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  1. Identity
    1. Biological features
    2. Images gallery
  2. Profile
    1. Historical background
    2. Main producer countries
    3. Habitat and biology
  3. Production
    1. Production cycle
    2. Production systems
    3. Diseases and control measures
  4. Statistics
    1. Production statistics
    2. Market and trade
  1. Status and trends
    1. Main issues
      1. Responsible aquaculture practices
    2. References
      1. Related links
    Identity


    Trionyx sinensis  Wiegmann, 1834 [Trionychidae]
    FAO Names:  En - Chinese softshell turtle,   Fr - ,  Es -
       
    Biological features
    Colour olive grey to greenish brown with numerous yellow-bordered black spots and yellowish dots in younger individuals; yellow spotting tends to disappear in adults; many adults show no pattern and have uniformly olive carapaces. Round to oval carapace; ridge of carapace in males slightly sunken with round-shape at posterior; longer neck and tail than females; plastron sunken for clasping female carapace during copulation; neck can be extended to end of carapace; more active than females. Shell of females rough with oval carapace; plastron almost arched; tail and neck is thicker than male; space between two posterior legs larger than male; more timorous and meek than males. Generally, males differ from females in being shallower and having long, thick tails, with the vent near the tip. Females are more domed and the tails barely extend past the carapace rim. Females are normally larger than males, to allow for egg development.
    Images gallery
    The female lay eggs in/on sandThe female lay eggs in/on sand
    Hatcheries in small rectangular tanksHatcheries in round basins
    Grow-out pondsThe female turtle
    Profile
    Historical background
    The soft-shell turtle Tryonyx sinensis is the most common turtle species that has been raised in China and Southeast Asia (e.g. Thailand, Japan and Taiwan P.C.); more than a thousand turtle farms exist in southern China alone. This species is favoured for commercial production because of its high reproductive potential, widespread consumer acceptance and the available experience in farming it.

    Turtle farming also exists in Viet Nam, at least on a family farm scale. As early as 1993 researchers noted the existence of several hundred families near Hai Duong province (northern Viet Nam) raising turtles. By 2004, commercial herds of several tens of thousands of soft-shell turtles were in operation near Ha Tinh province (North Central Viet Nam); the operators having studied the turtle farming techniques in Thailand. They later expanded this operation in southern Viet Nam.
    Main producer countries
    Soft shell turtles are farmed in China (Liaoning, Shaanxi, Anhui, Zhejiang, Guangdong); the north of Viet Nam; Taiwan P.C.; the south of Far Eastern Russia; Korea; the Bonin Islands; Indonesia (Timor); Japan; and Thailand. They have also been introduced into West Malaysia and the USA (Hawaii).
    Main producer countries of Trionyx sinensis (FAO Fishery Statistics, 2006)
    Habitat and biology
    Soft-shell turtles are voracious but grow slowly. They are almost wholly aquatic but come ashore when the weather is favourable to sunbathe (in order to maintain body temperature; this also controls parasites) and for egg laying. They breathe normally through their lungs but can also absorb oxygen while submerged, either through their skin or by passing water over membranes in the throat or cloaca. They remain buried at the bottom of their aquatic habitat (rivers, streams, lakes, marshes, and rice fields) for most of the day.

    Soft-shell turtles have an aggressive disposition, as do all carnivores; however, they appear timorous and submerge themselves in hiding places under water when a noise or human/animal shadows occur. When turtles are starving, they are cannibalistic. If turtles are injured, they are savagely bitten by the other turtles.

    In nature the soft-shell turtle Tryonyx sinensis is predominantly carnivorous; the most common foods eaten are zooplankton, insects, crayfish, crabs, fish, molluscs and other aquatic invertebrates. Under farming conditions, turtles like spoiled (decomposed) predators; they compete against with other animals for prey; sweet potato and corn are also consumed. They eat well in summer, the food requirement being in the range of 5-10 per cent BW/day. In winter (December to March) the requirement is less (~3-5 per cent BW/day). However, turtles are very tolerant of starvation.

