SRAC Publication No. 170

VI August 1997 PR

In-Pond Raceways

Michael P. Masser and Andrew Lazur*

There are four basic types of fish culture. This control is achieved research on developing raceways culture systems: open-ponds, only if flow rate and water quality that would float in a pond (or any cages, raceways, and recirculating are relatively stable over time. body of water) and have a con- systems. Each system has advan- Stocking densities for raceways stant flow of water, supplied by tages and disadvantages in cul- are usually higher than for other air-lift pumps. The idea was to ture performance, water quality, culture systems. Densities of 10 to develop a raceway system pow- ease of management, and econom- 15 fish per cubic foot are not ered by air-lift pumps that could ic returns. unusual for raceway systems. float in existing ponds and have In fish culture, traditional race- These high densities have distinct some of the advantages of tradi- ways are enclosed channel sys- disadvantages including: more tional raceways such as: 1) higher tems with relatively high rates of rapid disease spread, less reaction fish densities, 2) better water qual- moving or flowing water. This time when problems occur, and ity, 3) waste collection, 4) precise high rate of water movement large volumes of effluent with disease treatment, and 5) better gives raceway systems distinct dilute fish wastes. control over feeding, grading, har- advantages over the other culture vest, etc. In a pond, this system In general, water cannot be eco- would also have the advantage of systems. Advantages of raceways nomically pumped through race- can include: not discharging wastes into the ways; it must flow through them public domain since the pond ■ higher stocking densities by gravity. The need for large vol- would act as reservoir and treat- ■ improved water quality umes of good quality water is the ment system. principal reason raceways have ■ reduced manpower been limited to sites with large The development of an air-lift dri- ■ ease of feeding springs. Most raceway culture in ven In-Pond Raceway (IPR) began at Auburn University in 1991. ■ ease of grading the U.S. is with coldwater species such as trout and is based around However, literature searches have ■ ease of harvest locations with high volume, cold revealed that systems of some- what similar design or concept ■ precise disease treatments springs, or creeks. A few raceway systems for warmwater species had been developed, and even ■ collection of fish wastes have been located at sites with patented, since the turn of the ■ less off-flavor warm geothermal springs. century. Most raceway operators believe Problems involving lack of water Raceway construction they have more control over their movement through cages in fish production, and they see this watershed ponds led to the devel- In-Pond Raceways consist of rec- as the major benefit of raceway opment of air-lift pumps to move tangular boxes that can be con- water through them (see SRAC structed in various sizes and from Publication No. 162, Cage Culture several types of materials depend- *Auburn University; University of Florida – Cage Construction, Placement, and ing on the intended use. IPRs Aeration). This in turn led to have been used in research and

