birds and even other blue crabs. Seasonal appearance: Early spring to late fall. Blue Crab (Callinectes sapidus)Color: Olive green carapace, with brilliant blue claws. Blue crab larvae are part of the Bay’s planktonic community, serving as food for menhaden, oysters and other filter feeders. More information about adaptation strategies. It weighs 1 to 2 pounds (0.45 to 0.9 kg) when fully grown. Blue Crabs. Land crabs have even more adaptations to prevent drying out. Stowaway blue crabs on ship ballasts have even showed up in the Mediterranean. Females have red-tipped claws. The blue crab's incubation time is 14-17 days, which is when the eggs are brooded. 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 … The blue crab's carapace (or shell) is about 7 inches (17.8 cm) wide and 4 inches (10.2 cm) long. Florida Fish and Wildlife Conservation Commission Species Profile Blue crabs live in estuaries along the United States' Atlantic and Gulf coasts. Additional Resources. 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