By Kenneth Williams

Introduction
Tilapia have become one of the most widely cultured food fish in the world. Hieroglyphs found in ancient Egyptian tombs suggest that these fish were raised in ponds as long as 4000 years ago. The tilapias originated in central Africa and have been introduced throughout Asia, Europe, the middle east and the Americas. Although world wide there are many different species of tilapia , the most commonly available species in Oklahoma is Tilapia aurea, the blue tilapia.

These fish are tropical and will die at water temperatures below 50 degrees F., therefore the only populations that survive the winter are to be found in power plant lakes or in the extreme southern sections of the gulf coast states. In these areas of the country where they can overwinter they are considered a nuisance fish because they rapidly reproduce, out compete native fishes for food and become stunted.

Tilapia are well suited for culture as a food fish for several reasons. The fish tolerate very poor water quality conditions and will survive oxygen depletions that would kill most other fish (fig. 1), so they can be stocked in very small ponds at high densities and still thrive.

Tilapia will produce acceptable weight gains on a variety of inexpensive low quality feeds which reduces production costs. Tilapia also are resistant to most diseases commonly associated with fish culture.

Cage culture of Tilapia
Cages are a very convenient means of raising tilapia in the farm pond. The cage prevents unwanted reproduction by allowing the eggs to pass through the bottom mesh before they can be fertilized, and the fish are easily harvested. Also cage culture does not interfere with recreational sport fishing in the farm pond. In fact, excess feed and fish waste fertilize the pond and increase sport fish production. Disadvantages of the cage include some risk of a fish die off or reduced growth due to chronic low levels of dissolved oxygen. (avg. less than 3mg/l). Also the caged fish must be fed daily to achieve adequate weight gains.

Cage Construction
Cages can be purchased from several sources or easily constructed by the fish farmer from materials available from companies serving the aquaculture industry. Cages can be made almost any size or shape but most round cages are 4 feet deep and a little less than 4 feet in diameter because rolls of plastic mesh or plastic coated welded wire are sold in 4 foot widths. Rectangular cages are usually 8 ft. x 4 ft. x 4 ft. or 8 ft. x 8 ft. x 4 ft deep. Optimum mesh size appears to be 1/2 x 1 inch. Plastic coated, welded wire is preferable for cage construction because of its durability. Muskrats and other animals cannot chew holes through this mesh. An anti_fouling paint can be applied to cage mesh if excessive algal growth reduces water flow through the cage. This is most commonly a problem in clear bodies of water. A feeding screen made from 1/8 inch plastic mesh, 1 ft. wide is attached to the upper inside perimeter of the cage to keep feed from floating out before it can be eaten. The cage is floated with blocks of foam or plastic jugs and anchored to a dock, cable or the pond bottom to prevent movement. The top of the cage is usually made of the same material as that used for the rest of the cage. However, in clear ponds an opaque cover that blocks the light may encourage light sensitive fish to accept feed more readily. Cage construction materials cost from $2.00 to $2.60 per cubic foot of cage. Cages have a life span of 10 to 20 years with proper care.

Plastic Coated Wire Mesh Cages

1. Cage construction will require slightly less than 20 feet of wire mesh. Use 16 gauge 2 X 1 inch mesh in rolls 48 inches wide. Wire mesh is normally sold in 100 ft. length rolls but often can be purchased in shorter lengths.

2. Cut an 11 ft 3 in. piece of wire mesh and form the material into a cylinder with approximately 4-6 inches of overlap at the adjoining ends. Fasten the length of the joint with a double row of stainless steel or copper hog rings spaced 1-2 inches apart.

3. Cut two pieces of wire mesh to a size that will cover the top and bottom of the cage.

4. Attach the bottom cage mesh with hog rings placed in every mesh slot around the edge of the cage then trim the excess material with side cutters or tinsnips.

5. Cut an 11 2 ft. x 12 inch feeding screen from 1/8 inch Vexar plastic mesh. Attach the feeding screen to the inside, top perimeter of the cage with a few hog rings. Place rings at top and bottom edges of the screen about every 6-8 inches.

6.The top of the cage must be constructed to open as necessary. The wire mesh can be attached to the top of the cage with plastic coated copper wire, cable ties or a more elaborate hinged lid can be made from other materials. The top of the cage must be securely closed to prevent escape of fish should the cage sink or capsize. A solid top that will shade caged

fish is recommended in clear water; however, convenient access for feeding is necessary. A small, mesh covered opening in the top of the cage is adequate.

