Patent Publication Number: US-8985055-B2

Title: System and method for super-intensive shrimp production

Description:
PRIORITY CLAIM 
     The present application is a divisional application of and claims priority to U.S. patent application Ser. No. 12/775,611 entitled “System &amp; Method for Super Intensive Shrimp Production,” filed May 7, 2010, which is incorporated by reference herein, and both applications claim priority under 35 U.S.C. §119 to U.S. Provisional Patent Application Ser. No. 61/177,863, filed May 13, 2009, which is incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a system and method for super-intensive shrimp production using low water depth, low water volume, or low amounts of floor space. The system and method may employ raceways having particular slopes to facilitate water draining, water circulation, or shrimp harvesting. In particular embodiments, the system and method may use particular shrimp raceway designs which may be combined with particular water quality tolerances and water treatment systems. 
     BACKGROUND 
     Shrimp harvesting from the world&#39;s oceans can no longer safely meet demand for shrimp. Accordingly, methods for controlled and enhanced shrimp production or shrimp farming have been developed. The currently predominant methods typically use ponds for commercial production of shrimp. These methods, while successful, still suffer some drawbacks including the use of substantial amounts of water and requirements for large amounts of space by the structures in which the shrimp are grown. Further, although shrimp are well-suited to aquaculture, they have specialized needs as compared to other aquaculture species that should be taken into account, which sometimes hinders the ability to adapt techniques useful with other species to shrimp production. Finally, because most shrimp do not grow well in environments where the temperature is less than around 26° C. for around a month or more, pond-based methods may be used only seasonally in non-tropical locations such as the United States. 
     Typical raceway designs presently being used have 0.6 to 3.7 meter water depth which results in greater floor space need and has management drawbacks resulting in greater production costs. The disclosure provides technology for stacked raceways, thereby reducing the floor space required and improving the internal rate of return. 
     Further, there is a need to develop technologies to allow shrimp production to be commercially successful inland and away from the coastal zone and near major markets such as Chicago, Las Vegas, Dallas, etc. Accordingly, a need exists for new technologies that allow intensive production of shrimp such as may be used in commercial farming. The technologies disclosed herein may allow non-tropical shrimp farming to be competitive with farming in the tropics or may also improve shrimp farming in tropical locations. 
     SUMMARY 
     According to one embodiment, the disclosure relates to a shrimp aquaculture structure including a set of at least two raceways of increasing average depth each having a length and width and including two ends, two end walls, two side walls having a top, a bottom, and a side wall depth, and a sloped bottom having an average internal depth and joining each side wall at two side wall junctions. The sloped bottom of each raceway may have a slope of between 0.05% and 20%. The bottom may slope down from a bottom apex to the side wall junctions or may slope up from a bottom nadir to the side wall junctions. At least one of the at least two raceways may be stacked at least partially on top of another of the five raceways. 
     According to a more specific embodiment, the structure may be part of a system that may also include water and a water circulation and maintenance system. The water may have an average depth in the set of raceways of 30 cm or less. The water in the set of raceways may be exchanged by the water maintenance or circulation system in an amount up to 1000% of the total volume of the water in the set or raceways per day. 
     According to another embodiment, the disclosure relates to a process of shrimp aquaculture by providing a set of at least two raceways of increasing average depth each having a length and width and having two side walls and a sloped bottom joining each side wall at two side wall junctions, wherein the sloped bottom of each raceway has a slope between 0.05% and 20%. In the method, the first raceway may be stocked with postlarval shrimp, which are then grown to a predetermined size. The shrimp may then be transferred to a second raceway having a greater average depth until the shrimp reach a second predetermined size. The shrimp may then be harvested or transferred to still further raceways with increasing average depths and growth to increasing sizes before transfer. The shrimp may finally be harvested. The shrimp may also be partially harvested between raceways. 
     According to a particular embodiment, the disclosure includes a method of shrimp aquaculture including stocking a first raceway with a first average depth with postlarval shrimp, growing the shrimp to a first average size of between 0.5 g and 2.5 g, transferring substantially all of the shrimp to a second raceway having a second average depth greater than the first average depth, growing the shrimp to a second average size of between 6 g and 11 g, transferring substantially all of the shrimp to a third raceway having a third average depth greater than the second average depth, growing the shrimp to a third average size of between 12 g and 19 g, transferring substantially all of the shrimp to a fourth raceway having a fourth average depth greater than the third average depth, growing the shrimp to a fourth average size of between 17 g and 25 g, transferring substantially all of the shrimp to a fifth raceway having a fifth average depth greater than the fourth average depth, growing the shrimp to a fifth average size of between 23.5 g and 33.5 g; and harvesting the shrimp crop. Each raceway may have a length and width, two side walls and a sloped bottom with a bottom nadir or a bottom apex, the sloped bottom joining each side wall at two side wall junctions, slope from the bottom nadir to the side wall 
     Embodiments of the current disclosure may achieve one or more of the following advantages: Aquaculture of shrimp using a total water volume per weight of shrimp produced significantly less, such as, as much as three times less, than with conventional techniques. 
     Aquaculture of shrimp in significantly lower average water depths (e.g. as low as 2.5 cm, or 2-3 times lower) than conventional techniques. 
     Aquaculture of shrimp using significantly less area (e.g. floor space) per weight of shrimp, such as up to three to five times less, than obtained with conventional techniques. 
     Aquaculture of shrimp achieving significantly greater shrimp production per cubic meter of water in which shrimp are grown, e.g. greater than 25 kg shrimp per cubic meter of water per crop and even as much as 70 kg shrimp per cubic meter or water per crop. 
     Aquaculture of shrimp achieving significantly greater shrimp growth, such as growth rates of greater than 1.5 per week higher than obtained with conventional techniques. 
     Aquaculture of shrimp at higher densities per cubic meter than obtained with conventional techniques, even with lower feed conversion rates. 
     Aquaculture of shrimp achieving significantly greater survival, such as 80% survival, than obtained with conventional techniques, even at production levels greater than 25 kg/m 2  per crop. 
     Aquaculture in a variety of climates and geographic locations, including those not typically compatible with shrimp aquaculture, by allowing climate modifications. 
     Aquaculture in enclosed or partially enclosed buildings such as warehouses and greenhouses. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete and thorough understanding of the present embodiments and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings, in which like reference numbers indicate like features, and wherein: 
         FIG. 1A  illustrates an end view of a raceway with a bottom nadir and  FIG. 1B  illustrates a side view of a raceway with a bottom nadir.  FIG. 1C  illustrates and end view of a raceway with a bottom apex. Drawings are not to scale. 
         FIG. 2  illustrates depths for a series of five raceways. Drawing is not to scale. 
         FIG. 3  illustrates dimensions and example physical shape characteristics for a stacked raceway system. Drawing is not to scale. 
         FIG. 4  illustrates the effect of water depth on shrimp survival. Values represent mean±standard error for 8 replicates except for depth of 10 cm which had 4 replicates. 
         FIG. 5  illustrates the effect of water depth on final shrimp weight. Values represent mean±standard error for 8 replicates except for depth of 10 cm which had 4 replicates. 
         FIG. 6  illustrates the effect of water depth on shrimp weight gain. Values represent mean±standard error for 8 replicates except for depth of 10 cm which had 4 replicates. 
         FIG. 7  illustrates the effect of water depth on shrimp growth rates. Values represent mean±standard error for 8 replicates, except for depth of 10 cm which had 4 replicates. 
         FIG. 8  illustrates the effect of water depth on shrimp biomass per square meter of tank bottom. Values represent mean±standard error for 8 replicates except for depth of 10 cm which had 4 replicates. 
