Abstract:
A scalable fish rearing raceway system is provided, incorporating a fish containment structure having two semi-circular end sections, and two or more parallel fish raceways, surrounding a central zone for housing water treatment systems and a secondary fish crop. Heavy particulates are eliminated from the main fish rearing channels by use of conical areas located at either end of the parallel elongated raceways. Continuous removal of dead or dying fish from the raceway is accomplished by means of a floating mortality catcher consisting of a screened ramp at the surface of the cones which continuously collect moribund and dead fish. Grading bars separate and move fish underwater to an adjacent raceway through a common fish transfer channel. This larger scalable fish production system substantially reduces the direct labor and capital costs associated with the production of fish as compared with conventional circular fish rearing tanks.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a scalable fish rearing raceway system and method of making same. More particularly, the present invention relates to a new and improved scalable fish rearing raceway system including a greatly increased fish culture zone, unique fish harvesting/grading channel component, and integrated monitoring and feeding means which greatly reduces direct labor associated with all aspects of the fish rearing process. 
   2. Description of the Related Art 
   As health conscious Americans begin to consume more fish products and the naturally occurring sources of fish become depleted, there is a growing need to fill the demand for fish products by turning to aquaculture. Aquaculture is defined as the production and husbandry of aquatic plants and animals in controlled environments. The term husbandry means the application of scientific principles to farming. Controlled environments are directed or regulated production environments ranging from a low level of control, termed “extensive,” where limited capital and management are applied, to a high level of control, termed “intensive,” where more comprehensive capital and management are applied to production. 
   Aquaculture has become a one billion dollar industry in the U.S. Nearly 30% of our edible seafood supplies are currently supplied by aquaculture. Growing at a rate of 20% per year, aquaculture is the fastest growing sector of the agriculture industry. Aquaculture is an ecologically efficient means of providing seafood for American consumers while significantly reducing pressure on our limited wild fisheries resources. 
   Foreign competition is having a major impact on U.S. aquaculture operations. More than 60% of our seafood supplies are now imported, resulting in a large annual trade deficit ($6.9 billion). A growing fraction of aquaculture imports comes from the warm climates of South America and Asia. These countries have the advantage of lower production costs by using abundant quantities of warm water that are available in the tropics. Often there are few or no environmental laws controlling their discharges which result in environmental degradation and little or no overhead costs associated with complying with environmental laws. Imports of fish grown in Chili, Costa Rica, Ecuador, Taiwan, China, Vietnam and Indonesia have increased markedly as the foreign competition adopts new culture technologies, often developed here in the U.S. These competing products are produced with low energy, water, labor, and environmental costs. As a result, many U.S. aquaculture products are not competitive with foreign aquaculture products. 
   Efficient, economical and productive aquaculture in the United States would meet the growing demands of fish in the American diet, would remove a huge burden on our natural wildlife resources and would also reduce our dependence on imports. 
   Previously, open ponds were developed for use in aquaculture. These earthen ponds were scalable and required relatively small initial capital expenditures to construct, but required large land masses, were inefficient because of the ratio of square footage and consumptive gallons of water required per unit produced. Additionally the growing conditions and water quality in these ponds was difficult to monitor and control, harvesting was hit or miss, diseases were common and solid waste products and particulates were difficult to remove. Today, fresh water is becoming a rare commodity and there is an increasing need for more efficient usage of both land and water resources. 
   The current cutting edge technology for aquaculture in the United States employ round tanks that are provided with extensive pipe systems to provide fresh water and oxygen. Each of these tanks is equipped with fish feeders, control and monitoring equipment to continuously check water quality, water flow, dissolved gas content of the water and other parameters that would affect fish growth. 
   These tanks require a high level of maintenance which includes frequent manual removal of dead fish to minimize the incidence of disease within the confines of the tank. Upon death, fish will first sink to the bottom of the tank, then within the first 24 hours, plus or minus 2 to 4 hours depending upon water temperature and decomposition rates, will float to the surface. Thereafter, the carcass will continue to float on the surface waters of the tank where it will continue to decompose and serve as an incubator for disease causing organisms. The process of decay also produces by-products such as nitrogen compounds which adversely affect the water quality within the tank. This necessitates continuous monitoring and immediate removal of dead and dying fish. 
   Additionally, the size of the fish held within the tank must be kept relatively uniform to reduce the incidence of cannibalism in the fish population. The fish sorting required to maintain the sizing restrictions often requires mechanical or physical handling and relocation of the fish resulting in stress and trauma which can adversely affect the mortality, overall health and growth rate of the fish. 
   The harvesting of fish from such facilities is usually accomplished in much the same manner as harvesting of fish has occurred for centuries, use of nets for physical removal from the tank. This method is often less than efficient and may result in additional stress and physical damage to the fish during harvesting. 