1 commercial production at several the IPRs are positioned close to the raceway about 4 to 6 feet from locations in the South and the walkways. Security should the water discharge of the air-lifts. Midwest since 1992. The smallest also be considered in construction. This board should be attached IPRs have been used for produc- Theft and vandalism can be a with about 1 inch extending above tion of fish fry and were only problem in any type of high den- the water surface when the about 84 cubic feet in volume sity fish culture system. pumps are running. The eddy (6x4x3.5 feet). The largest to date zone behind this board is the feed- have been used for commercial ing area of the raceway. Feed production of catfish and were dropped in this area is held approximately 670 cubic feet in against the board, keeping it from total volume (24x8x3.5 feet). being washed out of the raceway. Cage-type mesh material (usually IPRs have been constructed from 1 marine and treated plywood, /2-inch mesh) is used to keep plastic sheets, and plastic liners. cultured fish inside the IPR and Each of these materials has exclude wild fish from entering, advantages and disadvantages. without restricting water flow. Plywood becomes saturated with Mesh is placed in front of the air- water and extremely heavy unless lifts and at the discharge end of coated with non-toxic water-resis- the raceway. The mesh in front of tant marine paint. Plastic sheets the air-lifts should be in an “L”- shape, forming a trough across the (usually 1/4 inch thick) expand and contract with heat, making raceway about 6 to 8 inches in their shape irregular. Plastic liners front and 4 to 6 inches below the (80 mil) cannot be walked in (dur- air-lift’s water discharge. This ing harvest or grading) and may trough traps debris and wild fish collapse due to wave action. that enter through the air-lifts, without restricting water flow. A A frame around the outside of the Figure 1. IPR with dock–note that second mesh screen is placed IPR is used for attachment of the about 1 foot from the rear of the blower housing and air-manifold are plywood or plastic. Both treated raceway and extends completely lumber and metal frames have at the forward end of the raceway. across the width and height of the been constructed. All IPR materi- raceway. The rear screen keeps the als, including screws and nails, One of the most common IPRs has cultured fish from leaving the need to be water-resistant and raceway and wild fish from enter- non-toxic. Although treated lum- been built of treated plywood, framed with treated 2x4 lumber or ing through the water discharge ber contains some toxic com- opening. pounds, these have not been a steel, and coated with epoxy problem in the IPRs because of paint. Sizes have been either 16 or Hinged lids or doors should cover the high water exchange rates. 24 feet long, 4 feet wide, by 4 feet the top of the IPR to discourage However, it may be advisable to deep (only 3 feet underwater). predators and stop fish from coat the wood with non-toxic Figure 2 shows the basic design of escaping by jumping out. Usually marine paint. this raceway. The air-lift pump is several small lids are preferable to attached to the front or “intake” one or two large ones because of The IPR is designed to float in end of the IPR, and the waste col- weight and the need to access any body of water; therefore, a lection system (if needed) is only certain sections of the race- recommended component is a attached to the “discharge” end. way at a time. Mesh material dock or pier for ease of manage- The intake end wall of the race- (similar to that described above) ment (e.g., feeding, water testing, way is constructed so its upper should be used in the section over etc.). It is possible to anchor the edge is approximately 9 inches IPR to a stationary pier or to the below the sides of the raceway. pond bottom if water levels do This space allows the air-lift not fluctuate. However, if pump to be adjusted for flow con- anchored to the pond bottom trol (see air-lift pump section). without a dock, then daily activi- The rear discharge wall of the ties must be conducted from a raceways is constructed so that its boat. The IPR pier should be con- lower edge ends about 4 inches structed of walkways (3 to 4 feet above the raceway bottom. This wide) to allow access to all sides allows discharged wastes to be of the IPR and provide space for drawn off the bottom of the race- attaching equipment (see Figure way for removal. 1). For ease of management the Figure 2. IPR (out of the water) pier must be constructed so that An “eddy board,” usually 2x6 or showing position of air-lift system 2x8, is placed across the width of and eddy board.

2 the feeding area so feed can be dropped into the raceway without opening the lid. The remaining Wire mesh door lids can be constructed of a solid material or can be covered with a material such as shade cloth to Demand feeder reduce light and its associated stress on the fish. A 16x4x4 foot IPR has an effective culture vol- ume of 210 cubic feet (15x4x3.5 feet) or 1,571 gallons. A 24-foot- long IPR would have an effective

Waste collecting system

Treated plywood Air-lift system External frame

Figure 3b. Drawing of IPR showing attachment of air-lifts, tube settler, lids, and Figure 3a. IPR (out of the water) demand feeder. built from treated plywood showing external frame and attachment of tube settler.

Tube settler waste Air manifold collecting system

Water flow Flexible rubber tube Oxygen tubing system

Air-lift system

Wire mesh door Wire mesh door

Figure 3c. Drawing of IPR in cross section and top view showing attachment of air-lifts, tube settler, demand feeder, and emergency oxygen tubing system.