         FIG. 9  illustrates the effect of water depth on shrimp biomass per cubic meter of water used to grow the shrimp. Values represent mean±standard error for 8 replicates except for depth of 10 cm which had 4 replicates. 
         FIG. 10  illustrates the effect of water depth on feed conversion. Values represent mean±standard error for 8 replicates except for depth of 10 cm which had 4 replicates. 
         FIG. 11  illustrates the effect of feed rate and density on survival. Values represent mean±standard error of means for 4-5 replicates. 
         FIG. 12  illustrates the effect of feed rate and density on survival. Values represent mean±standard error of means for 4-5 replicates. 
         FIG. 13  illustrates the effect of feed rate and density on final weight. Values represent mean±standard error of means for 4-5 replicates. 
         FIG. 14  illustrates the effect of feed rate and density on growth. Values represent mean±standard error of means for 4-5 replicates. 
         FIG. 15  illustrates the effect of feed rate and density on growth. Values represent mean±standard error of means for 4-5 replicates. 
         FIG. 16  illustrates the effect of feed rate and density on density. Values represent mean±standard error of means for 4-5 replicates. 
         FIG. 17  illustrates the effect of feed rate and density on feed conversion. Values represent mean±standard error of means for 4-5 replicates. 
         FIG. 18  illustrates the effect of feed rate and density on feed conversion. Values represent mean±standard error of means for 4-5 replicates. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure relates to systems and methods for super-intensive production of shrimp. Embodiments of the disclosure may include water quality tolerances to facilitate super-intensive shrimp production as well as structures for use in such production. According to one embodiment, shrimp raceways may use low average water depth. Unlike conventional shrimp raceways, which typically have an average water depth of approximately one meter (range of 0.6 to 3.7 meters), low average water depth raceways (e.g. 30 cm or less) may be readily stacked (two or more raceways on top of each other), allowing growth of high amounts of shrimp per area (e.g. amount of floor space utilized). 
     According to one embodiment of the disclosure, shrimp may be grown in a raceway or series of raceways having low water volume and low average water depths. The low water volume and low average water depths may allow the construction of stacks of two or more at a reduced cost, thus increasing the internal rate of return desirable for commercialization of shrimp farming. In a particular embodiment, there may be between two and seven raceways, particularly five raceways, including combined raceways. 
     These raceways may also, in a specific embodiment, be stacked to minimize the square meter of ground used in shrimp production. In general, each raceway may have a structure as shown in  FIG. 1 . The raceways may have end walls  10  that may typically be between 2 m and 10 m wide. The remainder of the raceway will typically have the same width as the end walls. The raceways also may have side walls  20  that may typically be between 2.5 cm and 50 cm, more particularly 5 cm and 20 cm deep. Although side walls  20  do not necessarily have to have the same depth, in many embodiments they will. In other embodiments, the side walls may have different depths for different raceways. In still other embodiments, the side walls may have different depths along the same raceway. 
     The raceways as shown in  FIGS. 1A and 1B  may also have a sloped bottom  30  with a bottom nadir  40   a  which meets side walls  20  at side wall/bottom junctions  50 . Alternatively, as shown in  FIG. 1C , the raceways may have a sloped bottom  30  with a bottom apex  40   b  which meets side walls  20  at side wall/bottom junctions  50 . Sloped bottom  30  may be made from a single panel, two panels that join at bottom nadir  40   a  or bottom apex  40   b , or multiple panels. The raceways may also have an internal depth  60 , measured from the top of the highest sidewall  20  to the bottom nadir  40   a  or from the top of the highest sidewall  20  to side wall/bottom junctions  50  (when a bottom apex  40   b  is present). The internal depth  60  may be the same throughout the raceway or it may vary along the raceway. Regardless, the raceway may have an average internal depth that may typically be between 8 and 25 cm. The raceway may also have an average depth representing the average distance between the tops of side walls  20  and bottom  30 . In general, the depth of side walls  20 , internal depth  60 , the average side wall depth, the average internal depth, and average depth may be greater in raceways for larger shrimp than in raceways for smaller ones. The depth of side walls  20 , in one embodiment, may be between 2.5 cm and 50 cm, more particularly between 5 cm and 25 cm. Similarly, the internal depth  60  or the average internal depth, in one embodiment, may be between 2.5 cm and 50 cm, more particularly between 5 cm and 20 cm. The average depth may also be between 2.5 cm and 50 cm, more particularly between 5 cm and 25 cm. In embodiments in which the raceways contain water, it may have an average internal depth of less than 30 cm. The raceways may have a length  70  that may be any length, but in particular embodiments may be at least 10 meters long, more particularly between 20 and 60 meters long, but may be as long as 100 meters. 
     In some embodiments, the slope of sloped bottom panel  30  as measured from side wall/bottom junctions  50  to bottom nadir or from bottom apex  40  to side wall/bottom junctions  50  may be between 0.05% and 20%, particularly between 0.1% and 10%, more particularly between 0.2% and 5%. Alternative bottom arrangements, such as bottoms with multiple sloped panels, may also be used. 
     In some embodiments, the width of the raceway and possibly also the slope of sloped bottom panels  30  may both be varied depending on the dimensions of the building or other facility in which the raceway is housed as well as construction costs. Although  FIGS. 1-3  illustrate raceways of generally the same size and shape, raceways in a set of raceways may vary in size and shape. Variations may be useful, for example, to accommodate building configurations, circulation systems, and the like. 
     The raceways may be arranged such that one end is higher than the other end. Alternatively, the raceways may be approximately the same height along their entire length. If the two ends are not the same height, the higher end will have shallower water and the lower end will have deeper water. Raceways may also be generally horizontal but with one end shallower than the other. The slope of the raceway from end to end may, in some embodiments, be between 0% and 1.0%, more particularly between 0.05% and 0.5%. The slope of each raceway from one end to the other may affect ease of transfer of shrimp from one raceway to another, particularly in stacked raceways, as well as ease of waste removal. 
     According to some embodiments, the raceways may be used in a system of raceways with increasing average water depth for larger shrimp. Each raceway corresponds to a stage in shrimp production, i.e. raceway one corresponds to a first stage. Time spent in each raceway may depend on the production methodology used, the shrimp growth rate, and the desired final size. When possible, the overall process may be performed so that the amount of time spent in each raceway stage is equal. Although example depths for raceways are provided below, in general the depths of each raceway, including its average depth, may depend on the size of the shrimp it is intended to contain, with larger shrimp in raceways with greater depths. 
     Shrimp size as discussed in the current specification is typically measured in terms of average weight. One of ordinary skill in the art will understand that, for example, a stock of 2 g shrimp may contain shrimp having a variety of weights, but the average weight of all the shrimp in that stock would be approximately 2 g. 
     For example, postlarval shrimp between five and thirty days old maybe stocked into a first raceway. The postlarval shrimp may be maintained in the first raceway for three to eight weeks. Typically, the biomass of at the end of the first raceway period may be between 1 and 5 kg/m 2  bottom  30  surface area. The final shrimp individual size may be between 0.5 and 2.5 g. In one specific embodiment shown in  FIG. 3 , the shrimp may have a biomass of 1 to 5 kg/m 2  of bottom  30  surface area and an individual size of between 1.0 and 2.0 g. Time spent in raceway one may be approximately one to two months. 
     Shrimp may then be moved to raceway two and grown for three to eight weeks until the biomass is between 1 and 5 kg/m 2  of bottom  30  surface area. The final shrimp individual size may be between 6 and 11 g. In one specific embodiment shown in  FIG. 3 , the shrimp may have a biomass of 1 to 5 kg/m 2  of bottom  30  surface area and an individual size of between 7.5 and 9.5 g. Time spent in raceway one may be approximately one month. 
     Shrimp may then be moved to raceway three and grown for three to eight weeks until the biomass is between 1 and 5 kg/m 2  of bottom  30  surface area. The final shrimp individual size may be between 12 and 19 g. In one specific embodiment shown in  FIG. 3 , the shrimp may have a biomass of 1 to 5 kg/m 2  of bottom  30  surface area and an individual size of between 14 and 16 g. Time spent in raceway one may be approximately one to two months. At the end of the time spent in raceway three, in some embodiments the shrimp may be partially harvested and removed from the aquaculture process. 
