Areas where Pseudochattonella sp. has been reported. The green dots indicate presence in concentrations <10 cells / ml; yellow 10-50 cells / ml; and red> 50 cells / ml. Image: Claudia Uribe.

Algal bloom causes farmed fish deaths in Chile

An algal bloom has caused significant mortalities at salmon farms in the Aysén region of Chile, and a weather forecast for high temperatures and low wind speeds means it may get worse.

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Since Friday, January 7, cells of the harmful microalgae Pseudochattonella sp. have been causing harm to fish in both north and south Aysén.

Claudia Uribe, executive director of microalgae monitoring company North Patagonia, told Fish Farming Expert’s Chilean sister site,, that in the south near Puerto Aguirre the microalgae had reached concentrations above 50 cells / ml, with a maximum registered until yesterday of 163 cells / ml. That concentration is considered critical for salmon and has generated significant mortalities in some farms and the activation of contingency plans by the affected companies.  

Claudia Uribe: Conditions favour an increase in algae levels.

Sheltered sites

“Until now, the sites with the highest concentration are sheltered sites, which have also been affected by the quadrature (minimal range) tides and low wind speed, which increases the residence rate of the microalgae in the sites,” Uribe explained.

The microalgae species is recognised by its golden-yellow colour, its irregular (wavy) edges, and its slow, circling movement.

According to Uribe, for the next few days some rainfall is expected in the Puerto Aguirre area, but the high temperatures and low wind speeds continue, “conditions that will favour the permanence and eventual increase of the concentrations of Pseudochattonella sp.”