SIRSFT is based on an integrated approach to shrimp production:
Super Intensive Raceway Shrimp Farming Technology (SIRSFT) is comprised of modular sub-components, that are compartmentalized by function for fabrication and application. Design is important because everything must operate seamlessly when sub-assemblies are integrated.
Desiring to meet the pressure of driving higher rates of production per unit area along with minimizing costs, all sub-components are designed to be modularized for rapid onsite assembly. In addition, all sub-components are fabricated in standardized Hi-Cube 53 ft intermodal containers. These structures are made of steel and are structurally rigid allowing for vertical stacking.
RAS (Recirculating Aquaculture System)
Being heterotherms, Litopenaeus vannamei (Pacific white-leg shrimp) have to be maintained at sustainable temperatures to maximize life functions. For practical purposes this means under controlled conditions the environmental temperature must be maintained at 26-33oC, with 32oC being ideal. All water is prepared from sea salt and processed using equipment as illustrated in figure to the left. The water quality is maintained with respect to salinity, solid waste removal, dissolved oxygen control, ammonia-nitrogen control, carbon dioxide control and pH.
Shrimp will consume feed 24/7, thus a system to accomplish this is important to maximize shrimp production. There are several problems associated with traditional sinking shrimp feed in a system of this nature. For example, feed spread across the water surface or by injection at a single point is rapidly hydrated on contact. The water quickly leaches away nutrients and/or chemotractants. Thus, not only is the non-floating shrimp feed less nutritious, over time the shrimp cannot even detect it and it becomes nutritive source for bacteria resulting elevated ammonia production. It is also difficult to judge whether the shrimp have eaten all of such feed because it cannot be seen through the water. As a result, shrimp may easily be fed too much feed, leading to waste and water pollution, or too little feed, resulting in less rapid growth. Non-optimal feeding may also occur because non-floating shrimp feed must be spread over the surface of the water by the feeding system; otherwise it will simply sink in one area and not provide feed to shrimp disbursed in many parts of the production unit. This makes it difficult to use mechanical feeding systems that disperse the feed. The inability to use mechanical systems renders it difficult to feed shrimp whenever more feed is needed, regardless of the time of day.
Overall, new systems and methods of providing feed for growing shrimp in production units was necessary to address one or more of the above problems as well as other difficulties associated with non-floating shrimp feed. In particular, consideration of the labor required to provide feed for shrimp in a large number of stacked production units became a serious limitation. In addition, there was no way to distribute feed over the length of a raceway. Thus, serious wastage of feed would occur. A floating feed could eliminate a lot of the problems. Most importantly feed could be added at a single point and consumption could be readily monitored visually as to how much remained floating over time. This allowed for regulation of the feed rate and maintenance of of a state of shrimp satiation to maximize growth.
Floating feed is readily consumed by shrimp without negative effects on growth. The technology for preparation of a floating feed using extrusion cooking processes is well developed (see General Discussion of Current Topics as they Relate to Aquatic Feed Production and Use of Extrusion Cooking). Floating feed is used exclusively with the SIRSFT system. Feed is disbursed by each raceway from one of four hoppers using a computer controlled distribution system designed for this purpose. The reason for four hoppers relates to the different shrimp sizes in the upper vs bottom section of a stack. Specifically, feed pellets for a 1 g shrimp must be much smaller than that for a 25 g shrimp.
The required number of PLs to meet production levels when using integrated shrimp super intensive multi-phasic production technology (SIMPT) is high. Therefore, the first part of the multi-phasic production cycle is carried out separately in a nursery. Shrimp post-larvae (PLs) are stocked into shallow water tanks stacked vertically at a density of 4000-8000/m2, in a self-contained structure, containing salt water aerated and maintained at 31-33oC. Ammonia is toxic to shrimp, to control this a biofloc is established. Specifically, for the first four to eight days an autotrophic bacterial population is used to convert ammonia to nitrite and then nitrate. After this period heterotrophic bacteria are added to establish a biofloc. Ammonia is utilized thereafter by the bacteria.
GOPA (Grow-Out Production Assembly)
Growing shrimp in decreased water depths is fundamental to the ability to go vertical for the production of shrimp, i.e., it allows for increased output per m2 of floor footprint and facilitates shrimp farming in warehouses.
Shown in the figure below is a basic production sub-unit (PSU). There is an end cap labeled harvest pit in the figure shown below and a linear section along which water is circulated in a counter clockwise direction. The harvest pit facilitates sedimentation of waste due to slowed water circulation. The harvest pit also facilitates shrimp harvest.
Two vertically stacked inter-modal containers form one shrimp grow out production assembly (GOPA). PSUs are fabricated in the GOPA. Per the functional use of the GOPA, the configuration in the upper and lower containers that constitute the GOPA are different as can be seen in the figure shown to the left.
PSUs #1, #2A, #2B and #3A are assembled in the upper container. PSUs #3B, #4A and #4B are assembled in the lower container. Operationally, each GOPA in effect is comprised of seven vertically arranged PSUs.
Operating from a conservative perspective, one of many possible shrimp production models based on a biomass of 3 kg/m2 is presented in the table below. In this model, four phases are employed. In practice Phase 1 is executed by stocking PLs into a nursery where they are raised to a juvenile stage (0.7-1g) for ~1 month. Phase 2 is executed by transferring the juvenile shrimp to PSU #1A of the GOPA. After approximately one month the biomass will begin to exceed the carrying capacity of the system. Therefore, the shrimp density must be reduced. This is accomplished by sub-dividing the shrimp evenly between production PSUs #2A and #2B, thereby initiating Phase 3. Transfer is accomplished by gravity, this entails connecting a tube between production PSU #1 and #2A or #2B. Shrimp suspended in water move from the superior PSU, to the inferior PSUs. Integral to establishing a synchronous production cycle, as soon as #1 is emptied, it is restocked with juvenile shrimp transferred from the nursery in order to initaiate the next cycle.
After ~4 additional weeks, the carrying capacity of #2A and #2B will have been exceeded. The shrimp biomass of PSUs #2A and #2B are then evenly divided between PSUs #3A, #3b, #3C and #3D thereby initiating Phase 4. After approximately four additional weeks the shrimp will have reached an average size of around 26g, a desirable market size. The shrimp can then be harvested and offered for sale. Production is synchronous and using this model, Phase 4 shrimp can be harvested thirteen times per yr, yielding a total of 5776 kg per GOPA.
“The ability to stock shrimp at high density and maintain the biomass at ~3kg/m2, drives the dramatic production yield engendered by the application of SIRSFT. “It is also the reason that such systems can be commercialized and be highly profitable.”