The megalopae and juvenile crabs are consumed by various fishes and birds, as well as other blue crabs. They are mobile predators whose salinity requirements change at different stages in their lives. Thinner legs require less oxygen, hence less energy. Juvenile and adult blue crabs serve as food for fish, birds and even other blue crabs. Striped bass, red drum, catfish and some sharks depend on blue crabs as part of their diet. Blue crabs are sexually dimorphic.Males are slightly larger than females and have bright blue claws. These crabs enter estuaries as juveniles and grow quite quickly, maturing after one year. Blue crabs are subject to predation throughout their life cycle and are particularly susceptible when they are soft during the molting process. Additional Resources. Blue crab larvae have a salinity requirement of at least 20 ppt, and show poor survival below this threshold. Florida Fish and Wildlife Conservation Commission Species Profile As larvae, they are vulnerable to fishes, jellyfish and other planktivores. 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. There, however, the crab is invasive. Description. Crabs are crustaceans with five pairs of legs. The Blue Swimmer Crab is a popular food in Australia and is targeted and caught in large numbers by professional and recreational fishers. Stowaway blue crabs on ship ballasts have even showed up in the Mediterranean. Blue crabs have been introduced to various international waters such as in Black Sea, Mediterranean Sea, Baltic See, European Water and Japanese water. Land crabs have even more adaptations to prevent drying out. 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 … They drink water from dew and the ground, they get it from food, and even from water vapor. The blue crab's incubation time is 14-17 days, which is when the eggs are brooded. 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. Blue Crabs. 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. 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 live in estuaries along the United States' Atlantic and Gulf coasts. 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. During this time females migrate to the mouths of estuaries so that larvae may be released into high salinity waters. 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. It weighs 1 to 2 pounds (0.45 to 0.9 kg) when fully grown. Facts about Blue Crabs 8: the natural predators. Females have red-tipped claws. Habitat: Shallow and brackish waters, eelgrass beds, muddy bottoms. The blue crab's carapace (or shell) is about 7 inches (17.8 cm) wide and 4 inches (10.2 cm) long. Seasonal appearance: Early spring to late fall. The scarlet king crab lives even deeper than the golden king crab, and has legs that are much thinner in respect to their length. Females have red-tipped claws. 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