7. Attach four suitably sized floats around the top of the cage. Plastic jugs can be used but may need to be replaced occasionally throughout the year. Styrofoam blocks 12 in x 6 in x 6 in also work well. Cable ties make quick inexpensive fasteners for floatation materials. Alternatively, the cage can be suspended from a frame constructed of 4" PVC pipe. Securely glue the joints to prevent leakage.

It is very important that the cage not be allowed to sink to the bottom of the pond where dissolved oxygen may be low. Almost certain fish stress or death will result.

Cage Maintenance
Although tilapia tend to clean the algae from the cage mesh, Bryozoa, a gray jelly_like mass, may sometimes accumulate on the cage. It should be raked off with a stick or broom periodically to insure adequate water circulation through the cage. Cleaning one or two times per month is adequate where this organism is present.

Cage floats may require adjustment or replacement occasionally during the growing season. Also regularly inspect the cage door to make sure it is tightly closed. A strong wind can blow the lid open and allow fish to escape.

Pond Requirements
The pond should be 1/2 acre or larger and at least 6 feet deep throughout the summer months for successful caged tilapia culture; although smaller ponds in open fields that receive plenty of summer breezes may also have potential.

Aquatic Vegetation Control

Excessive amounts of aquatic vegetation, more than 1/3 of the pond covered, should be controlled with grass carp stocked at a rate of about 10 per acre. Grass carp are much less expensive and considerably more effective than chemicals for aquatic vegetation control. Control is usually achieved the second year after stocking and weeds should remain under control for 7-10 years after introduction of this fish.

Stocking Rates
Fingerlings 6-8 inch (2-4oz) are stocked in spring, usually in mid_April, when the water temperature has reached 650F. Fingerlings should reach a harvestable weight of 1 pound or more by mid to late October.

Fish are stocked at a rate of 300 per cage (1 cubic yard) with a maximum of 1000 fish per acre. Higher stocking densities can be achieved if aeration is available or the fish are stocked in the open pond.

Fingerlings are currently priced at about $0.50 each.

Feeds And Feeding
Caged tilapia should be fed a floating, pelleted channel catfish ration. Studies have shown that tilapia attain their maximum growth rate when fed continuously on demand a 36% protein complete channel catfish diet. However, a ration containing 25-30% protein including some fish meal will perform almost as well at much less cost.

Although a meal diet is as efficient as the pelleted diet and even more efficient when feeding small fish it is difficult to use in cage culture because the meal tends to drift out of the cage. An 8 inch piece of tin flashing substituted for the feeding screen normally used in the cage may help solve this problem.

Feed the fish all that they will eat in about 10 minutes. This is equal to about 3% of their total body weight. Recent studies indicate that the fish meal component of the feed can be completely replaced by less expensive vegetable proteins such as soybean meal if the total amount of protein in the ration is at least 36%. At current prices a soybean based fish food would reduce production costs of tilapia without greatly reducing weight gain.

A vitamin/mineral pack should be included in the diet of caged tilapia. It has been reported that the tilapia can synthesize some vitamins in the gut, notably vitamin B 12, however, when the fish has limited access to natural foods it would be prudent to include these supplements in the diet. The vitamin/mineral packs currently used for channel catfish seems adequate for the tilapia.

It is often the best management practice to feed fish in the late morning hours, between 9:00 am and 12:00pm. This allows oxygen levels in the pond to rise from their daily early morning lows to levels better suited to the metabolism of the fish. Digestion requires more oxygen, therefore the fish eat better and digest the food more efficiently when oxygen levels in the pond are above 3ppm.

Tilapia feed best at water temperatures between 72-95 degrees F. Feeding and growth begin to slow as the water drops below 70 degrees F. While water temperatures much above 100 degrees F. can be lethal.

Because tilapia have a very small stomach, actually only an enlarged bulb of the intestine, they grow best when fed 2-3 times per day. Although adequate growth can be obtained with a single daily feeding.

Growth Rate
Tilapia grow at a rate of 1 to 2 grams per day or 1- 2 ounces per month depending on food quality and water temperature. Therefore 2-4 ounce fingerlings should be stocked in the spring to obtain harvested fish that average 1 pound after a 7 month growing season. 1/2 ounce fingerlings can reach weights of 1/2 to 3/4 pound in one growing season.