3 culture volume of 322 cubic feet solids from the bottom of the race- (23x4x3.5 feet) or 2,409 gallons. An way. Results of this study on fry IPR with dimensions of 24x8x4 production were promising, how- has an effective culture volume of ever. 644 cubic feet (23x8x3.5 feet) or 4,817 gallons. Air-lift pumps IPRs have also been constructed Air-lifts provide a simple and effi- using plastic liners. There are sev- cient means of moving large vol- eral synthetic compositions (i.e., umes of water. Rising air bubbles chemically different) of plastic lin- inside an air-lift’s tube act like a ers. These are commercially avail- piston pushing water above it. able in 19 to 80 mil thickness, with However, this is efficient only if 40 mil being adequate for use in the water is lifted a small height most IPR situations. Liners are above the surface. In fact, most ultraviolet light-resistant and have air-lifts will not lift water over 3 a lifetime of at least 10 years. or 4 inches above the water’s sur- Liner manufacturers can fashion face. Air-lifts work most efficient- liners in many shapes and sizes, ly when they are releasing water so it is possible to have a liner at or very near the surface. A sin- custom-made for a specific IPR gle 3-inch air-lift discharging at Figure 4a. Air-lifts attached to a sheet design. The flexible nature of a the surface will move between 50 of plywood at the front of raceway, liner allows the raceway to be and 60 gallons per minute if built showing garden hose attachment at a moved to the pond bank or pier as described below. and collapsed for easy harvesting water depth of 32 inches. of the fish. Air-lifts have the added benefit of aerating incoming water when 90o elbow or “L” is glued to the A disadvantage of plastic liner dissolved oxygen (DO) concentra- top of each air-lift. Each air-lift is construction is that the walls can tions are much below saturation. designed so that air from the collapse inward from wave action, In research trials, when pond DO blower enters the pipe at approxi- reducing the raceway volume fell below 2 mg/L the DO in the mately 32 inches below the center unless a frame is used to maintain IPRs has been maintained at 3 of the PVC “L”. Regenerative its shape. Also, the attachment of mg/L even with high biomass. blowers are most efficient at pow- solid waste collection systems and Because of the mixing action of ering air-lifts if the air is injected air-lifts is more difficult since it is water and air in the air-lifts, between 30 and 34 inches below hard to glue materials to the liner. supersaturation is virtually elimi- the surface of the water. Cost of plastic liners is also a con- nated in the water entering the Optimally the air-lifts are sub- sideration. Depending on thick- IPR. merged to the halfway point of ness, the type of liner, and custom the “L” or to the top of the “L”. shaping, they can range in price Air-lift pumps consist of a battery of single air-lifts. Individual air- Each air-lift is attached to a ply- from $0.50 to several dollars per wood or plastic panel. A circular square foot. This cost is only for lifts are constructed from a 36- inch long section of 3- or 4-inch cut-out is made so that each “L” the liner and does not include protrudes through the panel and frame, blower, air-lifts, etc. PVC pipe. A 4-foot-wide raceway has room for the attachment of 9 into the raceway area. Silicon seal- A small IPR (8x3x3 feet) of 23 mil 3-inch diameter air-lifts. A PVC er can be used around the cut- plastic liner has been tested for outs to seal the “L’s” to the panel. use as a fry rearing unit. For this purpose an IPR offers advantages as mentioned before and also pro- Water outlet vides a steady supply of plank- tonic food organisms essential for good growth and survival of fry. A saran mesh sock of 250 microns was placed over the air-lift dis- charge or outflow to prevent any predaceous insects or fish from Air inlet entering the raceway. The saran sock will not screen out plankton Vinyl-coated wire in the water. Problems were encountered with fouling of the Water inlet rear mesh screen because of its Figure 4b. Drawing of air-lift pump design showing attachment of individual small mesh size and removing air-lifts to plywood or plastic sheet.

