Season’s first algae bloom strikes Trusal, Caleta Bay farms in Chile

Several salmon-farming centers in southern Chile have activated contingency plans responding to harmful algae blooms, the Chilean National Fisheries and Aquaculture Service (Sernapesca) reported recently.

The 18 farming centers under contingency plans are located in the Reloncaví Estuary and have a combined biomass in the water of 79,727 metric tons (MT). To date, two salmon-farming companies operating in the area – Trusal and Caleta Bay – have been hit by mass mortalities. As of 17 November, Sernapesca reported that the mortalities affected 1,140 MT of coho and trout species.

“We at Sernapesca are monitoring and supervising compliance in person, remotely, and via documents with the contingency action plans of each affected farming center and in coordination with the institutions,” Sernapesca Los Lagos Regional Director Cristian Hudson told Chilean media. “Up to now, the situation is being addressed normally by the owners of the affected centers … [and] we will maintain surveillance until the contingency is closed.”

The algal bloom is due to the proliferation of the microalgae Thalassiosira pseudonana, which does not seem to affect bivalve mollusks or other fish besides salmon and trout, Sernapesca said.

Chile’s Fisheries Development Institute (IFOP) said the spring season offers ideal amounts of light and nutrients for microalgae to feed off of, resulting in regular algal blooms. In recent years, microalgae blooms have become more frequent due to climate change and rising water temperatures. In 2022, a January bloom and the resulting issues cost Blumar over USD 3 million (EUR 2.7 million). Overall, Chilean salmon farmers lost 5,200 MT of salmon in 2021 to blooms. Those events pale in comparison to the disasterous 2016 season, when over 24 million fish, weighing in at more than 38,000 MT, were killed, representing more than USD 800 million (EUR 733 million) in economic impact from lost production. 

As for the current algae bloom, Hudson confirmed that the Trusal and Caleta Bay centers are the only ones affected by mass mortalities.

According to Alejandro Clément, general manager of environmental consultancy and laboratory Plancton Andino, the bloom actually occurred following a cold weather event, “which goes against all logic.”

“There was hail, wind, [and] rain; it snowed at 800 meters above sea level … in the southern mountain range of Chile,” Clément told Aqua. “The temperature dropped, so it is absolutely the opposite of common sense, which says where there is more sun, the [algae] grow more; here, there was less sun, it was colder, and there was more rain. I think the increased flow of freshwater due to rain may have provided the right nutrient conditions for this algae to flourish.”

Although the current algal bloom is not a direct consequence of El Niño, Sernapesca has been reporting since September on the possible ... 

Photo courtesy of Sernapesca