   The round shape of these tanks provides an uneven current speed within the tank. Water on the outer perimeter of the tank is propelled at a higher rate of speed than the water in the center of the tank. Each species of fish prefers a particular rate of speed of water resulting in a sizeable percentage of the tank having a flow rate that will not be suitable for optimal fish habitat. If the water flow is slowed to provide for optimal fish habitat in the outer perimeter of the tank, the particulates in the water may settle to the bottom of the tank where removal of such particulate matter would require additional mechanical means of removal. 
   The current technology is very expensive to build and maintain, and becomes even more labor intensive and costly as the number of tank units increase. Round tanks are not readily scalable to larger systems because of the inherent problems in flow rate differentials and water mixing (as discussed below). This limits the diameter-to-depth ratio of round tanks to about 10:1. Since water depths are typically 5 feet or less for practical considerations (fish management, personnel safety, and construction cost), the effective maximum diameter of round tanks is about 50 feet. This has become a significant problem in constructing economically efficient large fish farms. The extreme number of round tanks required for large-scale fish production is counter-productive as they result in increased operational costs and no construction savings, on a cost-per-pound of fish produced basis. As effective as round tanks can be for small niche aquatic businesses or research systems, they do not offer the economy-of-scale opportunities necessary in the competitive environment of large-scale commercial aquaculture. 
   The concept of, and methods for aquacultural fish raising are well known and documented. Examples of different types of devices, methods and systems, water treatment units and techniques that might be suitable for aquaculture are disclosed in U.S. Pat. Nos. 6,382,134 B1, 6,192,833, 5,961,831, 4,915,059, 4,913,093, 4,516,528 and 4,300,477. 
   Fish rearing systems utilizing recycled water as a means of maintaining an aquaculture system have been explored. U.S. Pat. No. 6,382,134 B1 describes such a system. The system incorporates traps and screens for removal of particulate matter, denitrification devices, a disinfection device and ammonia treating devices. The system also incorporates an aeration device (for addition of oxygen and removal of carbon dioxide) and a means of monitoring water quality. 
   While this novel invention provides for means of removal of many of the gross particulates from the water by means of a trapping section at the bottom of the tank, it does not address the major problem of removal of dead and dying fish on a continuing basis. As previously mentioned, the dead or dying fish will sink to the bottom for the first 24 hour period after death, before floating to the top where they might be removed by mechanical means (with sunken dead fish potentially removed by the trapping section at the bottom of the tank). The presence of dead or dying fish represents a major potential source of disease which could affect the fish population in an entire system. Disinfection of a small portion of the water without prompt removal of the source of infection would not prevent the spread of the infection throughout the fish population due to physical contact with the decaying matter. 
   Prompt and continuous removal of dead and dying fish appears to offer the best preventative measure against widespread contamination and spreading of disease throughout a contained fish population. Therefore it would be highly desirable to have a new and improved scalable fish rearing raceway system and method of making same which would provide for continuous removal of dead fish from the raceway. The continuous mechanical removal of dead and dying fish significantly reduces labor costs associated with the frequent human monitoring and manual removal of such fish and reduces the transmittal of infectious diseases by the immediate removal of the dead and dying fish. 
   An aquaculture system which teaches a process or system for raising aquatic organisms is disclosed in U.S. Pat. No. 6,192,833. Therein, a system is provided that incorporates a raceway for producing and maintaining the organism and an algal growth channel with monitors and paddlewheel for flow control. 
   This system does not provide for means of particulate removal or removal of dead or dying fish. There is no means of providing for sizing of fish and, additionally, there is no provision for a harvesting channel. This novel invention does not provide for scalability of such a channel. 
   Therefore, it would be highly desirable to have a new and improved scalable fish rearing raceway system and method of making same for aquaculture products which would provide a sequential combination of subsystems for removal of the solid particulate matter as well as dead and dying fish. Furthermore, it would be highly desirable if such a system provided a separate channel or holding area for harvesting fish, moving fish to other tanks, and for uniform optional sizing of fish that can be incorporated into the raceway or channel, and which would be scalable. 
   The aquaculture system disclosed in U.S. Pat. No. 5,961,831 consists of one or more culture tanks connected to a closed system of filters and ultraviolet or ozone sources for water purification prior to returning water to the culture tanks. This invention also provides for sensors for continuous monitoring of water quality. However, as seen previously, there is no provision for removal of dead and dying fish which represents one of the most important potential reservoirs of disease within an aquaculture environment. 
   Therefore, it would be highly desirable to have a new and improved scalable fish rearing raceway system and method of making same which would provide for methods of particulate removal, but perhaps most importantly, provide for continuous mechanical removal of dead fish from the raceway by means of a floating mortality catcher consisting of screened ramps which collect moribund and dead fish, as well as a novel system for the prompt removal of freshly sunken dead fish. 
   As previously mentioned, many of the inventive systems utilized by aquaculture up until very recently have used multiple tanks for rearing of fish. Most of these systems were designed to utilize relatively small round tanks. Increasing the diameter of these small round tanks reveals inherent design restrictions that prevent efficient usage of the entire interior of the tank for rearing fish due to the centrifugal current differential within the confines of the circular space. Since increased tank diameter exacerbates the differential in water velocity within the tank, these large round tanks become inefficient in terms of space utilization. Additionally, the ability to scale them to a larger size would not be cost effective. Moreover, the space between the numerous tanks is essentially wasted space with respect to fish rearing operations. 
