FAO official common names: Fr - Crevette blanche des Indes; Es - Langostino blanco de la India
Taxonomic and biological features:
Distribution Penaeus indicus is found from the Indo-West Pacific: East and South East Africa to South China, Papua New Guinea and North Australia (FAO, 1980).
Habitat and behaviour Penaeus indicus (Figures 1, 2 and 3) is found at depths of 2 to 90 m, inhabiting bottom mud or sand. It is most abundant in shallow waters of less than 30 m depth, on sand or mud (FAO, 1984a). The adults are marine and breed offshore, while postlarvae and juveniles are estuarine (FAO, 1980). They are euryhaline and live in brackish, estuarine and marine environments with temperature ranges between 18 and 34.5 oC and salinities of from 5 to 50 ppt (Kutty, Murugapoopathy and Krishnan, 1971; Branford, 1981; CIBA, 1992b; Khan, Aravindan and Kalavati, 2001; Macia, 2004). The optimal salinity for juvenile P. indicus is 10 to 15 ppt.
Marine shrimp life cycle The life history of P. indicus (Figure 4. Penaeid life cycle) has an offshore planktonic larval phase; an estuarine, benthic postlarval, juvenile phase and an inshore ocean adult and spawning phase (Dall et al., 1990, FAO, 2008). Mating between a recently moulted (soft-shelled) female and a hard-shelled, smaller male occurs at night in the ocean (Hudinaga, 1942; Emmerson, 1980b; CIBA, 1992a). Penaeus indicus generally spawn on the surface at water depths of over 7 m (Panikkar and Menon, 1956; FAO, 1985a) and up to 36.6 m (Hall, 1962). Females produce between 212 800 (Mohan and Siddeek, 1995) and 1 254 200 eggs (18.26 cm shrimp) (Jayawardane, McLusky and Tytler, 2002) that hatch within 15 h. Fecundity increases with prawn size (Teikwa and Mgaya, 2003), and wild broodstock tend to produce better quality eggs than pond-reared broodstock (Regunathan, 2008). Penaeus indicus has six non-feeding naupliar stages, three protozoeal and three mysis stages (Rao, 1973; Courties, 1976; Emmerson, 1977). Postlarvae move towards the coast and enter estuaries and mangrove swamps that serve as nursery grounds.
Penaeus indicus females commence breeding at between 27 (137 mm TL) and 35 mm carapace length (Emmerson, 1980b; Teikwa and Mgaya, 2003; Franco, Ferreira and Nobre, 2006). This corresponds to 5–6.5 month old females. The full life span of P. indicus is about two years (Jayakody, 1988). Males attained sexual maturity at 2.8 to 3.4 cm carapace length (Teikwa and Mgaya, 2003).
Morphological characteristics Shrimp have an exoskeleton (the "shell") that is periodically shed during moulting) to allow further growth. Shrimp have a head (thorax) and a tail, and an abdomen with six segments (Figures 8 and 9). The last abdominal segment is the telson. The thorax has a spine called the rostrum, one pair of eyes, two pairs of antennae, three pairs of maxillipeds for feeding and five pairs of walking legs. Each abdominal segment except the telson has a pair of fins called pleopods on the ventral side. Shrimp use the pleopods for forward swimming and the telson and pleopods to propel backwards rapidly when the abdomen is flexed. The maximum total length of P. indicus is about 184 mm for males and 228 mm for females, although adult shrimp are usually much smaller (170 mm). The maximum carapace length is 56 mm (FAO, 1980) (Figures 7 and 9).
The eyestalks and antennal scales are bluish and the margins of the uropods are blue with a bright red fringe. The antennae are not banded, and the antennules are spotted (Racek, 1955). The body is semi-translucent, with olive green to grey-blue speckles (Figure 5). The pereopods are generally the same colour as the body. Pleopods are pink or red and the distal part of the uropods green or red, with the fringe of setae usually red. Juveniles are whitish, with specks of the same colour as adults (FAO, 1984a).
The carapace is hairless. The rostrum is slender and long, with 7 to 9 teeth on the dorsal and 4 to 6 teeth on the ventral margin, with the blade of rostrum becoming moderately high in large specimens (FAO, 1984a) (Figure 6).
Males are identified by a petasma (Figure 10). Females have a closed thelycum (Pérez Farfante and Kensley, 1997).
Larval stages Penaeus indicus spawns most months of the year, with two annual spawning peaks (Jayawardane, McLusky and Tytler, 2002) (Figure 11). The shrimp eggs hatch within 15 h as a nonfeeding naupliar stage (FAO, 1985a). The unsegmented body has three pairs of appendages. The nauplius undergoes six moults (Moto, 1979) within 50 h into a protozoea (FAO, 1985a). The protozoea has three stages. Protozoea I (zoea I) has compound eyes under the carapace that are not externally visible (Motoh, 1979). Zoea II has a pair of stalked compound eyes and zoea III has a pair of biramous uropods (Motoh, 1979). After 4–6 days, the protozoea metamorphoses into a mysis. There are three mysis stages over 3 to 4 days. The mysis remain drifting in the water and metamorphose into postlarvae.
