Chile moves to tackle harmful algal blooms as El Niño heightens risk

Chilean authorities and salmon farmers are stepping up preparations for harmful algal blooms (HABs) in southern waters, with Chile's national fisheries and aquaculture authority Sernapesca warning that a stronger El Niño could heighten the risk in the months ahead.

Sernapesca has recently met with salmon farming companies and aquaculture service providers to coordinate responses to harmful algal bloom events affecting the south of the country. The meeting focused on blooms of the algae species Heterosigma akashiwo, which have been detected since March and have mainly affected fish farms in Salmonid Concession Groups 1 and 2 in the Reloncaví Sound area.

According to Sernapesca, 11 fish farms have so far been affected and have activated preventative action plans in response to the blooms.

During the meeting, authorities reminded companies of measures available under the current aquaculture pre-alert, which are intended to help prevent mass salmonid mortalities. These measures include allowing fish to be moved to other farms, issuing harvesting permits, and extending the time fish can remain at collection centres, among other actions.

Sernapesca said the meeting also helped reinforce procedures and points of contact for handling requests from aquaculture operators in the coming weeks.

Representatives of the Chilean Navy’s Directorate of Maritime Interests and Aquatic Environment (DIRINMAR), and the Undersecretariat of Fisheries and Aquaculture also took part in the meeting as part of broader public-sector coordination through the Inter-institutional Committee for Environmental Contingencies.

Mónica Rojas, deputy director of aquaculture at Sernapesca, said the current situation underlined the need for continued joint planning between the authorities and the industry.

“The current scenario anticipates the arrival of the El Niño phenomenon with greater intensity, similar to what happened in previous years when there was significant damage to aquaculture centers," Rojas stated.

“Therefore, it is necessary to strengthen coordination and preventative plans in this regard, not only with public institutions, but also with the aquaculture sector, to act jointly in the face of any contingencies that may arise,” she added.

The cyclical climate event El Niño, which creates warmer-than-average sea surface temperatures in the central and eastern tropical Pacific Ocean, is associated with a heightened risk of HABs. A major harmful algal bloom in 2016 killed nearly 12% of Chile's farmed salmon, coinciding with a strong El Niño that year.

More recently, in 2024, Chilean operators reported a harmful algal bloom causing mass mortality of farmed fish northeast of Isla Victoria, an island in the Chonos Archipelago of Chile, with more than 3,800 metric tons of fish lost due to a bloom of Pseudochatonella spp. An earlier HAB event was reported in Chile during November 2023, where 1,500 tonnes of fish were killed by the microalgae Thalassiosira pseudonana.

The latest southern Chile response also comes as authorities step up education and information efforts on harmful algal blooms elsewhere in the country.

In a separate announcement, Subpesca, Chile’s fisheries and aquaculture undersecretariat, said it had recently held public information sessions in the Atacama Region, designed to improve scientific understanding of HABs among coastal communities, with additional sessions planned in Coquimbo and Valparaíso over the next months.

Subpesca said the initiative "allows science to be brought closer to the communities, strengthening knowledge and risk prevention; moving towards a more informed management of harmful algal blooms and the effects of climate change."