- 1 Freshwater Prawn Culture – The Farming of Macrobrachium Rosenbergii
- 1.1 Systematic Position of Prawn
- 1.2 Food of Prawn
- 1.3 Cultivable Species of Prawn
- 1.4 A. Hatchery Phase
- 1.5 B. Growth Phase
- 1.6 Semi-intensive Method of Prawn Culture
- 1.7 1. Selection of Farm Site and Designing of Pond
- 1.8 2. Preparation of pond to Stock the Prawn Seed
- 1.9 3. Selection and Stocking of Prawn Seeds
- 1.10 4. Post-Stocking Care of Prawn
- 1.11 5. Harvesting
Immunology is one of the Biology Topics focused on understanding the immune system and its response to pathogens and diseases.
Freshwater Prawn Culture – The Farming of Macrobrachium Rosenbergii
Prawn is a type of arthropod of the class Crustacea. Because of its high demand in the international market, prawns become popular commercially. Prawns are available both in fresh water and in salty water. Among various types of prawns. Macrobrachium rosenbergii, Penaeus monodon (tiger prawn), Penaeus indicus, and Metapenaeus monocerous are noteworthy. Shrimps and prawns are generally various decapod crustaceans belonging to the families Penaeidae and Palaemonidae. In recent times, the term ‘prawn’ has been used more for freshwater forms of Palaemonids and ‘shrimp’ for marine penaeids.
Systematic Position of Prawn
The systematic position of freshwater prawn
- Phylum: Arthropoda
- Sub-phylum : Mandibulata
- Class: Crustacea
- Sub-class: Malacostraca
- Order: Decapoda
- Family: Palaemonidae
- Genus: Palaemon, Macrobrachium
The systematic position of marine water prawn
Phylum to order same as before
- Family: Penaeidae
- Genus: Penaeus
Life Cycle of Penaeid Shrimp
Rivers, ponds, canals, bheries, estuaries, having fresh water or sea having salty water are the habitats of prawns. By habit, the prawns show photonegative movement and move along the bottom of the water bodies. In the post-larval stage, the prawns live in the shallow coastal water of sea or estuaries and in confined waters. Most of the maturity of the prawns occurs in seawater. Breeding of most of the prawns occurs in the estuary from October to July. The prawns of the genus, Macrobrachium liberate their eggs in the down waters of rivers.
Food of Prawn
The prawn is an omnivorous animal. They take live small animals and plants at the bottom waters and they also take dead or decaying matter in the bottom water. However, they prefer algae, aquatic insects, and snails in aquatic bodies. They also devour excreta of other animals, larvae, and small shrimps as food. For good growth of the prawns, they are given supplementary foods. The supplementary foods are prepared according to the formulae given below:
|Grains of cereals||17.3%|
|Dust of prawn head||20%|
|Coconut oil cake||15%|
Cultivable Species of Prawn
Several cultivable species of prawns are Penaeus indicus, P.monodon, P.marginensis, Metapenaeus affinis, M. Dobsonian, M. monoceros, etc.
Culture of Giant Fresh Water Prawn
These are the fastest growing economically important delicious species. The adult prawns can thrive both in fresh as well as brackish water zones whereas their larvae require a salinity of about 12 ppt.
Culture practice in India: The culture practised in India comprises two major phases hatchery phase and the growth phase.
A. Hatchery Phase
Shape: Hatchery tanks are of various shapes – rectangular and circular.
Material: They may be made of various ingredients like plastic, fiberglass, reinforced concrete, etc.
Colour: The tanks are painted with dark colours so that food can be well spotted/located by the larvae.
Aeration: Aeration system is present in the bottom of the tank to ensure proper distribution of nutrients and larvae in the water in order to prevent cannibalism.
Management of Water Systems
Green Water System:
Involves the production of phytoplanktons like Chlorella sp. The plankton in the aquaculture pond create turbidity and the water appears green or greenish brown. In order to maintain the phytoplankton bloom, a 4 : 1 mixture of urea and NPK (Nitrogen : Phosphorous : Potassium = 15 : 15 : 15) respectively is added to the tap water, in the tank. Zooplankton like Rotifers can also be maintained by adding about 0.6 ppm CuSO4 into the tank water.
Clear Water System:
Water quality is maintained through chlorination followed by dechlorination, usage of UV light, usage of antibiotics, and strong aeration. The process requires deft management and skilled labour.
