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

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 50cm and 75cm 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 280C and 300C 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 75cm deep nests had a 46.4 (+ 10.2) hour longer emergence lag than hatchlings from 50cm deep nests. Hatch and emergence success were similar to 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 75cm nests had similar running speeds but lower condition index than their conspecifics from 50cm deep nests