| The numbers of amphibians are going down in the globe. Tiger Frog (Hoplobatrachus rugulosus) has been listed in the IUCN Red List of threatened species. It is also defined as National Class II protected animal species in China. A common understanding on its endangered status has been reached. Hainan Island is the main distribution region of H. rugulosus in China. In history H. rugulosus had distributed extensively in the whole island. In recent years it is difficult to find the trace of H. rugulosus in wild. Even some scholars think that H. rugulosus has disappeared in Hainan. So it is very urgent to understand and grasp the current situation of H. rugulosus resources and to take measures to protect H. rugulosus effectively.In order to protect H. rugulosus in Hainan Island, the author conducted investigations of many times and experiments in the island, grasped the situation of distribution, number of individual in populations, illegal trade, the relationship between use of paddy field and the population, law enforcement for protection, feeding habits, detention time of food in stomach and artificial breeding in Hainan, established a method fit for basis units to distinguish wild or breeding individual through combing the practical situation in Hainan, and explored the optimal breeding model in Hainan Island by using the technology of applying estradiol benzoate in incubation water to promote number of females. In that H. rugulosus resource will be protected effectively.According to the poaching traces and field studies of tiger frog, it was identified that tiger frogs were distributed in 16 cities or counties in Hianna: Haikou, Wenchang, Qionghai, Wanning, Lingshui, Sanyan, Chenmai, Dingan, Tunchang, Qiongzhong, Lingao, Danzhou, Changjiang, Dongfang, Baisha and Ledong from 1991 and 2007. The populations were studied by using "Labeling and recapturing" method in the 5 cities or counties:Haikou, Sanyan, Qionghai, Baisha and Changjiang on March, April, May and August in 2006. According to the numbers of captured and recaptured individuals and the calculation by the formula of N=Mxn/m(N is the estimated value of the population of tiger frog, M is the captured number of first time, n is the captured number of the second time, m is the captured number of the second time with the label of the first time), it was estimated that there were 96 individuals on March in 2006 and 56 individuals on March in 2007 in 227 mu cropland in Dapo town in Haikou city. In Guilingyang study spot there were 37 individuals on April in 2006 and 0 individuals on April in 2007.In Tayang town in Qionghai city there were 18 individuals on April in 2006 and 9 individuals on April in 2007. In the valley of Mt. Bawanling in Qicha town in Changjiang city there was no frog both in 2006 and in 2007. In Qingsong town in Baisha county there were 58 individuals in 2006 and 63 individuals in 2007. In Gaofeng town in Sanya city there were 21 individuals in 2006 and 11 individuals in 2007. It was found that the major habitats of tiger frogs were paddy field, lotus field, water celery field, ditch in cropland, discarded cropland, muddy pond for tilapia fish, discarded pond, taro field and so on. It was indicated that there were certain numbers of wild population of tiger frog, but the number changed dramatically. It needs more study on the factors impacting on the wild populations, so as to protect wild tiger frogs.Paddy field is one of the major habitats of tiger frogs. During the development process of high efficient agriculture in Hainan Island, the new practice of banana planting in water field and the production of reverse season vegetables caused the change of land use. The plough way of paddy field was also changed. The study on use of paddy field and the number distribution of tiger frog was conducted in Fengfuyang since 2006 and extended to nearby Houfuyang and Changlong in 2008 in Dongchang Farm in Haikou city. It was found that on March in 2006 there were tiger frogs in paddy field, sweet potato field, water celery field, banana field, taro water field and muddy pond for tilapia fish, but not in tangerine field, sugar cane filed and taro dry field in Fengfuyang in Dongchang Farm. On March in 2007 there were tiger frogs in paddy field, sweet potato field, water celery field, banana field, taro water field and muddy pond for tilapia fish, but not in tangerine field, sugar cane filed and taro dry field in Fengfuyang in Dongchang Farm. On March in 2008 there were tiger frogs in sweet potato field, water celery field, taro water field and muddy pond for tilapia fish, but not in wax gourd field, banana field, tangerine field, sugar cane filed and taro dry field in Fengfuyang in Dongchang Farm. There were tiger frogs in paddy field, banana field, water celery field and taro water field, but not in sweet potato field, sugar cane field and taro dry field in Houhuyang in Dongchang Farm. There were tiger frogs in sweet potato field, water celery field, banana field and taro water