THE BREEDING AND SECONDARY PRODUCTION OF THE FLAT-TREE-OYSTER ISOGNOMON-ALATUS (GMELIN 1791) IN TROTTS-POND, BERMUDA

Isognomon alatus (Gmelin), the flat mangrove oyster, is very abundant in Trotts Pond, Bermuda. The oyster occurs mainly on the submerged pro p roots of the red mangrove Rhizophora mangle (L.), averaging 250 oyst ers root(-1) or 2,700 m(-2). The sex ratio found was 68 female:26 male :6 indeterminate. Mature oysters of both sexes were present throughout the year, but maximum breeding activity, shown by maximum gamete volu me fraction followed by a fall and by a peak in spatfall, occurred in the spring. No larvae were detected in the plankton during the course of the study. The mean caloric content of the oysters was 5.23 cal mg( -1). The mean dry weight biomass was 399.3 g m(-2), and the total of s omatic gonadal and shell production was 863.9 g m(-2) per year giving a production:biomass ratio of 2.2:1.