4 This keeps water from escaping used as air-line between the air- the raceway around the “L’s”. manifold and the individual air- 1/2Ó Tubing Connector Air-lifts are attached to the panel lifts. The air-line attaches over the with screws or by pressure straps. tubing connectors from the air- Bolts or screws should not extend manifold to each air-lift. 1 into the pipe more than /2 inch, The key to making all the air- as debris can become caught on lifts work properly is that they this obstruction and reduce water all must be constructed exactly flow through the air-lift. Each air- alike, and each requires a con- lift in an IPR system must be striction orifice at the attachment built identically to all others and of the air-line to the air-mani- attached to the same air-manifold fold. The constriction orifice and blower in order to work should have a 3/16- to 1/4-inch properly. hole in its center. This orifice can The panel to which the air-lifts are be made from PVC or Plexiglas attached fits into tracks along each sheeting (1/8 to 1/4 inch thick) side at the front of the raceway. and hot-glued to the PVC tubing These tracks allow the air-lift connector. If constructed in this pump to be raised or lowered to fashion, a 1-horsepower blower adjust the height and therefore the can efficiently power 27 individ- water flow through the air-lifts. ual air-lifts or enough for 3 sepa- 3/16Ó oriface The intake of the air lift should be rate 4-foot-wide raceways with 9 Figure 5b. Drawing of PVC tubing approximately 36 inches under- air-lifts each. water. The intake can be moved connector with restriction orifice. upward or downward to utilize different water temperatures or tube, 3 feet long. Air injection, conditions. For example, if water discharge, screening, and warmer and more oxygen-rich vertical slide adjustments are sim- surface water is desired, the ilar to those described for the PVC intake could be turned upward air-lifts above. This design allows (starting at the bottom of the 36- as many as 13 air-lifts in a 4-foot- inch vertical section) using elbows wide area. and pipe to place the intake closer to the water’s surface. A longer Figure 5a. PVC tubing connectors Emergency systems vertical extension could be used if with restriction orifice(s). The IPR needs emergency back-up cooler water was desirable. This systems in case of electrical dis- would depend upon the quality of Water flow through the IPR(s) ruptions or mechanical failures. A the deeper water. with this air-lift pump design can backup blower is recommended Air is supplied to the air-lift be regulated by raising or lower- in case of blower failure. In addi- pumps by a regenerative blower. ing the air-lift pump, or by stop- tion, the two blowers can be Regenerative blowers are high- ping the air flow to individual air- equipped with a pressure sensor volume, low-pressure units. The lifts. With all 9 air-lifts function- that will turn on the backup blow- blower is attached to an air-mani- ing properly the flow rate aver- er in the event of a failure. Sensors fold that holds a large volume of ages about 450 gallons per can be purchased that will sense air under constant pressure. With- minute. At this flow rate a not only power failures but air- out the proper volume in the air- 16x4x3.5-foot raceway completely pressure loss (in the case of a manifold the air-lifts will not flushes in less than 4 minutes. At cracked air-manifold). These sen- function effectively, and the regen- this flushing rate the carrying sors can be attached to phone erative blower will be damaged capacity of the 9 air-lift IPR dialers which will call managers due to overheating. Typically a appears to be approximately 3,000 and alert them to problems and 1-horsepower blower requires a pounds with warmwater species can automatically trigger emer- minimum of 20 feet of 4-inch PVC (e.g., catfish), a stocking rate of gency generators or oxygen sup- or 12 feet of 6-inch PVC air-mani- 13.4 pounds per cubic foot. ply systems. fold (approximately 2,500 cubic Air-lift pumps have also been A simple oxygen supply system inches). One-half-inch PVC tubing constructed in a box or square can be constructed using cylinders connectors are tapped into the air- design. In this type of pump a of bottled oxygen connected to a manifold and into the air-lifts (at box is made from plywood or normally-closed electric solenoid 32 inches as described previous- plastic panels 3 inches wide with valve that opens if electrical ly). A section of garden hose vertical partitions every 3 inches, power is interrupted. High-pres- (5/8 inch), polypropylene, or resulting in a unit with each indi- 1 sure tubing leads from the cylin- plastic tubing ( /2-inch ID) can be vidual air-lift a 3-inch square ders to each raceway and is deliv-

