Shrimp Cultivation (or) Prawn Cultivation Techniques
The following content details about Shrimp Cultivation Methods and Shrimp culture techniques and ideas. We also discuss shrimp feeding, pond management, etc..
Over the years, aquaculture in India has evolved from a subsistence and backyard activity to that of a technology-driven commercial and profitable venture. India is nowÂ secondÂ in world aquaculture production next to China.
The estimated brackish water area suitable for undertaking shrimp cultivation in India is around 11.91 lakhs ha spread over 10 states and union territories viz; West Bengal, Orissa, Andhra Pradesh, Tamil Nadu, Pondicherry, Kerala, Karnataka, Goa, Maharashtra, and Gujarat. Of this only around 1.2 lakhs ha are under shrimp farming now and hence lot of scope exists for entrepreneurs to venture into this field of activity. The following table gives the state-wise potential and present level of development.
The success of commercial aquaculture in India is attributed to the availability of vast untapped surface water resources, standardization of many new products and associated techniques of input and output subsystems, an extension of technology and practical knowledge to the farmers. Now let us dive into actual cultivation of shrimp.
Suitable Soil Type for Shrimp Culture:
- The type of soil is the most critical in site selection since the shrimp will spend most of their time on the pond bottom during the culture period. Usually, clay or loam-based soil containing more than 90% clay and pH between 6.5-8.5 is preferable. Sites with sandy or silty soil should be avoided due to their porous nature that may lead to erosion, seepage of water and easy infiltration of waste into the soil. Prior to the construction of ponds, samples of soil should be taken randomly from 5-10 spots at the surface and at 1 meter deep and sent to a laboratory for the analysis of soil texture and pH. Such data will be useful during pond construction and preparation.
- Mangrove or acid sulfate soils are not suitable for shrimp pond culture due to their high organic matter contents and acidic nature that require a high water exchange rate and low stocking density. A pond built on mangrove soil will also encounter the problems of hydrogen sulfide and ammonia accumulation in the pond bottom. In the acid sulfate soil areas, the soil will develop high acidity when dried and then flooded which will lead to difficulty in stabilizing the pH of the pond water and in inducing the growth of plankton during the culture period.
Pond Design and Construction for Shrimp Culture:
In Shrimp Cultivation, a shrimp pond should be designed according to the characteristics of the selected site and the culture system. There is no unique design, but optimum and functional farm layout plan and design should be based on the physical and economic conditions prevailing in the locality.
Pond Management for Shrimp:
Before a pond can be stocked for a new crop, the excessive wastes, which accumulate in the pond during the previous crop, must be removed and the soil and water conditioned. Growing of shrimp in an improperly prepared pond may lead to difficulty in pond management during the culture period, which could result in a decrease in production capacity of the pond.
Stocking of Shrimp:
The most suitable species for culture in India are the Indian white prawn Penaeus indicus and tiger prawn P. monodon. The stocking density varies with the type of system adopted and the species selected for the culture. As per the directives of Supreme Court, only traditional and improved traditional shrimp farming can be undertaken within the Coastal Regulation Zone (CRZ) with a production range of 1 to 1.5 t/ha/crop with a stocking density of 40,000 to 60,000/ha/crop. Outside CRZ extensive shrimp farming with a production range of 2.5 to 3 t/ha/crop with a stocking density of 1,00,000/ha/crop may be allowed.
Seed Selection for the Cultivation of Shrimp:
Selection of good quality seed for stocking into a pond is the first important step of the shrimp grow-out management. The farmer must ensure that he or she gets healthy seed by purchasing them from reliable hatchery or hatcheries. It may not always be possible to obtain the desired shrimp seed due to limitations in availability and quantity.
The following parameters should be taken into consideration in purchasing shrimp seed for stocking.
Seeds of PL 15-20, indicated by the appearance of 4-6 spines on the rostrum, are recommended for stocking in a pond. The healthy PL should have the muscle-to-gut ratio in the sixth abdominal segment of about 4:1 or the thickness of the gut should be about the thickness of the muscle. Practically, seed from the first and second spawning of broodstock with uniform size can be used.
The postlarvae should have the normal appearance of trunk, appendages, and rostrum. The abdominal muscle must be clear, no discoloration or erosion on any parts of the body, the gut should be full of food, and the muscle should fill the carapace.
Postlarvae with the presence of pigment cells in the uropods should be used since this indicates the stage of development. PL that will have high survival and growth rates will be light gray, brown to dark brown and black in color. Signs of red or pink coloration are normally related to stress.
Healthy seed swims straight, respond rapidly to external stimuli such as a tap on the side of the basin, actively swim against the current when the water is stirred, and cling to the sides rather than aggregate or be swept down into the center of the container when the current has subsided.
(v) External Fouling
Seeds should be free from external parasites, bacteria, and other fouling organisms. The presence of these organisms indicates unhealthy conditions, which will affect the growth and survival of the PL. It is recommended that before purchasing, the farmer should visit the hatchery to check the seed once or twice either in the early morning or late afternoon, especially one day prior to stocking. However, healthy seed with some fouling may be used when the animals are in good condition after treatment.
(vi) Pathogen Free
Seed should be checked for the presence of viral occlusion bodies. Seed with large numbers of occlusions indicate stress conditions and will not so vigorous in the pond.
