pond culture of Tilapia fish ( ICAR )

Because of their high protein content, large size, rapid growth (6 to 7 months to grow to harvest size),[3] and palatability, a number of coptodonine and oreochromine cichlids—specifically, various species of Coptodon, Oreochromis, and Sarotherodon—are the focus of major aquaculture efforts. Tilapia has become the third most important fish in aquaculture after carp and salmon; worldwide production exceeded 1.5 million metric tons (1.5×106 long tons) in 2002[2] and increases annually.temperate regions, mixed-sex culture is referred to as young-of-the-year culture because fry produced in the spring are grown to marketable size by autumn. Growth diminishes significantly at temperatures below 68 F and death will occur below 50 F. Two major strategies for producing tilapia in ponds, mixed-sex culture and male monosex culture, revolve around controlling spawning and recruitment.
Nutritional values;
           Tilapia from aquaculture contain especially high ratios of omega-6 to omega-3 fatty acids.
      
There is no restriction on pond size, but for ease of management and economical operation, shallow (3 to 6 feet), small (1 to 10 acres) ponds with drains are recommended. Newly-hatched fry should be used because older, stunted fish, such as those held over winter, will reach sexual maturity at a smaller, unmarketable size. aurea, T. The growout season is shortened by about 2 months to account for spawning and rearing of l-gram fry for stocking growout ponds. One advantage is that the fish are able to utilize natural foods. nilotica and their hybrids, all of which reproduce at an age of 5 to 6 months.

Two to three crops of fish can be produced annually in the tropics compared to only one crop in temperate regions. Tilapia recruitment, the production of fry and fingerlings, may be so great that offspring compete for food with the adults. In mixed-sex populations, the weight of recruits may constitute up to 70 percent of the total harvest weight. The pond bottom should be dried to eradicate any fry or fingerlings that may interfere with the next production cycle. In the continental United States, the southernmost parts of Texas and Florida are the only areas where tilapia survive outdoors year-round with the exception of geothermally-heated waters, most notably in Idaho. One month-old, l-gram fry are stocked at 2,000 to 6,000 per acre into growout ponds for a 4- to 5-month culture period. The original stock becomes stunted, yielding only a small percentage of marketable fish weighing 1 pound (454 grams) or more. Expected survival is roughly 70 percent.

Species such as Tilapia zilli, T. At harvest, average weight is approximately 0.5 pound (220 grams), and total production is near 1,400 pounds/acre for a stocking rate of 4,000/acre. Tilapia suitable for mixed-sex culture are T. At temperatures below 54 F, tilapia lose their resistance to disease and are subject to infections by bacteria, fungi and parasites.

In temperate regions, tilapia must be overwintered in heated water. The preferred temperature range for optimum tilapia growth is 82 to 86 F. Management of tilapia ponds ranges from extensive systems, using only organic or inorganic fertilizers, to intensive systems, using high-protein feed, aeration and water exchange. Draining is necessary to harvest all of the fish. hornorum, or T. The major drawback of pond culture is the high level of uncontrolled reproduction that may occur in growout ponds. Supplemental feeds with 25 to 32 percent protein are generally used. In the southern region, tilapia can be held in ponds for 5 to 12 months a year depending on location.

Mixed-sex culture:
Mixed-sex populations of fry are cultured together and harvested before or soon after they reach sexual maturity, thereby eliminating or minimizing recruitment and overcrowding. Early spawning is needed to maximize the growout period. A restricted culture period limits the size of fish that can be harvested.

In mixed-sex culture, tilapia are usually stocked at low rates to reduce competition for food and promote rapid growth. Geographic range for culturing tilapia in ponds is dependent upon temperature. A harvesting sump is needed to concentrate the fish in the final stage of drainage. Pond culture is the most popular method of growing tilapia. mossambica are not suitable for mixed-sex culture because they reproduce at an age of 2 to 3 months and at an unmarketable size of 30 grams or less.

Sex-reversal is more technically complicated and requires obtaining recently hatched fry and rearing them in tanks with high quality water. Secondary sex characteristics may also be used to help distinguish sex. Male monosex culture permits the use of longer culture periods, higher stocking rates and fingerlings of any age. Fingerlings that weigh less than 20 grams should not be overwintered because their survival rate will be low.

Overwintering facilities consist of geothermal springs, greenhouses and heated buildings. A disadvantage of male monosex culture is that female fingerlings are discarded.
. Manual sexing (hand sexing) is the process of separating males from females by visual inspection of the external urogenital pores, often with the aid of dye applied to the papillae. In temperate regions, fingerlings are produced during summer and stored in overwintering facilities for the next growing season. hornorum and T. This saves time, space and feed. Hybridization maybe used to produce a high percentage of male fish. Expected survival for all-male culture is 90 percent or greater. aurea. Male fingerling rearing
With male monosex culture, fry are usually reared to fingerling size in a nursery phase, and then male fingerlings are separated from females for final growout. If manual sexing is used, it is done prior to overwintering. Females use considerable energy in egg production and do not eat when they are incubating eggs. None of these methods is consistently 100 percent effective, and thus a combination of methods is suggested. All-male fingerlings can be obtained by three methods: hybridization, sex-reversal and manual sexing. In the tropics, fingerlings maybe produced year-round. High stocking densities reduce individual growth rates, but yields per unit area are greater. Experienced workers can reliably sex 15-gram fingerling T. If the growing season can be extended, it should be possible to produce fish weighing one pound (454 grams) or more. In greenhouses and heated buildings, recirculating systems are used to hold large quantities of fingerlings. Producing sufficient numbers of hybrid fry maybe difficult because of spawning incompatibilities between the parent species. Ponds stocked at 20,000 fry/acre will produce 100-gram fingerlings in 18 weeks, while 40,000 fry/acre will produce 50-gram fingerlings in 12 weeks, and 72,000 fry/acre will produce 27-gram fingerlings in 9 weeks. The hybrids may then be manually sexed or subjected to a sex-reversal treatment. Hybridization and sex-reversal reduce the number of female fingerlings that must be discarded during manual sexing. The best fingerling size for overwintering depends on the number of fingerlings that will be needed and the available storage capacity. mossambica, 30-gram T. nilotica, and 50-gram T. Both hybridization and sexreversal may produce less than 100 percent males.

Manual sexing is commonly used by producers. All three methods are sometimes used. Fingerlings can be overwintered in long, narrow ponds that are covered with clear plastic if the winter is mild.

Male monosex culture
Males are used for monosex culture because male tilapia grow faster than females. Reliability of sexing depends on the skill of the workers, the species to be sorted and its size. Fry of 1 gram or less are stocked in nursery ponds and fed high-quality feeds. Problems nevertheless still exist with hybridization and sex-reversal. Fingerlings can be held in cages located in geothermal springs or in small ponds or tanks through which warm spring water is diverted