field and muddy pond for tilapia fish, but not in tangerine field, sugar cane field and taro dry field in Changlongyang in Dongchang Farm. On March in 2009 there were tiger frogs in sweet potato field, water celery field, banana field, taro water field and muddy pond for tilapia fish, but not in tangerine field, sugar cane filed and taro dry field in Fengfuyang in Dongchang Farm. There were tiger frogs in banana field, water celery field and taro water field, but not in sweet potato field, sugar cane field and taro dry field in Houhuyang in Dongchang Farm. There were tiger frogs in banana field, water celery field, taro water field and muddy pond for tilapia fish, but not in sweet potato field, tangerine field, sugar cane field, taro dry field, lemon field and guava field in Changlongyang in Dongchang Farm.It was also found that paddy field, water celery field, taro water field, muddy pond for tilapia fish and banana water field with overgrown weeds were good habitats of tiger frogs. It was indicated that the changes of paddy field into water celery field, taro water field or muddy pond for tilapia fish did not affect the individual number of tiger frog’s population. The changes of paddy field into banana field, tangerine field, sugar cane field, sweet potato field, lemon field, wax gourd field or guava field affected the individual number of tiger frog’s population apparently. So it must be careful to change the use of paddy field.A survey of the market trading of H. rugulosus in Hainan was conducted during 2006—2008. The results showed that trades of H. rugulosus were found in 18 cities or counties in Hainan lasting 10 months in each year excepting for January and February. There were professional poachers in Hainan. The ways of poaching had changed. The illegal trades were because of a consuming market arising from wrong dietetic idea, easy capture and great benefits from the illegal trades. For protection of H. rugulosus the suggestions are propounded that strengthening enforcement of the law, promoting the public awareness through environmental education activities, conducting scientific researches on H. rugulosus, enhancing the monitoring of the species and complementing the natural population through artificial breeding of the species.During the 3 years’market investigation 2691 individuals were checked, parasitic disease was found, while skin rot disease, gastroenteritis, cataract, red-leg disease, gill rotten disease and so on which often occuerred in artificial breeding were not found. Through dissecting 309 individuals of tiger frog, it was found that 195 individuals had no food residue and 114 individuals had food residue in their stomachs. The chief composition of the food residue included animal species belonging to Mesogastropoda Viviparidae, Araneida Atypidae, Scolopendromorpha Scolopendridae, Orthoptera Gryllotalpidae, Orthoptera Gryllidae, Coleoptera Coccinellidae, Coleoptera Scarabeidae, Lepidoptera Sphingidae, Anura Ranidae, Decapoda Potamidae, Orthoptera Acrididae and plant species belonging to Cyperales Gramineae, in which Acrididae accounted for 23.3%, Gryllotalpidae 22%, Coccinellidae 11%, Potamidae 9.39%, Gryllidae 9.39%, Atypidae 9.39%, Scarabeidae 4.21%, Sphingidae 4.21%, Viviparidae 2.91%, Scolopendridae 2.67%and Ranidae 1.94%. It was also found that the body size of tiger frogs was not significantly different with the composition of feeding food, and the sex of adult tiger frog was not significantly different with the composition of feeding food.Tiger frogs, bought from breeding farm with 60 days,90 days,120 days and150 days old, were divided into groups by the age of days. They were fed with mixed diet for 1 week, then hunger stricken for 24-hours, and then fed artificial food, locusts, mole crickets, crickets, spiders, snails, ladybugs, tiger frog, crabs and other single type of food. Defecating conditions were observed and excrements were examined by X-ray. It was found that locust, mole cricket, cricket and spider stayed for basically similar time in the stomach of the frogs with same age of days. The detention time of these types of food was 48h±24h for the group of 60 days’ old of frog,48h±12h for the 90 days’,48h±6h for the120 days, and 48h±5h for 150 days. Snails, ladybugs, young tiger frogs and river crabs stayed for basically similar time in the stomach of the frogs with same age of days. The detention time of these types of food was 96h±24h for 60 days old of frog,96h±12h for 90 days,72h±12h for 120 days, and 48h±12h for 150 days.The detention time of the expanded mixed feed for frogs was 24h±12h for 60 days old of frog,24h±6h for 90 days,12h±6h for 120 day, and 12h±2h for 150 days. It is indicated that the detention time of single type of the expanded mixed feed for frogs deceased with the increase of frog size.The results showed that the optimal time is 10 hours in Hainan for collection of evidence for law enforcement. When the time is more than 120 hours, it lost the meaning of evidence. The results