Recirculating Water System:
Water quality is maintained by involving mechanical, and biological filtration, usage and ozone, chlorination, and dechlorination. Broad stock management – Freshwater ponds are prepared scientifically for shrimp culture. These are fertilized with cattle dung 15 days prior to stocking of prawn seed. The ponds are usually land-based or impoundments that are prepared by drying and tolling to remove pests, and predators for metabolizing organic matter. This is generally followed by liming in order to reach optimum pH and to keep the bottom free from microorganisms. Inorganic fertilizers such as urea and superphosphate are then applied to develop natural food organisms (floating and bottom-living). In order to create a steady supply of berried prawns throughout the year, it is essential to develop viable broodstock in captivity through the following steps:
- Preparation of ponds.
- Prawns of post-larval or juvenile stages are stocked in ponds.
- Juveniles are fed with high-quality ingredients in the form of pellets.
- In the absence of pellets, supplementary feed of plant and animal origin can be given.
- Within 6 months of culture, the prawns are mature enough.
This happens in the freshwater and berried prawns are collected by means of a cast net from the pond for the hatchery. For long distances, berried female prawns are transported in bags under oxygen pressure. Each bag contains 2-5 prawns. However, for shorter distances, they can be transported in open containers with fresh or brackish water.
Spawning – The berried prawns are then released into a tank filled with brackish water of 5 ppt salinity for spawning purposes. About 5-10 prawns are released per square metre depending upon the size. Mating occurs between hard-shelled males and ripe soft-shelled females. The females keep vigorously fanning the eggs to keep them aerated.
Hatching of larva and collection – A few days after the hatching of the larva, the females are removed from the tank. The temperature of the water is maintained between 26-31°C, with a salinity of about 12 ppt. Larvae are reared in specialized larval-rearing tanks.
B. Growth Phase
Larva Rearing Phase:
The newly hatched larva requires brackish water for its survival and development. They (Zoea larvae) are planktonic and undergo eleven stages of metamorphosis. After a period of about 20 days, the post-larval stage is observed, harvested, and transported to the nursery ponds for growth. For the growth and survival of the larvae and post-larvae of Macrobrachium rosenbergii and other species, one needs to keep certain aspects in mind.
- Water, be it freshwater/brackish, needs to be clean and free from toxic materials.
- Temperature needs to be maintained between 29-31°C for larval rearing.
- Salinity: 7.0-8.5 ppt.
- Dissolved O2: 6-4 ppm
- Total hardness: 40-100 ppm
- Water quality should also be maintained through filtration through biological filters using materials like gravel, activated charcoal, molluscan shell, etc.
- The post-larval stage needs to be acclimatized gradually to fresh waters.
- The suitable feed can comprise a variety of foods such as small shrimp (Acetes sp.), Artemia nauplii, etc. for larvae.
- The conditions required for hatching of a freshly hatched (disinfected with 70 ppm of formalin) Artemia nauplii. are:
- Salinity: 12-35
- Light: 200 lux
- Temperature: 28-35°C
- Dissolved O2: 2-8 ppm
- Stoking density: 1-2 gm/L
- Prepared feed:
- Fish flesh: 68%
- Egg (poultry): 20%
- Skimmed milk powder: 5%
- Wheat flour: 5%
- Vitamins + Minerals: 2%
Post-Larvae feed on:
- Living aquatic animals like aquatic worms and larvae of insects.
- Small parts of snails, clams, squids, brine shrimps, etc.
- Plant sources – Broken grains such as rice, vegetables like peas, sweet potato, tapioca, and oil cakes.
If the feeding can be done in the proper region as per schedule, survival rates are maximum. Initially feeding of Artemia is done twice a day and in later developmental stages, once in the late evening along with prepared feeds.
Some Important Diseases of Macrobrachium Rosenbergii with Symptoms, Infestation Stage:
|Type of Disease||Name of Disease, Causative Agent, and Symptoms||Infected Stages|
|Bacterial Infection||Chitinolytic bacteria.
Exoskeleton erosion, along with loss of appendages and lesions.
|Filamentous bacteria (Lencothrix sp.)
