Contribution no. 70 of the Aquaculture Department, Southeast Asian Fisheries Development Center.

Eggs of Penaeus monodon are classified into five different types on the basis of morphological criteria and hatching rates — A1 eggs undergo normal development with 58% hatching rate; A2 eggs show delayed and/or abnormal development with 32% hatching rate; and B, C and D eggs are unfertilized and do not hatch. Wild (unablated) females have the highest proportion of A1 eggs and highest hatching rate, followed by ablated wild stock; ablated pond stock show the lowest proportion of A1 eggs and the lowest hatching rate. There is a highly linear relationship between the percentage of A1 eggs and the hatching rate in spawnings from ablated females of both pond and wild stock. Discussion concentrates on the development of these egg types, comparison with other studies and the importance to hatchery operations of these findings.