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When a farm is ready for operation, the optimum stocking density of PL in a pond should be determined in accordance with the production capacity of the farm and the culture system, which include the soil and water quality, food availability, seasonal variations, target production, and farmer’s experience. It is recommended that farmers should start a new crop with a low stocking density to access the production capacity of the pond. If production is successful, then the stocking density could be increased for subsequent crops. Overstocking should be avoided since it may result in management problems and loss of entire production.
The stocking density between 10-20 PL/m2 is usually practiced in a semi-intensive culture. In intensive culture, a well-managed pond with consistent good water quality can stock up to 25-30 PL/m2 at 1.2 m water depth and up to 40-50 PL/m2 at 1.5 m water depth or deeper. However, it must be emphasized that intensive cultures involve high densities and can only be sustained in well-managed farms under an experienced farmer.
Feed Management of Shrimp:
- Cost of feed constitutes a major part of the production cost and accounts for 50% to 70% of the total variable cost. The use of feeds will improve shrimp production and increase profits. The availability of nutrients from feeds depends on the type and quality of the raw material used, the formulation, the feed processing, feed storage conditions, and the feeding management. Therefore, feed and feeding practices for semi-intensive or intensive shrimp farming require a basic understanding of nutrition and feed requirements.
- Shrimp diets may be supplementary or complete. In an extensive system, the shrimps need a complete diet. Although natural food items have good conversion values they are difficult to procure in large quantities and maintain a continuous supply. At present most of the aquaculture farms depend on imported feed with an FCR (Food Conversion Ratio) of 1:1.5 – 1.8. The feeding could be done by using automatic feed dispensers, or by broadcasting all over the pond. If feeding trays are employed in selected pockets in the pond wastage in feed can be reduced.
Nutrient Requirements for Shrimp:
Shrimp requires approximately 40 essential nutrients. These nutrients are provided in various amounts by natural food and supplemental feeds. Although the nutrition principles are similar for all animals, the quality and quantity of nutrient requirements vary from species to species. The recommended levels of nutrients and dietary components for black tiger shrimp are listed in the table below.
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Water Quality Management:
Water conditions in the rearing pond deteriorate through the production cycle due to uneaten food, animal’s excretion, etc. Generally, shrimp farmers use dissolved oxygen (DO), pH, ammonia, watercolor, and water odor as indicators to judge the water quality of the pond.
These parameters are observed regularly by using either scientific equipment or the farmer’s experience in order to control them within the optimum range.
Harvesting and Handling of Shrimp:
- Successful harvesting can be achieved if the shrimp can be harvested in good condition within a short period of time. The harvesting technique should not damage or excessively contaminate the shrimp with waste. Rapid harvesting will reduce the risk of bacterial contamination and the shrimp will still be fresh when reaching the processor.
- Complete harvesting can be carried out by draining the pond water through a bag net and hand picking. The average culture period required is around 120-150 days during which time the prawns will grow to 20-30 gm size (depending on the species). It is possible to get two crops in a year. Harvested shrimps can be kept between layers of crushed ice before transporting the consignment to market.
Methods of Harvesting of Shrimp:
Two methods of harvesting are generally practiced on farms. These are either by draining the pond and catching the shrimp in a bag net or by netting the shrimp within the pond.
- For the first method of harvesting, ponds and outlets should be appropriately designed and be able to completely drain the pond within 4-6 hrs. A bag net should be able to be fixed to the outlet to collect the shrimp that are carried by the out flouring water. The best time for harvesting is early in the morning and it should be completed before mid-morning. In ponds that can only be drained at low tide, the harvest should be conducted whenever possible. The shrimp should be regularly removed from the harvesting bag in small quantities to prevent damage.
- When netting the shrimp within the pond, either a small electric net or a large seine net can be used. The water level of the pond should be reduced to 0.5-0.75 m deep and workers will need to go inside the pond for netting. This method is less advantageous the pond bottom will be disturbed, thus causing contamination of the shrimp. It is also slower and may take a long time to complete.
With either method, it is necessary to hand-pick the remaining shrimp in the pond, after the pond is drained. The harvested shrimp can be quickly killed by giving them a temperature shock (dip in iced water) to prevent damage and to improve storage.
Timing of Harvesting and Selling:
- The timing of harvesting shrimp depends on the condition of the shrimp in the pond and also the market price. Shrimps are sampled by a cast net from different areas of the pond to determine their average body weight and general condition. The proportion of soft shell shrimp should not be more than 5% at the time of harvest. This proportion could be obtained by scheduling the harvest halfway between two moultings.
- The time of molting is indicated by the presence of exuviae in the pond. For example, if the average body weight of the shrimp is 30 gm, then the harvest should be planned for 7-8 days after the exuviae are observed, as the next molting cycle can be observed after 14-16 days. Harvested shrimp should be iced and transported to cold storage or processing plants in less than 10 hrs.
Diseases, Prevention, and Treatment of Shrimp:
Cultured shrimps suffer from various diseases due to infectious and non-infectious causes. Infectious diseases are caused by viruses, bacteria, fungi, and certain parasites. Treatment cannot be carried out effectively when shrimp diseases occur in a pond. The best way to get rid of diseases is by practicing good farm management or prevention. In this regard, information on various kinds of diseases and their prevention procedures are useful.
Quality Control and Marketing of Shrimp:
Quality Control plays a major role in Profits and Marketing. It is very important to make sure the end product is healthy.
That’s all folks about the cultivation of shrimp and cultural practices. Keep developing aquaculture!.