One of the barriers to development of a viable shrimp aquaculture industry in the United States has been the high cost of coastal land. However, the euryhaline marine shrimp Litopenaeus vannamei is capable of survival and growth at salinities as low as 0.5 ppt, provided the water contains sufficient quantities of certain critical ions. Under two-thirds of the U.S. there is groundwater with salinities that may be capable of supporting shrimp culture. Inland production of shrimp using groundwater can provide an alternative to traditional coastal aquaculture and diversification of agriculture.

Salinity in groundwater derives from a number of sources, including salt domes, geologically old water trapped from the last ice age, deep geothermal wells, and saltwater intrusion from coastal areas. Depending on the source of the groundwater, the ionic composition and and total salinity may vary considerably. Using well water for inland marine shrimp culture faces many challenges for development. Information on the essential environmental ions involved in shrimp osmoregulation (Na+, Cl-, Ca2+, Mg2+, K+) and the minimum concentrations necessary for survival and growth of marine shrimp cultured in freshwater is lacking. Researchers at Harbor Branch are working to identify the minimum essential environmental ion concentrations necessary for normal growth and survival of L. vannamei , which will help in determining potential inland sources of water suitable for intensive shrimp culture.

Short-term survival experiments on L. vannamei postlarvae were conducted to determine minimum levels of the major seawater cations that are required for survival (Na+, K+, Ca++, Mg++. These studies demonstrated the following:

- The ratio of the divalent ions (Ca++, Mg++) to the monovalent ions (Na+, K+) is critical. At an overall salinity of 1 ppt, survival was poor when the concentration of divalent ions exceeded the concentration of monovalent ions. 24 and 48-hour survival rates were best when a 75:25 ratio of monovalent:divalent ions was used.

- In experiments in which CaCl and NaCl were added to distilled water in various ratios and concentrations showed that there is an interaction between sodium and calcium. When Na+ concentrations are low (< 300 ppm) concentrations of C++ ion in excess of the Na+ concentration are lethal. Survival improves as the ratio of Na+: Ca++ increases. This result suggests that when concentrations of sodium are low, high calcium ion concentrations can interfere with sodium uptake.

- K+ is essential for short and long-term survival L. vannamei. Very low survivals of shrimp were observed in short-term survival studies when potassium concentration were less than 1 ppm. Studies by other researchers have indicated that K+ should exceed 15 ppm for good survival in pond production systems.

- In experiments in magnesium was added to 1 ppt solutions of sodium chloride and calcium chloride (75:25 ratio of Na+:Ca++), no improvements in survival were observed at any level of magnesium addition.

Further research is required to examine long term effects of low ion concentrations and ion ratios on shrimp physiology and growth.

Although marine shrimp is the highest seafood import in terms of dollar value, the high cost of coastal land, user conflict, and strict requirements regarding effluent discharge have, at least in part, prevented the expansion of shrimp aquaculture in the U.S. Shrimp production from U.S. aquaculture is expected to be over 9 million pounds (4,000 mt) for 2001, but future increases are likely to come from inland production. Researchers at Harbor Branch have been working to advance our knowledge of the ionic requirements for low salinity culture of shrimp, and to understand how shrimp perform in low salinity environments. Other research has focused on developing and testing the performance of marine shrimp in low salinity indoor intensive recirculating systems.

Shrimp culture in Central and South America and in Southeast Asia has traditionally been carried out in the in large coastal lagoons using a semi-intensive production technology. In the United States, however, the traditional approach to shrimp culture is not feasible due to the high cost of coastal land, cold winters, and strict environmental regulations. A potential alternative to the traditional pond culture technology is to culture the shrimp in intensive indoor recirculating aquaculture systems. These systems allow shrimp to be cultured year round on relatively small parcels of land. Recirculation technology reduces the water requirements and discharge from the culture system, minimizing environmental impacts. However, the capital, energy and labor costs for indoor systems are much higher per unit of production than are typical for pond production systems.

Harbor Branch researchers have been investigating ways increase the productivity of indoor production systems for shrimp while reducing capital, energy and labor costs. In 1998 HBOI was funded by the Florida Department of Agriculture and Consumer Services to evaluate the economic feasibility of commercial production of Litopenaeus vannamei in freshwater recirculating aquaculture systems. As part of this study, HBOI set up a comparison of single and three-phase production systems. In a single-phase production system, post-larval shrimp are stocked into a non-partitioned culture tank and remain in that same area until harvested for market. In a three-phase production system, the growout is divided into three culture phases of equal length, each taking place in progressively larger amounts of area. By allocating only the amount of area needed for each phase of the growout process, space is used more efficiently. In theory, a continuously operated three-phase production system should allow annual production to be increased by 80% compared to a single-phase system. Multiple production trials over the course of a year corroborated this finding, as projected annual productivity of the three-phase systems tested was 1.74 times greater than the annual productivity of the single-phase systems.

An economic analysis was performed to analyze the profitability of a hypothetical enterprise based on the 3-phase design. A 10-year cash-flow model was developed for an enterprise consisting of twelve production greenhouses, an acclimation/quarantine greenhouse, a feed shed, workshop, and three retention ponds. The production parameters, construction costs, and operating costs for the model were based on the results obtained in the production trials described above. Assuming the shrimp reach a size of 18 grams in 180 days with an average survival of 61% and a harvest density of 150 shrimp/m2, the breakeven price was $4.59/lb. Assuming the shrimp were sold for an average price of $5.25/lb, the internal rate of return (IRR) for the hypothetical enterprise was 13%. Most investors would require an IRR of at least twice this value before they would be willing to consider entering into such a risky venture. However, sensitivity analyses revealed that if the survival could be increased to 70%, or the shrimp could be grown to an 18 gram market size in 150 days, the IRR would be doubled. If shrimp could be grown to market size in 150 days with an overall survival of 70%, the IRR would increase to a very attractive 48%, with a breakeven price of $3.72/lb. If the shrimp could be sold for at least $4.50 per pound of whole shrimp, the enterprise would earn an IRR of 26%, the minimum return necessary to cover the opportunity cost and risk associated with the investment.

Harbor Branch researchers published a manual on the production of shrimp in indoor recirculating production systems. This manual is available for downloading as a pdf file in the Publications section of this web site.