On fouling and boring organisms and mortality Of pearl oysters in the farm at Veppalodai, Gulf of Mannar

Abstract

Pearl oysters of the species Pinctada fucata were reared in the Gulf of Mannar, off Veppalodai, by raft culture, for production of cultured pearls. Observations revealed a heavy growth of fouling and boring organisms on the pearl oysters, necessitating frequent shell-cleaning operations. Barnacles, bryozoans and spats of molluscs, Avicula and Crassostrea, were the significant fouling organisms, and a seasonal trend was observed in their dominance. The spionid polychaete Polydora and the clionid sponge Cliona celata were the important boring organisms causing considerable damage to the shells. Infection by polychaetes, as observed from the blisters and tumour-like growths on the inner aspect of the shells, was 78.4% and by sponge 20.7% among the shells examined.