On the occurrence of Megalopae of Atergatis integerrimus and A. Roseus in the Ennore estuary near Madras

Abstract

The megalopae were absent in the collections during January to August, 1985andJanuary to May, 1986. Maximum number of megalopae were seen during September and October. The occurrence of megalopae is influenced by the lunar phase and the tidal ryhthm. Except on six occasions the megalopae were more during the high tide. Maximum number occurred during newmoon in September and October '85. In 1986 during full moon, the megalopae were abundant during September and October. Collections were made by fixed net for one hour during high and low tide of all four phases of the moon the megalopae enter the estuary in maximum numbers during the high tide on new moon and full moon nights. This pattern of abundance also shows that the breeding season for the crab Atergatis integerrimus and A. roseus is from June to December with peak in September and October.