The final phase of freshwater prawn (shrimp) production is grow-out of juveniles to adults for market as a food product.
Research in Mississippi, Kentucky and other southern states has demonstrated this can be a profitable enterprise, and this publication provides guidelines for stocking and managing a freshwater prawn production pond.
Unless you have a hatchery/nursery, you must purchase juveniles for the pond grow-out phase. There are commercial hatcheries in Texas, California and Mexico that produce postlarvae and juveniles.
The 1996 price is about $65 per 1,000 juveniles. You can minimize shipping costs if the hatcheries are located within a 10- to 14-hour driving distance of your grow-out facility.
Otherwise, it is best to have the juveniles shipped via plane, but this significantly increases the cost.
Site selection and pond design:
Ponds used for raising freshwater prawns should have many of the same basic features of ponds used for the culture of channel catfish. A good supply of freshwater is important, and the soil must have excellent water-retention qualities.
Well water of acceptable quality is the preferred water source for raising freshwater prawns. Surface runoff water from rivers, streams and reservoirs can be used, but quality and quantity can be highly variable and subject to uncontrollable change. The quality of the water source should be evaluated before any site is selected.
Locate ponds in areas that are not subject to periodic flooding. Before building ponds specifically for producing freshwater prawns, check the soil for the presence of pesticides. Prawns are sensitive to many of the pesticides used on row crops. Also, analyze the soil for the presence of residual pesticides.
Do not use ponds that are subject to drift from agricultural sprays or to runoff water that might contain pesticides. The surface area of grow-out ponds ideally should range from 1 to 5 acres, but larger ponds have been successfully used. The pond should be rectangular in shape to facilitate distribution of feed across the entire surface area.
The bottom of the pond should be completely smooth and free of any potential obstructions to sein-ing. Ponds should have a minimum depth of 2 to 3 feet at the shallow end and a maximum depth of 3.5 to 5 feet at the deep end. The slope of the bottom should allow for rapid draining.
You can obtain assistance in designing and laying out ponds by contacting a local office of the Natural Resources Conservation Service (formerly Soil Conservation Service). SRAC Publications #100, 101, 102 and 103 provide additional information on pond design and construction.
Collect a soil sample from the pond bottom to determine whether lime is needed. Take soil samples from about six different places in each area of the pond, and mix them together to make a composite sample that is then airdried.
Put the sample in a soil sample box, available from your county Extension agent, and send it to the state soil testing laboratory in your state, typically operated by the Cooperative Extension Service, and request a lime requirement test for a pond. There may be a small charge for this service. If the pH of the soil is less than 6.5, you must add agricultural limestone to increase the pH to a minimum of 6.5, and preferably 6.8.
After filling the pond, fertilize the pond to provide an abundance of natural food organisms for the prawns and to shade out unwanted aquatic weeds. Liquid fertilizer, either a 10-34-0 or 13-38-0, or one of the highly water soluble powders (12-49-6 or 10-52-0) give excellent results. Apply 1/2 to 1 gallon of liquid fertilizer or 4 to 6 pounds water soluble powder per surface acre to the pond at least 1 to 2 weeks before stocking juvenile prawns.
If a phytoplankton bloom has not developed within a week, either make a second application of the fertilizer, or add water from an adjacent pond that has an adequate bloom to seed the bloom in the prawn pond.
Do not apply liquid fertilizer directly into the water because it is denser than water and will sink to the bottom; liquid fertilizer should be diluted with water 10:1 before application. It can be sprayed from the bank or applied from a boat distributed in the propwash of an outboard motor.
The water soluble powders can be applied directly to the water surface, or distributed with a boat or via currents created by a paddlewheel aerator. If a water source other than well water is used, it is critically important to prevent fish, particularly members of the sunfish family (e.g., bass, bluegills and green sunfish) from getting into the pond when it is filled. Screening or filtering the incoming water is highly advisable. The effects of predation on freshwater prawns by these kinds of fish can be devastating.
If there are fish in the pond, remove them before stocking prawns, using 1 quart of 5 percent liquid emulsifiable rotenone per acre-foot of water when water temperatures exceed 70o F. Rotenone is a restricted use pesticide, and either a commercial or private pesticide applicators license is required to purchase and apply this material. Assistance in obtaining this license or certification can be obtained through your county Extension office.
Stocking of juveniles:
Juvenile prawns must be gradually acclimated to conditions in the grow-out pond to prevent temperature shock or other types of stress. Water in which postlarvae and juveniles are transported should be gradually replaced by the water in which they will be stocked.
This acclimation procedure should not be attempted until the temperature difference between the transport and culture water is less than 6 to 10°F. The temperature of the pond water at stocking should be consistently at least 68°F (20°C) to avoid stress because of low temperatures.
Juvenile prawns appear to be more susceptible than adults to low water temperatures. Juveniles, preferably derived from populations that have been sizegraded, ranging in weight from 0.1 to 0.3g, should be stocked at densities of 12,000 to 16,000 per acre.
The size grading results in more uniform growth and helps to reduce the percentage of smaller, non-marketable individuals at harvest. Lower stocking densities will yield larger prawns but lower total harvested poundage.
The density selected should be determined by the particular market that is targeted. For example, if the market demands whole, live or fresh ice-packed prawn, stocking at lower densities will result in larger, more marketable individuals.
The duration of the growout period depends on the water temperature of the ponds, and the time generally is 120 to 180 days in the southern U.S. Prawns could be grown year-round if a water source is found that provides a sufficiently warm temperature for growth.
Information Sourced From:
Louis R. D’Abramo and Martin W. Brunson
