About 270,000 puffer fish farmed in a bay off Nagasaki Prefecture have died due to the outbreak of red tide, resulting in damage of around 400 million yen, a local fisheries cooperative said Tuesday.

The dead tiger puffers are equivalent to around one-fourth of the 1.1 million of the fish farmed in Imari Bay off Matsuura, Japan's largest puffer-producing city.

The red tide has spread throughout Imari Bay following its outbreak in late July, according to the Shinmatsuura fisheries association. Neutralizing agents have been used to contain the red tide, but the amount of damage is expected to increase further.

Puffers are lethally poisonous but carefully prepared meals of the fish are one of Japan's most celebrated and luxurious dishes.

The massive fatalities likely resulted from an outbreak of toxic plankton covering puffer gills, causing breathing difficulties for the fish.

Along with tiger puffers, 62,000 other farmed fish including bluefin tuna and yellowtail have also been found dead in the bay.