Universities Research Journal 2011, Vol. 4, No. 2

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1 Universities Research Journal 2011, Vol. 4, No. 2 Comparative Study on Hatching Rate and Incubation Period of Sea Turtles from Kadongalay Island and Thameehla Island in Ayeyrawady Region and Oyster Island in Rakhine State Kay Thi 1, Htar Htar Kyi 2, Moe Moe Kyaw 3 and Theingi Soe Myint 4 Abstract Hatching rate and incubation period of Lepidochelys olivacae on Kandongalay Island, Bogalay Township, Chelonia mydas on Thameehla Island, Nga-pu-taw Township in Ayeyrawady Region and Eretomchelys imbricata on Oyster Island in Rakhine State, Myanmar were studied from October 2008 to November Sixteen transplanting nests on Kadongalay Island, twenty-seven transplanting nests on Thameehla Island and eighteen transplanting nests on Oyster Island were studied in detail. On Kadongalay Island, turtles used to come and lay eggs from October to February yearly, on Thameehla Island, all the year round and on Oyster Island, June to September yearly. The mean hatching rate of Lepidochelys olivacae was 78.22%, Chelonia mydas, 73.83%, and Eretmochelys imbricata, 85.07%. Therefore, the hatching rate of Eretmochelys imbricata from Oyster Island was higher than that of the other rookeries. It can be said that the study on hatching rate of sea turtles would be of great help for the conservation of endangered sea turtles. Key words: Kadongalay, Thameehla, Oyster Island, Lepidochelys olivacae, Chelonia mydas, Eretmochelys imbricata, hatching rate, and incubation period Introduction Five sea turtle species are generally recorded in Myanmar (Marquez, 1990); Chelonia mydas (Green turtle), Dermochelys coriacea (Leatherback turtle), Eretmochelys imbricata (Hawksbill turtle), Lepidochelys olivacea (Olive ridley) and Caretta caretta (Loggerhead turtle). They make their nests along the Myanmar Coast. Only Olive ridely comes to lay their eggs on Kadongalay Island, Bogalay Township in Ayeyarwady Region, Green turtles and a few new number of Olive ridley in Thameehla Island, Nga-pu-taw Township in Ayeyarwady Region and 1. Professor(Head), Department of Zoology, Sittway University 2. Lecturer, Department of Zoology, Sittway University 3. Assistant Lecturer, Department of Zoology, Sittway University 4. Assistant Lecturer, Department of Zoology, Sittway University

2 12 Universities Research Journal 2011, Vol. 4, No. 2 Hawksbill turtle and Green turtles on Oyster Island in Rakhine State. In this research, the comparative study on the hatching rate of Olive ridley on Kadongalay Island, Green turtle on Thameehla Island and Hawksbill turtle on Oyster Island was carried out. All nes ts are transplanted in order to avoid human disturbance. The results of hatching rate and incubation period will be of great help for sea turtle conservation. Materials and Methods Study sites Kadongalay Island (15 49 N and E) was formed with deposited sand at the mouth of Bogalay River, Ayeyarwady delta in Bay of Bengal. Kadongalay Island is five miles in length and three quarter mile in breadth. The sand type is with siliceous sand type. Thameehla Island (Diamond Island) (15 51 N and E) was existence at the mouth of Pathein River, Ayeyarwady delta region. The area of Thameehla Island is acres. The total length of Thameehla Island is twelve miles. The reefs serve as the natural habitat for sea turtles because of the plentiful supply of food in them. Therefore, the female turtles lay eggs all the year round on Thameehla Island. The sand type is with calcareous sand type. Rakhine State Oyster Island (20 11 N and E) is located in the Bay of Bengal. The length of the island is 0.11 kilometer and the width, 0.04 kilometer. It is situated in the northwest of Sittway. It is 24 miles far away from Yay-gyan-pyin village. It takes four hours to reach Oyster Island from the Yay-gyan-pyin village by motor boat. The sand type is with calcareous sand type with fragment of coral. The mere flora of this island is coconut palm. (Fig. 1 Source : Forest Department) Study period During the period from October 2008 to November 2010 and spotlight survey was conducted in selected study sites. Transplanting of nests All nests near the vicinity of human habitat were transplanted. When young turtles were hatched, they were released into the sea immediately. The nest temperature was recorded by digital thermometer; total depth and