     Shrimp may then be moved to raceway four and grown for three to eight weeks until the biomass is between 1 and 5 kg/m 2  of bottom  30  surface area. The final shrimp individual size may be between 17 and 25 g. In one specific embodiment show in  FIG. 3 , the shrimp may have a biomass of 1 to 5 kg/m 2  of bottom  30  surface area and an individual size of between 20.5 and 22.5 g. Time spent in raceway one may be approximately one to two months. At the end of the time spent in raceway four, in some embodiments the shrimp may be partially harvested and removed from the aquaculture process. 
     Shrimp may then be moved to raceway five and grown for three to eight weeks until the biomass is between 1 and 5 kg/m 2  of bottom  30  surface area. The final shrimp individual size may be between 23.5 and 33.5 g. In one specific embodiment show in  FIG. 3 , the shrimp may have a biomass of 1 to 5 kg/m 2  bottom  30  surface area and an individual size of between 27 and 29 g. Time spent in raceway one may be approximately one to two months. At the end of the time spent in raceway five, all of the shrimp may be harvested and removed from the aquaculture process. 
     In another embodiment, shrimp may enter the first raceway at a size where there are 40-41 shrimp per pound and leave at a size where they are 21-25 shrimp per pound. 
     When transferring shrimp between raceways, all of the shrimp may be transferred or only a partial transfer may occur. For instance, in the above example, all shrimp may be transferred when shrimp are moved from raceway one to raceway two and from raceway two to raceway three, but only portion of the shrimp may be transferred when moved from raceway three to raceway four and from raceway four to raceway five. All shrimp may again be removed when recovered from raceway five. Whenever partial transfers are made, in some embodiments shrimp to be transferred may be selected by size. 
     Raceways may be arranged as shown in  FIG. 3 , or they may be arranged in cyclical opposition to each other to allow synchronous growth. 
     According to a more particular embodiment, the raceways may have dimensions appropriate for the size shrimp they are intended to accommodate. One such example raceway is shown in  FIG. 2 . In  FIG. 2 , the first and second raceways may have a side wall depth  200  of 5 cm and an internal depth  210  of 8 cm at the shallow end and a side wall depth  220  of 9 cm and an internal depth  230  of 12 cm at the deep end. The average side wall depth may be between 3 cm and 14 cm. In this example raceways one and two are a combined raceway with an internal divider  170  ( FIG. 3 ) and the raceway one portion located at the shallow end. However, raceways one and two might also be separate raceways, with raceway one having dimensions similar to the shallow end and raceway two having dimensions similar to the deep end. The first and second raceways may, in some embodiments, be designed to hold shrimp between 1 mg and 2 g in size and may have an average depth of 5 cm. 
     The third raceway may have a side wall depth  240  of 8 cm and an internal depth  250  of 11 cm at the shallow end and a side wall depth  260  of 12 cm and an internal depth  270  of 15 cm at the deep end. The average side wall depth may be between 7 cm and 22 cm. This raceway in one example may hold shrimp between 1 g to 8 g in size and have an average depth of 9 cm. The fourth raceway may have a side wall depth  280  of 11 cm and an internal depth  290  of 14 cm at the shallow end and a side wall depth  300  of 15 cm and an internal depth  310  of 18 cm at the deep end. The average side wall depth may be between 11 cm and 30 cm. This raceway in one example may hold shrimp between 7 g to 20 g in size and have an average depth of 13 cm. The fifth raceway may have a side wall depth  320  of 14 cm and an internal depth  330  of 17 cm at the shallow end and a side wall depth  340  of 18 cm and an internal depth  350  of 21 cm at the deep end. The average side wall depth may be between 15 cm and 38 cm. This raceway in one example may hold shrimp between 15 g to 40 g in size and have an average depth of 17 cm. In this example of  FIG. 2 , the raceways are 2 m wide. 
     Raceways according to the current disclosure may be arranged in any manner suitable for the space in which they are located, but in particular embodiments they may be arranged to minimize use of floor or ground space. For example, the raceways may be stacked on top of one another. Stacking raceways may minimize required floor space and may also have other benefits, such as helping to prevent shrimp from jumping out of the raceways. In general, shrimp do not require light for growth, so raceways in some embodiments maybe placed in configurations without regard for light availability. Freeboards and other structures may be used to hold the raceways in place. In one example embodiment, the distance between stacked raceways may be between 80 cm and 110 cm. 
     In one example configuration, shown in  FIGS. 2 and 3 , sets of four raceways may be stacked on top of one another. Each of raceways may have a width of 2 meters and a length of meters. The raceways may be placed on top of one another, with a combined raceway one and two 100 at the top of the stack. Raceway three  110  may be next lowest, raceway four  120  may be below raceway three and raceway five  130  may be at the bottom of the stack. In the example shown, each raceway is 95 cm above the raceway below. Freeboard  140  may be used to help hold the raceways in place. In some embodiments freeboard  140  may be between 2 and cm tall, more particularly it may be 5 cm tall. Although  FIGS. 2 and 3  show stacks four troughs high, other numbers of troughs may be stacked. For example, trough stacks may be between two and ten troughs high. 
     Raceways of the present disclosure may be used with any type of water maintenance or circulation system. However, in a particular embodiment, raceways may be generally arranged so that the shallow end is the water intake end, i.e. where water enters or is added to the raceway, and the deep end is the water discharge end, i.e. where water exits the raceway. Particular systems that may be used with the raceways of the current disclosure include recirculating systems, reduced to zero water exchange systems, and flow-through systems. Although in many embodiments the same type of system may be used for each raceway/stage of the system of method, it is possible to use different water systems for different raceways or to use combinations of different systems, e.g. at different times, with each raceway. The amount of water used in each type of system varies. For example, a flow-through system may pump water from a natural source and thus use high volumes of water in total. One of ordinary skill in the art will understand that the water volumes cited throughout this specification may refer to total water used or to total water present in the raceways at a given point in time depending largely on the recirculation system in place. According to a particular embodiment, for any one raceway or the system overall, between 0 and 1000% of the total water volume of the raceway may be exchanged per day. 
     Water may be moved from one raceway to another in connection with and to facilitate transfer of shrimp from one raceway to the next. This method may be particularly useful when raceways are stacked and water can simply move from an upper raceway to a lower one by gravity. In one embodiment, raceways combining two or more stages, such as the combined raceway one and raceway two described above, may have removable partition or a partition containing a portal to allow flow of water from earlier stages to later stages. 
     In one embodiment, at least one raceway may contain a pump for water circulation. In another embodiment, at least one raceway may contain a pit, particularly a pit at one end, from which water may be drained. The pit may also be used for harvesting the shrimp. In some embodiments, water may be added to one end of a raceway and removed from the other end. In still another embodiment, at least one water circulation system may use intakes or outlets located along the raceway sides in addition to or in place of intakes or outlets at and end of the raceway. 
     In selected embodiments, water may flow through the raceways along their lengths. Water may also be circulated clockwise or counterclockwise within the raceways. In some systems, certain of the raceways may have flow or circulation or combinations of both and some may not. In one particular embodiment, bottom apex  40   b  may be higher than junctions  50  to provide uniform velocity of circular water circulation across the raceway. 
     Particular embodiments of the raceway system may also contain waste removal elements. For example, the raceways may contain pits at the end for waste collection. In some systems, waste removal elements may be included for some raceways and not others. 
     In certain embodiments of the disclosure, water quality in each trough may be maintained within set parameters. Example parameters are given in Table 1. While these example water quality parameters are expected to work well with the system of  FIGS. 2 and 3 , adjustments may be made for different systems. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Water Quality 
               