5 ered through milli-pore tubing in economic standpoint, the high Traditional raceway culture has the bottom of each raceway, simi- stocking rates of the IPR are prob- often utilized demand or auto- lar to a hauling tank system. Flow ably necessary to offset the cost of matic feeders. Research on catfish regulators control the volume of construction and operation. in the IPR has shown that oxygen delivered and must be Finally, it is important to remem- demand feeders work well. In adjusted depending on the bio- ber that stocking densities must fact, with catfish and tilapia there mass of fish in the raceways. be balanced with pond size. In were no differences in growth or Typically a single cylinder of oxy- open-pond catfish production it is feed conversion using demand gen will maintain a raceway for common to stock 6,000 or more feeders as compared with twice- several hours. This system is also fish per surface acre but expect to a-day hand feeding. used to maintain adequate oxy- harvest only 3,500 to 4,000 Fish cultured in raceways have gen supplies during therapeutic pounds of catfish per year. In better feed conversions than fish bath treatments for disease (see cages, catfish are normally grown in open ponds with the disease section which follows). stocked at only 1,500 to 2,000 fish possible exception of tilapia. This per surface acre (unless aeration is is also true of the IPR. In 5 years Species and stocking supplied), and all the fish are har- of research on catfish and tilapia, rates vested in a given year. In the case the average feed conversion ratio of the IPR, it is recommended to (FCR) was 1.45:1 (pounds feed fed To date, species that have been stock no more than 6,000 fish per to pounds of fish produced). successfully cultured in IPRs acre and expect to harvest all of include: channel, blue, and hybrid Finally, because of the high densi- the fish (see economics section) in ty and lack of any natural foods, catfish; trout, striped bass and its a given year. hybrids, yellow perch, bluegill, raceway culture depends on high and tilapia. Probably any species As a note of interest, several quality complete diets. In IPR that tolerates flowing water can species of freshwater mussels research on catfish and tilapia at be cultured in an IPR. have also been cultured behind Auburn University, a 36 percent catfish in the IPR in an attempt to protein commercially available Channel catfish and Nile tilapia reduce effluent wastes. The mus- diet was fed in most experiments, have been successfully polycul- sels were somewhat effective at rather than the 32 percent protein tured in the IPR. In one experi- reducing solid wastes in the efflu- diet that is commonly used in ment tilapia were mixed in the ent, and some species of mussels pond culture. Most cage produc- IPR at a 1:10 ratio with catfish. In showed significant growth under ers also use a 36 percent protein other experiments tilapia were these conditions. This research complete diet. isolated in a separate section of may have implications for the cul- the IPR behind the catfish and ture of freshwater mussels (the Disease treatments were not fed, under the assump- shells of these species are used as tion that they would eat any nuclei for cultured pearls) or in Disease treatments in raceways uneaten catfish feed, catfish the culture of other shellfish are usually drip treatments. The wastes, and plankton. The tilapia species in brackish or marine therapeutant is dripped into the grew well in both these experi- environments. incoming water, and a specific ments. concentration is maintained for a Blue catfish and channel X blue Feeding certain period of time, usually 1 hybrid catfish did not perform as hour. Problems with this method well in the IPR as channel catfish Feeding rates (percent body are that the concentration is diffi- in experiments at Auburn weight per day) and times cult to maintain, a large amount University. However, producers depend more on species cultured of therapeutant is used, and ther- in more northern climates have than on the culture system. For apeutant is released into the envi- reported success in culturing information on feeding rates and ronment with the discharge. these in raceways. These observa- time of feeding, check other In the IPR, the emergency oxygen tions may indicate more about the SRAC literature on specific system can be used to conduct temperature preference of the species. Floating feed is recom- therapeutic bath treatments. In blue catfish than about the culture mended for the IPR, because the this case the air blower is turned system. manager can see fish eat and off and the emergency oxygen determine if any feed is being supply system is used. With no Stocking rates for most of these wasted or uneaten. The IPR does species have varied between 9 water flow the raceway is treated allow the use of sinking feeds, as a tank of known volume. The and 15 fish per cubic foot of effec- including medicated feed if neces- tive culture volume. At least in therapeutant is mixed into the sary. For information on how to raceway at the prescribed concen- the case of catfish, no difference calculate feed rates see SRAC in growth or food conversion has tration and maintained for the Publication No. 164, Cage Culture recommended time period. DO been found between stocking at 9 – Handling and Feeding of Caged or 14 fish per cubic foot. From an concentrations should be checked Fish. and the oxygen supply regulated

6 during the treatment. After treat- ment the air blower is turned on, and the therapeutant is flushed Oxygen flow meter out of the raceway within a few Oxygen tubing system minutes. Obvious advantages of this system are that less therapeu- Water level tant is used, a more precise con- centration is achieved, and if problems occur the treatment can be terminated quickly. Waste reduction One of the anticipated benefits of the IPR was to capture or reduce Tube settlers wastes from the system. By doing this the IPR system would be more “environmentally friendly” 2Ó PVC to submerged pump and/or could produce more fish per acre, particularly when com- pared to cages in watershed Water flow ponds. However, it should be noted that fish wastes are mostly soluble, and solids are almost neutrally buoyant and therefore Figure 6b. Tube settler drawing showing construction with schedule 20 PVC and difficult to settle. If the pond uti- attachment of oxygen flow meter. lized is large and the stocking density per acre low, it may not be included settling basins, tube set- has ranged from 65 to 98 percent, necessary to practice waste reduc- tlers, sand and synthetic mesh fil- which is similar to cage research tion at all, since the pond should ters, plant and gravel biofilters, in the same pond. Tilapia survival be able to absorb and decompose artificial wetlands, and filter-feed- has averaged around 97 percent; the waste effluent through natural ing species in polyculture. The most of these losses have been cycles. best methods appear to be poly- due to escapement. Commercially Several different low cost and low culture with filter feeding species operated IPRs have reported bet- maintenance methods of trapping (see species and stocking rates ter overall survival. or reducing wastes from the IPR section), and tube settlers (for the Reaction time is another problem have been researched. These have solids) coupled with some type of with the IPR as with other high plant biofilter or artificial wetland density production systems. outside of the raceway. Actual Backup systems, either generators costs of these waste reduction sys- or pure oxygen systems, are tems and their total impact on the absolutely essential as power dis- pond environment have not been ruptions are inevitable. Since gen- adequately evaluated. erators eventually run out of fuel and oxygen cylinders become Problems depleted, electrical and/or pres- All culture systems have advan- sure sensors with phone dialers tages and disadvantages. Like are prudent components of these other high density raceway sys- systems. tems the IPR has problems related Predators, particularly birds, rac- to disease, reaction time, and coons, and otters, are attracted to predators. IPRs. The lids and mesh barriers Diseases, particularly bacterial around the inflows and outflows diseases, are common in all high must be properly constructed and density systems, especially race- routinely maintained to exclude ways, cages, and recirculating sys- these persistent predators. tems. Bacterial diseases, particu- larly Enteric Septicemia of Catfish Economics (ESC) and Columnaris, have been Cost of constructing an IPR sys- Figure 6a. Tube settler constructed of problematic with the IPR catfish tem can vary greatly depending research at Auburn University. 3/4-inch schedule 20 PVC. on the size and the materials used. Survival of catfish in IPR research The 16x4x4-foot IPR and dock sys-