3 Universities Research Journal 2011, Vol. 4, No width of clutches, the curve carapace length (CCL) and the curve carapace width (CCW) were measured by the measuring tape. Nest location and date of laying eggs were recorded, and then watched until the time of hatching out. The temperature of the nest was measured three times a day, at 9 am, 3 pm, and 9 pm. Transplanting nests survey on Thameehla Island Twenty-seven transplanting nests of Thameehla Island were observed during the study period. The procedure of transplanting nests on Thameehla Island was similar to that of the construction on Kadongalay Island. Transplanting nests survey on Oyster Island Eighteen transplanting nests were constructed on Oyster Island during the period from June 2010 to October 2010 in detailed. All nests were transplanted due to the nesting areas becoming narrower and narrower and were potential of damaged by flood. The procedure of transplanting nests on Oyster Island was similar to that of the construction on Kadongalay Island. When the egg clutches were hatched, they were examined for hatched eggshell, unhatched eggs and undeveloped eggs. Examination of nests When the young turtles hatched from natural and transplanted nests, eggshells, death hatchling, unhatched eggs and undeveloped eggs were counted for each clutch. If the hatching date was known, incubation period can be calculated. Hatching rate was also calculated. After the hatchlings emerged, broken shells and unhatched shells from the clutch were removed. The nest temperature was recorded by digital thermometer; total depth and width of clutches were measured using the measuring tape. Statistical analysis Statistical analysis of ANOVA test and t-test was carried out using Statistical Package for Social Science (SPSS) Version 11.5 software. Significant was tested at 0.05 (2-tailed) level. The analysis of the recorded data were tabulated using Microsoft Excel Programme. Values were given as mean ± standard deviation.

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5 Universities Research Journal 2011, Vol. 4, No Hatchlings of olive ridley Lepidochelys olivacea (Olive ridley) Hatchlings of green turtle Chelonia mydas (Green turtle) Hatchlings of hawksbill E. imbricata (Hawksbill turtle) Plate 2 Study species of hatchlings and adults

6 16 Universities Research Journal 2011, Vol. 4, No. 2 Results Hatching rate and incubation period of Lepidochelys olivacea in transplanted nests (hatcheries) and natural nests on Kadongalay Island Thirty natural nests (in situ) and sixteen transplanting nests of Lepidochelys olivacea were recorded at Kadongalay Island from October 2008 to January Sixteen transplanted nests constructed at upper slope were very close to human habitation area. The incubation periods of thirty natural nests and sixteen transplanting nests were recorded in table hatchlings from 30 natural nests and 1291 hatchlings from 16 transplanting nests were released into the sea during the study period. The numbers of hatchlings released were not significantly different between the natural nests and transplanted nests at Kadongalay Island (t =0.6717, P>0.05, t test). Hatching rate and incubation period of Chelonia mydas in transplanted nests and natural nests on Thameehla Island Twenty-seven transplanting nests of Chelonia mydas on Thameehla Island were observed during the study period. All nests were transplanted at upper slope where there were no weeds or grasses. The incubation parameters of twenty-seven transplanting nests were recorded as in table 2. Hatching rate and incubation period of the three study species on three different study sites (Kadongalay, Themeehla, and Oyster Islands) Sixteen transplanting nests of Lepidochelys olivacea on Kadongalay Island, twenty-seven transplanting nests of Chelonia mydas on Thameehla Island and 18 transplanting nests of Eretmochelys imbricata on Oyster Island were observed from October 2008 to November The incubation parameters of three study sites were recorded in table 3. The hatching rate of hawksbill turtle on Oyster Island was higher than that of the olive ridley on Kadongalay and green turtle on Thameehla Island (Table 4). The hatching rate of three study species, Lepidochelys olivacea, Chelonia mydas, and Eretmochelys imbricata were significantly different among the three study sites (Kadongalay, Thameehla, and Oyster Islands) (P < 0.05 %, ANOVA test) hatchlings on Kadongalay Island, 1760 hatchlings on Thameehla Island, and 2133 hatchlings on Oyster Island were released into the sea during the study period.