    Soft-shell turtles lay their eggs in sand or mud on the banks of the rivers, streams or pools in which they live. Viable sperm may be retained in the female oviducts for about 6 months after copulation, hence the lower proportion of males compared to females. The breeding season of T. sinensis begins early in the spring and continues through to late autumn. Turtle females spawn simultaneously on days when there is heavy thunderous rain. When a disturbed layer of soil and footmarks are observed on egg-laying sites, these cover newly-laid eggs. Gently upturning this soil and a thin layer of sand, small holes of 4-5 cm in diameter and 10-15 cm deep can be seen. The eggs are stacked in layers from the bottom to the mouth of the nest. Newly-laid eggs stick together; the eggshells are soft and leathery to the touch. After spawning, turtle females move to a place nearby their nest for a rest and to protect their eggs.

    After 5-7 days of spawning, T. sinensis females are ready to mate again. Females with a body weight of 4 000-5 000 g can produce 4-5 clutches in a single year. The diameter of large eggs is 17-20 mm, with a weight of 6.0-6.5 g. The appropriate temperature range for breeding is 25-32 °C.
    Production
    Production cycle

    Production cycle of Trionyx sinensis

    Production systems
    Seed supply and hatchery techniques 
    Selection of broodstock

    Mature parental turtles, which are selected from those turtles already held on the farm, must be of uniform size, in good health and without scratches or malformation. Turtles of at least one year old are selected. The optimum male to female ratio is 1 male to 5 females. Fresh chopped fish, shrimp and snails are fed in fixed feeding troughs at 2-3 per cent BW/day.

    Breeding ponds

    Breeding ponds are located in places where there is abundant water of good quality and a proper water supply and drainage system is provided. Typically, pond areas are 100-400 m2 with 1.5-1.8 m dikes and a water level of 1 m. Dikes are constructed large enough for turtles to bask in the sunlight and have a gentle incline that allows the turtles to crawl out onto the land area for basking as well as to find nesting places. This gentle slope not only allows turtles to crawl out onto the land but is sometimes used by turtles, particularly any which are sick, to warm up. The pond bottom is filled with fine sand or a mixture of soil and sand to a depth of 15-20 cm. A fence with a minimum height of 50 cm surrounds the ponds; its walls must be smooth, with the tops edged with steel of ~10 cm high facing towards the breeding pond. The foot of these walls is fixed firmly in the ground to a depth of ~40-50 cm. Planting trees on the dikes creates shade for the turtles to rest and nest. Nesting beaches with a sand depth of 50 cm are located in or close to the middle of the breeding pond in quiet places; their area varies in size depending upon the amount of mature parental stock in the pond (~20 turtles/m2).

    Breeding

    Soft-shell turtle females lay their eggs at night after crawling around the pond looking for a moist soft soil area and a ‘secret’ place for nesting. Females employ their hind legs or their snout to dig a hole with an entrance of 10-15 cm diameter; they also use their hind legs to layer and stack their eggs and then cover them with soil and sand. Females may ovulate 2-5 times/year, laying 8-12 to 20-30 eggs on each occasion. The white, spherical eggs average about 20 mm in diameter but may be as large as 24 mm. After heavy rainfall, turtles do not lay their eggs in the nesting beach provided but use the dike areas where the soil is soft. On these days eggs can be collected there.

    Egg collection and incubation

    Eggs are collected for incubation by gently digging up the sand/soil layer. Incubation is carried out in Styrofoam or plastic boxes. The incubation containers are filled with clean, fine sand to a depth of 4-5 cm and the eggs are placed in rows all over bottom of the boxes. The eggs are then covered with 4-5 cm of sand and the boxes closed with lids to maintain constant temperature. During incubation, the moisture content of the sand must be maintained at 80 per cent by regularly spraying water onto it. Incubation temperature affects hatching time – for example if the range is 30 34 °C hatching occurs at day 50-55, whereas at a range of 25-34-  °C it takes 60 days. After being transferred to the hatchery the eggs are left absolutely undisturbed, except for periodic moistening of the sand. At about day 50 the top layer of sand is removed, and hatching normally occurs around day 55. When the turtles hatch, they squirm their way to the surface and head toward the water. Newly-hatched turtles (hatchlings) must be transferred to water within 15 minutes or they easily die.

