Mortality of farmed pearl oyster Pinctada fucata (Gould, 1850) due to the blooming of Noctiluca scintillans and Cochlodinium sp. at Kollam Bay, Kerala

Blooming of the dinoflagellates Noctiluca scintillans was observed at Kollam Bay, Kerala during September 2003 (bloom-1) and Cochlodinium sp. in September 2004 (bloom-2) with cell densities of 9.8 x 10 4 and 1.4 x 10 5 cells l -1 respectively. These caused 27% and 100% mortality of the farmed pearl oyster Pinctada fucata in the raft farms of Central Marine Fisheries Research Institute moored in the Bay. The mortality of the pearl oysters can be attributed to the high dissolved ammonia 14.9 µmol l -1 during bloom-1 and high dissolved ammonia (14.7 µmol l -1 ) and total suspended solids (154.8 mg l -1 ) during bloom-2. These instances of harmful algal blooms (HAB) indicate that precautionary management protocols should be developed to relocate the farm stock to overcome such natural causes to prevent economic loss to farmers.