The Asian giant softshell turtle, Pelochelys cantorii (Trionychidae), occurs in China, India, Bangladesh, Myanmar, Laos, Thailand, Cambodia, Vietnam, Malaysia, Indonesia, and the Philippines and is one of the largest turtles in China (Zhao 1998; Das 2008). In China, P. cantorii was listed as one of China's First Grade Protected aquatic wildlife and is critically endangered in the wild (Zhao 1998). Pelochelys cantorii was listed as Endangered on the Red List of Endangered Species by the International Union for Conservation of Nature (IUCN) in 2000 (Asian Turtle Trade Working Group 2000). According to ancient texts, in China this turtle not only was widely distributed but also occurred in large numbers before the 11th century BC (Gu and Ma 2000). Within recent decades, populations of this aquatic species have been heavily depleted and severely fragmented, which can be attributed to over-collection for human consumption, and habitat destruction due to hydroelectric power engineering, urbanization, and water pollution (Lau and Shi 2000; Chen et al. 2013).

According the National Directory of Nature Reserves in 2015 from the Minister of Ecology and Environment for the People's Republic of China, 14 nature reserves were established between 1990 and 2007 to aid in the protection of P. cantorii. Among them, only one is a provincial-level nature reserve, while the others are municipal- or county-level reserves. Information on the present situation of the species in the reserves is not only scarce but also dated (Gu and Ma 2000; Gu et al. 2000; Ruan et al. 2001), thus information on the latest situation of this species in China is urgently needed for its protection.

The Guangning Nature Reserve for P. cantorii was founded in 2002 with a 5-km Suijiang River section. In this section of the nature reserve, 17 fishermen, who lived on boats with their families, have moved onshore and transferred to other industries since 2014. The last time the species was observed at Guangning Nature Reserve was in 2006 when 2 live individuals were accidentally caught by fishermen. The 2 turtles successfully bred in 2014 after 8 yrs in captivity, which was the first report of successful breeding in China (Zhu et al. 2015).

Our study investigated and surveyed the reserves involved in the protection of P. cantorii and the captive-breeding centers from 2015 to 2018. Additionally, a questionnaire-based survey was conducted in the Guangning P. cantorii nature reserve, where the first successful artificial breeding occurred. The conservation status of P. cantorii in China is summarized and suggestions for its conservation are put forward.

Methods: Semistructured Interviews. — To determine the conservation status of P. cantorii, 13 different nature reserves (S1 to S13) in the National Directory of Nature Reserves involved the protection of P. cantorii were surveyed by a field trip and semistructured interviews in China between 2015 and 2018; only the Nanxi River Nature Reserve (lat 22°30′05.17 ″N, long 103°57′55.84 ″E) was not surveyed (Table 1; Fig. 1). Respondents included fishery, wildlife, and nature reserve management authorities as well as 2–3 experienced fishermen. We used the number of nature reserve staff, amount of protection funds, deposited documents, and awareness and education as indices of the management status of P. cantorii nature reserves and water quality, nesting area, sediment, hydrological changes, and aquatic faunal biomass as indices of habitat status in nature reserves to identify suitable habitats for the species. Nature reserve management and habitat status were qualitatively ranked from 1 (poor) to 4 (excellent) based on the following factors:

Table 1. Nature reserves of Pelochelys cantorii that were investigated.

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Staff number: The number of management personnel in the Asian giant softshell turtle nature reserve (1 = none, 2 = 1 person, 3 = 2 people, 4 = 3 or more staff).

Protection funds: Special annual funds for the management and construction of protected areas (1 = none, 2 = 1–50,000 yuan, 3 = > 50,000–200,000 yuan, 4 = > 200,000 yuan).

Deposited documents: Conservation area construction, individual discovery records, management documents, and other related documents (1 = almost none; 2 = some, but not much value; 3 = more, but some omissions; 4 = more comprehensive).

Awareness and education: Publicity and protection work of the protected areas and the species, such as broadcasting, newspapers, billboards, and boundary markers (1 = almost none, 2 = low intensity, 3 = moderate intensity, 4 = strong).

Water quality: The water quality of the conserved river (1 = poor, serious pollution; 2 = general, some pollution; 3 = better, with little household garbage; 4 = good, basically pollution-free).

Nesting area: Suitable area for nesting and breeding (1 = no obvious bank on either side, 2 = less than 5 50-m-long riverbanks, 3 = many discontinuous beaches, 4 = many continuous riverbanks).

