Nick and the Hatchlings: A Master's Thesis on Hatchery Management

Nicholas (Nick) Tolen first joined the Perhentian Turtle Project in 2015, as a team leader, then returned in 2017 as a research coordinator at the nesting beach of Tiga Ruang. Having worked closely beside the local Department of Fisheries (DoF) staff, assisting with their hatchery management, Nick wanted to investigate whether the hatchery was producing all female hatchlings due to high incubation temperature


To better understand how hatchery management influences the fitness and resulting sex-ratios of hatchlings, Nick enrolled as a graduate student with the Sea Turtle Research Unit at the University Malaysia Terengganu. His research project measures the differences in incubating nest temperatures, and fitness attributes, like crawl and swim speeds, of hatchlings produced between the DoF managed hatchery at Tiga Ruang and the Chagar Hutang Turtle Sanctuary’s natural nesting beach on Redang Island. Nick uses iButton temperature data loggers to measure incubating nest temperatures at both sites, and from these measurements, he is able calculate an individual nest’sestimated proportion of female hatchlings. In addition to estimating the potential sex-ratios of hatchlings produced at the Tiga Ruang hatchery, Nick collected deceased hatchlings found in excavated nests for histological examination of their gonad tissues.


His results show that although a small portion of relocated nests were estimated to produce some male hatchlings, the majority of nests incubated in the Tiga Ruang Hatchery were estimated to produce 100% female hatchlings. The results from the histological examination of gonad tissue compounded the sex-ratio estimates, as the vast majority of specimens examined exhibit characteristics of female gonads.


Nick hopes the results from his study will help inform the local DoF staff on how to better manage their hatchery operations in order to produce healthy hatchlings at optimal sex-ratios. He suggests the DoF staff set up shade cloth to reduce hatchery sand temperature and bury relocated nest at least 40-60cm deep to reduce daily fluctuations in nest temperature.


Nick also recommends stopping by Kak Tie's roti stall anytime you visit the Perhentians.

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