Portunus pelagicus/ja: Difference between revisions

| image_caption = Male

| authority = ([[Carl Linnaeus|Linnaeus]], [[10th edition of Systema Naturae|1758]])

| synonyms = * ''Cancer pelagicus'' <small>Linnaeus, 1758</small>

'''''Portunus pelagicus''''', also known as the '''blue crab''', '''blue swimmer crab''', '''blue manna crab''' and '''flower crab''' is a species of large [[crab]] found in the [[Indo-Pacific]], including off the coasts of Indonesia, Malaysia, Thailand, the Philippines, and Vietnam; and in the intertidal [[estuary|estuaries]] around most of Australia and east to [[New Caledonia]].

==Description==

The males are bright blue in color with white spots and with characteristically long [[cheliped]]s, while the females have a duller green/brown, with a more rounded [[carapace]]. The carapace can be up to {{convert|20|cm}} wide.

==Behaviour==

[[File:Portunus pelagicus, Qatif 0.jpg|thumb|''Portunus pelagicus'' feeding, [[Qatif]], Saudi Arabia.]]

They stay buried under sand or mud most of the time, particularly during the daytime and winter, which may explain their high tolerance to [[ammonium]] (NH₄⁺) and [[ammonia]] (NH₃). They come out to feed during high tide on various organisms such as bivalves, fish and, to a lesser extent, macroalgae. They are excellent swimmers, largely due to a pair of flattened legs that resemble paddles. However, in contrast to another portunid crab (''[[Scylla serrata]]''), they cannot survive for long periods out of the water.

==Capture==

[[File:Blue swimming crab capture production thousand tonnes 1965-2022.svg|thumb|Global capture production of ''Portunus pelagicus'' in thousand tonnes from 1965 to 2022, as reported by the [[Food and Agriculture Organization|FAO]]]]

The species is commercially important throughout the Indo-Pacific, where they may be sold as traditional hard shells, or as "[[soft-shell crab|soft-shelled]]" crabs, which are considered a delicacy throughout Asia. The species is highly prized as a substitute for ''[[Callinectes sapidus]]''. This species is fished heavily and almost exclusively for meat consumption in the Persian Gulf, with the females sold at higher prices than males.

These characteristics, along with their fast growth, ease of larviculture, high fecundity, and relatively high tolerance to both [[nitrate]] and [[ammonia]], (particularly [[ammoniacal nitrogen]], NH₃–N, which is typically more toxic than ammonium, as it can more easily diffuse across the gill membranes), makes this species ideal for aquaculture.

!State

!Minimum carapace

!Bag limit

!Boat limit

!Possession Limit

!Notes

|[[South Australia]]

|20 (Gulf St Vincent) or 40 (combined with sand crabs)

|60 (Gulf St Vincent) or 120 (combined with sand crabs)

|[[New South Wales]]

|[[Western Australia]]

|20 or 10 (West Coast)

|40 or 20 (West Coast)

|[[Cockburn Sound]] is closed. [[Peel-Harvey Estuary]] is closed from 1 September to 31 October.

|[[Queensland]]

|No limit

|No limit

|No limit

|[[Northern Territory]]

|Combined total for any crab species other than mud crabs.

==Ecology==

[[File:Portunus pelagicus.jpg|thumb|Male ''Portunus pelagicus'' can be [[territoriality|territorial]].]]

''P. pelagicus'' commonly enters estuaries for food and shelter. Its [[Biological life cycle|life cycle]] is dependent on estuaries as the [[larva]]e and early juveniles use these habitats for growth and development. Prior to hatching, the female moves into shallow marine habitats, releases her eggs, and the newly-hatched [[zoea|zoea I larvae]] move into estuaries. During this time, they feed on microscopic plankton and progress from the zoea I stage to the zoea IV stage (approximately 8 days) and then to the final larval stage of [[megalopa]] (duration of 4–6 days). This larval stage is characterised by having large chelipeds used to catch prey. Once the megalopa metamorphoses to the crab stage, they continue to spend time in estuaries which provides a suitable habitat for shelter and food. However, evidence has shown that early juveniles cannot tolerate low salinities for extended periods, which is likely due to its weak hyper-osmoregulatory abilities. This may explain their mass emigration from estuaries to seawater during the rainy season. Male ''Portunus pelagicus'' are believed to become more territorial in colder water. This may explain why male crabs are rarely sighted within a close proximity to each other in more temperate waters; it also may explain why their female counterparts seem more prolific in these areas.

==Cultural Significance==

The movement of this species of crab is the basis for the dance steps and movements of the ''Linambay'', a variation of the ''[[Moros y cristianos|Moro-moro]]'' that originates from [[Carcar]], [[Cebu]], in the Philippines, where the crab is called "Lambay".

{{Edible crustaceans}}

{{二次利用|date=19 June 2025, at 23:15}}