            
           
           
               
               
               
            
               
                 Optimum 
                 Typical 
                 Minimum 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                   26 ppt 
                   15 ppt 
                  0.5 ppt 
                 Salinity 
               
               
                 30 + 1 
                 30 + 1 
                 30 + 1 
                 Temperature ° C. 
               
               
                   &gt;4 ppm 
                   &gt;4 ppm 
                   &gt;4 ppm 
                 Dissolved Oxygen 
               
               
                 &lt;0.5 ppm 
                 &lt;0.5 ppm 
                 &lt;0.5 ppm 
                 TAN (total ammonia nitrogen) 
               
               
                 &lt;0.5 ppm 
                 &lt;0.4 ppm 
                 &lt;0.1 ppm 
                 NO 2   
               
               
                 &lt;5.0 ppm 
                 &lt;5.0 ppm 
                 &lt;4.0 ppm 
                 NO 3   
               
               
                 7.8-8.4 
                 7.8 to 8.4 
                 7.8 to 8.4 
                 pH 
               
               
                   
               
            
           
         
       
     
     Overall, salinity and other conditions may be adjusted to achieve various goals, such as economic viability, for the aquaculture system. For example, inland, where salt water is not readily available, it may be desirable to sacrifice shrimp growth rates or viability by using lower salinity due to costs of salt. Salt water or other water may be obtained directly from natural sources or from non-natural sources. Water from any source may be treated to improve its suitability for use in shrimp aquaculture. For example it may be filtered, such as biofiltered. In particular embodiments, salt water from any source with a salinity between 0.2 ppt and 45 ppt may be used. 
     Raceways of the current disclosure may also contain features to help prevent shrimp from jumping from the raceways or, particularly if located outside, to prevent other animals from accessing the shrimp. These features may be present on all raceways or a portion thereof, for example raceways with larger shrimp more able to jump out. One possible such feature is a cloth or plastic mesh barrier  150  on top of each raceway or between each raceway (if stacked) to inhibit shrimp from jumping out. Another possible such feature is a cloth or plastic mesh barrier  160  around all sides of the raceway to inhibit shrimp from jumping out. Some arrangements may use one or more different features. For example, in the stacked arrangement shown in  FIG. 3 , there may be a barrier  150  above combined raceways one and two a barrier  170  around all sides of the lower raceways. 
     Raceways of the current disclosure may be made of any suitable material or combinations of materials. For example, side walls  20  and sloped bottom  30  as well as end walls  10  of the raceway may be made of one or more of the following: fiberglass, cement, wood with plastic liners, and the like. Materials may be selected based on at least cost or size of the raceway. For example, more structurally sound materials may be used for larger raceways, even if more costly. 
     Using the systems and methods described herein, shrimp may be produced in an amount of 7 to 70 kg/m 3 /crop. Up to 18 crops per year may be grown with some systems. Survival rate (% of shrimp initially stocked that are later harvested) may be between 70% and 98%. Growth rates may be between 1.3 and 3.0 g/week. Feed conversion ratios may be as low as 1.0 to 1.6. Shrimp may grow as large at 18 to 35 g/shrimp, depending on the time of harvest. Each of these results may be achieved using an average water depth for all raceways of 30 cm or less, more particularly 20 cm or less. 
     In general trade-offs between various desirable features may be made as needed. For example, there is typically a trade-off between stocking density and growth rate. Stocking density may be decreased in many situations to achieve higher growth rate, which is typically more determinative the economic viability of aquaculture. Lower stocking density may also improve viability. 
     Although raceways may be stacked to obtain advantages in area required for shrimp farming, unstacked raceways may also benefit from the other raceway features described herein. For example, unstacked raceways may benefit from low average water depth and low water volume. 
     The shrimp aquaculture system and methods of the current disclosure may be used to produce shrimp for any purpose. However, four particular shrimp farming purposes to which the system and method are suited include: a) production of shrimp for human consumption, b) production of bait shrimp, c) nursery phase production for stocking pond production, and d) production of broodstock. The stage of growth and hence the raceway/stage at which shrimp are harvested may vary depending in the end use of the shrimp. For example, shrimp intended for stocking pond production may not need to reach the sizes described above in some examples for later raceways, such as raceways four and five. In particular embodiments, shrimp may be partially harvested at one or more growth stages. 
     The shrimp aquaculture system and methods may be used in any climate or geographic region. In particular embodiments, it may be used in a climate or geographic region in which the temperature is below 26° C. for more than one month of the year, or which is otherwise unsuitable for year-round shrimp aquaculture. The system and methods may be used under climate-controlled conditions in such locations. For example the system and methods may be used in an enclosed or partially enclosed structure such as a greenhouse or warehouse. In such uses, stacked raceways may be particularly beneficial as they may reduce the total infrastructure and climate control costs. 
     EXAMPLES 
     The present disclosure may be better understood through reference to the following examples. These examples are included to describe exemplary embodiments only and should not be interpreted to encompass the entire breadth of the invention. 
     Example 1 
     Effect of Depth on Growth and Survival of Juvenile  Litopenaeus vannamei  in 4′ Outside Tanks at 100 Shrimp/m 2    
     Sixty prototype tanks located outdoors were used to test the ability of shrimp to grow in low water depths such as may be found in embodiments of the current disclosure. Shrimp were variety PL 07-03. Other marine shrimp may also be used in embodiments of the current disclosure. For example,  L. vannamei  is only one of about 200 shrimp species. Although it accounts for approximately 60% of current commercial shrimp production, black tiger shrimp account for another 20-30% of commercial shrimp production and approximately eight other species account for the remaining 0.01-10% of commercial shrimp production. One of ordinary skill in the art, using the tests and results from these experiments with  L. vannamei  and other portions of the disclosure, may adapt the aquaculture systems and methods for use with other shrimp species, particularly the other commercial shrimp species. 
     Shrimp were grown for a total of eight weeks. No recirculation was used. Water was exchanged with filtered seawater from the Port Aransas Channel daily for 8 hours at a rate of 0.5 gallons per minute. This resulted in an exchange volume of 240 gallon/tank/day and 14,400 gallons/day for the sixty tank system. Water exchange amounts for tanks with different water depths are shown in Table 2. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Water exchange 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 Exchange 
                 Volume 
                 Percentage 
               