Harvesting
The blue tilapia should be harvested from the cages when the water temperature drops below 60 degrees F. usually late October or early November. The fish will average about one pound; the males generally being larger than the females.

Diseases and Water Quality
Tilapia are relatively hardy and disease free; however, they are susceptible to stress induced disease problems, particularly in water cooler than 60 degrees F. and begin to die when water temperature drops below 50 degrees F. The most commonly encountered problems occur when the fish are handled in 65 degree F. or cooler water. This stresses and weakens the fish giving disease a better chance to invade

Saprolegnia, a fungus that looks like brown patches of cotton, is the most frequent problem found with these fish and it can be controlled by waiting until water temperature has warmed to 65 degrees F. before handling them. There is also evidence that damage to kidney tissue is possible at water temperatures below 60 degrees F.

Water quality is often the most critical factor in fish culture, however with tilapia there is much room for error which makes it a very forgiving fish for the beginning fishculturist.

These fish are very hardy and can withstand much environmental abuse without affecting their growth rate which makes them excellent candidates for many fish culture applications.

Open Pond Culture
Tilapia can be successfully raised in practically any farm pond when not caged. Ponds as small as 30 ft X 30 ft. and 3 ft. deep can be used for tilapia culture. There are however, some problems involved with open pond culture.

(1) Reproduction is uncontrolled. Spawning occurs about every 4 weeks as long as the water temperature is above 72 degrees F. Tilapia are mouth brooders which means that the female shelters the young in her mouth after the eggs have hatched. During this time she is unable to eat and so grows at a much slower rate than the males; frequently reaching only half her potential size.

Another problem arising from uncontrolled reproduction is large quantities of young which will not reach a harvestable size. They consume large quantities of food, They also lower water quality through their biomass which may exceed by several factors the weight of the original fish stocked, cause stunting of the entire population and create sorting problems when fish of only a certain size are wanted for market.

Therefore in most cases a means to control reproduction must be employed and this will be considered in a separate section.

(2) Harvest can be difficult. Even in a pond designed for fish culture tilapia can be difficult to seine efficiently. These fish tend to lay on their sides and burrow into the mud and under the net. This can be a severe problem in ponds filled with filamentous algae. Tilapia are also very adept at jumping over the net. A tall seine helps solve this problem. Partially draining the pond also makes the harvest easier. On a small scale a lift net might prove a workable solution to the harvest problem.

Open Pond Stocking Rates
Open pond stocking rates for tilapia can vary considerably depending on the needs of the fish culturist and the production methods employed.

For small ponds (less than 1/2 ac) or ponds that are only being supplementally fed with manures, grains or grain by_products the fish should be stocked at a maximum rate of 1 per square yard of surface area, which is about 5000 per acre. When tilapia are fed pelleted feed the stocking density may be as high as 3-4 fingerlings per square yard of surface area or up to about 20,000 per acre. At these densities aeration will probably be necessary.

Open Pond Feeds and Feeding
At high densities tilapia should be fed a regular catfish ration with a protein value of 25-36% as they will rapidly deplete natural food sources. At lower densities, the catfish ration can be fed or a variety of supplemental feeds may be used which can reduce costs of production. The fish should be fed about 3% of their body weight per day or all that they will consume in about 20 minutes. Tilapia grow much better when fed several times per day although growth may be adequate on a single daily feeding schedule. For this reason one or more demand feeders placed over the pond are recommended. This allows the fish to feed continuously through the day and gain the benefits of multiple feeding without heavy labor demands on the fish culturist.

Organic Fertilization
Organic manures have been used with success in many developing countries Although these are used primarily to fertilize the water and increase natural production, the tilapia will often feed directly on these materials. Conversion factors are often poor but over all cost of production can be reduced significantly with the use of manures and crop wastes. Manures can be applied at a rate of 500 to 2000 pounds per acre initially, followed by repeat applications up to 200 pounds per week. Rate of application will vary with water temperature, dissolved oxygen levels, weather conditions and fish biomass.