   The invention in U.S. Pat. No. 4,913,093 describes such a multi-tank aquaculture system. A method of culturing fish in a plurality of tanks with each tank comprising a relatively independent growing environment would require enormous capital and labor expenditures per fish produced. In addition, the invention requires periodic subdivision of the fish population into separate tanks when the capacity of the tank is reached. Physically sorting and moving the fish from tank to tank would result in a great deal of trauma and possibly injury to the fish. 
   Therefore, it would be highly desirable to have a new and improved scalable fish rearing raceway system and method of making same which would provide scalability, low capital expenditure, low labor cost per fish produced, efficient use of space, a means of separating fish by size, and a means by which those fish might be moved or harvested in an efficient manner without trauma or injury. 
   Another aquaculture rearing system is described in U.S. Pat. No. 4,300,477 which provides for clustered, vertical rearing tanks. Multiple, stackable habitats in the form of baskets are attached to a strongback member which houses a removable feeding rod. There is no means provided for removal of heavy particulates, dead or dying fish or providing for circulation of water through the tank. 
   Progressive space increments are provided by two different size baskets and removable dividers. The fact that these multiple habitats are individually removable suggests that the size of the baskets are relatively small and that the number of units of fish per basket is severely limited. This ratio of capital expenditure (and labor costs) per unit produced is extremely high. Additionally, the trauma involved in physical separation of the fish by size into each basket would be very high. 
   Additionally, there is no means provided for removal of dead or dying fish on a continuous basis, so the likelihood of spread of disease from the presence of dead or dying fish would seem to be overwhelming. 
   Therefore, it would be highly desirable to have a new and improved scalable fish rearing raceway system and method of making same which would provide a method by which particulates in the wastewater stream would be automatically removed. It would also be highly desirable to provide such a new and improved aquaculture raceway system with a means of providing fresh circulating oxygenated water, a water treatment process, and a means of removing dead and dying fish on a continuing basis. It would also be highly desirable to provide such fish sorting, removal of dead and dying fish, provision of fresh or reconditioned circulating water in a cost effective, efficient and scalable manner. 
   The present invention proposes a new and improved circular raceway for use in an aquaculture system and method of using same. The proposed raceway is easily scalable, is cost effective and efficient, and provides for more uniform water current velocities throughout the production tank. 
   SUMMARY OF THE INVENTION 
   Therefore, the principal object of the present invention is to provide a new and improved scalable fish rearing raceway system and method of making same. More particularly, the present invention relates to a new and improved scalable fish rearing raceway system including a greatly increased fish culture zone, water velocity control means, unique fish harvesting/grading channel component, and integrated water quality monitoring and feeding means which greatly reduces direct labor associated with all aspects of the fish rearing process. 
   It is a further object of the present invention to provide such a new and improved scalable fish rearing raceway system and method of making same that incorporates an integrated water treatment unit which would remove particulates, dead and dying fish, excess nitrogen and carbon dioxide compounds and provide for aeration of the water before returning the water to the scalable fish rearing raceway system. 
   It is yet a further object of the present invention to provide such a new and improved scalable fish rearing raceway system and method of making same which may be stocked with fish of the same size for batch growth or may alternatively provide for optional grading bars for automatically grading fish by size. 
   Briefly, the above and further objects of the present invention are realized by providing a new and improved scalable fish rearing raceway system and method of making same which provides for the largest tank ever used to culture warm water fish at high densities, utilizing an elongated portion to maintain optimal current speed. This larger production unit substantially reduces the direct labor associated with the monitoring, feeding and harvesting of fish on a per fish basis, and requires lower capital costs since it requires fewer components such as monitors, feeders, emergency oxygen diffusers and other equipment per unit of fish produced. 
   A novel means of eliminating heavy particulates is seen in the use of conical areas located at either end of an elongated raceway, out of the main fish channel. Effluent water leaves the raceway through these hydrocones where heavy waste particles settle in the conical zones aided by the centrifugal forces of the circular flow patterns and exit the bottom drains in the cones to the outside drain boxes. In addition, heavy waste is also removed by means of screened channels cut into the floor of the linear raceways. 
   Continuous removal of dead fish from the raceway is accomplished by means of a sinking fish mortality catcher consisting of a screened ramp at the entrance to the hydrocones which collect both moribund (sunken) and “long” dead (floating) fish. A similar device is mounted at the main drain box on the outside of the raceway to capture dead and floating fish. The continuous removal of dead and dying fish significantly reduces labor costs associated with the frequent manual removal of such fish and reduces the transmittal of infectious diseases by the immediate removal of the dead and dying fish. 
   This heavy waste containing water is removed from the circular raceway to a center water treatment channel where a crop of secondary detritevore feeding fish forage on particulate matter. 
