On the fishery, biology and the hatchery technology of the portunid crab Portunus pelagicus (TH 099)

Abstract

Crabs belonging to more than 4500 extant species of decapod crustaceans are included in the infraorder Brachyura. The brachyura show extreme versatility in distribution. They are found in all climates, and in terrestrial, semi terrestrial and from the shore to deep sea, in marine, brackish as well as freshwater environments. Although earlier surveys have recorded above 640 species of crabs from Indian waters, only eight species are commonly referred to as 'edible crabs' inhabiting the coastal waters and adjoining brackishwater environment and support localised and sustenance fishery to some extent. Crabs are members of Crustacea, a class of invertebrate phylum Arthropoda that includes the animals with jointed legs and a hardened outer covering or exoskeleton. Crab belong to the order Decapoda a name which refers to this fact that the members of this order have 5 pairs of legs. The true crabs are placed in the suborder Brachyura an appropriate name for this group, as their shortened flap-like abdomen or tail is folded under the body CRees, 1963). The presently studied crab Portunus (Portunus) pelagicus, is a marine species belongs to the family Portunidae and subfamily Portuninae. Although the latest nomenclature of the crab is Portllnus (Portunus) pelagicus (Linnaeus), for the sake of brevity, ' Portllnus pelagicus' is used throughout the text. In the Indian Ocean, the crab fauna of Portunidae family is included under sub families, PodoPhthaimidae (Borradaile), Catoptrinae (Sakai), Portuninae (Rafinesque), Caphyrinae (Alcock), Carcininae (Macleay) and Polybiinae (Ortmann). Most of the edible crabs caught from marine and brackishwater environments belong to the sub family Portuninae. In the seas around India, five genera of Portuninae have been reported by various authors. They are Scylla, Por/unlls, Charybdis, Lupocyc/us and Thalamita. Among them the first three genera contribute to the commercial crab fishery. The richness, variety and fishery of marine crabs of Indian seas have been investigated by many workers over the past 100 years. Among them the notable works are of Alcock (1895,1896,1898-1900), de Man (1908), Kemp (1915,1919a,b), Chopra ( 1931 , 1939), Prasad and Tampi (1951, 1953), Menon (1952), Jones and Sujansingani (1952), Chhapgar (1957,1962), Sankarankutty (196Ia, b,1965), George and Nayak (1961), Ramamurthy (1972), Prasad and Nair (1973), Rao el al. (1973), Dhawan el al. (1976) and Kurup el al. (1990)