Manuring produces a bloom of phytoplankton which the tilapia are able to strain out of the water with their gill rakers (finger_like projections attached to the gill arches). The phytoplankton is then concentrated in the back of the mouth on a sticky mucus pad and then swallowed. Different species of tilapia vary in their ability to strain these microscopic plants. Some have many, finely spaced gill rakers and are very efficient, while others have fewer, wider spaced rakers and are less efficient in their use of this food source. The gill rakers of the blue tilapia are in between these two extremes.

The blue tilapia is an omnivorous fish and will consume a wide variety food items in the diet. Along with manuring the pond, vegetables, grains, cottonseed meal, insects, worms, mill sweepings, brewery wastes and legumes may be fed.

When large amounts of organic matter are placed in a pond problems with low dissolved oxygen concentrations in the water may develop. Feeding may have to be reduced or stopped until oxygen levels rise above 3 ppm. Over time, heavy use of organic fertilizers will build up a thick layer of muck in the bottom of the pond which can make fish harvest difficult. It may have to be removed periodically. This mud is extremely rich in nutrients making it a valuable addition to garden or crop lands.

Tilapia Fingerling Production
With many species of fish, breeding and fingerling production require some technical expertise or skill. This is not true of tilapia.

Stock the brood fish in a ratio of 2 females to 1 male,. at a density of 200-400 fish per acre. Plastic swimming pools 3 ft. x 14 ft. may also be used. These can be stocked with 2 males and 4 females. Place about 6 in. of sand in the bottom of the pool so that the males can build nests, and also 2 or 3 hollow concrete blocks or other items to provide a hiding/resting spot for the females.

Spawning begins when the water temperature exceeds 72 degrees F. and continues until the temperature drops below 72 degrees F. Tilapia reach sexual maturity in the second year when they are about 6 in. long in the wild but pond raised tilapia have spawned at 3 in. Males construct a circular nest 12-18 in. in diameter and 4-6 in. deep. The female deposits 300-2000 eggs in the nest, then scoops them up in her mouth. The male then releases milt into the nest. The female picks up the milt and the eggs are fertilized in her mouth. The eggs are incubated in the mouth and hatch in 7-8 days.

The young fry are cared for about 8-10 days after hatching. During this time they will venture out of the mouth cavity but remain near the mother, returning into her mouth if alarmed or in danger. This behavior insures a high fry survival rate even though relatively few eggs were produced.

Females do not eat during the hatching period, which is why they tend to reach only half the size of males. Spawning takes place about every 4 weeks as long as the water temperature remains warm.

A well fertilized pond will provide the fry and fingerlings with an abundant food supply. However, growth will be more rapid if a high protein meal is fed supplementally. Six to eight weeks after hatching the fingerlings can be transferred to grow out ponds. Fry produced and cultured very early in the year in heated facilities and harvested in mid_November can reach weights of 1/4-1/2 pounds.

Controlling Reproduction In Open Ponds
Control of reproduction is probably the most important management problem in the culture of tilapia. If reproduction is left unchecked the result will be be a pond full of young and stunted fish, very few of which will reach a desired size at harvest.

Many methods for control of tilapia reproduction have been used. Hybrid crosses of some species are often used because the resulting fish are all male and fast growing. Currently the most popular hybrid is the female Tilapia nilotica with the male Tilapia hornorum. Sexing and crossing tilapias is not particularly difficult but does require some skill. It can also be difficult for the small fish farmer to find the right species to cross. In Oklahoma the blue tilapia, Tilapia aurea, is the only species commonly available. For this reason other means of reproductive control must be considered for the small scale operation. Although in the future it is likely that all male , hybrid crosses will be commonly available.

Hand sexing of the fish for the selection of males is possible. The males are stocked in grow out ponds and the females are placed in brood ponds or discarded. This procedure has several problems associated with it. Sexing the fish accurately requires some skill and practice. A few females placed in the same pond with the males is all that it takes to render the method useless. Discarding the females can become expensive if the fingerlings must be purchased in mixed male/female lots as is the common practice. Even with well trained workers it is questionable whether this method is consistently practical.

Sex reversal of all females in a population of fry is possible through the use of hormones such as methyl testosterone. This drug is fed to the fry for a period of three weeks after hatching and results in all male fingerlings. Currently this practice may not have FDA approval.

The most practical method of reproductive control of tilapia for the small scale farmer may be through the use of predatory fish. Large mouth bass (Micropteris salmoides) is probably the most popular and is effective in controlling fry and young tilapia fingerlings. Stocking rates will vary with the stocking rate of tilapia, water clarity and size of bass. 25 to 100 bass per acre should provide adequate control. However, the fish culturist will have to fine tune the rate to local conditions.