   The water then enters an oxygenation zone. This oxygenation zone may also contain submerged biofiltration media to enhance nitrification of ammonia waste. A screen prevents the secondary detritivore feeding fish from entering this area. Several surface paddlewheel aerators are used to remove dissolved carbon dioxide gas from the water. The water then enters a U-tube oxygenation system which consists of four cells where injected oxygen gas is dissolved into the water. This highly oxygenated water is returned to the fish culture zone of the raceway through a series of water jets in the floor of the raceway located at the distal ends of the linear sections of the raceway. Water is also fed into the raceway from two alternative sources: (a) an extensive filtration system composed of particulate removal by fish and mechanical screens, two nitrification reactors and a series of constructed wetland ponds; and (b) well water which has been filtered through a desaturation column to remove dissolved nitrogen gas. 
   Several probes monitor and control dissolved oxygen levels in the water. These monitors are connected to a centralized alarm and computer monitoring system. If necessary, an emergency oxygen system is activated which injects oxygen into the water from an alternative source, when oxygen levels reach a critical level. 
   Additionally, the raceway is equipped with feed silos that can dispense feed of several sizes and multiple frequency throughout the day. The number and size of fish present is monitored and graded by an electronic underwater scanning device (using infrared or acoustical technology) coupled to a computer microprocessor which reduces the handling stress associated with the counting, grading and netting of fish. 
   The raceway can be stocked with uniform sized fish which are grown to market size as a batch culture. Alternatively, grading bars can periodically separate the larger fish, which are then counted and moved underwater to an adjacent raceway through the common fish transfer channel, and the resulting space restocked with smaller fish. This provides a continuous grading and restocking method which results in less cannibalism and a much greater annual yield (in pounds of fish produced). 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above mentioned and other objects and features of this invention and the manner of attaining them will become apparent, and the invention itself will be best understood by reference to the following description of the embodiment of the invention in conjunction with the accompanying drawings, wherein: 
       FIG. 1  is a plan view of one embodiment of the scalable fish rearing raceway system constructed in accordance with the present invention, illustrating a single stand-alone parallel linear fish rearing area with semi-circular ends, and the positioning of the central water treatment zone, two hydrocone structures, passive fish mortality removal ramp, and fish harvesting/grading channel; 
       FIG. 2  is a side elevational cross-sectional view of the scalable fish rearing raceway system constructed in accordance with the present invention, illustrating the positioning of the central water treatment zone, two hydrocone structures and fish harvesting/grading channel; 
       FIG. 3  is an enlarged partial plan view of one end of the of the scalable fish rearing raceway system constructed in accordance with the present invention, illustrating the hydrocone structure, passive fish mortality removal ramp and fish harvesting/grading channel in greater detail; 
       FIG. 4  is a an enlarged partial side elevational cross-sectional view of one end of the of the scalable fish rearing raceway system constructed in accordance with the present invention, illustrating the floor spoilers, the hydrocone structure, and the fish harvesting/grading channel in greater detail; 
       FIG. 5  is an enlarged partial plan view of the opposite end of the of the scalable fish rearing raceway system constructed in accordance with the present invention, illustrating the hydrocone structure, passive fish mortality removal ramp, water inflow piping, effluent outflow piping and drain box structures in greater detail; 
       FIG. 6  is a vertical cross-sectional view of one floor drain box constructed in accordance with the present invention, illustrating the grate and drain pipe structure; 
       FIG. 7  is an enlarged partial side elevational cross-sectional view of the opposite end of the of the scalable fish rearing raceway system constructed in accordance with the present invention, illustrating the hydrocone structure; 
       FIG. 8  is an enlarged partial plan view of the central portion of the scalable fish rearing raceway system constructed in accordance with the present invention, illustrating the oxygenation U-tube and water propulsion means in greater detail; 
       FIG. 9  is a vertical cross-sectional view of one U-tube overflow head weir board accepting means constructed in accordance with the present invention, illustrating the positioning of optional weir boards when inserted into place; 
       FIG. 10  is an enlarged partial side elevational cross-sectional view of the central portion of the scalable fish rearing raceway system constructed in accordance with the present invention, illustrating the oxygenation U-tube and water propulsion means in greater detail; 
       FIG. 11  is an enlarged partial plan view of the hydrocone structure in accordance with the present invention, illustrating the position of the mort catcher platform in greater detail; 
       FIG. 12  is an enlarged partial side elevational cross sectional view of the hydrocone structure in accordance with the present invention, illustrating the mort catcher ramp and platform in greater detail; 
       FIG. 13  is a plan view of another embodiment of the scalable fish rearing raceway system constructed in accordance with the present invention, illustrating a double array of parallel linear fish rearing areas with semi-circular ends, and the positioning of the central water treatment zone, two hydrocone structures in one of the raceways and common fish harvesting/grading channel; and 
       FIG. 14  is a plan view of yet another embodiment of the scalable fish rearing raceway system constructed in accordance with the present invention, illustrating a parallel linear fish rearing area with semi-circular ends with the central water treatment zone, and two hydrocone structures, attached to a second parallel linear fish rearing area with semi-circular ends with no central water treatment zone or hydrocone structures and common fish harvesting/grading channel. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring now to the drawings, and more particularly to  FIG. 1  thereof, there is shown a new fish rearing system  10  which consists of two elongated parallel fish channel raceways  12  and  14  and two semi-circular end sections  16  and  18  which are located at either end of the elongated fish channel raceways  12  and  14 . 