               
                   
                 Depth (cm) 
                 (gal/tank/day) 
                 (gal/tank) 
                 (%/day) 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 10 
                 240 
                 31 
                 774 
               
               
                   
                 20 
                 240 
                 62 
                 387 
               
               
                   
                 40 
                 240 
                 124 
                 194 
               
               
                   
                 60 
                 240 
                 185 
                 130 
               
               
                   
                 80 
                 240 
                 247 
                 97 
               
               
                   
                 100 
                 240 
                 309 
                 78 
               
               
                   
                 120 
                 240 
                 371 
                 65 
               
               
                   
                 140 
                 240 
                 433 
                 55 
               
               
                   
               
            
           
         
       
     
     Each culture tank has a radius of 0.61 m and a bottom area of 1.17 m 2 . The depths and volumes of each tank are listed in Table 3. 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Tank volumes 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Depth 
                   
                 Volume 
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 (cm) 
                 m 3   
                 L 
                 gal 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 10 
                 0.12 
                 117 
                 31 
               
               
                   
                 20 
                 0.23 
                 234 
                 62 
               
               
                   
                 40 
                 0.47 
                 468 
                 124 
               
               
                   
                 60 
                 0.70 
                 702 
                 185 
               
               
                   
                 80 
                 0.94 
                 936 
                 247 
               
               
                   
                 100 
                 1.17 
                 1170 
                 309 
               
               
                   
                 120 
                 1.40 
                 1404 
                 371 
               
               
                   
                 140 
                 1.64 
                 1638 
                 433 
               
               
                   
               
            
           
         
       
     
     Tanks were aerated using two 1.5″*1.5″*1.5″ air stones per tank. The location and number of air stones for each tank is provided in Table 4. 
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 Number and location of air stones 
               
            
           
           
               
               
               
               
               
            
               
                 Water 
                 40 cm above 
                 20 cm 
                 10 cm 
                 5 cm 
               
               
                 depth 
                 bottom in 
                 above 
                 above 
                 above 
               
               
                 (cm) 
                 3″ air lift 
                 bottom 
                 bottom 
                 bottom 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 10 
                 0 
                 0 
                 0 
                 2 
               
               
                 20 
                 0 
                 0 
                 2 
                 0 
               
               
                 40 
                 0 
                 2 
                 0 
                 0 
               
               
                 60 
                 0 
                 2 
                 0 
                 0 
               
               
                 80 
                 1 
                 1 
                 0 
                 0 
               
               
                 100 
                 1 
                 1 
                 0 
                 0 
               
               
                 120 
                 2 
                 0 
                 0 
                 0 
               
               
                 140 
                 2 
                 0 
                 0 
                 0 
               
               
                   
               
            
           
         
       
     
     Salinity was not regulated, but was between 25-40 ppt. Temperature was also not regulated but was between 26 and 32° C. Tanks were located outdoors in full sun. 
     Throughout the experiment shrimp were fed Rangen 45/10 commercial feed (Rangen, Inc., Angleton, Tex.). Shrimp were fed three times per day manually according to the schedule in Table 5. 
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 Feeding schedule, percentage of daily total 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Temperature 
                 8 AM 
                 11:50 AM 
                 4:30 PM 
               
               
                   
               
               
                   
                 25° C. and above 
                 33.3% 
                 33.3% 
                 33.3% 
               
               
                   
                 23-24° C. 
                 33.3% 
                   0% 
                   33% 
               
               
                   
                 below 23° C. 
                   0% 
                 33.3% 
                   0% 
               
               
                   
               
            
           
         
       
     
     Shrimp were fed at a rate of 2.0 g/shrimp/week or 0.29 g/shrimp/day. Specific details regarding feeding are in Table 6. Each column in Table 6 represents the test results of a different test sample. A total of four test samples were used to determine the effect of feed rate on production. 
     
       
         
           
               
             
               
                 TABLE 6 
               
               
                   
               
               
                 Feed rate in g 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 Feed/shrimp/week (g) 
                 1.5 
                 2.0 
                 2.5 
                 3.0 
               
               
                 Feed/shrimp/day (g) 
                 0.21 
                 0.29 
                 0.36 
                 0.43 
               
               
                 Feed/shrimp/feeding (g) 
                 0.071 
                 0.095 
                 0.119 
                 0.143 
               
               
                 Feed/100 shrimp/m2/feeding (g) 
                 8.36 
                 11.14 
                 13.93 
                 16.71 
               
               
                   
               
            
           
         
       
     
     Shrimp were fed 11.14 g/tank/feeding. The total amount of feed needed is shown in Table 7. Uneaten feed and dead shrimp were not removed. 
     
       
         
           
               
             
               
                 TABLE 7 
               
               
                   
               
               
                 Amount of feed needed for a maximum of eight weeks 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 Density (shrimp/m2) 
                 100 
               
               
                   
                 Shrimp/tank 
                 117 
               
               
                   
                 Feed/shrimp/week (g) 
                 2.5 
               
               
                   
                 Number of weeks 
                 8 
               
               
                   
                 Number of tanks 
                 60 
               
               
                   
                 Total feed needed for trial (kg) 
                 140 
               
               
                   
                 Total feed needed for trial (lb) 
                 309 
               
               
                   
               
            
           
         
       
     
     A total of 7020 shrimp were used in the experiments. Water depth in the experiment and stocking density as well as growth throughout the experiment are provided in Table 8. 
     
       
         
           
               
             
               
                 TABLE 8 
               
             
            
               
                   
               
               
                 Stocking density and growth 
               
            
           
           
               
               
               
            
               
                   
                 Density 
                   
               
            
           
           
               
               
               
               
            
               
                 Depth 
                 Shrimp 
                 Size (g) 
                 Final biomass (g) 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 (cm) 
                 /tank 
                 /m 2   
                 /m 3   
                 Initial 
                 Final 
                 /tank 
                 /m 2   
                 /m 3   
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 10 
                 117 
                 100 
                 1000 
                 6.0 
                 18.0 
                 2111 
                 1804 
                 18040 
               
               
                 20 
                 117 
                 100 
                 500 
                 6.0 
                 18.0 
                 2111 
                 1804 
                 9020 
               
               
                 40 
                 117 
                 100 
                 250 
                 6.0 
                 18.0 
                 2111 
                 1804 
                 4510 
               
               
                 60 
                 117 
                 100 
                 167 
                 6.0 
                 18.0 
                 2111 
                 1804 
                 3007 
               
               
                 80 
                 117 
                 100 
                 125 
                 6.0 
                 18.0 
                 2111 
                 1804 
                 2255 
               
               
                 100 
                 117 
                 100 
                 100 
                 6.0 
                 18.0 
                 2111 
                 1804 
                 1804 
               
               
                 120 
                 117 
                 100 
                 83 
                 6.0 
                 18.0 
                 2111 
                 1804 
                 1503 
               
               
                 140 
                 117 
                 100 
                 71 
                 6.0 
                 18.0 
                 2111 
                 1804 
                 1289 
               
               
                   
               
            
           
         
       
     
