Fauna
Invertebrate

Asian Blue Swimming Crab

Portunus pelagicus

Also known as Flower Crab, Blue Swimmer Crab, Blue Manna Crab, Sand Crab

Asian blue swimming crabs patrol sandy shallows, estuaries, and seagrass beds, using paddle-shaped hind legs to swim gracefully through the water column. Adult males boast vibrant cobalt-blue patterning across their carapace and legs, while females display a more subdued mottled brown camouflage. During high tide, these agile predators dig backward into the sand to ambush wandering prey or escape larger marine hunters.

MarineCrustaceanCoastal
Asian Blue Swimming Crab reference1 / 7
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Not EvaluatedConservation statusIUCN Red List categoriesLCNTVUENCREWEXNot Evaluated — not placed on the risk ladderRed List categories, explained →
Key facts
Diet & preyBivalves, Small marine worms, Small fish
Predators
  • Turtles
  • Octopuses
  • Large predatory fish
ThreatsOverfishing, coastal development, habitat degradation
HabitatsShallow coastal waters, sandy bays, mangrove estuaries, seagrass beds
Life span3–4 years
Classification
  1. FamilyPortunidae
  2. SpeciesPortunus pelagicus
Range & activity
Range data is not available yet.
Safe observation
Interaction riskLow
  1. Low
  2. Moderate
  3. High
  4. Very high
Why interaction risk is low
Powerful chelipeds can inflict deep, painful pinches; handle only with protective gear.
Why it is dangerous
Large, elongated chelipeds exert immense crushing force and can break human skin or crush fingers.
How to recognize a risky encounter
Look for flattened paddle-shaped back legs and bright blue markings on broad, spinous claws.
What to do
Avoid bare-hand handling; use heavy tongs or observe quietly without attempting capture.
Responsible observation
  • Safe observation: Watch them swimming along sandy shallows at high tide or under dock lights at night.
  • Handling caution: Never pick up by the legs; grasp securely from the rear of the carapace to avoid pinches.
Related species
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