Turtle farming is the practice of raising turtles and tortoises of various species commercially. Raised animals are sold for use as gourmet food, traditional medicine ingredients, or as pets. Some farms also sell young animals to other farms, either as breeding stock, or more commonly to be raised there to a larger size for further resale.
Turtle farmers worldwide raise primarily freshwater turtles (primarily, Chinese Soft-shelled Turtles as a food source and Sliders and Cooter Turtles for the pet trade); therefore, turtle farming is usually classified as aquaculture. However, some terrestrial tortoises (e.g. Cuora mouhotii) are also raised on farms for the pet trade.
It is believed that there have only been three serious attempts to farm sea turtles. Only one of them (in Cayman Islands) continues, with a strong tourism component. The one in Australia's Torres Strait Islands folded down after a few years of operation, and the one in Réunion has been converted to a public aquarium (Kélonia).
Japan is said to be the pioneer of soft-shelled turtle (Pelodiscus sinensis) farming, with the first farm started by Mr. Kurajiro Hattori in Fukagawa near Tokyo in 1866. Initially stocked with wild-caught animals, the farm started breeding them in 1875. By the early 20th century Hattori's farm had about 13.6 hectares of turtle ponds; it was reported to produce 82,000 eggs in 1904, and some 60,000 animals of market size in 1907.
According to the report of the Japanese zoologist Kakichi Mitsukuri, who conducted a significant amount of research at Hattori's farm in the late 19th and early 20th century, the main food supplied to the turtles were crushed bivalve mollusks, Mactra veneriformis (シオフキガイ, shiofuki, in Japanese), from Tokyo Bay. This was supplemented with by-products of fish processing and sericulture as well as boiled wheat. The farm turtles lived in a symbiotic relationship with carp and eels, which were raised in the same ponds. The fish stirred up the mud, and the shy turtles felt more comfortable foraging in turbid water,
Hattori's company has survived into the 21st century, as the Hattori-Nakamura Soft-Shelled Turtle Farm, operating in Hamamatsu, Shizuoka Prefecture. According to a 1991 report, Japan's turtle farm industry continued to be mostly based in central Japan, but was expanding to the warmer southern parts of the country.
The majority of world's turtle farms are probably located in China. According to a study published in 2007, over a thousand turtle farms operated in China.  A later report by the same team (Shi Haitao, James F. Parham, et al.), published in January 2008, was based on an attempt to survey all 1,499 turtle farms that were registered with the appropriate authorities of the People's Republic of China (namely, the Endangered Species Import and Export Management Office, and the Forestry Bureaus of individual provinces). The farms were mostly located in China's southern provinces of Guangdong, Guangxi, Hainan, and Hunan, although more recent sources indicate Zhejiang as particularly important. Some of them have been operating since the 1980s, the industry steadily growing since.
According to the responses obtained from 684 of those farms, these farms had the total herd of more than 300 million animals, and sold over 128 million turtles each year, with the total weight of about 93,000 tons. Extrapolating from this sample, the researchers estimated that about 300 million farm-raised turtles are sold annually by China's registered turtle farms, worth (presumably, at the wholesale prices) around US$750 million. They note that a large number of unregistered farms exist as well.
The most common species raised by Chinese turtle farmers is the Chinese Soft-shelled Turtle (Pelodiscus sinensis), accounting for over 97% of all reported sales, both in terms of head count (124.8 million in the 684-farm sample) and weight. Large-scale production of this species appears to have been successful in satisfying China gourmets' demand for its meat, which has been reflected in the price drop: while in the mid-1990s wild-caught soft-shelled turtles retailed for CNY 500 per Chinese pound or jin (500 g), and farm-raised ones at over CNY 200 / Chinese pound, by 1999 the price for farm-raised soft-shelled turtles dropped to CNY 60 per Chinese pound, and by 2009, to merely CNY 15-16 (around US $2) per Chinese pound.