Bluegill and green sunfish can also be effective controls on tilapia reproduction. Like the large mouth bass, the sunfish will consume the fry, however, the sunfish will also very efficiently remove the eggs. This may be more effective than control of the fry because there are no young tilapia to compete for food and also the mouth brooding of the fry by the female cannot occur. This allows her to feed on a more continuous basis and gain more weight. More research needs to be conducted on optimum stocking rates for sun fish in tilapia ponds. Five hundred per acre would be a good starting point. Again, fine tuning to local conditions by the fish culturist will be necessary.

Polyculture
Tilapia have been used in polyculture with many different species of fish. In almost every case the results have been beneficial. Total pond production has been increased without corresponding increases in the cost of production because the tilapia tend to clean up waste feed and algae that otherwise go uneaten by the primary species cultured. Cage culture studies at Langston University have demonstrated increased production of channel catfish when they were stocked together with blue tilapia in cages along with increased total cage production due to the presence of the tilapia. Aggressive feeding behavior of the tilapia, particularly at low dissolved oxygen levels, may stimulate the channel catfish to consume more feed than they would if stocked alone in monoculture.

One problem associated with polyculture on a large scale is the difficulty of sorting different species at harvest time. Although not a problem for the small scale fish culturist, custom harvesters or processing plants may not be willing to accept mixed loads of fish.

Use Of Tilapia In Sewage Treatment And Insect/Weed Control
Because of the tilapia's tolerance to low dissolved oxygen levels and poor water quality; plus its ability to strain nutrients from the water, this fish is very suitable for use in sewage lagoons and oxidation ponds as a biological filter.

Several species of tilapia, most notably T. zilli, have been stocked in roadside ditches and irrigation canals for the control of aquatic vegetation and mosquitoes. Their tolerance of poor water quality and the omnivorous feeding habits of some of the species make the tilapia a good choice for control of many of these weeds and insects.

Overwintering Tilapia
The small scale fish culturist can over winter tilapia fingerlings and brood stock without much trouble if adequate facilities are available. There are several methods used to over winter these fish. The choice will depend on the situation and the resources of the fish culturist. The first method, developed at Texas A & M University, requires the use of very small ponds (about .10 ac or smaller and 3-4 ft. deep). An arched frame of 1 in. PVC pipe is placed over the pond and this frame is covered with black plastic, to absorb heat and also because it is more resistant to the deteriorating effects of ultraviolet light.

In Oklahoma and more northern locations these temporary green houses may have to be heated 1-3 months during the winter. A wood burning stove or solar air or water heaters may be the most economical means to heat these structures.

The fish should be fed about 1% of their body weight 3 days per week as a maintenance diet if the water temperature is consistently below 70 degrees F. More can be fed if the water temperature is higher.

If your over wintering location is subject to high winds during the winter, the plastic green house method may not be practical as strong winds can destroy this material. A more substantial shed structure can be constructed to slide over the pond in windy locations. This shed may be built in several pieces for ease in moving and storing.

Another method for holding fish over winter is to enclose and insulate a small barn or portion of a larger one. This area can be heated or the tanks used to hold the fish may be heated. The size and number of tanks used to hold the tilapia depend on the number of fingerlings needed the following spring and the size desired for individual fingerlings.

A tank 15 ft. x 3 ft x 2.5 ft. deep can hold 500 fingerlings if it has water flow through and aeration. Heated water can be dribbled into the tanks or a submersible heater can be used to maintain the desired water temperature. The tanks must be cleaned about every two weeks depending on the amount of feed, size of tank and amount of water flowing through the system.

Before deciding to over winter tilapia, determine the costs of construction, equipment and heating. On a small scale it may be more cost effective to purchase fingerlings each year than to attempt to over winter them.

Reduce the costs of heating water where possible by using solar heating devices. These may be as simple as a coil of black garden hose under a piece of plastic or solar air heater but they can substantially reduce energy costs.

Enterprise budget
Economic budgets for tilapia culture vary considerably. This is particularly true of open pond culture where feeding will be supplemented or replaced with organic fertilization. For this reason the budget presented here is for cage culture, one of the more popular methods of small scale tilapia production.