   The new fish rearing system  10  also incorporates an inner water treatment zone  20  where a secondary detritivore fish species, such as tilapia or carp, may be stocked to remove particulate matter. Two hydrocone structures  22  and  24  are located at either end of this inner water treatment zone  20 . The hydrocone structures  22  and  24  are provided with overflow trays  23  and  25 . The overflow trays  23  and  25  direct the water from the top of the hydrocone structures  22  and  24  to the inner water treatment zone  20 . 
   A harvesting/grading channel  26  is located at one end of the fish rearing system  10 . A partition wall  27  is located along a portion of the midline of the harvesting/grading channel  26 . The harvesting/grading channel  26  is connected to the fish rearing system  10  by means of a harvesting/grading portal area  28 . The harvesting/grading portal area  28  receives the distal end of the permanent stationary grader panel  30  along the midline of the harvesting/grading portal area  28 . The permanent stationary grader panel  30  raises up and down as needed (raising up out of the water when not in use for continuous grading). 
   Sloped screens  72  and  74  are located within an inner water treatment zone  20  which may be equipped with submerged biofiltration media to enhance nitrification of ammonia waste. This inner water treatment zone  20  is adjacent to the central pump head tank  32 . This central pump head tank  32  pumps water through the U-tube oxygenation system  60  to the water jet outlets  34  and  36  at one end of each of the elongated fish channel raceways  12  and  14  by means of the water jet supply pipes  35  and  37 . 
   Paddlewheels  40  and  42  are located at the proximal end of each of the elongated fish channel raceways  12  and  14 . Alternatively, the paddlewheels can be located within the inner water treatment zone  20 . Fresh water enters the elongated fish rearing system  10  by means of an inflow fresh water pipe  44 . 
   Two drain boxes  46  and  48  are located at each end of one of the elongated fish channel raceway  14  and remove effluent water from the elongated fish channel raceway oval  10  by means of effluent pipes  50  and  52 . The effluent water enters the drain boxes  46  and  48  through a hydrocone drain line  54 , and drainpipes as exemplified by drainpipe  59  for the fish channel drain boxes  56  and  58 . Water may be drained from the center zone  20  by means of the center zone drain pipe  55 . 
   The water velocity in the fish zone is a function of the water returning from the inner water treatment zone  20  after it has been pumped through the U-tube oxygenation system  60 . This water re-enters the fish zone through the water jet outlets  34  and  36  at both ends of the tank. The U-tube pumps primary function is to provide a constant non-variable flow of water into the U-tubes for oxygenation. Secondarily, these pumps provide the force to bring water into the central water treatment area  20 , and to provide  the energy to create a water velocity field in the fish zone. In this regard, they create a constant water velocity resulting from their pumping rate, pressure, and the specific floor nozzle design of water jet outlets  34  and  36 . When the tank was initially put into production, we found that the water velocity was too high in the fish zone, and resulted in excess exercising of our fish and poor fish growth. Therefore, we designed and added controllable floor spoilers  38  and  39 , comprising flush hinged plates that can be raised immediately downstream of the water jet outlets  34  and  36 . These controllable floor spoilers  38  and  39  act much like a spoiler on an aircraft wing and re-direct the water leaving the water jet outlets  34  and  36  into a more upward direction. This results in an overall reduction of water velocity within the fish zone that is proportional to the spoiler deflection angle. With these spoilers  38  and  39 , one can control the water velocity between 0 to 2.0 ft/second. In fact, if the spoilers  38  and  39  are raised to their full up position, it is possible for one to reverse the water flow direction in the fish zone. In practice, one would normally set the spoilers to provide a water current that keeps the waste particulate matter (including dead fish) from settling, providing quick final removal by the drains  56  and  58  and hydrocone structures  22  and  24  (approximately 0.25–1 fps). This velocity can be optimized to improve tank water quality and quickly remove dead fish, yet not force the fish to swim at an excessive speed, thereby maintaining normal fish metabolic rates and maximizing fish growth potential. However, spoilers  38  and  39  can be retracted to provide short periods of increased water velocity to provide increased tank cleaning when needed, or to enhance harvesting operations. 
   Referring now to  FIG. 2 , this illustration provides a side elevational cross-sectional view of the scalable fish rearing raceway system. The cross-section of semi-circular end section  16  shows the fresh water inflow pipe  44 . Heavy waste particles settle in the bottom of the hydrocone structures as exemplified by hydrocone structures  22  and  23 , and are removed by means of the hydrocone drain lines  53  and  54 . The cross section of the overflow trays as exemplified by overflow trays  23  and  25  directs excess water into the inner zone  20 . 