A variety of other species are farmed as well, including the rare Cuora trifasciata, fetching a hefty price (almost US $1,800 per turtle, as opposed to around $6.50 for a common Pelodiscus sinensis, or $80 for a Cuora mouhotii sold to pet trade) due to its rarity and purported medicinal value.
In a report from a Tunchang County, Hainan, turtle farm, published by James F. Parham and Shi Haitao in 2000, the researchers give a general idea of what such an enterprise looks like. According to the owner, the farm, established in 1983, had some 50,000 animals of over 50 different aquatic and terrestrial species. The majority (30,000) were the common Pelodiscus sinensis.
There were also 7,000 to 8,000 of Mauremys mutica, and at least 1,000 of the prized Cuora trifasciata. The adult turtles lived in an 8-hectare outdoor breeding area, while the young ones were kept in indoor raising ponds. 
Hybridization between various turtle species often occurs on the farms. This has often been unintentional (because various species frequently are not segregated; this was especially characteristic of the early days of the industry). Sometimes, however, hybridization is encouraged, e.g. to produce the hybrids of the valuable Cuora trifasciata (the Golden Coin Turtle) and the more common Mauremys mutica; these hybrid turtles, apparently known as Mauremys iversoni, can be sold to retail customers as if they were true pure-blood Golden Coin Turtles. 
Pelodiscus sinensis is fairly extensively farmed in Thailand as well, with the (ca. the late 1990s) estimate of about 6 million turtles hatching on Thai farms annually.
Turtle farming exists in Vietnam as well, at least on a family farm scale. As early as 1993, researchers noted the existence of several hundred families near Hai Duong raising various amphibians and reptiles, including turtles. By 2004, companies with herds of several tens of thousand of soft-shell turtles were in operation near Ha Tinh; the operators were said to have studied the turtle farming techniques in Thailand.
Turtle farming in the United States started in the early 1900s, with farms in Maryland and North Carolina raising diamondback terrapins, which is considered a delicacy in those parts. However, by the late 20th century few turtles were raised for food in the United States, and American restaurants mostly relied on wild-caught turtles. Still, in 2012 it was reported that red-ear sliders raised in Oklahoma were sold in Virginia's and Maryland's Asian supermarkets.
Since the 1960s, a number of turtle farms have operated in Oklahoma and Louisiana. According to Louisiana agricultural scientists, just that state has around 60 turtle farms, producing some 10 million turtles a year. (In 2004, it was reported that there were 72 turtle farms licensed by the State of Louisiana.) The industry is said to have started "70-some years" ago (i.e., in the 1930s) with farmers collecting eggs laid by wild turtles, getting them to hatch, and selling the hatchlings as pets.
The US turtle industry suffered a serious setback in 1975, when the US Food and Drug Administration prohibited interstate trade in small turtles (those smaller than 4 inches across), in order to prevent spreading salmonella infection. Although the ban has remained in force ever since, Louisiana farmers have adopted an anti-salmonella prophylactic treatment regimen developed at Louisiana State University by Ronald Siebeling and later enhanced by Mark Mitchell, and focused on raising turtles for export to foreign countries (to which the FDA ban presumably does not apply).
An idea of the volume of the US turtle industry can be obtained from the data recorded when some of their turtles are exported. Although the cumulative export data include both farmed and wild-caught turtles, the "farmed" component is usually predominant. According to a study by the World Chelonian Trust, 97% out of 31.8 million turtles and tortoises that were exported out of the U.S. over a three-year period (November 4, 2002 - November 26, 2005) were farm-raised. It has been estimated (presumably, over the same 2002-2005 period) that about 47% of the US turtle exports go to People's Republic of China (predominantly to Hong Kong), another 20% to Taiwan, and 11% to Mexico.  
Over one-half of all turtles exported from the USA over the study period were Trachemys scripta ( 17,524,786 individuals: primarily Trachemys scripta elegans (Red-ear Sliders) - 15,181,688 individuals, as well as other Trachemys scripta subspecies).
