According to the authority, Salmones Camanchaca reported the sudden death of the fish in its Pilpilehue site near the city of Castro, Chiloé, due to the presence of Pseudochattonella cf. verruculosa on the surface of the water.
The dead fish are being recovered from the water as quickly as available resources allow.
Sernapesca said it had been keeping farms in the area under surveillance since February because of the risk of HABs.
The evolution of the HAB is being evaluated today and Sernapesca will continue to monitor the farm grouping.