EFFECTS OF HATCHERY NEST DENSITY ON THE EMERGENCE SUCCESS AND QUALITY OF CHELONIA MYDAS HATCHLING

Abstract

To maximise hatchery efficiency, nests need to be placed as close as possible, while not compromising emergence success or hatchling quality. Hatcheries in Peninsula Malaysia presently place nests at about 0.6m and 0.7m intervals within and between rows, respectively. The aim of this experiment was to determine the effects of increasing the nest density on emergence success and quality of emerging hatchlings. In June 2002, twenty-nine nests were placed in normal density and ten nests were placed in high density in the Ma'Daerah hatchery, Terengganu, Malaysia. A sample of at least 10 hatchlings emerging from these nests were subjected to a running trial over 1.6m and were weighed, measured and scale counted. The emergence success and the proportion of hatchlings with abnormal scale counts did not differ between high and normal density nests. Hatchlings from the higher density nests ran significantly slower than those from normal density nests and had lower mass-length ratios. It is argued that slower running speeds represent a longer exposure to shore predation and decreased vigour for the offshore dispersal. Furthermore, lower mass-length ratio represents reduced residual yolk stores and lower energy reserves available for the swim frenzy period. The development of eggs in high density clutches could be affected by reduced gas exchange between the clutch and surrounding substrate. This could result from adjacent nests competing for oxygen from the same area. From the current results, it is recommended that nests continue to be relocated into hatcheries at normal density to maintain the quality of emerging hatchlings.