    Hatchling husbandry

    The hatchlings are kept in small rectangular tanks (40 cm x 50 cm) or round basins (50-60 cm diameter), depending on the number of eggs to be incubated. These are provided with water hyacinth or plastic rope as shelters for 1 week before being transferred to nursery 4-20 m2 tanks. Hatchlings are fed with cooked egg yolks and threadworms and the water is exchanged daily. Nursery tanks may be concrete or lined-ponds filled with a sand depth of 10 cm. Sand beaches or floating wood is provided for young turtles to bask and rest. Before use, the nursery units are disinfected with 100-150 ppm formalin, 2-3 ppm chlorine, 50-70 ppm potassium permanganate, or other chemicals such as lime; then filled with clean freshwater to a depth of 20-30 cm. Before stocking, the young turtles are disinfected in 10‰ NaCl solution or 1 ppm permanganate solution for 10 min before transfer to the rearing tanks. The hatchlings are stocked at 30-50/m2 and fed earthworms, threadworms, fresh chopped fish or shrimp.
    Ongrowing techniques 
    Pond design

    Grow-out ponds vary from 100 m2 to over 1 000 m2, depending upon the location of the farm and production capacity. The depth of the ponds varies from 1.0 to 1.5 m and a bottom layer of mud is maintained at ~10-20 cm. The rearing ponds are generally located near canals or rivers so that there is a continuous flow of fresh water into the ponds. In locations where there are tidal fluctuations, gates are used to control the flow of water, in order to maintain a minimum water depth of ~0.8 m. The other characteristics of the grow-out ponds are the same as the breeding ponds but without the breeding beach.

    Selection of animals for stocking

    Young turtles selected from the hatchling containers after 2 months should be of uniform size, in good health and free from pathogens. The initial stocking density when the turtles are 10-15 g in weight is 10-15/m²; density is reduced as the turtles grow to 5-10/m² at 100-200 g and 3/m² at 500 g.

    Pond management

    Dikes, fences and gates are regularly checked to minimize the escape of turtles. Water exchange is carried out weekly or when the water colour becomes dark (when water turbidity is <30 cm, turtles tend to leave the water. Noise and excessive handling of the turtles is avoided to prevent frightening them. Feed is presented on feeding trays that are placed near the pond surface and monitored daily to ensure sufficient food. Over-feeding should be avoided to minimize water pollution, which causes turtles to be susceptible to disease. Feeding is done twice a day and the ration is adjusted according to turtle weight [<200g: 7–10 percent BW/day; 200-500 g: 5-7 percent BW/day; >500 g: 3-5 percent BW/day]. After about 6 months of rearing, the turtles are graded to avoid fighting. Males and females are separated when they reach ≥500 g.

    Growth rate

    Soft-shell turtles are characterized by their slow growth rate, which is related to environmental conditions such as weather, temperature, food quality, etc. Their weight reaches 400-600 g after 1 year of culture and 1.0-1.5 kg within 2 years. In optimal culture conditions (low stocking density, favourable food and good management) their weight may reach 1.0-1.2 kg in a single year. From April to November, turtles eat well and grow quickly. When the temperature falls below 10° C, feeding rate decreases and growth is slower. Under the same culture conditions the growth of females is faster than males.
    Feed supply 
    The feed used consists of low value fish species, shrimp, worms, snails, pelleted or home-made feeds (mixtures of rice bran, sweet potato, soybean meal supplemented with premix and digestive enzyme). These feeds are sourced locally.
    Harvesting techniques 
    12-16 months after stocking in the rearing ponds, the turtles reach a weight of 1.0-1.5 kg or more. At this stage partial harvesting is carried out by using nets or by hand. Ponds are then completely harvested by draining and catching by hand.
    Handling and processing 
    Each turtle is individually placed in a plastic or cloth bag (mesh size: 3-4 mm) and then placed together in sacks, baskets or boxes and kept moist. Gentle handling and manipulation is essential to avoid damaging the turtles. Normally, the turtle farmers sell their output to wholesalers, who resell them to restaurants or to companies that export them to Thailand, Taiwan P.C., etc.
    Diseases and control measures
    In general, disease problems only occur among turtles raised under intensive rearing conditions. Turtle diseases can be prevented by maintaining adequate feed levels, proper nutrition, good water quality and low stocking densities; however, even in well-cared for turtles, infections may still occur. The most common diseases are described as follows:

    In some cases antibiotics and other pharmaceuticals have been used in treatment but their inclusion in this table does not imply an FAO recommendation.