of this study could help to make sure accurate time for analysis of tiger frog’s feeding in law enforcement, and to enhance the effectiveness of law enforcement. The information collected from the Forestry Bureau of Hainan Province showed that tiger frog breeding in Hainan Province began since 1995 and extended to the whole province in 1998. The annual production was more than 60 million,2 million,1.5 million, 5.58 million,6.48 million and 5.18 million kg in 2000,2003,2004,2005,2006 and 2007 respectively, and the output value was about 1.08 billion,80 million,60 million,33 million, 38 million and 30 million yuan in 2000,2003,2004,2005,2006 and 2007 respectively. In 2000 tiger frog breeding got the maximum annual production and the maximum annual output value in the history. Currently the production of tiger frog aquaculture is in a slow recovery phase and the price of marking frogs is hovering in the low valley bottom. The diseases found in tiger frog breeding farm were parasitic disease, skin fester disease and gastroenteritis from the survey of 94 farms in Hainan Island in 2008. Parasitic disease, skin fester disease and gastroenteritis were found in all the three breeding cycles in Haikou City, Wenchang City, Sanya City, and Qionghai City in 2008. It is found from the survey of 500 breeders of tiger frog that 96.6% of respondents believe that the low marketing price of tiger frog impacts the enthusiasm of farmers.95.5% of respondents believe that the feed is too expensive and 81.5% of the respondents think the feed suppliers monopolize the price of feed and manipulate the marketing price of frog. The characteristics of single family as main investor in tiger frog breeding in Hainan determined the little room to increase economic benefits through lowering the cost in tiger frog breeding. It has influenced to certain extent the wildlife resources of tiger frog since no sound processing for dead bodies of tiger frog with diseases, disposition of wastewater without control, release of patient frogs to surrounding environment without treating when economic loss appearing and so on in the breeding.According to the growth data from two frog farms in Haikou City and Wenchang City, it was found that under the condition of male and female mixed-breeding the average body weight of female individual was 22.15,55.14 90.57,126.48,163.07,199.38,232.76, 294.95 and 386.45g and that of male individual was 12.48,30.06,50.36,73.15,94.37, 114.59,130.92,160.11 and 193.15g for the frogs with the age of 40,50,60,70,80,90,100, 120 and150 days respectively. Under the condition of male and female separated-breeding (single sex breeding) the average body weight of female individual was 23.70,58.63,95.73, 133.85,173.30,212.13,248.22,318.56 and 415.00g and that of male individual was 12.67, 30.45,52.74,75.61,98.73,121.14,142.02,177.81 and 219.15g for the frogs with the same order of age above mentioned. Under the condition of male and female mixed-breeding the average body weight of adult female breeding frog was 495.95,546.79,576.83 and 598.41g and that of adult male breeding frog was234.60g,260.85g,282.47g and 396.92g for the groups with age of 200,250,300 and 365 days respectively. It indicated that under the same breeding conditions female frogs grew faster than males. Under different breeding conditions the best growth of female individual appeared in the single sex breeding case. So the best breeding model was single sex breeding of female.Through outdoor and indoor experiments it was found that under the outdoor environment conditions with the water temperature at 20℃±8℃,22℃±9℃,26℃±8℃and 30℃±8℃, the hatching rate of female tiger frog was 72%,67%,55% and 12% respectively. Under the indoor conditions with constant room temperature at 15℃,20℃, 25℃,30℃and 35℃, the hatching rate of female tiger frog was 86%,71%,67%,19% and 0% relatively. It was indicated that relatively low temperature could effectively increase the proportion of female tiger frogs, while relatively high temperature hatched a higher proportion of males. Under the outdoor environment condition with water temperature in breeding pond at 20℃±8℃and the concentration of estradiol in incubation water at 0 mg/L,0.01mg/L, 0.1mg/L and 1mg/L, the female frog accounted for 71%,56%,65%and 80%of all hatched frogs respectively. Under the outdoor environment condition with water temperature in breeding pond at 30℃±8℃and the concentration of estradiol in incubation water at 0 mg/L, 0.01mg/L, 0.1mg/L and 1mg/ L, the female frog accounted for 24%,58%,63% and 81% of all hatched frogs respectively. It was shown that estradiol benzoate apparently affected the sexual differentiation of tiger frogs. The results showed that as long as the same concentrations of hormone existed in water under different temperatures, the proportions of the female frog hatched were similar. It was indicated that under the combined action of temperature and hormone, the effect of hormone induction was more apparent. |
PDF Full Text Request