Sediment: Suitable medium for nesting, coastal sediment of the river section of the reserve (1 = rocky river bank, 2 = gravel bank, 3 = sandstone mudflats, 4 = sand bank).

Hydrological changes: The water temperature, water depth, water flow, and other hydrological changes before and after hydroelectric power engineering (1 = significantly altered, 2 = moderate changes, 3 = a little changed, 4 = unchanged).

Biomass: Changes in aquatic species and resources of fish, shrimp, crab, and shellfish in the river in the last 10 yrs (1 = significantly decreased, 2 = moderate changes, 3 = a little change, 4 = no significant change).

Fisherman Questionnaire. — In 2017, we conducted a survey questionnaire with fishermen along the river section of the Guangning Nature Reserve and hand-distributed 100 questionnaires. Before the questionnaire, the interviewer showed pictures of P. cantorii and the Chinese softshell turtle (Pelodiscus sinensis) to the respondents to test their knowledge of identification. The questionnaire had 5 questions: 1) Do you know the Chinese Class I Protection animal P. cantorii and can you tell P. cantorii from P. sinensis? 2) Have you ever seen a live P. cantorii? If so, note the time and estimated size. 3) Has the water quality of the river changed in the last 10 yrs? 4) How do you think the number and species of fish in the protected river has changed in the last 10 yrs? 5) Do you think this species is still present in the nature reserve?

The State of Artificial Domestication and Breeding. — A survey of P. cantorii domestication and successful breeding enterprises (S1, S11, S14–S16) was conducted (Tables 1 and 2). The information obtained included mainly the year turtles were taken into captivity, size and sex, breeding history, nesting facilities, nesting conditions, and hatching methods.

Table 2. Captive-breeding centers for Pelochelys cantorii that were investigated.

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Results: Management and Habitat Status. — According to the survey results (Table 3), the site S1, which is the only provincial-level P. cantorii nature reserve in China, did the best job of conservation management, with an index of 3.75. The second-ranked reserve was Guangning Nature Reserve (S12), with an index of 3.00. The first successful artificial hatching of P. cantorii in China occurred at this site, so some attention had been given by the government administration. The sites S5, S8, and S9 each had an index of 1.25. Habitats in the 13 reserves generally had been altered to some extent, with a total mean habitat status index of 2.22 (1.60–2.80).

Table 3. The state of management and habitat status in China (rated from 1 to 4, poor to excellent).

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Fisherman Questionnaire. — A total of 66 valid questionnaires were obtained and the ages of the respondents who lived along the river of Guangning Nature Reserve were between 45 and 72 years old. The percentage of respondents who had seen the species and could distinguish it from P. sinensis was 15%; however, an additional 21% of the respondents had heard of the species or seen a picture of it. The number of respondents who did not know the species was 64%.

According to respondents, only 1 individual P. cantorii was found before 1985, with an approximate size between 1 and 1.5 kg. From 1985 to 1995, a single P. cantorii was found, of approximate size range 20–25 kg. From 1996 to 2005, 7 P. cantorii were found, of which 3 were 5–10 kg, 2 were 10–15 kg, 1 was 15–20 kg, and 1 was > 20 kg. In 2009, a single individual was observed and was approximately 30 kg.

Nine percent of respondents thought the water quality remained unchanged and 9% thought the water quality had become slightly worse, but with little influence on the aquatic environment; 73% of the respondents thought the water quality was moderately polluted, and 9% felt that pollution was severe. Eleven percent of respondents thought the fish populations and other aquatic species had exhibited few changes, 77% thought the fish species diversity and quantity were reduced, 9% thought that there were more species but lower quantities of species, 1.5% believed that the populations were greater but there were fewer species, and 1.5% thought that both the species and populations had increased.

Sixty-six percent of respondents thought there were still living P. cantorii in the river, 9% thought there were no more living individuals in the river, and 25% did not give opinions. Although P. cantorii has been designated as a First Grade Protected Animal by China since 1989, 64% of respondents who live along the nature reserve river were unfamiliar with the species.