7 tem cost approximately $3,000 to two systems. However, the IPR Remember, these are only esti- build in 1994. This construction has higher construction costs (not mated budgets based on research cost does not include the air-blow- including pond construction), data and should be used as er or the backup oxygen system higher energy costs, and higher guidelines for evaluation purpos- (included in the budget, see Table feed costs (if using a 36 percent es only. 1). If constructed properly, an IPR protein feed for catfish). system should have a viable life of In Table 1, the stocking rate is Other uses 5 to 10 years (5 years in budget, increased on a per acre basis for Table 1). The IPR has also been utilized as the IPR and decreased for cages an effective fish holding system. Examining the economics of any (based on research and practical Several small processors of catfish new system is always difficult, experience) as compared to open- have built and used IPRs to hold and the reader should be aware pond production. The feed bud- fish for later processing or live that these are only examples for geted is a 36 percent protein diet sales. They report that the fish comparison. Assumptions have for the IPR and cages and a 32 adapt immediately to the IPR been made in Table 1 in order to percent protein for the open-pond. without any associated trauma, as compare the IPR system with tra- Feed conversions are based on usually occurs if large catfish are ditional open-pond or cage pro- actual research data. In this com- placed in cages. Feeding can also duction systems. In the example parison the IPR has the lowest be started to continue weight gain budgets presented, the data on breakeven costs and cages the or maintain the weight of the fish production and labor costs are highest. It should be noted that if they are to be held for a long based on composites of actual through evaluations of commer- time. The same processors have data from research conducted on cial catfish operations (SRAC - reported that catfish have been the IPR, cages, and open-ponds at PESCAT Project) a 1-acre pond is purged of off-flavor in the IPR Auburn University. too small, because of economies of within a few days to a week, as It should be noted that the IPR scale, for economical catfish pro- long as the pond in which the IPR has been shown to have lower duction. Therefore, the breakeven was located did not have an off- labor costs and better feed conver- cost is high in all of these hypo- flavor episode during the purging sion when compared to the other thetical situations. period. Conclusions TABLE 1. Economic comparisons between the IPR, cages and open- The IPR has been shown to be a pond catfish culture (1-acre pond).1 viable fish culture system for sev- eral fish species. The cost of pro- Open-pond2 Cage IPR duction (considering capital costs) Assumptions may be prohibitive for the culture of some species depending on yield (lbs) 3,806 2,830 5,352 their market value. Certainly, IPRs death loss (%) 6 10 10 will not replace the open-pond feed conversion 1.8 1.6 1.45 culture system for catfish or most % protein feed 32 36 36 other species as presently prac- Economic parameters (dollars) ticed. However, it may have a viable place in watershed ponds, variable costs 3,135.63 2,391.27 4,160.25 quarries, and possibly production fixed costs 787.72 850.16 1,111.26 in public waters where cage cul- total costs 3,923.35 3,241.43 5,271.51 ture is not practical. IPRs may also breakeven price (cents per pound) be feasible where wastes must be to cover variable costs 82.39 84.50 77.73 collected or mitigated, or where to cover total costs 103.08 114.54 98.50 high value niche markets can be 1Pond construction and management costs have not been included in the budgets. exploited. 2Open-pond production yields are based on actual average production values observed in the catfish industry in Alabama.

The work reported in this publication was supported in part by the Southern Regional Aquaculture Center through Grant No. 94-38500-0045 from the United States Department of Agriculture, Cooperative States Research, Education, and Extension Service.