   Sloped screens  72  and  74  are located on either side of the central pump head tank  32 . These sloped screens  72  and  74  retain the secondary detritivore fish stock in the inner water treatment zone  20 . A U-tube oxygenation system  60  is comprised of U-tube pumps  66  and  68 , and U-tube cone bottom outlets  62  and  64 . Water from pumps  66  and  68  is pumped through U-tubes  62  and  64 , through the central pump head tank  32 , to the water jet outlets  34  and  36  by means of the water jet supply pipes  35  and  37  (shown in greater detail in  FIG. 10 ). Here, the floor spoilers  38  and  39  are shown adjusted to about a 45 degree angle from the raceway floor. The harvesting/grading channel  26  is shown in cross-section with the partition wall  27  and the harvesting/grading portal area  28 . 
   Referring to  FIG. 3 , an enlarged partial plan view of one end of the of the scalable fish rearing raceway system, the hydrocone structure  24  and hydrocone overflow tray  25  are shown at one end of the inner water treatment zone  20 . The end portion of the elongated fish channel raceway  12  is adjacent to the semi-circular end section  18 . 
   A water jet supply pipe  37  located in the inner water treatment zone  20  provides oxygenated water to the water jet outlets  36  located in the fish channel raceway  14 . The paddlewheels  40  (shown in  FIG. 1  and  FIG. 5) and 42  (shown here) removes carbon dioxide from the water. A passive floating dead fish removal apparatus is constructed of a submerged screen panel  43 . Floating dead fish travel with the water flow in the direction of the arrow shown and with the aid of centrifugal force are sent to the outside wall into the screen panel  45  and deposited within drain box  46  for easy collection. The same apparatus could also be set up on the other end of the fish rearing system  10 , thereby depositing floating dead fish into drain box  48 . 
   A fish channel drain box  58  collects large particles of solid material which is removed from the elongated fish channel raceway  12  by the drain pipe for the fish channel drain box  59  to the drain box  46 . The combined effluent from the drain box  46  is removed for treatment by the effluent pipe  50 . 
   The harvesting/grading portal area  28  accommodates the distal portion of the permanent stationary grader panel  30  which when mechanically lowered into the water, sorts the fish by size on a continuous basis. Grader gates  76  and  78  provide continuous mechanical sorting of fish into the harvesting/grading channel  26 . This harvesting/grading channel  26  contains a partition wall  27  to provide ease in harvesting. 
   Turning now to  FIG. 4 , a cross-sectional view of one end of the of the scalable fish rearing raceway system, the water jet supply pipe  37  supplying oxygenated water to the water jet outlets  36  is illustrated. Floor spoiler  38  is shown at about a 45 degree angle from the raceway floor. Excess water with a reduced particulate load moves from the upper center layer of the hydrocone  24  to the inner water treatment zone  20  through the hydrocone overflow tray  25 . A hydrocone drain line  53  removes solid particulates from the sloped bottom. The cross section of the harvesting/grading portal area  28  shows the placement of the grader gate panel  76  allowing the larger fish to enter the harvesting/grading channel  26  containing the partition wall  27  during harvesting or grading operations. 
   Referring to  FIG. 5 , an enlarged partial plan view of one end of the of the scalable fish rearing raceway system, the hydrocone structure  22  and hydrocone overflow tray  23  are shown at one end of the inner water treatment zone  20 . The end portion of the elongated fish channel raceways  12  and  14  are adjacent to the semi-circular end section  16 . 
   A water jet supply pipe  35  provides oxygenated water to the water jet outlets  34 . The paddlewheel  40  removes carbon dioxide from the water. 
   Large particles of solid material are removed from the elongated fish channel raceway  14  after collection in the fish channel drain box  56 . The effluent from the hydrocone structure  22  flows to the drain box  48  by means of a hydrocone drain line  54 . The effluent from the drain box  48  is removed for treatment by the effluent pipes, namely effluent pipe  50  for drain box  48  and effluent pipe  52  for drain box  46  (as shown in  FIG. 1 ). 
   A center zone drainpipe  55  provides drainage for the inner water treatment zone  20 . Fresh water enters the semi-circular end section  16  by means of a fresh water inflow pipe  44 . The fresh water enters the semi-circular end section  16  to ensure complete mixing and to help regulate water velocity. 
   A submerged vertical screen panel  45  adjustably extends out from the entrance to hydrocone  22  to direct dead and dying fish into the hydrocone structure  22  (see  FIG. 5  and  FIG. 6  for more detail on the passive mortality removal apparatus). 
     FIG. 6  illustrates a vertical cross-sectional view of one fish channel drain box  56  with a drain box screen  86  and drain box drain pipe  88  structure. 