The Cayman Turtle Farm is a 23-acre marine park that operates in the West Bay district of Cayman Islands. They raise Green Sea Turtles, primarily for their meat, a traditional food in Caymanian culture which was increasingly scarce in the wild. The farm, established in 1968, can produce upwards of 1800 turtles a year, however, some of the farmed turtles are released. Between 1980 and 2006, the farm released some 30,600 turtles to the wild, and these individuals have subsequently been found throughout the Caribbean. Presently, the facility's "vision statement" is "to be the Cayman Islands’ premier tourism attraction".
Due to the lack of CITES certification, turtle products cannot be exported outside of the Cayman Islands and the United Kingdom. However, the farm claims on its website that "even the sale of turtle meat has a positive conservation impact because it greatly reduces poaching in the wild, which is often otherwise uncontrollable, both in terms of numbers and indiscriminate in terms of age and sex".
Effect on wild populations
Conservation experts display somewhat ambivalent view toward the effect of turtle farming on the wild turtle populations, many of which are endangered. As the conservation expert Peter Paul van Dijk noted, the farmed turtles gradually replace wild-caught ones in the open markets of China, with the percentage of farm-raised individuals in the "visible" trade growing from around 30% in 2000 to around 70% ca. 2007. On the other hand, he and other experts caution that turtle farming creates extra pressure on the wild populations, as farmers commonly believe in the superiority of wild-caught breeding stock and place a premium on wild-caught breeders, which may create an incentive for turtle hunters to seek and catch the very last remaining wild specimens of some species. 
Even the potentially appealing concept of raising turtles at a farm to release into the wild (as done with some numbers of sea turtles at the Caymans establishment) is questioned by some veterinarians who have had some experience with farm operations. They caution that this may introduce into the wild populations infectious diseases that occur on the farm but have not (yet) been occurring in the wild.
- Shi, Haitao; Parham, James F; Fan, Zhiyong; Hong, Meiling; Yin, Feng (2008-01-01), Evidence for the massive scale of turtle farming in China, Oryx (Cambridge University Press) 42: 147–150, doi:10.1017/S0030605308000562, retrieved 2009-12-26 Also at http://sites.google.com/site/jfparham/2008Shi.pdf
- Darrell Senneke, "Declared Turtle Trade From the United States - intro page"
- Links from Declared Turtle Trade From the United States - breakdown by species
- Declared Turtle Trade From the United States - Totals
- Hawksbill turtle ranching and captive breeding (CITES)
- La Ferme Corail: La Compagnie Réunionnaise d’Aquaculture et d’Industrie Littorale (French) (History of the Réunion farm)
- Just enough space to keep a turtle happy
- Mitsukuri, Kakichi (1906), "The cultivation of marine and fresh-water animals in Japan", in Rogers, Howard Jason, Congress of arts and science: Universal exposition, St. Louis, 1904, Houghton, Mifflin and company, pp. 694–732. The illustration from p. 701 is also reproduced on the book cover. The Japanese variety of Pelodiscus sinensis is referred to in Mitsukuri's article under its older name, Trionyx japonicus.
- Cultivation of marine and freshwater animals in Japan, Popular Science 67, August 1905: 382–383 (No author; mostly based on Mitsukuri (1906))
- "Update on Turtle Farming in China": an extract from a report of CITES animals committee meeting in Geneva (August 2003). Appears as Appendix 4 in: Subhuti Dharmananda. "Endangered species issues affecting turtles and tortoises used in Chinese medicine".
- Photo: Soft-shelled turtle farm ponds in foreground and broodstock building in background. The Hattori-Nakamura Soft-Shelled Turtle Farm. (Image ID: fish5196, NOAA's Fisheries Collection. Location: Japan, Hamamatsu. Photo Date: 2002. Photographer: Eileen McVey, NOAA Central Library.
