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Aquaponics Library |  |
6/2018
Frequently Asked Questions
1. Can freshwater prawns be raised in indoor tanks?
Three of four stages of freshwater prawn production in temperate climates require the use of indoor tanks. The hatchery stage requires tanks with recirculated brackish water and the nursery stage requires tanks with either recirculating or flow-through freshwater. In addition, in temperate climates indoor tanks are required to hold broodstock to provide the following years larvae. Growout of prawns in tanks is not an effective and cost efficient way to produce a market sized product. In tanks growth rates of large prawns are usually slow. In addition, the required feeding rates to produce marketable prawns in a profitable period of time, would likely deteriorate water quality.
2. What is the lowest water temperature freshwater prawns can tolerate?
Prawns survival in ponds is dependant on how rapidly the temperature changes. The lowest temperature prawns can tolerate and survive is approximately 57F (14C) if the temperature is lowered very slowly over a period of several days, but only 60F (15C) if the temperature change occurs during approximately one day. Therefore, you must remember that smaller ponds will exhibit a more rapid change in temperature than large ponds. Growth of prawns becomes slow at water temperatures below 68F.
3. How do freshwater prawns compare to saltwater shrimp?
Texture of freshwater prawns and saltwater shrimp are very similar. Freshwater prawns do not have the strong flavor of saltwater shrimp. We have found that freshwater prawns can be placed in a marinade and will absorb the flavor in a short period of time. This makes prawn ideal for boiling, sauteeing, or grilling.
4. Do freshwater prawns freeze well?
Yes, the Department of Food Science at Mississippi State University has conducted numerous studies on the shelf life of prawns frozen many different ways. It is best to freeze prawns with heads removed and tail shell still attached. If prawns are frozen in a conventional freezer in a block of ice the texture, flavor, and overall quality of the product will not change for approximately 6 months. If prawns are individually quick frozen (IQF), in a freezer which uses either gaseous nitrogen or carbon dioxide to quick freeze, the texture, flavor, and overall quality of the product will not change for approximately 9 months. Prawns tails frozen for more than one year with either method will have slightly softer texture, however the flavor will not change.
5. Do I need a permit to raise freshwater prawns?
Macrobrachium rosenbergii is classified as an exotic species in the United States. Each state has different requirements for introducing exotic species, usually the state Department of Agriculture will be able to provide this information. In the state of Mississippi a yearly permit is required. The cost of this permit is \$100 per year and is available through the Department of Agriculture and Commerce at (610) 354-6720. They may want to inspect your farm to make sure you have taken proper precautions to prevent the prawns from escaping through the drains in your tanks and ponds. However, the temperatures in the winter months in the U.S. are typically below the tolerance level of prawns and brackish water is required for larvae to survive, therefore there is no chance for the prawns to escape and survive to reproduce. Subtropical coastal areas may cause concern because conditions could exist which would allow prawn to escape and survive to reproduce in coastal esturaries, therefore, the state may require additional precautions to be taken to prevent prawns from escaping.
6. Are freshwater prawns susceptible to diseases common to marine shrimp?
Diseases of the marine shrimp are not common to cultured freshwater prawns and no outbreaks of any pathogens have been observed in Mississippi. Bacteria and fungal diseases which are common to most freshwater crustaceans could occur in freshwater prawns but have not been reported to cause any loss of prawns. No viruses have been shown to occur in cultured freshwater prawns. Therefore, compared to marine shrimp the risk of disease is minimal.