     The results in Table 8 show that the final amount of shrimp obtained per m 3  of water is much higher at lower tank depths. 
     Other results from the experiments described above or similar experiments were tabulated and presented in  FIGS. 4-10 . 
       FIG. 4  shows the effect of water depth on survival. Shrimp showed acceptable survival rates even in 10 cm water and at 20 cm survival rates were comparable to much greater water depths. 
       FIG. 5  shows the effect of water depth on final shrimp weights. Even at a water depth to 10 cm, final shrimp weights were comparable to that achieved with much greater water depths. 
       FIG. 6  shows the effect of water depth on shrimp weight gain. Weight gain was also similar at a depth of 10 cm to that achieved at much higher depths. 
       FIG. 7  shows the effect of water depth on shrimp growth rate. Growth rates at 10 cm were similar to higher water depths and actually better than growth rates at the highest tested water depths. 
       FIG. 8  shows the effect of water depth on biomass per m 2  of tank bottom. Water depths of 10 cm showed acceptable biomass levels and at water depths of 20 cm biomass levels were comparable to that achieved at higher water depths. 
       FIG. 9  shows the effect of water depth on biomass per m 3  of water used to grow the shrimp. Water depths of 10 cm and even 20 cm showed markedly higher biomass per m 3  of water than higher water depths. 
       FIG. 10  shows the effect of water depth on feed conversion rate (FCR). FCR is much higher at a water depth of 10 cm than even at 20 cm. 
     Example 2 
     Effect of Feed Rate and High Stocking Density on Growth and Survival of  L. vannamei  in an Outdoor Tank System with 20 cm Water Depth 
     Experimental Methods 
     PL 09-01 shrimp were used and fed Zeigler Feed (ZB ID: High Intensity Shrimp GER, 327293-33-86, SMP #ZBO9-121). Shrimp stocking density with estimated shrimp initial and final size, maximum biomass (g) and density (g/m 3 ) are provided in Table 9. 
     
       
         
           
               
             
               
                 TABLE 9 
               
             
            
               
                   
               
               
                 Stocking density with estimated shrimp size, maximum biomass, and 
               
               
                 density 
               
            
           
           
               
               
            
               
                 Density 
                 Estimated values (g) 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Shrimp/ 
                 Shrimp/ 
                 Shrimp/ 
                 Initial 
                 Max 
                 Max final 
                 Max density 
               
               
                 tank 
                 m 2   
                 m 3   
                 size 
                 size 
                 Biomass/tank 
                 (/m 3 ) 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 154 
                 132 
                 658 
                 6.0 
                 17.0 
                 2618 
                 11188 
               
               
                 260 
                 222 
                 1111 
                 6.0 
                 17.0 
                 4420 
                 18889 
               
               
                 375 
                 320 
                 1602 
                 6.0 
                 17.0 
                 6375 
                 27243 
               
               
                   
               
            
           
         
       
     
     The number of shrimp needed to obtain various densities is shown in Table 10. 
     
       
         
           
               
             
               
                 TABLE 10 
               
             
            
               
                   
               
               
                 Number of Shrimp 
               
            
           
           
               
               
               
            
               
                 /tank 
                 Number of tanks 
                 Total/density 
               
               
                   
               
            
           
           
               
               
               
            
               
                 154 
                 20 
                 3080 
               
               
                 260 
                 20 
                 5200 
               
               
                 375 
                 20 
                 7500 
               
            
           
           
               
               
               
            
               
                   
                 Total number 
                 15780 
               
               
                   
               
            
           
         
       
     
     No recirculation was used. Water was filtered seawater from the Port Aransas Channel. Water was exchanged on a 24 hour basis using a booster pump. Water exchange parameters for days 1-35 are shown in Table 11. Water exchange parameters for day 36 were changed due to higher mortality and on are show in Table 12. 
     
       
         
           
               
             
               
                 TABLE 11 
               
             
            
               
                   
               
               
                 Water Exchange Parameters Days 1-35 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                   
                   
                 Tank 
                   
                   
                   
               
               
                 Flow 
                 Flow/tk 
                 Flow/20 tk 
                 vol 
                 Ex/tk 
                 shrimp 
                 Ex/shrimp 
               
               
                 GPM 
                 (Ga/day) 
                 (Ga/day) 
                 (Ga) 
                 (%/day) 
                 #/tk 
                 (%/shrimp/d) 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 0.15 
                 216 
                 4320 
                 62 
                 348.4 
                 154 
                 2.26 
               
               
                 0.25 
                 360 
                 7200 
                 62 
                 580.6 
                 260 
                 2.23 
               
               
                 0.5 
                 720 
                 14400 
                 62 
                 1161.3 
                 375 
                 3.10 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 12 
               
             
            
               
                   
               
               
                 Water Exchange Parameters Days 36+ 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                   
                   
                 Tank 
                   
                   
                   
               
               
                 Flow 
                 Flow/tk 
                 Flow/20 tk 
                 vol 
                 Ex/tk 
                 shrimp 
                 Ex/shrimp 
               
               
                 GPM 
                 (Ga/day) 
                 (Ga/day) 
                 (Ga) 
                 (%/day) 
                 #/tk 
                 (%/shrimp/d) 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 0.25 
                 216 
                 7200 
                 62 
                 580.6 
                 154 
                 3.77 
               
               
                 0.50 
                 720 
                 14400 
                 62 
                 1161.3 
                 260 
                 4.47 
               
               
                 0.50 
                 720 
                 14400 
                 62 
                 1161.3 
                 375 
                 3.10 
               
               
                   
               
               
                 Ga = gallons 
               
            
           
         
       
     
     An O 1-2 culture system was used. Culture tanks had a radius of 0.61 m, a bottom area of 1.17 m 2 , a depth of 0.20 m, and a volume of 230 L. Tanks were aerated using two 1.5 inch×1.5 inch×1.5 inch air stones per tank with the stones located 5 cm above the bottom of the tank. Salinity was not regulated, but was expected to be between 25-40 ppt. The temperature was not regulated. Tanks were located outside in the full sun. 
     Shrimp were fed manually three times per day according to the schedule in Table 13. 
     
       
         
           
               
             
               
                 TABLE 13 
               
             
            
               
                   
               
               
                 Feeding Schedule: Percentage of Daily Total 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Temperature (° C.) 
                 8:30 AM 
                 01:00 PM 
                 4:30 PM 
               
               
                   
               
               
                   
                 25 and above 
                 33% 
                 33% 
                 33% 
               
               
                   
                 23-24 
                 33% 
                 0% 
                 33% 
               
               
                   
                 20-22 
                 0% 
                 33% 
                 0% 
               
               
                   
                 below 20 
                 0% 
                 0% 
                 0% 
               
               
                   
               
            
           
         
       
     
     Shrimp were assumed to grow at a rate of 1.2 g/week on average and thus were fed at the rate indicated in Table 14. 
     