- Wood, Fern (1991), "14", in Nash (editor), C.E., TURTLE CULTURE; Production of Aquatic Animals, World Animal Science, C4, Elsevier Science Publishers B.V., Amsterdam, retrieved 2013-10-21 (Originally appeared at the Cayman Islands Turtle Farm site, http://turtle.ky/scientific/culture.htm)
- "Turtle farms threaten rare species, experts say". Fish Farmer, 30 March 2007. Their source is Shi et al. 2007.
- Hilary Hylton, "Keeping U.S. Turtles Out of China", Time Magazine, 2007-05-08. There is also a copy of the article at the TSA site. Articles by Peter Paul van Dijk are mentioned as the main source.
- Zhang Jian (章剑), A new edition of the national standard "Chinese soft-shelled turtle pond aquaculture technical specifications" is to be published. Turtle news (中国龟鳖网), 18 November 2009 (appears to be a machine translation of the more comprehensible Chinese original, "国家标准《中华鳖池塘养殖技术规范》新版即将问世", at http://www.cnturtle.com/sdp/70503/2/main-996823/0.html )
- Zhang Jian (章剑), Chinese soft-shelled turtle value return, Turtle news (中国龟鳖网), 13 August 2009 (appears to be a machine translation of the more comprehensible "中华鳖价值回归", at http://www.cnturtle.com/sdp/70503/2/main-996823/0.html)
- Zhao Huanxin, "Low price hurts turtle breeding". China Daily 1999-06-30 (scroll to the end of the file to find that article)
- Shi, Haitao; Parham, James Ford (2000), Preliminary Observations of a Large Turtle Farm in Hainan Province, People's Republic of China, Turtle and Tortoise Newsletter 3: 4–6 Includes photographs of the facilities.
- Dalton, Rex (2003), Mock turtles, Nature 423 (6937): 219–220, doi:10.1038/423219a, PMID 12748611
- James E. Barzyk Turtles in Crisis: The Asian Food Markets. The article itself is not dated, but mostly refers to data in the range 1995-2000.
- Vern Weitzel, Wildlife Breeding: Village Snake and Turtle Farm near Hai Duong
- Thanh Quy (December 2, 2004), Going to Thailand to Learn How to Farm Soft-shell Turtles, Vietnam Economic Times (202)
- THEO EMERY (April 19, 2012), As Asians Flock to Northern Virginia, Laws and Palates Collide, The New York Times
- Louisiana Turtle Farmers Continue Fight for Domestic Market
- Turtle Farmers Try To Crack Back Into Domestic Market
- Declared Turtle Trade From the United States - Destinations (Major destinations: 13,625,673 animals to Hong Kong, 1,365,687 to the rest of the PRC, 6,238,300 to Taiwan, 3,478,257 to Mexico, and 1,527,771 to Japan, 945,257 to Singapore, and 596,965 to Spain.)
- Declared Turtle Trade From the United States - Observations
- Declared Turtle Trade From the United States - Trachemys scripta
- "Cayman Islands Turtle Farm". Retrieved 2009-10-28.[dead link]
- "Cayman Islands Turtle Farm : About us". Retrieved 2011-03-17.
- "Cayman Islands Turtle Farm : Research and Conservation". Retrieved 2011-03-17.
- Kunst, G.K.; Gemel, R. (2000), Zur Kulturgeschichte der Schildkröten unter besonderer Berücksichtigung der Bedeutung der Europäischen Sumpfschildkröte, Emys orbicularis (L.) in Österreich, Stapfia 69 (149): 21–62 (pp. 38-40)
- La tortue de jardin revient en force en France, AFP, 2012-11-21
- Shi, Haitao; Parham, James F.; Lau, M.; Chen, T.-H. (February 2007), Farming endangered turtles to extinction in China, Conservation Biology 42 (1): 5–6
- GUEST EDITORIAL: MARINE TURTLE FARMING AND HEALTH ISSUES, Marine Turtle Newsletter 72, 1996: 13–15