    DISEASEAGENTTYPESYNDROMEMEASURES
    Fungal infections Saprolegnia spp. Fungi White patches - tufts of dirty, cotton-like material on skin & whitish areas on the shell, usually secondary infections Exchange water: treat with 15-20 ppm KMnO4 or 7-10 ppm CuSO4 by immersion in the solution for 30 min/day, over a 3-4 day period
    Septicaemic cutaneous ulcerative disease Citrobacter freundii
    Serratia spp.
    Bacteria Pitted scutes & sloughing with an underlying purulent discharge; anorexia; lethargy; petechial haemorrhages on the shell & skin; liver necrosis Good hygiene; adding 20-30 mg/kg of streptomycin or penicillin to diet for 3-4 days
    Necrotic stomatitis Pseudomonas Aeromonas Bacteria Excessive salivation & redness of the mouth lining; cheese-like pus accumulates within the mouth; petechiae in oral cavity; ulceration or granuloma formation on mouth 3-6 mg/kg Amoxicillin or 5-10 mg/kg Enrofloxacin every 24-48 hr
    Swollen neck disease Hydrophyla sp. Pseudomonas sp. Bacteria Swelling of neck; closed eyelids; necrosis of feet & plastron 150-200 ppm formalin for 30-60 min; 20-30 mg/kg streptomycin or penicillin in feed for 3-4 days
    Unnamed Viral disease Virus pathogen Virus Poor appetite; red blood points on neck & back; ulcerated calipash skin; purplish red spots on scute; carapace perforations; white mucus layer adhering to limbs & neck No good therapy; best prevention by use of optimal stocking density & good pond management
    Softened shell or swollen eyes Lack of calcium & other minerals or lack of Vitamin A Nutritional deficiencies Deformed shells & soft bones or swollen eyes with closed eyelids Supplemental calcium, minerals & vitamin A in turtle diets


    Suppliers of pathology expertise

    No specific laboratories used. Farmers self treat or consult veterinary agencies.
    Statistics
    Production statistics
     
    Up to 2007, production of farmed soft-shell turtles was not recorded separately in aquaculture statistics by Japan. In addition, Viet Nam did not declare farmed production of any species of turtles.
    Market and trade
    Little recent data on market and trade specifically in soft shell turtles is available. However, it is recorded that Indonesia exported 828 tonnes of various turtles in 1998, representing at least 369,719 individuals. Trade observations in Sumatra estimated that at least 25 tonnes of live turtles were exported per week from Sumatra alone in 1999; this region accounts for only one-quarter of Indonesia’s declared turtle exports, suggesting that total Indonesian exports may be at the order of 5 000 tonnes annually. Malaysia exported a total of 2 469 504 live turtles in the first 9 months of 1999, of which 1 505 172 were captive-bred exotic species and 964 332 individuals were native species collected from the wild. Thailand showed a significant rise and fall in live freshwater turtle exports during the 1990s, reaching a peak of over 6 million animals in 1996 but collapsing to about 470  000 animals during the first 7 months of 1999. The vast majority of Thailand’s turtle exports comprise farmed soft shell turtles and export numbers were significantly influenced by import restrictions in consumer countries. No quantitative data are available for turtle exports from Cambodia, Laos, Viet Nam or Myanmar; export volumes are known to be substantial, however.