       
         
           
               
             
               
                 TABLE 14 
               
             
            
               
                   
               
               
                 Shrimp Feed Rate Per Week 
               
            
           
           
               
               
            
               
                   
                 Feed Rate (g/shrimp) 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 Feed/shrimp/10 weeks 
                 10 
                 15 
                 20 
                 25 
               
               
                 Feed/shrimp/week 
                 1.0 
                 1.5 
                 2.0 
                 2.5 
               
               
                 Feed/shrimp/day 
                 0.14 
                 0.21 
                 0.29 
                 0.36 
               
               
                 Feed/shrimp/feeding 
                 0.048 
                 0.071 
                 0.095 
                 0.119 
               
               
                 Feed/154shrimp//feeding 
                 9 
                 13 
                 18 
                 22 
               
               
                 Feed/260shrimp/feeding 
                 15 
                 22 
                 30 
                 37 
               
               
                 Feed/375 shrimp/feeding 
                 22 
                 32 
                 43 
                 54 
               
               
                   
               
            
           
         
       
     
     Dead shrimp and uneaten feed were removed. Dead shrimp were replaced for the first two days. Tanks with excessive molts were scooped beginning at day 22 to avoid clogging water systems. 
     Water temperature, DO and salinity were monitored daily and daily maximum and minimum temperature was logged. Ammonia (total ammonia nitrogen, TAN), nitrite, nitrate and pH were monitored weekly. An algae count was performed bi-weekly. 
     Growth and survival data was analyzed with stocking density and feed rate (FR) as independent variables. The system was a blocking factor. Dependent variables included survival, final weight, weight gain per shrimp per tank, growth (g/week), biomass (g/m 3 ), and feed conversion (FCR). Two way-ANOVA transformations were performed as follows: 
     
       
         
           
               
               
               
             
               
                   
               
               
                   
                 Variable 
                 Transformation 
               
               
                   
               
             
            
               
                   
                 Final Weight 
                 log of Final Weight 
               
               
                   
                 Weight Gain 
                 log of Weight Gain 
               
               
                   
                 Survival 
                 Arcsine of Survival 
               
               
                   
               
            
           
         
       
     
     Hydrological and Water Quality 
     During Example 2, temperature (as recorded by min/max thermometer) ranged from 22.0 to 36.9° C., and salinity from 21.6 to 38.8 ppt. Table 15 summarizes the mean values of tank morning DOs and temperatures, and weekly water quality parameters. 
     
       
         
           
               
             
               
                 TABLE 15 
               
             
            
               
                   
               
               
                 Water Quality and Hydrological Parameters 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 DO, AM 
                 Temp, AM 
                   
                 TAN 
                 Nitrite 
                 Nitrate 
               
            
           
           
               
               
               
               
               
            
               
                   
                 (mg/L) 
                 ° C. 
                 pH 
                 (mg/L) 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Mean 
                 4.9 
                 27.7 
                   
                 0.822 
                 0.01 
                 0.034 
               
               
                 Min 
                 1.2 
                 25.8 
                 7.29 
                 0.106 
                 0.003 
                 0.005 
               
               
                 Max 
                 6.7 
                 30.8 
                 7.97 
                 3.74 
                 0.61 
                 0.092 
               
               
                   
               
            
           
         
       
     