7 Universities Research Journal 2011, Vol. 4, No Table 1. Some incubation parameters of Lepidochelys olivacea eggs incubated in natural nests (in situ) and transplanting nests (hatcheries) on Kadongalay Island Parameters Natural nests Transplanting nests Total number of clutch Total number of eggs Total number of hatchlings Total number of damaged eggs Mean and S.D of clutch size 119.1± ±26.74 Mean and S.D of hatchlings 98.6± ±34.22 Mean and S.D of hatching rate 83.3± ±26.61 Mean and S.D of damaged eggs 20.5± ±32.57 Mean temperature 29.7 C 30.6 C Mean nest depth(cm) 44 cm 45 cm Mean incubation period 47 days 49 days Table 2 Some incubation parameters of Chelonia mydas eggs incubated in transplanting nests (hatcheries) on Thameehla Island Parameters Transplanting nests Total number of clutch 27 Total number of eggs 2405 Total number of hatchlings 1760 Total number of damaged eggs 645 Mean clutch size and S.D 89.07±11.03 Mean and S.D of hatching rate 73.83±16.41 Mean and S.D of damaged eggs 23.88±16.9 Mean temperature C Mean nest depth(cm) Mean incubation period 35 cm 49 day

8 18 Universities Research Journal 2011, Vol. 4, No. 2 Table 3. Hatching rate of sea turtles on Kadongalay, Thameehla, and Study sites Kadongalay Island Thameehla Island Oyster 139.5± ± ±3.38 Island Oyster Islands Table 4. Some incubation parameters of Lepidochelys olivacea, Chelonia mydas and Eretmochelys imbricata eggs incubated in transplanting nests (hatcheries) on Kadongalay, Thameehla and Oyster Islands Parameters Total number of clutch Total number of eggs Total number of hatchlings Total number of damaged eggs Mean clutch size and S.D Mean & S.D of hatching rate Mean & S.D of damaged eggs Mean clutch size ± S.D Lepidochelys olivacea Mean hatched eggs ± S.D Chelonia mydas Mean hatching rate ± S.D ± ± ± ± ± ±15.68 Eretmochelys imbricata ± ± ± ± ± ± ± ± ±0.95 Mean temperature 30.6 ºC C C

9 Universities Research Journal 2011, Vol. 4, No Parameters Mean nest depth(cm) Mean period incubation Lepidochelys olivacea Chelonia mydas Eretmochelys imbricata 45 cm 45 cm 50 cm 49 days 49 days 59 days Discussion Sea turtle species are now globally threatened and only seven species alive today (Harless and Morlock, 1979, Karen and Balazs, 1994). They are green turtle (Chelonia mydas), olive ridley (Lepidochelys olivacea), hawksbill turtle (Eretmochelys imbricata), loggerhead turtle (Caretta caretta), flatbackturtle (Natator depressus), Kemp s ridley (Lepidochelys kempii) and leatherback turtle (Dermochelys coriacea). All these six species are commonly found in ASEAN waters except the flatback, which is restricted primarily, to Eastern Indonesia. The black turtle or East Pacific green turtle (Chelonia agassizii) is recognized by some biologists, but morphological, biochemical, and genetic data published to date are conflicting, and the black turtle is currently treated as belongings to Chelonia mydas (Meylan & Meylan, 1999). Maxwell (1911) conducted an extensive investigation of the turtle banks of coastal Myanmar. At that time turtles nested on Thameehla Island (Diamond Island N and E), Kaing-thaung Island (15 44 N and E) and Thaungkadon (15 43 N and E) in Ayeyarwady coastal regions respectively. The Colonial Administration to local businesspersons, who harvested and sold eggs, leased these beaches. About 1.5 million olive ridley turtle eggs and 1.6 million green turtle eggs were harvested annually. Today green turtles and a few number of olive ridley turtles come to lay eggs on Thameehla Island in Nga-pu-taw Township and olive ridley turtles lay eggs on Kadongalay Island in Bogalay Township, Ayeyarwady Region. In Rakhine State, green turtle and hawksbill turtles lay eggs on Oyster Island in Sittway Township, olive ridley turtles on Sittway beach in Sittway Township and Ah-lae-than-kyaw bank in Maung-taw Township,