   Turning now to  FIG. 7 , a cross-sectional view of one end of the of the scalable fish rearing raceway system, the water jet supply pipe  35  supplying oxygenated water to the water jet outlets  34  is illustrated. A hydrocone overflow tray  23  is seen in the hydrocone structure  22  which delivers reduced particulate load water to inner water treatment zone  20 . A hydrocone drain line  54  removes solid particulates from the sloped bottom. A fresh water inflow pipe is seen in the cross section of the semi-circular end section  16 . 
   Referring now to  FIG. 8 , there is illustrated a central pump head tank  32  within the inner water treatment zone  20  and adjacent to the elongated fish channel raceways  12  and  14 . Sloped screens  72  and  74  are located on either side of the central pump head tank  32 . Four pumps  92 ,  94 ,  96  and  98  are connected to U-tube chambers  102 ,  104 ,  106  and  108  which terminate in U-tube cone bottom outlets  62 ,  63 ,  64  and  65  within the central pump head tank  32 . The U-tube chambers  102 ,  104 ,  106  and  108  provide increased hydrostatic pressure to assist oxygen to dissolve into solution. The U-tube bottom outlets  62 ,  63 ,  64  and  65  maximize gas transfer and require less horsepower because of the low pumping head pressure in this configuration. The pumps supply highly oxygenated water to the water jet supply pipes  35  and  37  which return the treated and oxygenated water back to the fish rearing raceways  12  and  14 . Additionally, the pump suction intakes provide the driving force to pull water from fish rearing raceways  12  and  14  through the circular velocity hydrocone and into the inner water treatment zone  20 . Weir board overflow slots  112  and  114  control head tank  32  water levels. 
     FIG. 9  illustrates weir board overflow slots  112  with optional multiple weir board inserts  118  (the additional of which raises the water spill over level) in a weir board support housing  116 . 
   Referring now to  FIG. 10 , there is illustrated the U-tube oxygenation system  60  in greater detail. The sloped screens  72  and  74  are located on either side of the pumps  96  and  98  intakes. These sloped screens  72  and  74  separate the inner water treatment zone  20  from the U-tube oxygenation system  60 . The pumps are connected to the U-tube cone bottom outlets  62  and  64  by means of the discharge pipes  122  and  124 . The U-tube cone bottom outlets  62  and  64  are housed in the U-tube chambers  106  and  108 . The pumps deliver water through the U-tubes  62  and  64  into the U-tube  106  and  108  to the water jet supply pipes  35  and  37  that return the treated and oxygenated water to the fish rearing raceways  12  and  14 . 
   Turning to  FIG. 11 , the hydrocone structure  130  is shown in greater detail illustrating the direction of water flow as it enters the water inlet  132 . The mort catcher ramp  134  is positioned in such a manner that the settled debris and any non-floating moribund or dead fish are carried passively up the ramp  134  onto the mort catcher platform  136  by the horizontal and radial movement of water to the hydrocone structure  130  (water flow shown by arrows). The floating debris and dead fish are then easily removed from the mort catcher platform  136 . The drain outlet  138  is located in the center of the hydrocone structure  130  and any heavy particulate matter settles in the hydrocone structure  130  aided by the centrifugal forces of the circular water flow patterns and is removed by the hydrocone drain line  54 . A portion of the adjacent fish channel drain box  56  and the paddlewheel  40  are shown. 
     FIG. 12  is a side view of the hydrocone structure  140 , illustrating the mort catcher ramp  134  and mort catcher platform  136  in greater detail. The drain outlet  138  is seen at the center of the sloped bottom of the side view of the hydrocone structure  140 . 
   Referring now to both  FIG. 11  and  FIG. 12 , when in operation, the continuous removal of dead fish from the raceway is accomplished by means of two separate devices:
         (a) a sinking fish mortality catcher which passively captures freshly dead and dying fish, and (b) a floating fish mortality catcher designed to passively capture the few non-fresh dead fish that manage to bypass the first device.       

   Because freshly dead or dying fish are usually denser than the surrounding water medium, they sink to the bottom of the fish zone and are carried by the water current around the main fish tank floor. Centrifugal action created by the water changing directions at both circular end zones causes all particles heavier than water, including freshly dead and dying fish, to be passively transported along the floor toward the center wall structures (see arrow in  FIG. 11 ) until the fish reach the submerged entrance  132  to the hydrocone structure. Similarly, any particulate matter less dense than water, including non-fresh or “bloated” dead fish, will move to the outer wall water surface by the same centrifugal water forces. The continuous removal of dead and dying fish significantly reduces labor costs associated with difficult and frequent manual netting of such fish, and greatly reduces the transmittal of infectious diseases by the immediate removal of bacteria and parasites associated with the dead and dying fish. 