     Average total ammonia nitrogen (TAN) values for treatments ranged from 0.39 to 1.86 ppm, nitrite from 0.006 to 0.011 ppm, and nitrate from 0.025 to 0.052 ppm. Results of a two-way ANOVA indicated that the differences in TAN values due to density and feed rate were significant. However, differences in TAN values due to interaction of density and feed rate were not significant. With 2.11 ppm, the TAN value is significantly higher at density 1602 m 3  than the lower densities (0.54 and 0.66 ppm for 658 and 1111/m 3  respectively). Difference in mean TAN levels between densities of 658/m 3  and 111/m 3  was not significant. Also, significantly high levels of TAN were observed at feed rate 2.5 g/shrimp/wk (1.14 ppm). However, differences in TAN levels below feed rate of 2.5 g/shrimp/wk were not significant. The differences in nitrite and nitrate levels due to density, feed rate, and interaction of density and feed rate were not significant. Mean values of nitrite remained below critical limit (range: 0.005 and 0.061 ppm). Nitrate levels ranged from 0.01 and 0.087 ppm in the trial. Levels of daily tank pH ranged from 7.29 to 7.97. High levels of TAN at density 1602/m 3  and at feed rate 2.5 g/shrimp/wk may have affected growth and survival. The observed levels of nitrite and nitrate did not appear to have appreciable impact on growth and survival under the conditions of Example 2.  FIGS. 11 through 18  illustrate the survival, final weight, growth, biomass, and feed conversion (FCR) values from the growth trial. At the end of the 52 day trial, shrimp survival ranged from 57.5% (1602/m 3  and at 1.5 g/shrimp/wk feed rate) to 99.1% (658/m 3  and 2.0 g/shrimp/wk feed rate) with final weights from 14.1 g (658/m 3 , and 1.0 g/shrimp/wk feed rate) to 24.4 g (658/m 3 , 2.5 g/shrimp/wk feed rate). Average weekly growth remained between 0.85 g (1111/m 3 , 1.0 FR) and 2.42 g (658/m 3  and 2.5 FR). 
     Survival 
     Results of two-way ANOVA indicated that the differences in shrimp survival due to density, feed rate, and interaction of density and feed rate were all significant. Results are shown in  FIGS. 11 and 12 . Results from one-way ANOVA for density indicated that, at density 658/m 3 , survival was significantly low at feed rate of 1.0 (95.2%) compared to survivals at feed rates above 1.0 (97.8%, 99.1%, and 99.9% for feed rates 1.5, 2.0, and 2.5 respectively). Differences in survivals above feed rate of 1.0 were not significant. While at density 1111/m 3 , survival (72.5%) was significantly low at feed rate 1.5 compared to the rest of the feed rates, survival was significantly high at feed rate above 1.5 at density 658/m 3 . However, survivals within two lower and two higher feed rates did not differ significantly. For feed rate, results of one-way ANOVA indicated that, at feed rate 1.0, difference in survivals in two lower densities were not significant. Also, lowest survival of 64.7% was observed at highest density of 1602/m3. At feed rate 1.5, significant decrease in survival was observed with density. At feed rate 2.0, lowest survival (85.7%) was at 1111/m 3 . Differences in survivals between densities 658/m 3 , and 1602/m 3  were not significant. At feed rate 2.5, differences in survivals were not significant between any density treatments. 
     Survivals at the lowest density ranged from 95.2% to 99.9%, lowest survival being at feed rate 1.0. Considering the water depth to be only 20 cm, survivals from this lowest density are surprisingly high. Survival for density 1111/m 3  ranged from 72.5% to 94.0%, lowest survival being at feed rate 1.5. Low survival at feed rate 1.5 could not be explained under the conditions of trial. Survival at the highest density ranged from 57.5% to 96.9% for stocking density 1602/m 3 . Although survivals at two low feed rates were lower (57.5% and 64.7%) compared to high feed rates (96.3% and 96.9% for 2.0 and 2.5), it is not believed that feed rate would contribute to difference in survival. 
     Higher survival above feed rate of 1.5 indicates that higher feed rates did not affect survival between different densities. Low survival values can be correlated to higher levels of ammonia, and high stocking density. In this trial, feed was not adjusted for mortality. Thus, the uneaten feed might be responsible for water quality conditions not suitable for optimal growth and survival. 
     Final Weight 
     Results of a two-way ANOVA indicated that the differences in final weights due to stocking density, feed rate, and interaction of density and feed rate were all significant. Results are presented in  FIG. 13 . Results of one-way ANOVA (for density) indicated that, final weights increased with feed rate for densities 658/m3, and 1111/m 3 . At highest density of 1602/m 3 , significantly higher final weight (18.5 g) was observed at feed rate 1.5. Differences in final weights for rest of the feed rates were not significant. One-way ANOVA (for feed rate) indicated that, final weights were highest for densities 658/m 3  and 1602/m 3  (14.1 g vs. 14.9 g) without any significant difference between them compared to 12.7 g for density 1111/m 3 . At feed rate 1.5, differences due to stocking density were not significant. At feed rate of 2.0 and 2.5, finals weights decreased with increasing density with differences being significant between them. 
     Growth 
     Results of a two-way ANOVA indicated that the differences in weekly growth due to stocking density, feed rate, and interaction due to density and feed rate were significant. Results are shown in  FIGS. 14 and 15 . One-way ANOVA for density indicated that weekly growth increased with feed rate at densities 658/m 3  (range: 1.03 to 2.42 g/wk) and 1111/m 3  (range: 0.85 to 1.92 g/wk). At 1602/m3, lowest growth was observed at feed rate 1.0. Growth at feed rates 1.5 was significantly higher (1.62 g/wk) than growth at all feed rates, probably due to low survival (57%) in this treatment. Growth at feed rate 2.5 (1.32 g/wk) was at par with growth at feed rate 1.0 and 2.0. (1.14 and 1.39 g/wk). One-way ANOVA for feed rate indicated that, growth at feed rate 1.0 was significantly lower (0.85 g/wk) at density 1111/m 3 . Differences in growth between densities 658/m 3  and 1602/m 3  (1.03 vs. 1.14 g/wk) were not significant. Differences in growth between densities at feed rate 1.5 were not significant. Growth significantly increased with decreasing density at feed rates 2.0 and 2.5. 
     It is clear from the results that stocking density affected shrimp growth. Lowest density indicated higher growth. Also, growth appears to be directly proportional to feed rate at 658/m 3  and 1111/m 3 . Feed rate of 2.5 stocked at 658/m 3  and 111/m 3  resulted in highest growth rate of 2.4 and 1.91 g/wk respectively under the conditions of experiment. Thus, at density of 658/m 3 , feed rate could likely be increased above 2.5. Although, a similar trend in growth values is indicated with density 1111/m 3 , growth at each feed rate is lower (range 0.85 to 1.90) than those observed at density 658/m 3  (range 1.03 to 2.41) indicating a possibility of limiting feed rate at density 1111/m 3  as well. Density effect was more appreciable in case of 1602/m 3 , wherein growth at all feed rates were at the same level (1.14 to 1.39 g/wk) except for feed rate of 1.5 (1.62 g/wk). 
     Biomass 
     Results of two-way ANOVA indicated that the differences in biomass due to stocking density, feed rate, and their interactions were all significant (P&lt;0.05). Results showing effects of stocking density are shown in  FIG. 16 . At density 658/m 3 , differences in biomass due to feed rate were significant (P&lt;0.5). Biomass increased with feed rate. The lowest and highest biomass of 8851 g/m 3  and 15906 g/m 3  at feed rates of 1.0 and 2.5 g/shrimp/wk respectively indicated a possibility of limiting feed rate at 2.5 g/shrimp/wk. At density 1111/m 3 , difference in biomass at two lower feed rates (12947 and 14675 g/m 3 ) was not significant. However, feed rate of 2.0 indicated a significantly lower biomass (18625 g/m 3 ) due to low growth rate compared to a feed rate of 2.5 (21535 g/m 3 ). Higher biomass at feed rate 2.5 g/shrimp/wk may indicate a possibility of limiting feed rate at density 1111/m 3 . At density 1602/m 3 , biomass at two lower feed rates were significantly lower (15445 g and 16982 g/m 3 ) than the biomass at higher feed rates (25549 g and 25092 g/m 3 ), mostly due to high mortality and water quality issues from uneaten feed. The highest biomass was 25549 g/m 3  at feed rate 2.0 g/shrimp/wk. This high level of biomass under the conditions of the trial has not been reported elsewhere to the best of our knowledge. Due to high mortality at low feed rates, feed rate effect at density of 1602/m 3  is not quite clear under the conditions of the trial. Biomass increase due to stocking density is obvious due to higher number of stocks at higher density. 
     Feed Conversion 
     Results of two-way ANOVA indicated that differences in feed conversions due to stocking density, feed rate, and interaction of density and feed rate were all significant. Results are shown in  FIGS. 17 and 18 . One-way ANOVA for density indicated that, at density 658/m 3 , FCR was significantly lower (1.17) at feed rate 2.0. There were no significant differences in FCR values between rest of the feed rates (FCR range 1.26 and 1.29). Differences in FCR values between feed rates were not significant for densities 1111/m 3  (FCR range: 1.73 to 2.00) and 1602/m 3  (FCR range: 1.89 to 3.59). Results of one-way ANOVA for feed rate indicated that FCR values for feed rate of 1.0 were significantly lower for two low densities (1.27 and 1.75 for densities 658/m 3  and 1111/m 3  respectively) compared to high density (3.59 for 1602/m 3 ). FCR increased with density at feed rate 1.5. At feed rate 2.0 significantly low FCR (1.72) was observed at density 658/m 3 . Differences in FCR values for two high densities were not significant (1.82 and 1.89). FCR increased with density at feed rate 2.5. Feed conversions ranging from 1.17 to 1.29 at the lowest density indicate higher feed consumption resulting in higher growth. Feed conversions were in general towards higher side at two higher densities compared to the low density. High feed conversions at density 1602/m 3  resulted from high mortality and thus excess feed remained unutilized. 
     High levels of production from this Example 2 resulted from feed and other tank management practices. Low water depth coupled with high water exchange may we significant. Due to low water depth, visual observation of tank bottom became increasingly easy compared to traditional tanks or ponds operating at high water depths. Dead shrimp, if any, were removed without significant delay. By doing so, tank water could be kept from fouling due to mortality. This lack of fouling was also aided by high water exchange. Uneaten feed were observed only in tanks with high mortality. In general, high water exchange was beneficial in flushing the tank bottom, and offsetting poor water quality conditions resulting from uneaten leftover feed. 
     Overall, Example 2 shows that the following results can be obtained with water depth as low as 20 cm: 
     Shrimp survival of 99.9% with over 24 g final weight, and 2.42 g/wk growth, with over 15 kg/m 3  biomass with FCR 1.26 can be achieved at density 658/m 3 . 
     Shrimp survival of 94% with over 20 g final weight, and 1.91 g/wk growth, with 21 kg/m 3  biomass with FCR 1.73 can be achieved at density of 1111/m 3 . 
     Shrimp survival of 95%, over 16 g final weight, and 1.39 g/wk growth, with 25 kg/m 3  biomass with FCR 1.9 can be achieved at density 1602/m 3 . 
     Growth rate of 1.91 g/wk with survival of 94% at a feed rate of 2.5 g/shrimp/wk at density of 1111/m 3  with a production of 21 kg/m 3 . 
     Growth rate of 1.39 g/wk with survival of 95% at a feed rate of 2.5 g/shrimp/wk at density of 1602/m 3  with a production of 25 Kg/m 3 . 
     A feed rate of 1.5 g/shrimp/wk may be adequate for density 1602/m 3  without affecting growth. 
     Although only exemplary embodiments of the invention are specifically described above, it will be appreciated that modifications and variations of these examples are possible without departing from the spirit and intended scope of the invention. For example, one of ordinary skill in the art will appreciate that measurements, particularly of raceway dimensions, shrimp weight and time are approximate and may be varied to some degree without departing from the spirit and scope of the invention. One of ordinary skill in the art will also appreciate that in most instances, the weight of the water contained accounts for most of the raceway weight. Accordingly, it may be possible to stack raceways having walls higher than described herein, but in which water depth is nevertheless around the recited wall heights.