Gills get clogged and interfere with respiration Vivrio sp.
|Fungal Infection||Saprolegnia sp. and Fusarium sp. cottony moulds appear on the exoskeleton||Egg, larval stage, juvenile to adult.|
|Protozoan Infection||Epistylis sp., Zoothamnium sp., Vorticella sp.|
Culture of Tiger Prawn (Penaeus monodon)
There are different methods of prawn culture e.g., conventional method, extensive method, semi-intensive method, intensive method, and super-intensive method. The semi-intensive method is mostly practiced among them.
Semi-intensive Method of Prawn Culture
The culture method includes 5 steps namely-
- Selection of farm site and designing of the pond.
- Preparation of a pond to stock the prawn seed.
- Selection and stocking of prawn seeds.
- Post-stocking care of prawns.
1. Selection of Farm Site and Designing of Pond
(a) Selection of Site:
The farm site is selected on the basis of the following points :
- The site should have a mixture of sand, clay, and alluvium in appropriate proportion upto a depth of 1 meter.
- Excessive sand or acidic soil is unsuitable for prawn farming. The site should have the facility for entry and exit of tidal water.
- The tidal water at the site should be 50-100 cm in depth to generate an ideal atmosphere for prawn farming.
- The area should have sufficient annual rainfall, should not remain dry in any time period of the year and salt concentration shouldn’t be less than 25 ppt.
- The site should be far away from agricultural fields and industrial establishments.
(b) Pond Preparation:
A farm should have a separate nursery and stocking pond. The nursery pond should have a measure of 500 sq mt with 0.8 m depth and the stocking pond should be 1000 sq mt × 1 m in measurement. A pond should be rectangular with a length and breadth ratio 1 : 4. The side banks should have high dykes which during high tide remain 60-90 cm above the water level. The dyke should also be firm enough so that it is not damaged by water pressure. A proper sluice gate should be there for rapid entry of tidal water and the sluice gate should have a nylon net to control the entry of water.
2. Preparation of pond to Stock the Prawn Seed
Water from the pond is initially removed to get the pond dried. Then the bottom soil is ploughed to overturn the dry soil. Following this, the soil is mixed with 300 kg of lime per hectare of land. Lime treatment is done to reduce the acidity. The cow dung or faecal material of fowl is mixed at a rate of 1000-2000 kg per hectare. However, chemical manure such as urea or superphosphate should also be applied three times at a rate of 100 kg per hectare of land.
If the water of the pond is difficult to dry, mohua oil cake may be applied in the pond to destroy the unwanted fishes and insects as well as arthropods. Later on, mohua oil cake is converted into manure which promotes the growth of plankton as food for prawns. However, for the culture of prawns, the physicochemical properties of the pond should be as under:
|Temperature||26 – 33°C|
|Clarity||20 – 35 cms|
|pH||7.5 – 8.5|
|Nitrite||< 0.25 ppm|
|Dissolved O2||3-10 ppm|
|Ammonia||< 1.0 ppm|
|Hydrogen Sulphide||< 0.25 ppm|
Heavy metals and pesticide concentrations should be below 0.001 ppm. After 10 days of application of manures in the pond, it is fed with water to increase its level by about 10-15 cm. After several days when algae and planktonic organisms develop in the pond, it is again fed with water to increase the level to 60-80 cm.
3. Selection and Stocking of Prawn Seeds
Pure hatchlings of P. monodon and P. indicus are produced presently in the hatchery. However, due to some problems relating to transportation, seeds are collected from natural sources. With the help of various types of nets, the seeds of tiger prawns are collected from tidal water. From June at Sundarban, March in Kalinga of Orissa, November in Andhra Pradesh, May-June in the Malabar region of Kerala, and from October in Coromondal of Tamilnadu, the seeds are collected by conventional methods. The seeds of tiger prawns may easily be recognized by the transverse red lateral lines on the body. The seeds of the prawn are applied in the pond at a concentration of 30,000/hectare or 4000/bigha of waterbody. When the larvae attain a full-grown size, they are released into the stocking pond.
4. Post-Stocking Care of Prawn
Prawn farming in saline water needs some supplementary food for better growth of prawns. Such supplementary food is prepared in the following composition:
|Rice bran (oil-less)||25 g|
|Fish Meal||40 g|
|Soybean Meal||29 g|
|Vitamin & Mineral Salt||2 g|
Initially, for rearing the post-larvae of prawns, no supplementary food is required. At this stage, they live on the natural food particles. After about 10 days supplementary food is applied in the pond at dawn and dusk in adequate amounts. The method and quantity of supplementary food application in the pond is done in the following manner:
|Week||Food in % in relation to body weight|
|1. After 10 days of stocking 1st week (every day)||20 parts|
|2. 2nd week||18 parts|
|3. 3 week||16 parts|
Caring of the Rearing Pond or Stocking Pond:
- Monitoring of pH, salinity level, and turbidity of water is essential. These parameters differ in clean and saline water.