   The sinking fish mortality catcher consists of an inclined screened ramp  134  located immediately inside the submerged water entrance  132  to the hydrocone. The screened ramp  134  starts at the floor and climbs to the water surface along a 90 degree arc of the circular hydrocone wall. To further enhance the rapid capture and removal of these dead or sick fish, a submerged vertical screen panel  45  adjustably extends out from this entrance to direct fish into the screened ramp before they have actually moved close enough to the entrance to be drawn in by water suction alone (also see  FIG. 5 ), thereby increasing the size of the entrance. Once through the submerged entrance  132 , water current carries the fish to the floor of the inclined screen ramp  134 . A separate short wall on the inside edge of this ramp forces the incoming water to uniformly and horizontally pass through the screen ramp  134  along its entire length. The horizontal force vector of the water passing through the screen causes the fish to be passively moved along the screen and carried to the water surface where they are collected in a small screened trap  136  for final disposal. However, the water velocity that carries dead fish into the hydrocone and mort catcher is not great enough to capture or hold healthy fish which may freely enter and exit the hydrocone entrance  132  at will. 
   Additionally, a floating fish mortality catcher (not shown in  FIG. 12 , for detail see  FIG. 3 ) is mounted at the outside wall edge on the downstream side of the oval fish section adjacent to one of the main drain boxes. A vertically oriented screen panel extends into the water current at approximately 45 degrees relative to the water flow and passively directs floating dead fish outside of the raceway into the main drain boxes where they are collected in a screened trap for final disposal. These devices are also applicable to any tank shape, including round tanks, where centrifugal water action is available to passively move sinking dead fish towards the center floor of the tank and floating dead fish towards the outer wall water surface of the tank. 
   Turning now to  FIG. 13 , there is shown an alternative embodiment, a double array fish rearing system  150 . Two elongated oval raceways  152  and  154  are constructed adjoining one another, both connected to a common harvesting/grading channel  156  and having a common inner wall  161 . By constructing double and multiple arrays such as this having common inner walls, both economy of construction and more efficient land use (less area is required to produce more fish crop) is realized. 
   A partial hydrocone structure  146  and an unused space  148  illustrate two possible embodiments that may be employed depending upon the requirements of the system. Two hydrocone structures  142  and  144  are shown at one end of each of the two elongated oval raceways  152  and  154 . Additionally, an unused inner zone  158  and an inner water treatment zone  160  represent potential embodiments. Drivable overpass bridges  162  and  164  provide convenient access to service vehicles. 
   Water inlets  170  and  172  provide fresh water from a water source  168  in this particular embodiment. Drain outlets  174  and  176  direct effluent from the system into the effluent (tilapia) channel  175 . The effluent then flows to a centralized water treatment system such as the SMART system described in U.S. Pat. No. 6,447,681, employing the biofilm carrier elements as described in U.S. design patent D465,357 (both granted to Kent Sea Tech Corporation), and on to a constructed wetland  178  for further removal of particulates and waste compounds. 
   Finally,  FIG. 14  illustrates another embodiment of a double array of fish rearing system  180 . A common harvesting/move channel  192  is connected to a full raceway  182  and a full volume raceway  188  having no inner zone. Both raceway  182  and  188  share a common wall  183  which confers a space saving advantage as well as a decreased overall construction cost. 
   The full raceway  182  is shown here with an inner water treatment zone  184  and two hydrocone structures  216  and  218 . Interconnecting end portals lead to a common fish harvesting/grading channel  192  which allows grading, counting and transfer of fish completely underwater, with no netting stress to fish. Furthermore, underwater electronic means of sizing, grading and counting fish is employed within the harvesting/grading channel  192 , to further reduce fish stress related to these necessary activities. 
   A center wall structure  190  is shown in the full volume raceway  188  not containing an inner water treatment zone (as previously described). Alternatively, one or more raceways similar to raceway  188  having no inner water treatment zone can be connected to a centralized common water treatment system such as that described in U.S. Pat. No. 6,447,681 granted to Kent Sea Tech Corporation. Flow modulators  222  and  224  are located at either end of the full volume raceway  188 . An electronic control panel  198  gives operators input from monitoring equipment which are linked to an alarm system and also provides operators with control of the components of the system. Two driveable overpass bridges  194  and  196  allow access to the double array fish rearing system  180  by service vehicles and other equipment. 
   Inlets  204  and  206  provide fresh water from the water source  202 . Drain outlets  210  and  212  direct effluent from the embodiment of double array of fish rearing system  180  to the effluent (tilapia) channel  208 . The effluent continues to a centralized water treatment system such as the SMART system described in U.S. Pat. No. 6,447,681, possibly employing the biofilm carrier elements as described in U.S. design patent D465,357 (both granted to Kent Sea Tech Corporation), and on to constructed wetland  214  for further removal of particulates and waste compounds. 
   Finally, the system described herein has the further advantages of being easily covered to prevent bird predation, and to provide shade, for example, to shade carp in the inner zone (as well as fish in the exterior raceway channels). Moreover, the water velocity within the system (both fish rearing raceways and the inner water treatment zone) is readily controlled by a combination of adjusting the pumps, flow jets, and floor spoilers, all integrated into the system. 
   It should be understood, however, that even though these numerous characteristics and advantages of the invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, chemistry and arrangement of components and parts within the principal of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.