10 20 Universities Research Journal 2011, Vol. 4, No. 2 green turtle and olive ridley Yan-bywe Island in Kyauk-phyu Township, Marn-aung Island and Tha-byu-chai in Than- twe Township. The temperature during the incubation process had an effect over the sexual differentiation of sea turtles. At the range from C, all hatchlings were females, while all hatchlings were males at the range from C. Since the temperature was C, the sex ratio of the hatchlings was female and the average temperatures of 28.6 C and 29 C the sex ratio of the hatchlings was male. Hatching rate and incubation period are related to the environmental conditions of the nests. Environmental conditions refer to temperature in the nest, humidity, effect of tidal waters, conditions in which roots of trees, plants and weeds can or cannot seep into the nests, and biological enemies such as man, hawks, kites, crabs, wild cats and wild dogs. Temperature and humidity were very important to obtain a high survival rate. The mean and standard deviation of hatching rate of natural nests was 83.3 ± and transplanting nest, ± Therefore, the hatching rate of natural nests was higher than that of the transplanting nests. The best way for hatching turtles was hatching them in natural nests. Although, natural nest have to be transplanted due to the unavoidable circumstances, if they were carried out systematically, it will be of great help for sea turtle conservation. The mean and standard deviation of twenty-seven transplanting nests on Thameehla Island was ± Since also the average temperature range was 27 C 29.3 C, the sex ratio of the hatchlings at Thameehla Island beach in nature was 1:1. During the study period, the average temperature in the transplanting nests was optimal (27 C 29.3 C), and a high survival rate was observed. During the rainy season, the average temperature of Oyster Island was 28.5 C-29.1 C, the sex ratio of hatchlings from Oyster Island was 1:1. The range of incubation period of Eretmochelys imbricata was days. In normal condition incubation period varied by species and depended on the temperature, humidity, and depth of the nest. The observation of the nests on Oyster Island was carried out in rainy season. The incubation period of study species increased due to the rise of nest s temperature between 28.5 C-29.1 C in rainy season. During the study period, the average temperature of the nests was optimal, and obtained a high survival rate.

11 Universities Research Journal 2011, Vol. 4, No Sixteen transplanting nests of Lepidochelys olivacea on Kadongalay Island, twenty-seven transplanting nests of Chelonia mydas on Thameehla Island and eighteen transplanting nests of Eretmochelys imbricata on Oyster Island were compared from October 2008 to November The mean and standard deviation of hatching rate of Lepidochelys olivacea on Kadongalay Island was ± 26.61, Chelonia mydas on Thameehla Island, ± 16.41, and Eretmochelys imbricata on Oyster Island, ± In three study sites, the hatching rate of Eretmochelys imbricata on Oyster Island was higher than those of the others. Eighty percent hatching rate have been obtained at Oyster Island and the nests were constructed on the upper slope. The single plant species of the island was coconut palm on Oyster Island, roots of trees, plants and weeds cannot destroy the turtle nests. The biological enemies are rare on this island except some crab (Ocypode species). Bacteria, which eat decaying matter of undeveloped eggs, can destroy other good eggs. Bacteria, which exist in soil, as well as bacteria born of decaying matter of undeveloped eggs can cause low hatching rate. No bacteria affected the nests on three study sites. Oyster Island is not liable to natural disasters such as flooding before Nargis cyclone. Therefore, the hatching rate of sea turtles on Oyster Island was better than those of the Kadongalay and Thameehla Islands. Low hatching rate on Thameehla Island was probably due to the following: (1) Sometimes, eggs are transferred only at dawn. Transferring could not be completed within 2 hours of the eggs being laid. (2) The eggs could not be handled systematically during transferring. (3) During the rainy season, freshwater from the hilly areas unexpectedly flooded the hatchery located at the foothill. To prevent this, ditches should be built around the hatchery. Sea turtles in Myanmar have faced the extinction due to rapid economic development of human being and natural calamities. The study on hatching rate and incubation period of sea turtles in Myanmar coastal regions was required to prevent their extinction. There are several essential environmental conditions required to achieve the most successful incubation of sea turtle eggs under natural conditions. Sea turtle eggs required well-ventilated, low salinity, high sand humidity of clutch site. Sea turtles usually lay eggs above the level of tidal inundation and at least 30 cm below the beach surface. Sand that is regularly washed over by seawater