- Tidal water is essential to be fed in the stocking pond off and on.
- The mouth of the sluice gate is to be fitted with a net so that the prawns do not get out of the farm.
- The depth of the pond should always be 30-80 cm.
- The salinity of water should remain at a level of 10-30 ppm.
- Oxygen concentration in water should remain at an adequate level. On necessity, O2 may be mixed with pond water mechanically.
After about 3-5 months of stocking the seeds in the pond, the prawns become marketable. They are then harvested from the stocking pond for marketing. Harvesting may be done by various methods with the help of a khapla net, or netting followed by localized bright lighting in the pond area, and prawns are collected as harvest. Besides, prawns are also captured by fitting nets at the exit of the sluice gate during neap tide. Prawn culture by scientific method may give a harvest of 4000 kg/hectare.
Paddy Cum Prawn Fishery:
In West Bengal, the Sundarban area and the irrigation canals of South 24 Parganas are used by the fishermen for prawn cultivation. Normally the water level of the irrigation canals remains about 30” below the paddy field. During June-July when the water level of the irrigation canal rises, slightly saline water of the canal is made to enter the paddy field by cutting the boundary wall of the field. With this exercise seeds of prawn may enter the paddy fields. The boundary walls of the field are then repaired. The field usually remains filled with sufficient plankton and food particles because of manuring and the fries of prawns may grow rapidly by having the available food particles. At the time of ripening of the crops, the water level of the field drops down and the prawns are then captured for marketing. There is about 3-4 months time interval between rowing and harvesting of paddy in the year and this time period is sufficient to allow a sizeable growth of the prawn for marketing.
Prawn Culture in Bheries:
The Sundarban area of West Bengal having brackish water provides a favourable atmosphere for prawn farming. In this area, there are many shallow bheries retaining slightly saline water and these are used for prawn farming. A bheri is usually connected with the tributary of a river and the riverside of the bheri is blocked by dyke which is fitted with a sluice gate for entry and exit of water. The mouth of the sluice gate is fitted with bamboo-made appliances that may allow entry of prawns, but their exit is prevented. Breeding of prawns occurs during January and February and water of the estuary is made to enter into the bheri and with this prawn fries enter profusely into the bheri. The bheri usually remains full of micro-organisms, plankton, and food particles for prawns. By devouring the food particles, the fries grow rapidly and by the month of September, the prawns attain the marketable size for export. In this way, prawn culture is practiced intensively in bheris of our country.
Some Commercially Viable Prawn and Shrimp Species in India:
|Name||Distribution in India||Max. Size||Commercial Importance in Fishery|
|Palaemon styliferus (Rushna chingri)||Along the eastern and western coasts.||90 mm||Gangetic delta fishery.|
|Macrobrachium rosenbergii (Golda chingri)||Lakes and estuaries in India||320 mm||Fishery in Kerala during monsoons.|
|Macrobrachium malcolmsonii||Rivers and brackish waters||200-230 mm||Northeast coast during monsoons.|
|Macrobrachium rude||Southwest and Eastern coast of India||130 mm||Orissa|
|Metapenaeus brevicornis (Chamne chingri)||The northern region of both coasts||125 mm||A very important contributor to the fishery on both the coasts. Juveniles caught from estuaries.|
|Metapenaeus monoceros (Honne chingri)||Indian Coasts||180 mm||Important fishery of commercial importance.|
|Metapenaeus dobsoni||Southwest coast of India||125 mm||South West coast fishery. Juvenile one caught from estuaries and river mouth.|
|Penaeus Indicus (Chapda chingri)||Coastal water of India||230 mm||Important in estuaries and along the Indian coast.|
|Penaeus monodon or Tiger Prawn (Bagda chingri)||Eastern coasts (brackish water)||320 mm||Important commercial species in Bengal & Orissa.|
|Penaeus semisulcatus (Hende bagda)||Eastern coasts||250 mm||Bheri fishery|