Budget for one cage containing 300 blue tilapia.

Variable costs:

Fingerlings, 6in. (3oz.) 315 (+5% mortality) @ $0.50 ea. - $157.50

Feed 600 lb@ $0.17/lb - $102.00

Transportation of fingerlings 200 miles @ $0.40/mile - $80.00

Interest of 10 % on operating capital for 7 months - $19.80

Total variable cost: $359.30

Fixed costs:

Cage construction materials $103.00/cage amortized over 10 yr. Life span. - $10.30

Aquatic culture license - $17.50

Misc. materials (dip net, maintenance, etc.) - $30.00

Total fixed cost: $57.80

Total start up cost: $417.10

Break even price per lb. to cover variable costs: $1.20

Break even price per lb. to cover total yearly costs: $1.39

Transport and Handling
Transport tilapia in an aerated hauling tank. Use an oxygen supply system if available. Replace some of the water with fresh water along the way if the trip is long or the fish appear to be gasping at the water's surface. Do not use chlorinated tap water. This will kill the fish. 1/2 cup of salt can be added to about 50 gal. of water as a treatment against external parasites and as a means of reducing the stress of transportation.

Temperature stress can also harm tilapia. Do not transport these fish until the water temperature in your pond and the fingerling producer's is above 65 degrees F. This will avoid many problems, particularly reducing the incidence of bacterial or fungal invasions of wounds received during transportation.

It is generally better to fill the hauling tanks with water available at the fingerling producer's ponds. This water will be about the same temperature that the fish are being held in so there will not be a temperature shock when the fingerlings are loaded into the hauling tanks. Be sure the producer’s water is not contaminated with other fish or invertebrates.

If there is more than a 5 degree F. difference in temperature from hauling tank to the pond in which the fish will be stocked, temper the water over a 20-30 minute period by slowly mixing some pond water into the hauling tanks. However, if the fish appear to be suffering from oxygen depletion in the hauling tanks, it is better to give them a bit of a temperature shock and get them quickly into some oxygen rich water than it is to slowly temper the water.

Always handle fish as gently as possible. It is always much easier to prevent disease than to cure it. Injuries to the fish from spine punctures and loss of scales are prime sites for bacterial invasions. These injuries can be reduced by dipping only a few fish at a time with the dip net and releasing them from the net after it is in the water. Do not pour fish from a height into the open cage. Avoid removing the slime layer that coats the fishes body. This is the first line of defense for the fish against disease and parasitism.

After releasing tilapia into a cage, quickly shut the lid. These fish are very prone to jumping out of the cage at the slightest opportunity.

Processing
Tilapia can be processed much like the channel catfish, and have a similar dress out percentage of about 60 % for whole dressed fish and 35% for fillets. Unlike catfish, very little meat will be found on the belly or ribs of tilapia. Most meat on tilapia lies along the back and down the tail. There are some intermuscular bones in these fish but they are easily removed during the filleting process by making a "V" shaped cut about 1 in. long through the anterior mid-line of the fillet. Removal of this section will result in a boneless fillet. Tilapia have a firm, light, flakey flesh that always rates high with consumers. It tends to be much less oily and milder in flavor than channel catfish.

Marketing
Tilapia are now beginning to be marketed in the United States on a large scale. However, marketing studies conducted at Auburn University have indicated very good consumer acceptance of this fish when competitively priced and displayed with channel catfish. A survey of major producers by "Aquaculture" magazine and personal communications also suggest that present supplies do not meet market demand. Little or no national advertising or marketing promotions have been conducted for tilapia and the fish is sold under a variety of names which confuses consumer recognition.

These market names include: super fish, saint Peter's fish, African perch, miracle fish and cherry snapper. Consumer recognition and acceptance should be expected to improve in the future. One problem associated with tilapia marketing is that in most parts of the country tilapia die during the winter so the fish must be harvested and either sold fresh or frozen by early winter. This adds up to a short season for fresh fish which currently is most preferable to the consumer. Most of the tilapia produced will have to be processed into frozen product. Strong demand and higher prices for out of season fresh fish may make over wintering facilities for tilapia economically attractive.

Tilapia are becoming more consistently available in food stores and organized promotions and marketing groups are now established. To date, domestic production is a small percentage of total tilapia sales in the U.S. Most tilapia are imported.