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TOPIC-Biology of Penaeus indicus

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Biology of penaeus indicus

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DISTRIBUTION :

Penaeus indicus is found in indo-pacific regions, East and South east Africa to South China and North Australia.

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HABITAT & DISTRIBUTION :

• Penaeus indicus is found at depth of 2-90m.
• Mostly present in shallow water less than depth of 30m.
• They are euryhaline and live in brackish water, estuarine and marine environment with temperature ranges b/w 18-34.5°c, salinity 5-50ppt.
• The optimal salinity for juvenile 10-15ppt.

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• Penaeus indicus is known by many common names around the world including Indian white prawn , Tugela prawn, white prawn, banana prawn and redleg banana prawn.

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ECOLOGY & LIFE CYCLE :

• Penaeus indicus is a marine decapod with estuarine juveniles.
• It prefers mud or sandy mud at depth of 2-90m.
• Adult shrimp grows to a length of about 22cm.
• Mating will be takes place between recently moulted female and a hard shelled males which occurs during night time in ocean.
• P. indicus generally spawn on the surface at water depth of 7-36.6m

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Life cycle of penaeus indicus

FECUNDITY :

• Fecundity rate increases with prawn size and wild broodstock tend to produce better quality eggs.
• Females produce 2,12,800 - 12,54,200 that hatch within 15hrs.

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LIFE CYCLE OF Penaeus indicus :

• After hatching, free swimming nauplis are obtained which further passes through protozoea, mysis and then to postlarval stages, which resembles the adult prawn.
• Non feeding (nauplis) - 6stages

Protozoea - 3stages

Mysis – 3stages

• Post larvae moves towards the coast and enter estuaries & mangrove swamps that serve as nursery grounds and grow upto the length of 110-120mm and sub - adults return to sea and get developes into fish.

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• Nauplis undergoes 6moults within 50hrs into a zoea.
• Zoea has compound eyes under the carapace that are externally visible.
• Zoea ll has a pair of stalked compound eyes.
• Zoea lll has a pair of biramous uropods.
• After 4 - 6days the Zoea metamorphosis into mysis.
• There are 3mysis stages over 3-4days.
• The mysis remain drifting in the water and metamorphosis into post larvae.

BREEDING CONDITION:

• P.indicus females breeding at b/w 27 and 35mm carapace length that means 5-6.5months old females and males attains sexual maturity when it's carapace length 2.8 - 3.4cm.

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LIFE SPAN OF Penaeus indicus:

• The life span of penaeus indicus is 2 years.

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MORPHOLOGICAL CHARACTERISTICS :

• Shrimp have an exoskeleton that is periodically shed during moulting to allow further growth.
• Shrimp have a head, thorax and a tail, and an abdomen with 6 segments.
• The last abdominal segment is the telson.
• The thorax has a spine called rostrum, one pair of eyes, 2 pairs of antenna, 3pairs of maxillipeds for feeding and 5pairs of walking legs.
• Each abdominal segment except the telson has a pair of fins called pleopods on the ventral side.

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• Shrimp use the peleopods for forward swimming and the telson and pleopods to propel backwards rapidly when the abdomen is flexed.
• The maximum length of p.indicus is about 184mm.

Male P.indicus - 184mm

Female P. indicus - 228mm

• Maximum carapace length is 56mm.
• Eyestalk & antenna scales are bluish in colour
• Margins of uropods are blue with bright red finge.
• Antennae are not banded & antennules are spotted.
• The body is semi-transluent with olive green to grey blue speckles.
• The pereopods are generally the same colour as body.
• Pleopods are pink or red and the distal part of the uropods are green or red with the Fringe of setae usually red.

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• Carapace is hairless.
• Rostrum is slender and long with 7 to 9 teeth on the dorsal, 4-6 teeth on ventral margin.
• Male reproductive organ - petasma
• Female reproductive organ - Thelycum

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REPRODUCTIVE SYSTEM AND MATURITY STAGES :

• Sexual dimorphism is prominent in P.indicus
• In males full gonadal maturation is charactrised by the presence of fully developed spermatozoa with spikes.
• Generally ,swelling and whitish colouration of the terminal ampoules are considered as an indication of gonadal maturity.

• Fully mature ovary is dark green in colour occupies major portion on dorsal side of the animal.
• It has lateral expansion in the first abdominal segment.

SPAWNING:

• During spawning female releases eggs through the oviducts and sperm from the spermatophores stored in the thelycum.
• Fertilization is occurred externally.
• The important environmental factors that infulence ovarian maturation are,

1. Light

2. Temperature

3. Salinity

4.PH

LIGHT:

• Light seems to play a significant role in ovarian maturation of penaeid prawns in captivity.

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TEMPERATURE:

• The role of temperature on ovarian maturation in non- abalated P.indicus attains maturity rapidly at the water temperature 28 -30˚c in the maturation pools.

SALINITY:

• It is a limiting factor for ovarian maturation and P.indicus attains maturity more or less egual to that of sea water.

PH:

• Abaleted females of P.indicus matured and spawned when PH was maintained between 8.0-8.2 in maturatin pool.
• When PH was drotpped to 7.9 abaleted females of the same species did not attain maturity.

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COLLECTION OF SEED :

• Seeds can be obtained from the wild or by establishment of hatcheries.
• In traditional paddy fields systems the juveniles which have congregated near sluice gate.
• 36% - 43% of the P.indicus are entered into fields.
• Earlier wild seeds were also collected and sold to shrimp farmers.
• Now-a-days the dependence on wild seed has been reduced due to the establishment of hatcheries.

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BROOD STOCK :

• Intensification of cultured shrimp is limited by seed supply.
• Matured individuals can be collected from the wild during their spawning seasons in March, April, July, August in tropical regions.
• A temperature range of 27-31°c.
• Salinity 30-35ppt.
• Hatcheries in the developing countries still depends on wild seed.
• Maturation can be induced by eye stalk ablation technique.
• Abalated female can spawn after 4 days with a peak observed at 5-6days.
• It is very expensive to raise spawners in captivity and ablated shrimps result in less hardly fry with low survival rate.

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• Fecundity of the Abalated females may not differ.
• The hatch rates of ablated females was found to be markedly less 37.8% to 58.1% than that of unablated females 69.2%.
• Wild females are more fecund per unit weight than ablated females.
• Quantitatively the no. Of spawns, eggs & naulii produced by ablated females is 10,8 and 6 times respectively that of unablated females.
• 150mm size of females are used for broodstock & spawning.
• Males which are usually 140mm size are Matured at 148mm and 128mm size.

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HATCHERY MANAGEMENT:

• Circular tank should contain 2 - 5 tonnes capacity are used to rear larvae from nauplis to mysis stage.

Salinity - 32ppt

PH - 8.2

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• Feed is not provided to nauplis as it is non feeding stage.
• Protozoea stage is supplied with a mixed culture of diatoms.

FEED : Artemia nauplis, egg - prawn - custard mix.

• Post larval rearing can be continued in the same tank.

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GROW - OUT TECHNIQUES :

• Grow out techniques can be of 3 types

1. Extensive method

2.Semi - Intensive method

3. Intensive method

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HARVESTING :

• In traditional farming harvesting is done by fitting conical nets on the sluice gates& opening them during low tide
• The shrimp are trapped in the net as the water recedes
• The remaining shrimp are harvested by cast netting.
• In semi - Intensive and intensive practices harvesting is done by complete draining of the pond.
• The rest of shrimp are collected by hand.