Mangrove crab
Scylla serrata
FAMILY
Portunidae
TAXONOMY
Cancer serratus Forskål, 1775, Red Sea.
OTHER COMMON NAMES
English: Indo-Pacific swamp crab, mud crab, Samoan crab, serrated swimming crab; French: Crabe des palétuviers; Spanish: Cangrejo de manglares.
PHYSICAL CHARACTERISTICS
Large, reaching a carapace width of 11 in (280 mm). Carapace is smooth, with four teeth between eyes and nine alongside the eye. Claws are massive; last pair of legs is flattened for swimming.
DISTRIBUTION
Found widely throughout the tropical Pacific and Indian Oceans, from Africa and the Red Sea to Australia, Japan, and east to Tahiti. Introduced into Hawaii in the 1920s. The distribution and other information given here is a synthesis of information regarding a number of very closely related species of Scylla that were not previously distinguished from one another.
HABITAT
Typically found in such muddy and brackish-water areas as mangrove forests, estuaries, and river mouths.
BEHAVIOR
Typically nocturnal, spending the daytime in a burrow that can be up to 6.5 ft (2 m) deep. The flattened, paddle-like rear legs can be used for swimming or for rapidly burying itself in the sediment.
FEEDING ECOLOGY AND DIET
An aggressive predator that uses its large, powerful claws to break open and feed on bivalves, snails, and barnacles; also preys on crabs, shrimp, and fish.
REPRODUCTIVE BIOLOGY
Mating occurs in summer after the female molts, and she may remain in the male's burrow for several days after mating. Stored sperm can remain viable in the spermatheca for at least seven months. Clutches contain 2–8 million eggs and take 2–4 weeks to develop; brooding females may move offshore during this period. Larvae complete five zoeal stages in 2–3 weeks, and the megalops stage lasts at least six days.
CONSERVATION STATUS
Not listed by the IUCN. Severely overfished in many countries, and also affected by loss of critical mangrove habitat. Regulations protecting immature specimens and egg-bearing females (which are considered a delicacy) are often nonexistent or ignored. Although increasingly being cultured, these are essentially "grow out" operations that rely on wild-caught juveniles, so wild populations continue to be depleted. Considerable research has been conducted on large-scale production of laboratory-reared larvae, with promising results.
SIGNIFICANCE TO HUMANS
Important in both commercial and artisanal fisheries. Sometimes considered a serious pest in oyster culture operations.
