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Cherdsukjai, Phaothep; Kittiwattanawong, Kongkiat; Adulyanukosol, Kanjana
(detail)
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2014 |
Dugong aerial surveys 2011-2012: declining trend of the dugong population in Muk-Talibong Island, Thailand.
Proc. Design Symposium on Conservation of Ecosystem (The 13th SEASTAR2000 Workshop) 2: 50-54. 4 tabs. 1 fig. Mar. 2014.
–ABSTRACT: The Muk-Talibong Islands in Trang Province are a habitat for the largest group of dugongs on Thailand's Andaman coast. Since 1994, the Phuket Marine Biological Center has regularly conducted aerial surveys over the area with various kinds of aircraft. In 2011 and 2012, the small aircraft model Tecnum P92J was used in line transect aerial surveys. Survey efforts were four flights (15.01 hours) and seven flights (17.14 hours) respectively. In 2011, the dugong detection rate was 51±50 animals per day, with a maximum count of 122 animals. In 2012, however, the dugong detection rate was 26±14 animals per day, with a maximum count of 54 animals. As a result of comparing the dugong detection rates for both years, we found that the number of dugongs is decreasing, even though the aerial survey periods in each year were the same month and tidal time. Windspeed is likely to be a physical factor that might lead to these results. Ranges of wind speed were 0-6 knot in 2011 and 5-17 knot in 2012. The wind speed affects waves and turbidity, and this may negatively affect visual detection of dugongs. Therefore, further aerial surveys in different weather conditions and dugong stranding reports may help to better understand the declining trends of dugongs in the area.
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Cherdsukjai, Phaothep; Buddhachat, Kittisak; Brown, Janine; Kaewkool, Manthanee; Poommouang, Anocha; Kaewmong, Patcharaporn; Kittiwattanawong, Kongkiat; Nganvongpanit, Korakot
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2020 |
Age relationships with telomere length, body weight and body length in wild dugong (Dugong dugon).
PeerJ 8: e10319. 4 tabs. 5 figs. + online supplemental information. doi:10.7717/peerj.10319 Nov. 11, 2020.
–ABSTRACT: The ability to estimate age and determine the growth status of free-ranging dugongs (Dugong dugon) is vital to providing insight into the basic biology of this endangered species. Currently, age estimation in dugong carcasses relies on counting dentin growth layer groups (GLGs) in tusks, but a disadvantage is they need to be intact. We explored whether measures of telomere length could be used as an alternative approach to age estimation in dugongs given that in other species, telomere length and age are inversely related. In this study, relative telomere length (rTL) was measured by qPCR in skin samples from 24 dugongs of varying ages determined by counts of GLGs. In addition, relationships between age by GLG counts and body weight and length and were examined. Our findings indicate that age estimated by GLGs was negatively correlated with telomere length using the logistic formula with a rate of telomere attrition of approximately 0.036 rTL/year between the ages of 5–20 years. By comparison, both body weight and length were positively correlated with GLG-based age, with growth rates of ~8.8 kg/year for weight and ~3.58 cm/year for length, respectively. After that, growth rates slowed substantially and then plateaued. The results suggest that physical maturity in dugongs occurs at 20 years of age and that measures of rTL might serve as a tool for age estimation in dugongs, living and deceased.
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Bibliography and Index of the Sirenia and Desmostylia 