Australian Journal of Zoology Australian Journal of Zoology Society
Evolutionary, molecular and comparative zoology
RESEARCH ARTICLE

Effects of hatchery shading and nest depth on the development and quality of Chelonia mydas hatchlings: implications for hatchery management in Peninsular, Malaysia

Jason van de Merwe A B D , Kamarruddin Ibrahim A C and Joan Whittier A D

A School of Biomedical Sciences, Department of Anatomy and Developmental Biology, University of Queensland, St Lucia, Qld 4072, Australia.

B Current address: School of Environmental and Applied Sciences & Centre for Aquatic Processes and Pollution, Griffith University, Gold Coast, Qld 4214, Australia.

C Current address: Turtle and Marine Ecosystem Center (TUMEC), Rantau Abang, 23050 Dungun, Terengganu, Malaysia.

D Corresponding author. Email: j.vandemerwe@griffith.edu.au

Australian Journal of Zoology 53(3) 205-211 http://dx.doi.org/10.1071/ZO03052
Submitted: 14 October 2003  Accepted: 13 April 2005   Published: 16 June 2005

Abstract

One of the decisions made by hatchery managers around the world is what degree of shading and nest depth are required to maximise the production of high-quality hatchlings at optimal sex ratios. The primary objectives of this study were to determine the effects of (1) hatchery shading and nest depth on nest temperatures and emergence lag, and (2) nest temperatures and nest depth on hatchling sex ratio and quality. In 2001, 26 Chelonia mydas clutches from Ma’Daerah beach, Terengganu, Malaysia, were relocated alternatively at depths of 50 cm and 75 cm into a 70%-shaded and a 100%-shaded hatchery. Data loggers were placed into the centre of each relocated clutch to record the temperature every hour over the course of incubation. When the hatchlings emerged, a sample of the clutch was run, measured and weighed and a separate sample was examined histologically for sex characteristics. Nest temperatures ranged between 28°C and 30°C and generally showed increases over the second half of incubation due to metabolic heating of the clutch. There was no significant correlation found between nest temperature and any of the hatchling parameters measured. Hatchlings from 75-cm-deep nests had a longer emergence lag (46.4 (±10.2) h) than hatchlings from 50-cm-deep nests. Hatch and emergence success were similar to those of natural populations and hatchling sex ratios were male dominant, with an average of 72% males. There was a poor correlation between mean middle-third incubation temperatures and sex ratio. Hatchlings from 75-cm-deep nests had similar running speeds but lower condition index than their conspecifics from 50-cm-deep nests.


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