12 22 Universities Research Journal 2011, Vol. 4, No. 2 (high tides) can be too salty and cause reduced incubation success of the eggs. The eggs are killed by flooding with salt water. The turtle eggs can be expected to have approximately 75-82% incubation success when nest temperatures are in the range of 29 C-31 C. When nest temperature exceed 31.5 C, incubation success decreased. At nest temperature above 33 C, all eggs are killed. The whole world had been contributing to the conservation of endangered sea turtles. ASEAN countries including Myanmar have also been contributing to the sea turtle conservation. Local people should conserve sea turtles, which inhabit the Myanmar coastal regions. Acknowledgements We are greatly indebted to Rector Dr. Tin Maung Tun, Sittway University, for his permission to conduct this research. References Carr, A. (1952). Handbook of Turtles. The Turtles of the United States, Canada And Baja California. Cornell University. Press, Ithaca. Karen, A.B. and G.H. Balazs (1994). Newsletter of Marine Turtle Specialist Group. Limpus, C.J., Reed, P.C. and Miller, J.D Temperature Dependent Sex Determination in Queensland Sea Turtles: Intraspecific Variation in Caretta caretta In: Biology of Australasian Frogs and Reptiles. (Eds.G. Grigg, R. Shine and H.Ehmann). Royal Zoological Society: New South Wales: Maxwell, F.D. (1911). Report on the turtle-banks of the Irrawaddy Division. In: Reports on island and sea fisheries in the Thongwa, Myaungmya, and Bassein Districts and the turtle-banks of the Irrawaddy Division Government Printing Office, Rangoon. (Cited in Ecological Reconnaissance of Meinmahla Kyun Wildlife Santuary and Vicinity, Sourthern Ayeyarwady Delta, Myanmar by J.B. Thorbjarnarson, 1999). Marquez, M.R FAO species catalogue. Vol II: Sea turtles of the world. An annotated and illustrated catalogue of sea turtle species known to date. FAO Fisheries Synopsis. No.125, Vol. II. Rome, FAO. 81pp. Meylan, A.B. and P.A. Meylan.(1999). Introduction to the Evolution, Life History, and Biology of Sea Turtles. In: Researcha and Management Techniques for the Conservation of Sea Turtles. IUCN/SSC Marine Turtle Specialist Group. P-3. Publication No-4.

13 Universities Research Journal 2011, Vol. 4, No Mrosovsky, N. and Yntema, C. (1980). Temperature dependence of sexual differentiation in sea turtles: implications for conservation practices. Biol. Conserv. 18, Pritchard, P.C.H. and Mortimer, J.A. (1999).Taxonomy, External Morphology, and Species Identification. In: Eckert, K.L., K.A. Bjorndal, EA.Abreu- Grobois, and M.Donnelly (Editors) Research and Management Techniques for the Conservation of Sea Turtle. IUCNISSC Marine Turtle Specialist Group Publication No.4: Smith, M. A. (1931). The fauna of British India, including Ceylon and Burma.Reptilia and Amphabia. Vol. 1. Loricata, Testudines. Taylor and Francis Ltd, London.