Toxic red tide is a disastrous phenomenon causEd. by sudden blooming of certain killer microorganisms often encountered in the seas. Certain killer red tides have caused wide-spread losses to human life and to the fishing industry at several places. Various measures adopted to control or contain such harmful events have either proved ineffective or are economically unviable. Red tides generally break out under favourable environmental conditions such as calm, sunny weather and gently breeze or when two dissimilar water masses meet, or when factory effluents, domestic sewage or agricultural fertilizers are released into the sea. Only 23 of the 2000 species of dinoflagellates are known to be toxic. The most notorious forms are Pyrodinium bahamense var. compressa, species of Gonyaulax and Gymnodinium. Toxic dinoflagellate red tides are known to cause 3 types of seafood poisoning viz. paralytic shellfish poisoning (PSP), diarrheic shellfish poisoning (DSP) and Ciguatera poisoning