The State of Artificial Domestication and Breeding. — According to the results of our research, there are 13 adult P. cantorii in captivity at 5 sites in China. Three of these sites have successfully bred P. cantorii (Table 4). One site (S14) is the Guangning Nature Reserve for P. cantorii (1 male and 1 female), where eggs laid by the female in 2014 and 2016 were hatched at indoor temperatures with vermiculite as the hatching medium. The other site (S15) is the Gaoming research base of turtle breeding (2 males and 2 females), where eggs laid by 2 P. cantorii females in 2015 were hatched in manually controlled temperatures with vermiculite as the hatching medium (Fig. 3). The third site is the Xishuangbanna Lancang River–Mekong River basin P. cantorii and Chinese algae-eater (Gyrinocheilus aymonieri) Nature Reserve (S16; 1 male and 2 females), where 92 hatchings were hatched in natural nests in sand banks, although all died while being raised in the way that P. sinensis are cultured. Apart from these 3 sites, 2 P. cantorii individuals (both females) are in captivity in Qingtian Provincial P. cantorii Nature Reserve in Zhejiang (S1) and 2 P. cantorii individuals (gender unknown) are in captivity in the Sihui Nature Reserve for P. cantorii in Guangdong (S11).

Table 4. Artificially incubated young Pelochelys cantorii (through October 2018).

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At present, after nearly 5 yrs of research, artificial breeding for P. cantorii has made some achievements with S15 doing the best job. The hatching rate at S15 was over 60% and the annual survival rate of hatchlings was over 74% from 2016 to 2018.

Discussion. — Historically, P. cantorii was widely distributed in China, but in 1989 the species was designated as a national priority aquatic species to protect. The nature reserves for P. cantorii that were established from 1990 to 2007 are weakly effective as they lack personnel, funds, and management as determined in this study. Because of the construction of water conservation projects, the sandbars for laying eggs in the turtles' historical habitat (Wu and Wang 1987) have largely disappeared and the species has rarely been observed in the past 10 yrs. The biodiversity and resources of the fish species in the river have been reduced to varying degrees, which affects the survival and development of turtles to a certain extent. Although in 1989 the species was designated as a national priority aquatic species to protect, this species has served as food for humans throughout the history of China, yet most of the people surveyed did not know P. cantorii, so there is a possibility that P. cantorii could be confused with P.sinensis and illegally consumed (Wu and Wang 1987). For P. cantorii, its large size and the fact that sexual maturity is delayed have accelerated its extinction. Other large, edible trionychid species with delayed sexual maturity are endangered, such as the Yangtze giant softshell turtle, Rafetus swinhoei (Wang et al. 2013), the Euphrates softshell turtle, Rafetus euphraticus (Ghaffari et al. 2008, 2014), and the narrow-headed softshell turtle, Chitra indica (Sirsi et al. 2016).

The breeding program has achieved some successes (Zhu et al. 2015; Wildlife Conservation Society 2017; Hong et al. 2018); however, knowledge of the species' biology is still limited from the literature we examined. For example, mating patterns, wintering conditions in the wild, growth and development, age and size at sexual maturity, and other aspects of its ecology and natural history are not well understood. Although a certain number of hatchlings can be obtained, scientific research on turtle conservation biology should be strengthened in order to carry out breeding and release work.

In China, P. cantorii individuals typically occur in side channels of the main drainage system, which is in line with their living habits. Some of the local old fishermen stated that the turtles were migratory animals that lived in the main river and nested in small channels. According to our investigation, historically, the species was distributed in rivers in China such as the Mekong River basin, the Pearl River, the Hanjiang River, the Minjiang River, and the Oujiang River systems, which all drain into the ocean. The species occurs occasionally in coastal marine waters (Das 2008); therefore, if enough sample locations could be collected, we could study the genetic differentiation of P. cantorii among different river systems to understand its complete natural life history. At the same time, there is very little information on the intraspecific genetic structure of P. cantorii (Zhang et al. 2018), considering that levels of genetic diversity are generally low among turtles. Knowledge of genetics is increasingly recognized as a critical element of conservation biology (Moritz 1994; Soltis and Gitzendanner 1999; Alacs et al. 2007; IUCN 2018). It would be of great significance to study whether there is genetic diversity of P. cantorii among different river systems.

Because P. cantorii can dive into the sand for a long time, the traditional methods for the survey of fish resources, including acoustic methods, are very difficult to use and not effective. Therefore, an effective method such as environmental DNA (Ficetola et al. 2008; Davy et al. 2015; Beauclerc et al. 2019) is urgently needed to investigate the status of the species.

In general, although P. cantorii was widely distributed historically, populations have become smaller and increasingly fragmented spatially due to anthropogenic activities in recent years. Based on the result of our survey, while publicizing the status and conservation of this poorly known species, we should also strengthen conservation biology research, conduct resource surveys using new technology, and perform genetic analyses. Habitat protection and restoration should also be given consideration in P. cantorii conservation. Active efforts have been made to enhance the species' artificial breeding, proliferate the species, and release P. cantorii into suitable aquatic environments and the success of these efforts will ultimately depend on the existence of adequate habitat.