    Other available data relates to the trade in turtle shells, not turtle meat (for example, Taiwan P.C. imported an average of 29 tonnes of soft shell turtle shells annually between 1999 and 2008). Trionyx sinensis are used for traditional medicine and as food. The shells of turtles are usually used as a by-product in restaurants; they mainly originate from turtle farms. In the Chinese medicine, market shells are traded in whole pieces of plastron from hard shell turtles and are unlikely to be the by-product of turtle meat (usually consumed as turtle soup in Asia). The number of exporting countries involved has decreased in the trade records. No records of turtle shells were found from South Asia, such as Bangladesh and Pakistan, in 1992–1998. In 2006–2008/2009, turtle shells were only imported from China, Indonesia, and Viet Nam to Taiwan P.C.
    Status and trends
    Although the soft shell turtle is a protected species, turtles that are reared in farms can be traded. Soft shell turtle farming provides a means of poverty alleviation in developing Asian countries. However, in order to encourage this, selective breeding programmes are required to improve disease resistance and improved methods of farming need to be developed.
    Main issues
    The main issues are the need to:
    • Promote turtle farming for poor families.
    • Improve farming methods and disease management.
    • Provide capital for farmers to initiate this form of aquaculture.
    Responsible aquaculture practices
    In addition to promoting normal practises in responsible aquaculture, as promoted by FAO, the rules of CITES must be observed.
    References
    Bibliography 
    Chen, T.H., Chang, H.C. & Lue, K.Y. 2009. Unregulated trade in turtle shells for Chinese traditional medicine in East and Southeast Asia: the case of Taiwan. Chelonian Conservation and Biology, 8(1):11-18.
    Cherepanov, G.O. 1995. Ontogenetic development of the shell in Trionyx sinensis (Trionychidae, testudinata) and some questions on the nomenclature of bony plates. Russian Journal of Herpetology, 2(2):129-133.
    Choo, B.L. & Chou, L.M. 1984. Effect of a sand substrate on the growth and survival of hatchlings of the softshell turtle, Trionyx sinensis Wiegmann. Aquaculture, 40(4):325-333.
    Grahame, J.W., Webb, S., Charlie, M. & Michelle, G. 2008. Captive breeding and marketing of turtles. Rural Industries Research and Development Corporation.
    Haitao, S., Parham, J.F., Zhiyong, F., Meiling, H. & Feng, Y. 2008. Evidence for the massive scale of turtle farming in China. Oryx, 42(1): 147-150.
    Nuangsaeng, B. & Boonyaratapalin, M. 2001. Protein requirement of juvenile soft-shelled turtle Trionyx sinensis Wiegmann. Aquaculture Research, 32, Suppl. 1:106-111.
    Qiya, Z., Zhengqiu, L., Yulin, J., Shaochang, L. & Jianfang, G. 1997. Discovery of virus pathogen from soft-shelled turtle Trionyx sinensis. Chinese Science Bulletin, 42(6):503-507.
    Saad, C.R., Alimon, A.R., Tong, H.H. & Roustaian, P. 2003. Practical diet evaluation with hatchlings of soft-shell turtle, Trionyx sinensis Wiegmann, in the tropics. Journal of Applied Ichthyology, 19(1):62-63
    Samedi, M. L. & Iskandar, D.T. 2000. Freshwater turtle and tortoise conservation and utilisation in Indonesia. In: P.P. van Dijk, B.L. Stuart & A.G.J. Rhodin (eds), Asian Turtle Trade: Proceedings of a Workshop on Conservation and Trade of Freshwater Turtles and Tortoises in Asia. Chelonian Research Monographs, 2:106-111.
    Sharma, D.S.K. & Tisen, O.B. 2000. Freshwater turtle and tortoise utilisation and conservation status in Malaysia. In: P.P. van Dijk, B.L. Stuart & A.G.J. Rhodin (eds), Asian Turtle Trade: Proceedings of a Workshop on Conservation and Trade of Freshwater Turtles and Tortoises in Asia. Chelonian Research Monographs, 2:120-128.
    Shepherd, C.R. 2000. Export of live freshwater turtles and tortoises from North Sumatra and Riau, Indonesia: a case study. In: P.P. van Dijk, B.L. Stuart & A.G.J. Rhodin (eds), Asian Turtle Trade: Proceedings of a Workshop on Conservation and Trade of Freshwater Turtles and Tortoises in Asia. Chelonian Research Monographs, 2:112-119.
    TRAFFIC Southeast Asia. 2001. An overview of the trade in live South-east Asian freshwater turtles. An Information Paper for the 17th Meeting of the CITES Animals Committee. Hanoi, Viet Nam, 7pp.
    Van Dijk, P.P. & Palasuwan, T. 2000. Conservation status, trade, and management of tortoises and freshwater turtles in Thailand. In: P.P. van Dijk, B.L. Stuart & A.G.J. Rhodin (eds), Asian Turtle Trade: Proceedings of a Workshop on Conservation and Trade of Freshwater Turtles and Tortoises in Asia. Chelonian Research Monographs, 2:137-144.
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